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Recommended reading

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Aesthetically focused. Emphasizes texture, look and feel of materials. This look inspired the design of my presentation sheets.

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This source provides a good frame-work for designing for material experiences.

This document also mentions designing with pulp, which is a core ingredient of disposable nappies, laminated with the bioplastic PLA.

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Material Driven Design (MDD): A Method to Design for Material Experiences

1 Department of Design Engineering, Delft University of Technology, Delft, Netherlands2
Design Department, Politecnico di Milano, Milan, Italy

Keywords - Materials Experience, Experience Design, Materials, Material Driven Design, Designing with Waste.

Relevance to Design Practice - 'Material' has been a central point of research and practice agendas for decades in design. Yet, how to design for material experiences has been poorly addressed to date. The MDD method presented herein aims to support designers in structuring, communicating, and reflecting on their actions in design for material experiences.

Citation: Karana, E., Barati, B., Rognoli, V., & Zeeuw van der Laan, A. (2015). Material driven design (MDD): A method to design for material experiences. International Journal of Design, 9(2), 35-54.

*Corresponding Author: e.karana@tudelft.nl.

Bahareh Barati is a PhD candidate in the Department of Design Engineering at Delft University of Technology (DUT). She received her B.A. and M.A. degrees in Industrial Design from the University of Tehran, and her M.Sc. degree (cum laude) in Industrial Design Engineering from DUT. For her master's graduation project, she worked with Phillips Research, where she developed a probe set for sensory evaluation of textile materials. She was nominated for UfD-Royal Haskoning DHV Best Graduate Award (2013). Funded by a European Union project (FP7) on Light.Touch.Matters, her PhD research focuses on designing with underdeveloped computational composites. Her research aims to shed lights on methodological and multidisciplinary challenges in such design projects, to facilitate designing of meaningful material applications that can have impacts on societies and advance reasons for existence.

Valentina Rognoli is assistant professor in the Design Department at Politecnico di Milano, Italy, where she conducts research activity in the field of materials for design. After two years at Enzo Mari's studio in Milan, Valentina focused her PhD research on materials and their expressive-sensory dimension, and developed an 'Expressive-Sensorial Atlas of Material' to improve materials education and research in the field of design. Her current research topics delve into digital manufacturing, DIY Materials, and imperfect material aesthetics and repair. She recently has received funding from the European Union's Horizon 2020 research and innovation programme for the project on Digital Do It Yourself-DiDIY ( www.didiy.eu).

Anouk Zeeuw van der Laan is an industrial design engineer. She received her BSc and MSc degrees from Delft University of Technology (DUT). In her master's graduation project, in collaboration with Politecnico di Milano, she identified 'coffee waste' as a valuable raw material, and used it as the departure point in the design process. She was nominated for UfD-Royal Haskoning DHV Best Graduate Award (2014). After her graduation in 2013, she worked as a designer and a design researcher for material driven design projects, including a project conducted for Innventia (Sweden), which is a research and development company that works with innovations based on forest raw materials.

Introduction

By acknowledging the dualist view of product materials-that they are required to contribute to satisfying both functional and hedonic needs of people (Hassenzahl, 2010)-it became clear that new materials development and application must necessarily be multidisciplinary. Recognizing this situation, material scientists and industries involved in the development of new materials have reached out to academics and professionals in design, art, architecture, and crafts (Miodownik, 2007). The underlying goal in such consultations and collaborations is to guide the development of materials by both experiential and functional goals (Ball, 1997; Ball, 2001; Miodownik, 2007). Design communities are continually evolving their ability to contribute scientifically to such developments, through improved knowledge and skills in 'understanding', 'interpreting', 'envisioning', and 'designing' for user experiences-where user studies and/or ' design-driven innovation ' strategies (Verganti, 2009) can be a conceptual starting point.

The potential for collaboration between the worlds of materials science and design has also been highlighted in recent European projects aiming at the co-development of semi-developed smart materials , e.g., DiaBSmart ( http://www.diabsmart.eu ), DAMADEI ( http://www.damadei.eu ), and Light.Touch.Matters ( http://www.light-touch-matters-project.eu) . Common to all, material properties are manipulated and new techniques are explored and applied to ultimately ' tailor materials ' (Lindberg, Hartzén, Wodke, & Lindström, 2013; Lindström, Gamstedt, Barthold, Varna, & Wickholm, 2008) for desired applications.

Coming back to our underlying argument, although the design and material industries are becoming deeply engaged in the creative challenge to achieve material functionality and meaning, there is not a systematic method to date on how to define and design for material experiences when a (new) material is the main point of departure in a design project (i.e., material driven design ). Most of the works referred to as 'material-driven' in the literature take a particular material as a starting point and explore its technical/engineering properties to embody a product (e.g., Dietz, Guthmanna, & Kortea, 2006; Jordan et al., 2013; Knauer, 2014), or they emphasize hands-on experimentations and prototyping with materials in the design process (van Bezooyen, 2013). We acknowledge these important attempts to bring 'material thinking' to the early steps of design processes and to mobilize unique technical characteristics of materials in the design process. A distinguishing feature of our stance, however, is its experience-oriented perspective . We aim to support designers to define and design for meaningful experiences with and for a material at hand, qualifying the material not only for what it is, but also for what it does (Manzini, 1986), what it expresses to us, what it elicits from us (Karana et al., 2014), and what it makes us do (Giaccardi & Karana, 2015).

Theoretical Foundation

The MDD method is grounded on the following premises, which we elaborate upon through the progression of this paper:

Designing with a material entails a thorough understanding of the material in order to discover its unique qualities and constraints in comparison to other materials. This can be achieved through 'tinkering with the material'-a kind of explorative process of creation and evaluation-starting from the first encounter with the material, until its final product embodiment at the end of the process.

Designing with a particular material in mind requires action steps to be followed that are comparable to a conventional product design process: understanding the domain (i.e., research in the field, benchmarking, market analysis, etc.), creating design requirements and objectives, creating concepts, and selecting and detailing one of the concepts towards product embodiment.

Materials Experience in MDD

Understanding The Material in MDD

The relationship between materials (as the matter or substance of things) and experience (as a way to know the world and to enrich knowledge of it) has long been emphasized in pioneering philosophical works. In the field of art, Focillon (1992) and Dewey (1980) emphasized the unique role of 'material engagement' in one's process of thinking and reflecting. Physical encounters with materials (or the aesthetic experiences that derive from hands-on manipulation of materials) can positively influence the creative process. Niedderer (2012) showed how such practical enquiries , or learning by doing , is mobilized in understanding the relationship between material, process, and form with regard to the creation of elastic movement. Material engagement in craft is a means to logically think, learn, and understand through sensing and immediate experience of materials (Adamson 2007; Ingold, 2013; Nimkulrat, 2012). In his Inaugural Address at Goldsmiths' College, University of London, Professor Martin Woolley (1998) eloquently pointed out that clay on the hands of a potter alternates between being part of the potter, part of the process of crafting a ceramic artefact, and part of the end artefact itself. In other words, materials are 'collaborators' (Rosner, 2012) in the craft process, enabling artisans to construct, enact, and reaffirm their identities (Tung, 2012).

In design, tutors at the Bauhaus were particular advocates of learning about/with materials. Around 1920, Itten formulated his 'theory of contrasts', which became fundamental to his educational approach for the Vorkurs (basic course) at the Bauhaus. Itten asked students to explore sensorial contrasts relevant to materials, such as smooth-rough, soft-hard, and light-heavy. The theory of contrasts gave attention to the 'nature' of materials, having the purpose of showing the essential and diverse characteristics of different matter. Furthermore, these contrasts had to be felt and not just seen. With this approach, Itten's students were able to experience and appreciate the character of materials directly through hands-on exploration (Itten, 1975).

After Itten, Moholoy-Nagy developed a course at the Bauhaus focusing on tactile experience of materials (Wick, 2000). This represented a migration away from the 'school of seeing' towards a greater emphasis on the sense of touch. In order to exercise the tactile experience, Moholoy-Nagy organized tactile tables, wheels, and ribbons onto which materials were arranged according to specific sensorial criteria, usually in the form of two line scales that could be held at the same time, for example, from smooth to rough or from sharp to dull.

Both Itten's and Moholy-Nagy's approaches emphasized the role of sensory encounters and hands-on manipulation in material understanding, whilst promoting design activity oriented to enrich desired experiences in final designs. Many designers in the history of design followed this notion and designed products by tinkering with materials and exploring their diverse texture and finishing possibilities, alongside phenomenological aspects that promoted discussion on the merits (or otherwise) of using particular materials for particular products. Today we still see such an approach in some pioneering designers' works: see for example the works of Tokujin Yoshioka (paper, glass), Piet Hein Eek (scrap wood), Paulo Ulian (marble), and Alberto Meda (carbon-fibre composites). Furthermore, in the field of Human Computer Interaction (HCI), tinkering with materials has been emphasized as a central practice within research (Jacobbson, 2013) to produce new knowledge and experience. In HCI, tinkering is to do with crafting interactive artifacts using physical-digital materials (Buxton, 2007; Holmquist, 2012; Löwgren & Stolterman, 2004; Sundström & Höök, 2010; Zimmerman, Forlizzi, & Evenson, 2007).

Today we also encounter several material-consulting companies (e.g., Material Connexion, Materia NL), whose services include access to physical material libraries for the purpose of material browsing and tinkering. Within University College London, the 'Institute of Making' ( http://www.instituteofmaking.org.uk/about ), provides design students and professionals with a creative environment to explore the technical and sensorial qualities of materials and their inter-relationships to 'making'.

Accordingly, MDD encourages tangible interaction with the material in hand, from the first encounter through to exploring and understanding the material in detail with its unique qualities and limitations. Over time, the designer who takes a MDD approach is expected to become a master of a given material: he/she will know how the material behaves under different circumstances or how it reacts when subjected to different making techniques or manufacturing processes.

The Process of MDD

Product designers are educated to follow a systematic approach to conceptualize and evaluate ideas and to translate them into functions, forms, and materials embodied in a final design (Cross, 2008; Hubka & Eder, 1992; Pahl & Beitz, 1996; Pugh, 1981; Roozenburg & Eekels, 1995). They make this translation in a sequence of design phases, such as the problem formulation phase (understanding the domain, creating design requirements, and objectives), the conceptual design phase, the embodiment design phase, and the detailed design phase (Cross, 2008). Tung (2012) successfully showed how these design phases are followed in revitalizing a local craft and a material. Accordingly he suggested that first the local settings, products, and the particular material at hand should be understood. Then problems and opportunities are listed and the decision on what to design is taken. In MDD, these design phases are retained. First, the material at hand and the domain are understood to create design requirements and objectives. Existing products, which are made of the same/similar material(s) falling under the same material category, are screened (i.e. , material benchmarking). Design objectives and requirements are conceptualized and finally embodied into materials/products.

On the other hand, as explained earlier, a distinguishing feature of our approach is its experience-oriented perspective . How can we design for experiences with and for a particular material at hand? Thus, although the main design phases have proved successful in designing with a material at hand, they do not support designers in deciding and designing experiences for the material. Accordingly, grounded on the ingredients of experience design (Desmet et al., 2011), the activities to create design requirements and objectives and conceptualize them for materials experience are gathered under the following main steps in MDD:

Understanding the current situation : how the material at hand is appraised by intended users, how it is experienced on sensorial, interpretative, affective, and performative levels, and how these experiences relate to physical (engineering) properties of the material.

Material Driven Design (MDD) Method

Having worked in the materials and design domain for a considerable time, we have gained experience across a large number of MDD projects including designing with natural fibre composites (Lagorio, 2014; Taekema & Karana, 2011), designing with bio-plastics (Karana & Nijkamp, 2014), designing with waste coffee grounds (Zeeuw van der Laan, 2013), designing with liquid wood (Manenti, 2011; Rognoli, Salvia, & Levi. 2011), and designing with computational composites (on-going PhD research by Bahareh Barati, TU Delft). Learning from these projects, reviewing advantages and disadvantages of steps in the design process, and drawing upon theoretical foundations introduced in this paper, we developed the Material Driven Design (MDD) Method to facilitate design processes in which materials are the main driver. We envisage three scenarios where designers can apply the MDD Method.

[Scenario 1]

Designing with a relatively well-known material, which will be accompanied by a fully developed sample (e.g., oak, titanium, polystyrene, etc.). Although the material is likely to have some settled meanings in certain contexts (e.g., traditional, cosy, high-tech, etc.), the designer seeks new application areas to evoke new meanings and to elicit unique user experiences.

[Scenario 2]

Designing with a relatively unknown material, which will be accompanied by a fully developed sample (e.g., liquid wood, D3O, thermochromic materials, etc.). The material is unlikely to linked to settled meanings, affording the designer opportunity to define application areas through which unique user experiences, identities for materials, and new meanings may be introduced.

[Scenario 3]

[MDD Method Step 1] Understanding The Material: Technical & Experiential Characterization

In MDD, a designer is first expected to understand the material in hand and characterize it both technically and experientially, so as to articulate the material's unique role (in contrast to alternative materials) when applied in products. This step includes tinkering with the material to get insights on what the material affords, its technical/mechanical properties, as well as how it can be shaped/embodied in products; material benchmarking to position the material amongst similar and/or alternative materials, to generate insights on potential application areas, emerging materials experiences and other emerging issues within the design domain; and user studies to explore how the material is received by people, how it is appraised (i.e., experiences related to aesthetics, meanings, and emotions), as well as what the material makes people do (Giaccardi & Karana, 2015). It should be recognised that these activities, which will be further described below, are not required to be applied in a sequential manner. Rather, a simultaneous approach is preferred to create synergies and mutual nurturing.

Technical Characterization of the Material

What are the main technical properties of the material (e.g., its strength, fire resistance, etc.)?

What are the constraints/opportunities of the material?

What are the most convenient manufacturing processes to form the material?

What about other manufacturing processes? How does the material behave when subjected to other processes?

It is expected that by the end of technical characterization the designer will have a clear understanding of the engineering (i.e., technical/functional and manufacturing process related) limitations of the material, as well as its unique technical properties to be harnessed in the final design.

Important lessons that we learned during the technical characterization of waste coffee grounds were that the particles in general decreased the strength of the created composite material. The particles were found to be most suited to creating bulk materials. We also learned that waste coffee grounds can be used as nutrient for plants, and that coffee particles do not set on fire but instead smoulder. How the resulting composite material will be produced depends mainly on the matrix material (e.g., PLA, latex, ABS), but because the particles are relatively small, they are not expected to constrain production processes. In Figure 2 the designer's 'tinkering activities' for technical characterization of the material are presented.

Experiential Characterization of the Material

In the experiential characterization of the material, first we recommend the designer should reflect on the experiential qualities of the material on four different experiential levels: sensorial, interpretive (meanings), affective (emotions), and performative (actions, performances) (Giaccardi & Karana, 2015). Then, he/she should delve into understanding how the material is received by people, again by using the four experiential levels as a foundational structure. For example, reactions may be recorded such as 'wow' (affective), 'it is strange' (interpretive), 'it is very soft' (sensorial), as well as observations that people may tweak the material, pat it, smell it, etc. (performative). Designers should tinker with the material to create samples of varying form (e.g., rounded, amorphous) and sensorial qualities (e.g., rough, elastic), and to collect substitute materials (in case of a not fully developed material) which would potentially elicit contrasting or complementary experiences in any or all of the four experiential levels. These activities would support the designer in seeing interrelationships between intended or observed experiences and the formal properties of the material. Focus groups, online questionnaires, and interviews can be conducted in such experiential studies, from which the designer will seek answers to the following questions:

What are the unique sensorial qualities of the material?

What are the most and the least pleasing sensorial qualities of the material (according to users)?

Is the material associated with any other material due to its similar aesthetics?

How do people describe this material? What kind of meanings does it evoke?

Does it elicit any particular emotions-such as surprise, love, hate, fear, relaxation, etc.?

How do people interact and behave with the material?

To facilitate this process, we suggest constructing a mind-map to present an overview of the findings. Traditionally this can help the designer to discover underlying motivations of designing or using a material (or its components if it is a composite material) across a variety of forms, products and contexts. A mind-map can also effectively depict interrelationships between detected performances, meanings, emotions, and sensorial qualities. Consequently, the designer can make decisions on, for instance, aiming to retain a settled meaning of the material, or aiming to generate novel meanings in an end (product) application. The implication here is that material properties, which evoke or are particularly associated with a settled meaning, should be either kept or modified in the final design.

For the waste coffee grounds project, to explore what people did when they interacted with the material, and how they went about appraising the material, several material samples having varied aesthetic qualities were collected and used in focus group studies and interviews. The pre-settled meanings 'environmental friendly' and 'natural' were detected. Colours and scent were found as two important sensorial qualities of the material to elicit these meanings, as well as to communicate the origin of the material. We found that imperfect surface qualities of the material were embraced, as typified by one of the focus group participants: "they enhance the naturalness of the material and create authentic patterns ." Furthermore, people wanted to touch and smell the samples with rough and imperfect surfaces, which were associated with 'nature and soil'. After learning the main material component, people were generally surprised, particularly in relation to the more homogeneous samples. Even though the material is a waste material, it did not recall negative associations such as 'low-quality'.

During experiential characterization of the material, the designer is also expected to position the material within a group of similar materials and their applications (i.e., material benchmarking) by delving into literature, design magazines, material websites, etc. The aim of this step is to map the potential application areas (by also reflecting back to the required technical specifications of the material for these areas), as well as to understand what kind of experiential issues are emphasized in the domain that the material is positioned, and what experiential qualities of the material can be observed or emphasized in the descriptions of other applications. Next to that, the material benchmarking is expected to reveal other issues, strategies, or values increasingly emphasized within the design domain in the last decades (e.g., design for sustainability, cradle to cradle: C2C, slow technology, etc.).

For example, if the material is a food-based composite, other food-based composites and their applications should be explored (see Figure 3 for a short overview of the products screened for the illustrative case). As depicted in the Figure, we found four application areas for food-based composites, which were shortly analysed particularly on the aesthetics (sensorial) level (e.g., scent intensity, visible fibres, etc.), as well as possible experiential issues mentioned in the description of these products (e.g., naturalness, imperfection, authenticity, Wabi-Sabi, and Standard Unique), and other issues emphasized within the design domain in relation to the materials (e.g., C2C, local production, design for sustainability).

Note that, having completed the first step and explored what has been done so far and what the material 'is', a designer might already have an idea on a possible application area, where unique technical properties and experiential qualities of a material are incorporated or come forward. He/she may then directly proceed to Step 4, where material/design concepts are created. However, caution should be exercised since moving directly from Step 1 to Step 4 may lead to rather conventional solutions, or a re-design of an existing product, which is acceptable in some circumstances but is not within the spirit of innovation and radical design contribution. When designers (or clients) would prefer to explore the 'unknown', outside of their prior experiences and comfort zone where they can push their creativity towards new applications, then they can proceed to Step 2 of the MDD method. Alternatively, on completion of Step 1, the designer may have become inspired to express particular meanings of the material in the final application (e.g., high-quality, natural, delicate, sportive, etc.). In this case, skipping to Step 3, where the patterns to create these meanings are manifested, is recommended.

[MDD Method Step 2] Creating Materials Experience Vision

Accordingly, in Step 2 of the MDD Method, first the designer is expected to encapsulate and reflect on the overall material characterization. The questions to be answered in the creation of the Materials Experience Vision can be listed as follows :

What are its unique technical/experiential qualities to be emphasized in the final application?

How would people interact with the material within a particular context?

What would the material's unique contribution be?

How would it be sensed and interpreted (sensorial and interpretive levels)?

What would it elicit from people (affective level)? Would it, for instance, contribute to the fulfillment of a hedonic need (Hassenzahl, 2010, e.g., feeling related, feeling stimulated, etc.)?

What would it make people do (performative level)?

What would be the material's role in a broader context (i.e., society, planet)?

Answering these questions, the designer can construct the Materials Experience Vision, which may accommodate various statements that could be interpretative (e.g., the material will express naturalness), affective (e.g., the material will surprise people), or performative (e.g., the material will require delicate use). In addition, the unique role and purpose of the material within a broader context may be defined (e.g., the material will make people aware of their consumption patterns; the material will make people to appreciate products made of 'waste' materials, etc.).

When the designer desires to go beyond initial findings, dig deeper to unfold the 'un-seen', and elaborate on how the user-product interaction would be (if there is no strict time concerns in a project), then he/she can progress to a supplementary step. Vision in Product Design (ViP), developed by Hekkert and van Dijk (2011), is one possible method to support a designer wishing to take such a journey. In ViP, within a set domain, findings are clustered so that they form unique and original insights. Structuring the clusters reveals coherence and focus, and ultimately leads to a vision statement, from which a user-product interaction is defined. The designer may ultimately use anecdotes, metaphors, or mood-boards to communicate the intended vision.

We clustered and structured our findings so that we could show how they complemented or challenged each other, and how together they formed new and original insights relevant to the application context (see Appendix 1). From that, our final vision statement was: 'I want people to desire to experience the material and be captivated in the course of emotional bonding with the material, like a tempting exposure in a cathedral'. The metaphor illustrates both desire and captivation. Tourists are eager to see what is happening: they desire to see what they are there for. The captivation is found in their mass-presence and lack of sight but persistence to witness the event.

[MDD Method Step 3] Manifesting Materials Experience Patterns

Nevertheless, it can be difficult to link a created vision to formal qualities of new materials and products. Therefore, herein first the vision and the interaction is further analysed to obtain 'meanings' (such as feminine, familiar, high-tech, etc., under the interpretative level of materials experience), which can be more easily operationalized in user studies (Karana, 2009). For example, relating certain material properties to the meaning high-tech would be much easier than detecting material properties that make people desire to experience a material.

Accordingly, we first distilled two meanings from the created vision to be further explored. In order to do that, we sought examples of the envisioned interaction (including tempting exposure and emotional bonding) from daily life, existing products, and existing materials. In a brainstorming session, we identified two meanings that evoke the aimed interaction as 'modest' (i.e., in relation to those things that create an emotional bonding across a longer time span) and 'provocative' (i.e., in relation to those things that will entice or provoke interaction, like a tempting exposure in a cathedral).

In order to find patterns to evoke the aimed meanings, another supportive method, the Meaning Driven Materials Selection (MDMS), is incorporated in MDD. Developed by Karana (Karana & Hekkert, 2010), the method familiarises the designer with key aspects (such as shape, user, manufacturing processes, etc.) playing an important role in attributing meanings to materials (e.g., a material might be appraised as cheap because of its transparency or easily stretchable surface qualities, and its sharp-edged shape). Most importantly, the method supports the designer in understanding other people's understanding of preferential meanings. In MDMS, a group of people are approached to participate in a study where they are given the following three tasks: (1) select a material that you think is 'X' (such as high-quality, feminine, modern, etc.), (2) provide a picture of the material (embodied in a product) you selected, and (3) explain your choice and evaluate the material against a set of specially devised sensorial scales . The results are evaluated both qualitatively (by analyzing the provided images and descriptions from the participants) and quantitatively (by performing a statistical analysis of sensorial scale ratings).

We used The Meanings of Materials Model to visualize data sets for the meanings 'modest' (Figure 4, above) and 'provocative' (Figure 4, below) as ' materials experience patterns '. The results of the MDMS study for the waste coffee grounds project, as collages of materials (embodied in objects) selected by users and results from sensorial scale gradings are presented in Appendix 2.

Another finding was that the modest materials gathered through MDMS were usually embodied in products that are used for the purpose of protecting or storing other products (e.g., iPhone case, protective packaging, etc.), while provocative materials were embodied in products necessitating high mechanical performance. However, during technical characterization, waste coffee grounds were found to decrease the performance of the overall composite material; therefore it is not probable that a 'high-performance' application for the material would result in success. On the other hand, we concluded that both modest and provocative materials could be tempting for physical interaction when imperfect surface qualities were kept, which would create a rather mysterious texture, holding a hidden message to be explored or revealed by the user.

[MDD Method Step 4] Creating Material/Product Concepts

Herein Stage 4, the designer integrates all his/her main findings into a design phase. It may not commence exclusively here; for example, even after just Step 1, the designer might already have an idea for an application (product) domain. In such cases, material considerations and product concept creation go hand in hand, and the material is shaped accordingly. Alternatively, if at the arrival at Step 4 no product idea has been contemplated, the designer now starts to make material concepts incorporating results from Step 3 and his/her experience through tinkering with the material gained from Step 1. In both cases, the performance of the concepts with greatest potential is tested through mechanical tests in a number of iterations, whilst the material experiential qualities are evaluated through interviews and focus group studies, etc.

In Scenario 3, a specific challenge can be faced by designers if the material is a smart composite. In such cases, the designer might not be able to create the ultimate material, but create or find different material samples to exemplify or mimic the sensorial qualities, or physical behaviour of the material envisioned. Then the designer can use these similar materials, or their modified versions, to test and verify the concepts in mind and to facilitate the material development by communicating with material engineers. At the end of this step, the created material concepts are analysed and the most promising and diverse materials are selected to be used in the product concept creation.

The process of arriving at a product concept is shortly presented below.

We conducted a creative session with 50 Master's level design students at Politecnico di Milano, Italy. In groups of two or three, the students were given a material package including (Figure 7):

One of the material concepts as a physical sample

Technical data-sheet about the given material concept

Materials Experience Patterns for 'provocative' and 'modest'

The students were asked to design a product with the given material concept by using the given technical data sheet and materials experience patterns; thus the ultimate product was expected to express the meanings 'provocative' and 'modest'. In total, five product ideas for each material concept were created. Some of the ideas were for products concerning a 'coffee ritual' (i.e., drinking or making). In most cases, there existed a strong link to nature. The aesthetics of the material, such as its dark brown colour, imperfect patterns, and texturization, were used to emphasize and enhance this link. Surprisingly, several gardening products were developed for all three material concepts (see Figure 8 for two of the created ideas).

We further analysed the ideas against their fit to the intended Materials Experience Vision; their feasibility (for cost and production); and their technical performance (whether the material can fulfill the required function). As a result, Cofflexi was found to be the least sustainable and feasible, due to excessive production processes, even though it was considered the most provocative and modest. The most successful concept was found to be Café Maché, especially considering the rapid transformation that the material can undergo. CapPurcino was also a good fit to the vision and had the most promising commercial potential.

Accordingly, we developed our final product concept using two of the material concepts (Zeeuw van der Laan, 2013). It is a set to grow greens at home, Cof2Grow (Figure 9). Café Maché was used for the packaging as well as a nutrient for tablets that contain seeds of preferred greens. The seeds sprout rapidly after adding water and the coffee grounds provide nutrients. The material changes quickly due to the growth inside, and after the seeds are fully grown and consumed, the entire tablet can be disposed of as organic waste. The tablets come with a pot that is made from CapPurcino, which can be reused. Taking into account the natural course of maturing of the material, it will change over time slowly due to the influence of UV and touch. Anticipating the process of curing the material, the pots are designed to have unique design features (e.g., different textures, different colour tones, etc.) for each cast. The product concept was carried to the next step to be tested in the lab and in the field, before final embodiment and detailing were completed.

In our final product concept, the selected materials were subjected to more in-depth technical tests. For the pot, we required several attempts to find a suitable component-ratio that resulted in correct sensorial qualities and sufficient mould fill. Sprouting seeds from the Café Maché tablets was a process of trial and error, to be further explored in the final embodiment and, ultimately, marketed product. Our reflection on the final experiential qualities of the material/product was as follows:

Sprouting the tablets deforms and darkens the Café Maché; a provocation and a captivating process that 'the user' wants the tablets to survive (after being deformed/sprouted).

Discussion

In this paper, we showed how the MDD method has proved successful in a particular project focusing on 'designing with waste coffee grounds'. The MDD method has also been effectively applied to other material driven design projects (see for example Lussenburg, van der Velden, Doubrovski, Geraedts, & Karana, 2014; Zeeuw van der Laan, 2014 ). The method will be further operationalized within dedicated courses on 'materials and design' given by the Faculty of Industrial Design Engineering in Delft University and Technology and The School of Design in Politecnico di Milan. In this way we aim to demonstrate the usability of the method in diverse projects falling under the three different scenarios explained in this paper (i.e., designing with a well-known material , a fully developed new material , a semi-developed new material ). These projects will shed light on some material specific challenges, which we did not tackle in the project presented in this paper.

For example, we acknowledge two possible challenges to be faced by designers in designing with semi-developed smart materials. We anticipate that the characterization step of such materials would be rather different from what is discussed in this paper. The reason is that designers' knowledge about the material must be accumulated not through direct benchmarking or tinkering but by making references to other materials or technologies (e.g., existing user interfaces, sensors, etc.). In this paper we have not discussed any tools or strategies that can support designers in exploring and understanding the unknown characteristics of such novel materials.

In the illustrative case, we have incorporated two other methods (ViP and MDMS) as sub activities of MDD to help formulate Materials Experience Visions and manifest materials experience patterns. There are many other tools and methods of potential use within MDD that could not be introduced within the scope of this paper. For instance, the Expressive Sensorial Atlas by Rognoli (2010) is a useful tool to tinker with materials (for both Step 1 and 4 in MDD), facilitating understanding of sensorial qualities of materials in relation to underlying technical properties and the concept of inter-subjectivity (i.e., to what extent people agree that a material possesses certain sensory qualities). On the other hand, certain aspects of the MDD Method itself should be further refined, whilst additional tools and methods should be further developed to ease the four Steps. For example, developing tools and methods to support designers in tinkering with materials for experiential characterization, and a more refined method to create a Materials Experience Vision will be two crucial subjects for future research.

Informal discussions with potential end users showed that the envisioned materials experience for our final product was realized to a considerable extent. However, it should be recognized that a thorough assessment of the final design concept in an experiential level will require an additional set of studies with end users in the lab and real life contexts. As success of a design method is not judged with a concrete end result, in this paper the detailing of the action Steps and showing how these steps guided the designer through their journey was our primary concern, rather than assessing the final product.

The MDD Method suggests a sequence of steps to be conducted in the design process. However, the nature of a design project (e.g., large or small scale production, time concerns, limited budget, redesign of an existing product, etc.) might alter the way in which the steps are conducted or the depth to which they are explored, or even might result in omission of one or more steps. For example, if a client (i.e., project owner) requires a redesign of their existing product (e.g., coffee machine) made of a new material (e.g., a natural fibre composite), then a designer will have the application in mind from the beginning of the design process, and inevitably will consider the material within its future context throughout the material characterization process. In other words, design requirements that come along with the context of 'coffee machine' will be merged and compared with 'independent' material qualities and limitations. The designer might also skip Step 2, where the Materials Experience Vision is created, since completing Step 1 he/she might have some ideas on what would like to be expressed (i.e., meanings such as high-quality, natural) with the final material embodiment within the given context. In such cases, a transition directly from Step 1 to Step 3 might be appropriate to find patterns to evoke intended meanings. As explained earlier in the paper, Step 1 of the method may lead to rather conventional solutions as it is grounded on the merits of existing products, materials, etc. It is the designer's responsibility (and a MDD project requirement) to explore the 'unknown' and push creativity towards new material applications for the future.

Finally, as with any proposed method, an effective use of MDD will be seen through enhancements with practice, and use by multiple designers. We are certain that designers will invent their own ways of conducting the steps, add new steps, and use new supportive tools having had some experience of MDD.

Conclusion

This paper has been concerned with how to proceed when a 'material' is the explicit point of departure in the design process and 'experience' is the expected outcome. We have presented a design method entitled Material Driven Design (MDD), which represents our first attempt to facilitate such projects, considering both technical properties of materials and their experiential qualities in relation to how they are received by users. The method suggests that when a material is the point of departure in the design process, the designer takes a journey from material properties and experiential qualities to materials experience vision, from materials experience vision to experiential qualities and to material properties, and finally to products. Activities to support this journey are organized under four main steps as: (1) Understanding The Material: Technical and Experiential Characterization, (2) Creating Materials Experience Vision, (3) Manifesting Materials Experience Patterns, (4) Designing Material/Product Concepts. The method is explained with an illustrative case on 'designing with waste coffee grounds', which ends with the creation of a product concept. The presented case illustrates one of the possible scenarios we envision for MDD projects, where a material is not yet fully developed. Applying the MDD method to projects exemplifying other scenarios will bring new insights and help us to refine the method's steps to a greater level of detail and application.

Acknowledgment

We would like to thank our reviewers and Owain Pedgley for valuable feedback to earlier versions of this paper. We would also like to thank Adam Fairweather from Re-Worked for his support through the 'coffee waste ground project'.

Endnotes

1. 1. Wooley, M. (1998, May 5). Inaugural lecture given. Goldsmiths College, University of London, London, UK .

2. 2. Wabi Sabi is a continuous search for beauty in the truths of the natural world, using nature and its flows and flaws as an inspiration, but without revealing the truths of nature, i.e., keeping its mystery and qualities (Juniper, 2003).

3. 3. Standard Unique is a principle that deliberately embodies imperfections that are a result of production processes, assembly, and/or material properties to have unique objects as an outcome (Rognoli & Karana, 2014).

4. 4. Note that if we had continued with the first vision statement we created before we applied the ViP method, we could proceed with the meanings which we mentioned in the vision statement, such as natural, unique, personal, etc.

5. 5. After conducting a number of studies in recently done PhD research by Karana (2009), a set of sensorial qualities grouped under different sensory modalities was listed and promoted as the qualities that are more commonly used for attributing meanings to materials. See Appendix 2 for the list of sensorial qualities.

References

1. Ashby, M., & Cebon, D. (2007). Teaching engineering materials: The CES EduPack. Retrieved June 1, 2015, from http://web.mit.edu/course/3/3.225/refs/Teaching_ Engineering_Materials.pdf

2. Dupont. (2007). Corian®: 40 years - 40 designers. Retrieved June 24, 2015, from http://www2.dupont.com/40_40/en_GB/press_room/DuPont_Corian_40Years_40Designers_eng.pdf

3. Howes, P. D., Wongsriruksa, S., Laughlin, Z., Witchel, H. J., & Miodownik, M. (2014). The perception of materials through oral sensation. Plos One, 9(8): e105035. http://dx.doi.org/10.1371/journal.pone.0105035

4. Hubka, V., & Eder, W. E. (1992). Engineering design (1st ed.). Zurich, Switzerland: Heurista.

5. Lindberg, S., Hartzén, A. S., Wodke, T., & Lindström, M. (2013). Hierarchic design and material identity. Retrieved June 1, 2015, from http://www.mouldpulp.com/docs/OD2_Lindberg_etal.pdf

6. Lindström, M., Gamstedt, K., Barthold, F., Varna, J., & Wickholm, K. (2008). Hierarchical design as a tool in development of wood-based composite applications. Retrieved June 24, 2015, from http://extra.ivf.se/eccm13_programme/abstracts/228.pdf

7. 50. Miodownik, M., & Tempelman, E. (2014). Light touch matters. The product is the interface. Retrieved June 1, 2015, from http://www.light-touch-matters-project.eu/press/b079f8dc0dce2500df08ef2e657821e4.pdf

8. Rognoli, V., Salvia, G., & Levi, M. (2011). The aesthetic of interaction with materials for design: The bioplastics' identity. In Proceeding of the Conference on Designing Pleasurable Products and Interfaces (No. 33). New York, NY: ACM.

9. Roozenburg, N. F. M., & Eekels, J. (1995). Product design: Fundamentals and methods (1st ed.). Chichester, UK: Wiley.

10. Rosner, D. K. (2012). The material practices of collaboration. In Proceedings of the Conference on Computer Supported Cooperative Work (pp. 1155-1164). New York, NY: ACM.

11. Taekema, J., & Karana, E. (2012). Creating awareness on natural fibre composites in design. Retrieved June 24, 2015, from http://www.nfcdesign.org/nfc/wp-content/ uploads/2012/06/TaekemaKarana2012.pdf

12. Tung, F. W. (2012). Weaving with rush: Exploring craft-design collaborations in revitalizing a local craft. International Journal of Design, 6(3), 71-84.

13. Van Bezooyen, A. (2013). Materials driven design. In E. Karana, O. Pedgley, & V. Rognoli (Eds.), Materials experience: Fundamentals of materials and design (pp. 277-286). Oxford, UK: Butterworth-Heinemann.

14. Van der Lugt, P. (2008). Design interventions for stimulating bamboo commercialization: Dutch design meets bamboo as a replicable model (Doctoral dissertation). Delft University of Technology, Delft, the Netherlands.

15. Van Kesteren, I. (2008). Selecting materials in product design (Doctoral dissertation). Delft University of Technology, Delft, The Netherlands.

Appendix 1

Clustering and structuring of findings to show how they complemented or challenged each other, and how together they formed new and original insights relevant to the application context. Two axes were identified: the horizontal axis represents the influence of the individual and whether this is intentional or impulsive, whereas the vertical axis describes the relationship between the user and the material. The distinction is between a physical and intangible (sentimental) relationship.

Appendix 2

The results of the MDMS study for the waste coffee grounds project: as collages of materials (embodied in objects) selected by users and results from sensorial scale gradings.

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Material Driven Design (MDD): A Method to Design for Material Experiences

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Materials research constantly offers novel materials as better alternatives to convention. Functional aptness is taken for granted at the first commercial launch of a new material. Nevertheless, this alone may not be enough for its commercial success and widespread use. The 'material' should also elicit meaningful user experiences in and beyond its utilitarian assessment.

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-Cotton and synthetics (polyester, nylon and acrylic) have the biggest environmental impact.
-According to Fashion For Good, conventional cotton production accounts for one sixth of all pesticides used globally, impacting farmers and local communities with harmful chemicals – a claim that is bolstered by figures from the World Health Organisation, which show that in developing countries approximately 20,000 individuals die of cancer and suffer miscarriages as a result of chemicals sprayed on conventional cotton.
-Cotton is one of the most environmentally demanding crops.
-Synthetics are not biodegradable, and they all rely on the petrochemical industries for their raw material, meaning this fashion industry staple is dependent on fossil fuel extraction.

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-Second to oil, the clothing and textile industry is the largest polluter in the world
-Nearly 20% of global waste water is produced by the fashion industry
-20,000 liters is the amount of water needed to produce one kilogram of cotton; equivalent to a single t-shirt and pair of jeans.
-About 15% of fabric intended for clothing ends up on the cutting room floor. This  waste rate has been tolerated industry-wide for decades.

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"I am so grateful for this opportunity! Thank you for the bold questions @edgexpo" 🙏🏾

"Typically, the visual form or design is based on the functionality, but the function of the clothing that I make differs from looking posh or preventing the cold. My clothes are designed for people to focus on the act of wearing the clothing."

"Let's keep fighting the fight for fashion as art."

- Hera Zhou | Shanghai

- 배혜진 Hyee Jin Bae | Seoul, Korea

- Maryanne E. Mokoko | USA/Cameroon

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Fashion Industry Environmental, Waste, and Recycle Statistics

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Fashion Industry General Statistics The global textile and garment industry is valued at 3 trillion dollars, and accounts for 2 percent of the world's Gross Domestic Product (GDP).1 The global retail apparel and footwear market-value forecast: 2022 at 1.7 trillion dollars; 2023 at 2.0 trillion, with United States, China, United Kingdom, Germany, and Japan accounting...

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-Re-usable cloth nappies are made from layers of fabric such as cotton, hemp, bamboo, microfiber, or even plastic fibres such as PLA or PU.
-Disposable nappies are made from a core containing a mix of cellulose fluff pulp and sodium polyacrylate and a waterproof outer layer of polyethylene
-Out of all “non-durable goods,” diapers were the second most generated waste by weight, surpassed only by discarded clothing and shoes. And we have over half a century’s worth of them taking up space.

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Environmental Effects of Disposable Diapers: Disposable baby diapers represent an incredible amount of environmental waste. Their potential harm to infants is no less devastating.
Read also: A Guide to Sustainable Kids' Clothing words by Andrew Karpisz
The Harmful Effects of Disposable Diapers

Convenience VS Waste

Disposable baby diapers produce an incredible amount of environmental waste. While disposable diapers may seem more convenient than cloth diapers, their environmental impact is terrifying. Not only do they form a sizeable portion of non-recyclable landfill waste, but they also contain many harmful chemicals that are subsequently dispersed into the environment. To safeguard the future, we need to consider alternatives.

The Big Problem With Disposable Diapers

In the United States, there are about four million babies born every year. During their first year of life, the average newborn uses about 2500 diapers. This means that from babies under one year old, Americans dispose of around a trillion diapers a year. If we include all children before potty-training age, the amount grows. Children in their second year of life need fewer diapers, around four to five a day. That's an extra 1400-1800 diapers a year, per child.

Production of synthetic diapers began in the 1960s and gained popularity over the following decade. In 2017, Americans disposed of over four million tons of used diapers, 80% of which just sits in landfills. Diapers are made of synthetic materials that aren't biodegradable.

Out of all "non-durable goods," diapers were the second most generated waste by weight, surpassed only by discarded clothing and shoes. And we have over half a century's worth of them taking up space.

Conventional diapers take hundreds of years to break down, which means that the diapers that you wore as a baby are likely still intact, sitting in a landfill. Brands like The Eco Pea Company are trying to change this by creating diapers that use more natural materials that have an easier time breaking down. This can go a long way towards countering the environmental effects of disposable diapers.

Chemical Compounds in Diapers

Aside from the sheer volume of waste, disposable diapers contain many harmful substances.

Tributyltin (TBT) - A biocide used to prevent the growth of bacteria. It's poisonous to marine life as well as humans. It damages fertility, unborn children, and our organs. TBT can be fatal if inhaled and doesn't degrade. TBT remains in our ecosystem and is entering our food chain.

Dioxins - A group of persistent organic pollutants. The bleaching process used on diaper material creates dioxins as a by-product. They're carcinogenic and linked long-term health problems. Dioxins are highly toxic, according to the EPA.

Adhesives, synthetic dyes, and perfumes - They are manufactured with and contain the chemicals on this list. Adhesives are used to hold the entire diaper together. Synthetic dyes create the cute pictures found on diapers, as well as the colored straps and the convenient strip telling you whether the baby needs to be changed. Diapers use perfumes to hide odors.

The Environment, A Major Concern of the Effects of Disposable Diapers

Sodium polyacrylate - Used as the absorbent stuffing. Menstrual pads containing this compound have been implicated in cases of toxic shock syndrome.

Volatile Organic Compounds (VOCs) like toluene, xylene, ethylbenzene, and dipentene - They're used to produce dyes, polymers, and adhesives. But the problem with these chemicals is that they are quickly released into the air when exposed to heat.

Plastics/polymers - Mainly polypropylene and polyethylene, but also includes polyester, polyurethane, and polyolefin. They're the primary materials used in product packaging, household products, and the production of plastic grocery bags, respectively. Most of a diaper is composed of these non-recyclable plastics.

Phthalates - While they're used to soften plastics, the diaper's adhesives, dyes, and perfumes also contain these chemicals. People of any age can have adverse reactions to phthalates, but unborn babies and young children are potentially more susceptible.

Petroleum/petrolatum - Used to keep diapers from leaking.

Most of us don't want these substances in our environment. Yet we are encouraged to place these compounds directly against our children's skin.

These chemical compounds are typically used to keep manufacturing costs low, but there are safe and healthy alternatives for parents who want to avoid them, just like there are for sustainable shampoo products. Look for diaper brands that state: hypoallergenic, fragrance-free, totally chlorine-free (TCF), phthalate-free, etc. Also, opting for sustainable brands with little to no patterns means lessening your baby's exposure to synthetic and toxic inks and dyes.

What About Alternatives?

Fortunately, we have other options that are better for our children and the environment.

Biodegradable Disposable Diapers

A few companies have started production of completely biodegradable diapers. They use plant-based materials instead of polyacrylate stuffing, artificial dyes, toxic materials, and plastics.

There is a higher price attached to these diapers, due to higher manufacturing costs. But you also get the comfort of knowing that your child won't be exposed to harsh chemicals. These diapers won't sit in landfills for centuries. If you want the convenience of disposable diapers without the waste, these are perfect.

Natural diaper brands like Eco Pea Co. can begin degrading in as little as 2-3 months as opposed to 500+ years. They also utilize water based ink that is environment-protected. Because bamboo is naturally odor-resistant and antibacterial, opting for a bamboo diaper subscription is not only better for our planet, but also safer for your child.

Reusable Cloth Diapers

If you can't stomach the high cost of biodegradable disposables, there is still another solution - cloth diapers.

Reusable cloth diapers have come a long way since their creation. The classic image of a cotton sheet held on with safety pins is no longer the reality. They've updated cloth diapers with contours, velcro or snaps, leak protection, and some pretty stylish prints. Now, these diapers are made of breathable fabrics and don't require soaking before washing (like they did previously).

With all-in-one cloth diapers, all you do is shake solids from the diaper, and throw them in the washing machine. After two wash cycles, they're good as new.

And if you're concerned about wasting water, you should know that it takes approximately nine gallons of water to produce a single disposal diaper. When you compare your entire household laundry to the number of disposables you'd use, the answer is clear.

Not only are they environmentally friendly, but cost about half as much as the seven thousand diapers a child uses before potty training. Are you having another child? The only cost is laundering if you chose not to do it at home. Reusables require scant investment instead of a constant drain on your wallet.

Let's say that you don't want to have to wash them at home. For the sake of convenience, there are plenty of companies that provide delivery and laundering services. There are green and eco-friendly cleaners as well, so your environmental impact from cloth diaper use has the potential to be negligible.

The cost of laundering services, combined with the purchase of cloth diapers, is almost equal to that of using disposable diapers. Cloth diapers save us significant energy, water, raw materials, and landfill space when compared to single-use diapers.

Final Thoughts on The Effects of Disposable Diapers

Diapers are a necessity for your child. The negative impact on our environment is not. It's possible to achieve the same protection at a lower cost and similar convenience for about the same as disposables.

It's our responsibility to use these earth-friendly options. Our total amount of waste produced globally is expected to double by 2030. This is one way we can lessen our impact. If we plan on giving the earth to our offspring, shouldn't we protect it while raising them?

Andrew Karpisz is a freelance writer for hire, husband, and proud stay-at-home father. He writes about parenting, self-improvement, and more. When he's not writing and researching, you can find him frolicking and playing with his 2-year-old daughter. He can be found on FB and Twitter at @TheAndrewAK.

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Effects of Disposable Diapers on Environment & Human Health

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Facts Surrounding the Effects of Disposable Diapers: Baby diapers can create an incredible amount of environmental waste, and pose a threat to infant health.

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The Redress Design Award (previously the Ecochic Design Award), now in its 8th year, attracts some of the best and brightest upcycling designers in the world. Finalists and semi-finalists in the past include Kevin Germanier, whose sustainable beaded masterpieces have been worn by Bjork and stocked in Matches, and Katie Jones who went on to win the Selfridges Bright New Things Award in 2016.

In 2018, this leading sustainable fashion competition went truly global, opening up to young designers from all parts of the world.

In the lead up to their grand finale, taking place in Hong Kong on September 6th, we are delighted to share the photoshoot of this year's 11 finalists. From Japan to Denmark - the standard of design and innovation is truly inspiring.

As a partner of the Redress Design Award, CO provides all finalists with one year of CO Pro membership and the winner with a year of CO Business Pro membership to support them in driving their business forward.

Scroll through this slideshow to see a sneak preview of the 11 finalists' collections. And tune in at www.redressdesignaward.com on 6th September for the live stream of the Grand Final in front of an audience of 1000 in Hong Kong.

Models: Bonnie Chen, Zuzana T

Creative Stylist: Angus Tsui

Photographer: Sam Tso

Make-up: Donald Chiu, Popstar Cosmetics & Karen Yiu, HK Makeup Artist

Hair: Marco Chan for KMS

Venue: The Mills, Hong Kong

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The Redress Design Award (previously the Ecochic Design Award) is now in its 8th year and for the first time has opened up to be completely global. Here, we present the finalists - 11 inspiring creatives using their skills as designers to transform the way we think about waste in fashion.

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Some upcycling designers use panels of waste fabric, instead of putting energy into returning the fabric into its original from and starting from scratch. They don't hide the fact that its recycled and instead utilize recycled fabrics like a form of collage.

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-There are at least five different polymers in your average disposable nappy.

-The top-sheet, closest to the baby’s skin, is commonly made of polypropene. Some brands also have a thin layer of lotion on the top-sheet to protect the baby’s skin. This layer of the nappy allows the baby’s urine to pass through and into the further nappy layers below.

-The layer below the top-sheet is the acquisition layer. This layer is usually composed of cotton and polyester and absorbs the urine, moving it away from the baby’s skin. Cotton absorbs up to 27 times its weight in water. Salts and other compounds in urine reduce the amount that it absorbs relative to this figure, but it still does a pretty good job of soaking it up.

- The absorbent layer underneath the acquisition layer contains some cotton too but also contains another polymer: sodium polyacrylate. This is a superabsorbent polymer which is able to absorb a whopping 800 times its own weight in distilled water. As with cotton, the amount of urine it can absorb is reduced by other compounds found within urine. Even so, it still manages a pretty impressive 30 times its own weight. As it absorbs the urine, it forms a gel, preventing wetness inside the nappy.

-The final disposable nappy layer is the water-resistant back-sheet. Commonly composed of polypropene and polyethene, this layer prevents the wetness contained in the nappy from transferring to the baby’s sheets or clothes.

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Five thousand: that's the number of nappy changes the average child will need. There are several nappy choices available to parents, but disposable nappies make up a large portion of the market - and there's a fair amount of chemistry behind how they keep a baby dry.

Several different polymers make up disposable nappies. Polymers are long-chained molecules formed from many small, repeating motifs - essentially the links in the chain. There are at least five different polymers in your average disposable nappy, each serving a slightly different purpose.

The nappies themselves are formed from several different layers. The top-sheet, closest to the baby's skin, is commonly made of polypropene. Some brands also have a thin layer of lotion on the top-sheet to protect the baby's skin. This layer of the nappy allows the baby's urine to pass through and into the further nappy layers below.

The layer below the top-sheet is the acquisition layer. This layer is usually composed of cotton and polyester and absorbs the urine, moving it away from the baby's skin. Cotton absorbs up to 27 times its weight in water. Salts and other compounds in urine reduce the amount that it absorbs relative to this figure, but it still does a pretty good job of soaking it up. On its own, however, it wouldn't be long before your baby's nappy would start to leak.

That's where our next layer comes in. The absorbent layer underneath the acquisition layer contains some cotton too but also contains another polymer: sodium polyacrylate. This is a superabsorbent polymer which is able to absorb a whopping 800 times its own weight in distilled water. As with cotton, the amount of urine it can absorb is reduced by other compounds found within urine. Even so, it still manages a pretty impressive 30 times its own weight. As it absorbs the urine, it forms a gel, preventing wetness inside the nappy.

The average six-month-old produces approximately 15 grams of urine per hour. Most nappies only contain around 2-4 grams of sodium polyacrylate, but this, along with the absorbent cotton, is sufficient to absorb several hours' worth of urine, keeping babies dry through the night.

The final disposable nappy layer is the water-resistant back-sheet. Commonly composed of polypropene and polyethene, this layer prevents the wetness contained in the nappy from transferring to the baby's sheets or clothes.

In more recent years, the outside surface of some nappies for younger babies have included a 'wetness indicator'. This is commonly in the form of a coloured line, which changes colour when the interior of the nappy is wet, letting parents know when the nappy needs to be changed.

What's the chemical story behind these indicating lines? I contacted several nappy companies to try and find out, with mixed success. One company simply informed me that they didn't sell their nappies in the UK any more (not what I asked!). Another was slightly more forthcoming and pointed me towards some general information on their site. This confirmed my suspicion that the lines used a pH indicator to provide the indication and a search through disposable nappy patents filled in the rest of the detail.

Many nappies that contain a wetness indicator seem to use a chemical called bromophenol blue. Bromophenol blue is a pH indicator - that is, it changes colour depending on the surrounding acidity or alkalinity. In nappies, bromophenol blue appears yellow when the nappy is dry, but the slightly alkaline pH of urine causes its colour to change to blue when the nappy is wet. Other patents suggest that some other nappies use chemicals that are sensitive to moisture as indicators, though it's unclear how these compounds cause a colour change to appear.

Having discussed the chemistry inside disposable nappies, it's time to discuss what happens to them after use. Those 5000 nappies per child add up - in the UK alone, they account for 2-3% of all household waste. And they stick around: it's estimated that a disposable nappy takes around 450 years to fully decompose in landfill. In 2008 the UK's Environment Agency estimated that, over the time a typical child wears nappies, disposables would create 550kg of carbon emissions through their manufacture, distribution, and disposal.

Given this potential environmental impact, turning to reusable nappies might seem like a no-brainer. However, the same study cautioned that taking into account the impacts of laundering reusable nappies, their carbon emissions impact was comparable to that of disposable nappies. This was based on a few assumptions, and the study identified that air drying instead of tumble-drying, reusing nappies with a second child, and several other factors could all bring down the impacts of reusables. It's also the case that reusables don't generate the same volume of waste that disposable nappies do.

Regardless of the debate of the benefits of reusables versus disposables, disposable nappies remain the more popular of the two. To try and combat the quantities of waste sent to landfill, some companies have started to investigate how the materials in used nappies can be recycled. One such plant near Venice in Italy aims to turn plastics from nappies into bottle caps and clothing. If enthusiasm for disposable nappies continues, perhaps this is the answer to the waste problem they pose - though it will need to be carried out at a much larger, worldwide scale.
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References/further reading

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The chemistry of disposable nappies: absorbency, wetness indicators and waste

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Five thousand: that's the number of nappy changes the average child will need. There are several nappy choices available to parents, but disposable nappies make up a large portion of the market - and there's a fair amount of chemistry behind how they keep a baby dry.

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Sodium polyacrylate, also known as waterlock, is a sodium salt of polyacrylic acid with the chemical formula [−CH2−CH(CO2Na)−]n and has broad applications in consumer products. This super-absorbent polymer (SAP) has the ability to absorb 100 to 1000 times its mass in water--The three companies have recently developed a new technology for recycling superabsorbent polymers (SAPs) in used diapers.- Disposable diapers are mainly composed of pulp, plastic, and SAPs. Recycled pulp has been effectively used as a raw material for building materials (e.g., exterior and interior wall materials), and plastic has been thermally recovered as solid fuel. -The recycling process for used disposable diapers used to face the challenge that SAPs, which would swell from absorbing urine, reduced the recovery rate of paper pulp, or even if SAPs were recovered, they were difficult to reuse because of the significant decrease in performance.

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Sodium polyacrylate, also known as waterlock, is a sodium salt of polyacrylic acid with the chemical formula [−CH2−CH(CO2Na)−]n and has broad applications in consumer products. This super-absorbent polymer (SAP) has the ability to absorb 100 to 1000 times its mass in water--The three companies have recently developed a new technology for recycling superabsorbent polymers (SAPs) in used diapers.- Disposable diapers are mainly composed of pulp, plastic, and SAPs. Recycled pulp has been effectively used as a raw material for building materials (e.g., exterior and interior wall materials), and plastic has been thermally recovered as solid fuel. -The recycling process for used disposable diapers used to face the challenge that SAPs, which would swell from absorbing urine, reduced the recovery rate of paper pulp, or even if SAPs were recovered, they were difficult to reuse because of the significant decrease in performance.

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Nippon Shokubai and LiveDo Corporation, both headquartered in Osaka, Japan, and Total Care System, headquartered in Fukuoka, Japan, are jointly developing a variety of technologies to promote the growth of systems that recycle disposable diapers, the use of which continues to increase. The three companies have recently developed a new technology for recycling superabsorbent polymers (SAPs) in used diapers. The technology can be applied to a wide variety of SAPs distributed worldwide.

On March 31, 2020, the Ministry of the Environment released the Guidelines for Recycling Used Disposable Diapers. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is also aiming to establish a guideline for the acceptance of used disposable diapers into the sewage system based on the New Sewerage Vision Acceleration Strategy. Recycling of used disposable diapers, the amount of which continues to increase, is thus expected to be promoted.

Total Care System was the first in Japan to build a recycling system for used disposable diapers, one of the few in the world, and it has been in the business for 15 years. Disposable diapers are mainly composed of pulp, plastic, and SAPs. Recycled pulp has been effectively used as a raw material for building materials (e.g., exterior and interior wall materials), and plastic has been thermally recovered as solid fuel. Currently, research and development of material recycling are underway.

Nippon Shokubai, which has the world's largest SAP market share (based on production volume), joined the initiative in November 2018 to explore recycling technologies for SAPs, which had remained a challenge, and succeeded in developing new recycling technologies through joint research with the two partners: major disposable diaper manufacturer LiveDo and Total Care System.

The recycling process for used disposable diapers used to face the challenge that SAPs, which would swell from absorbing urine, reduced the recovery rate of paper pulp, or even if SAPs were recovered, they were difficult to reuse because of the significant decrease in performance.

The three companies jointly developed the following technologies to overcome this challenge.

Technology to increase the recovery rate of paper pulp by processing SAPs, which swell from absorbing urine, and to improve the separation from paper pulp

Recovery technology that minimizes SAP performance degradation

These technologies are designed to reduce energy consumption during recycling and to protect the water quality of rivers and other bodies of water. They can also be applied to all SAPs produced by Nippon Shokubai, as well as to various SAPs around the world.
In addition to raising these technologies to a practical level, the three companies, which are a raw material manufacturer, a disposable diaper manufacturer, and a recycling business, plan to work together to develop and commercialize materials and products that are easy to recycle and new recycling technology for used disposable diapers.

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Japanese Companies Develop New Recycling Technology for SAP

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Nippon Shokubai and LiveDo Corporation, both headquartered in Osaka, Japan, and Total Care System, headquartered in Fukuoka, Japan, are jointly developing a variety of technologies to promote the growth of systems that recycle disposable diapers, the use of which continues to increase.

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-Superabsorbent polymer (SAP) (also called slush powder) can absorb and retain extremely large amounts of a liquid relative to its own mass.-Water-absorbing polymers, which are classified as hydrogels when mixed-The largest use of SAPs is found in personal disposable hygiene products, such as baby diapers, adult diapers and sanitary napkins.

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-Superabsorbent polymer (SAP) (also called slush powder) can absorb and retain extremely large amounts of a liquid relative to its own mass.-Water-absorbing polymers, which are classified as hydrogels when mixed-The largest use of SAPs is found in personal disposable hygiene products, such as baby diapers, adult diapers and sanitary napkins.

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Superabsorbent polymer powder

A superabsorbent polymer (SAP) (also called slush powder) is a water-absorbing hydrophilic homopolymers or copolymers that can absorb and retain extremely large amounts of a liquid relative to its own mass.

Water-absorbing polymers, which are classified as hydrogels when mixed, absorb aqueous solutions through hydrogen bonding with water molecules. A SAP's ability to absorb water depends on the ionic concentration of the aqueous solution. In deionized and distilled water, a SAP may absorb 300 times its weight (from 30 to 60 times its own volume) and can become up to 99.9% liquid, and when put into a 0.9% saline solution the absorbency drops to approximately 50 times its weight.[citation needed ] The presence of valence cations in the solution impedes the polymer's ability to bond with the water molecule.

The SAP's total absorbency and swelling capacity are controlled by the type and degree of cross-linkers used to make the gel. Low-density cross-linked SAPs generally have a higher absorbent capacity and swell to a larger degree. These types of SAPs also have a softer and stickier gel formation. High cross-link density polymers exhibit lower absorbent capacity and swell, and the gel strength is firmer and can maintain particle shape even under modest pressure.

IUPAC definition for superabsorbent polymer

Superabsorbent polymers are crosslinked in order to avoid dissolution. There are three main classes of SAPs:

1. Cross‐linked polyacrylates and polyacrylamides

2. Cellulose‐ or starch‐acrylonitrile graft copolymers

3. Cross‐linked maleic anhydride copolymers

The largest use of SAPs is found in personal disposable hygiene products, such as baby diapers, adult diapers and sanitary napkins. SAPs were discontinued from use in tampons due to 1980s concern over a link with toxic shock syndrome.[citation needed ] SAPs are also used for blocking water penetration in underground power or communications cable, in self-healing concrete, horticultural water retention agents, control of spill and waste aqueous fluid, and artificial snow for motion picture and stage production. The first commercial use was in 1978 for use in feminine napkins in Japan and disposable bed liners for nursing home patients in the USA. Early applications in the US market were with small regional diaper manufacturers as well as Kimberly Clark.

Until the 1920s, water-absorbing materials were fiber-based products. Choices were tissue paper, cotton, sponge, and fluff pulp. The water-absorbing capacity of these types of materials is only up to eleven times their weight and most of it is lost under moderate pressure.

In the early 1960s, the United States Department of Agriculture (USDA) was conducting work on materials to improve water conservation in soils. They developed a resin based on the grafting of acrylonitrile polymer onto the backbone of starch molecules (i.e. starch-grafting). The hydrolyzed product of the hydrolysis of this starch-acrylonitrile co-polymer gave water absorption greater than 400 times its weight. Also, the gel did not release liquid water the way that fiber-based absorbents do.

The polymer came to be known as "Super Slurper". The USDA gave the technical know-how to several US companies for further development of the basic technology. A wide range of grafting combinations were attempted including work with acrylic acid, acrylamide and polyvinyl alcohol (PVA).

Today's research has proved the ability of natural materials, e.g. polysaccharides and proteins, to perform super absorbent properties in pure water and saline solution (0.9%wt.) within the same range as synthetic polyacrylates do in current applications. Soy protein/poly(acrylic acid) superabsorbent polymers with good mechanical strength have been prepared. Polyacrylate/ polyacrylamide copolymers were originally designed for use in conditions with high electrolyte/mineral content and a need for long term stability including numerous wet/dry cycles. Uses include agricultural and horticultural. With the added strength of the acrylamide monomer, used as medical spill control, wire and cable water blocking.

Superabsorbent polymers are now commonly made from the polymerization of acrylic acid blended with sodium hydroxide in the presence of an initiator to form a poly-acrylic acid sodium salt (sometimes referred to as sodium polyacrylate). This polymer is the most common type of SAP made in the world today. According to U.S Food & Drug Administration, sodium polyacrylate is listed in Food Additive Status List, and there are strict limitations.

Other materials are also used to make a superabsorbent polymer, such as polyacrylamide copolymer, ethylene maleic anhydride copolymer, cross-linked carboxymethylcellulose, polyvinyl alcohol copolymers, cross-linked polyethylene oxide, and starch grafted copolymer of polyacrylonitrile to name a few. The latter is one of the oldest SAP forms created.[citation needed ]

Today superabsorbent polymers are made using one of three primary methods: gel polymerization, suspension polymerization or solution polymerization. Each of the processes have their respective advantages but all yield a consistent quality of product.

Hydrogel

A mixture of acrylic acid, water, cross-linking agents and UV initiator chemicals are blended and placed either on a moving belt or in large tubs. The liquid mixture then goes into a "reactor" which is a long chamber with a series of strong UV lights. The UV radiation drives the polymerization and cross-linking reactions. The resulting "logs" are sticky gels containing 60-70% water. The logs are shredded or ground and placed in various sorts of driers. Additional cross-linking agent may be sprayed on the particles' surface; this "surface cross-linking" increases the product's ability to swell under pressure-a property measured as Absorbency Under Load (AUL) or Absorbency Against Pressure (AAP). The dried polymer particles are then screened for proper particle size distribution and packaging. The gel polymerization (GP) method is currently the most popular method for making the sodium polyacrylate superabsorbent polymers now used in baby diapers and other disposable hygienic articles.

Solution polymers offer the absorbency of a granular polymer supplied in solution form. Solutions can be diluted with water prior to application, and can coat or saturate most substrates. After drying at a specific temperature for a specific time, the result is a coated substrate with superabsorbency. For example, this chemistry can be applied directly onto wires and cables, though it is especially optimized for use on components such as rolled goods or sheeted substrates.

Solution-based polymerization is commonly used today for SAP manufacture of co-polymers, particularly those with the toxic acrylamide monomer. This process is efficient and generally has a lower capital cost base. The solution process uses a water-based monomer solution to produce a mass of reactant polymerized gel. The polymerization's own exothermic reaction energy is used to drive much of the process, helping reduce manufacturing cost. The reactant polymer gel is then chopped, dried and ground to its final granule size. Any treatments to enhance performance characteristics of the SAP are usually accomplished after the final granule size is created.

The suspension process is practiced by only a few companies because it requires a higher degree of production control and product engineering during the polymerization step. This process suspends the water-based reactant in a hydrocarbon-based solvent. The net result is that the suspension polymerization creates the primary polymer particle in the reactor rather than mechanically in post-reaction stages. Performance enhancements can also be made during, or just after, the reaction stage.

On 13 April 2010, Cathay Pacific flight 780 from Surabaya to Hong Kong encountered a dual engine stall descending whilst descending into Hong Kong International Airport, the aircraft landed safely with no fatalities. The investigation concluded that superabsorbent polymer (SAP) spheres, a component of a fuel filter monitor installed in a fueling dispenser at Juanda International Airport caused the main metering valves in the fuel metering unit to seize. It was discovered that salt water had contaminated the fuel supply at Juanda International Airport after, which led to damage of the filter monitors and release of SAP spheres into the aircraft's fuel, eventually entering the main fuel supply lines.

Expanded polymer balls

Artificial snow for motion picture and stage productions

Candles

Cement-based materials (e.g. concrete)

Composites and laminates

Controlled release of insecticides and herbicides

Diapers and adult diapers

Drown-free water source for feeder insects

Expandable water toys

Expansion microscopy

Filtration applications

Fire-retardant gel

Flood control

Fragrance carrier

Frog tape (high-tech masking tape designed for use with latex paint)

Fuel monitoring systems in aviation and vehicles

Gel blasters (a cross between paintball and airsoft; used in China)

Hot and cold therapy packs

Magical effects

Medical waste solidification

Motionless water beds

Potting soil

Spill control

Surgical pads

Waste stabilization and environmental remediation

Water-absorbent pads

Water retention for supplying water to plants

Wire and cable water blocking

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A superabsorbent polymer (SAP) (also called slush powder) is a water-absorbing hydrophilic homopolymers or copolymers that can absorb and retain extremely large amounts of a liquid relative to its own mass. Water-absorbing polymers, which are classified as hydrogels when mixed, absorb aqueous solutions through hydrogen bonding with water molecules.

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Fluff pulp

Fluff pulps are used as a raw material in the absorbent core of personal care products such as diapers, feminine hygiene products, air-laid absorbent towelling, as such, or with superabsorbents and/or synthetic fibres. More than 80% of the pulps are used in baby diapers.

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Fluff pulp (also called comminution pulp or fluffy pulp) is a type of chemical pulp made from long fibre softwoods. Important parameters for fluff pulp are bulk and water absorbency.

Fluff pulp was first developed for use in disposable sanitary napkins. Kotex's first advertisement for products made with wood pulp (Cellucotton) appeared in 1921. Disposable diaper producers also were early to convert to fluff pulp because of its low cost and high absorbency. Normal usage of fluff pulp in a diaper was about 55 percent. In the 1980s started the commercialization of air-laid paper, which gave better bulk, porosity, strength, softness, and water absorption properties compared with normal tissue paper. Also in the 1980s started the use of superabsorbents in diapers and reduced the need for fluff pulp and is now down to 15 grams or even less. The demand of the pulp in diapers has gone from being the absorbent of liquid to giving the products dry and wet strength.

More than 90% of the fluff pulps are fully bleached chemical softwood pulps, of which more than 90% are kraft pulps.

The most common raw material source for fluff pulps are southern bleached softwood kraft ( SBSK) from loblolly pine. SBSK from other species and NBSK are also used to make fluff pulp. Thicker fibres are preferred to improve the bulk.

Fluff pulp is normally made rolls ( reels) on a drying machine (a simplified Fourdrinier machine). The objective of the drying/sheeting operation is to produce a uniform sheet ( paper density, moisture, and strength) to the converting operation. The pulp may be impregnated with debonders before drying to ease defibration.

The worldwide production of fluff pulps amounts to about 3.5 million tons.

Fluff pulps are used as a raw material in the absorbent core of personal care products such as diapers, feminine hygiene products, air-laid absorbent towelling, as such, or with superabsorbents and/or synthetic fibres. More than 80% of the pulps are used in baby diapers.

The most demanding application of fluff pulps is in air-laid products, used in serving utensils, various towel applications in homes, in the industry, and in hospitals. Fluff pulp for air-laid products is defibrized in a hammermill. Defibration is the process of freeing the fibres from each other before entering the paper machine. Important parameters for dry defibration are shredding energy and knot content.

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Fluff pulp (also called comminution pulp or fluffy pulp) is a type of chemical pulp made from long fibre softwoods. Important parameters for fluff pulp are bulk and water absorbency. Fluff pulp was first developed for use in disposable sanitary napkins. Kotex's first advertisement for products made with wood pulp (Cellucotton) appeared in 1921.

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SAP is not biodegradable and is often mixed with wood pulp

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SAP is not biodegradable and is often mixed with wood pulp

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The choice of a "green" or "ecological" diaper is not straightforward. In my previous review of Seventh Generation diapers, Whole Foods Private Label 365 diapers and gDiapers, I tackled the following issues:

1. Comfort, leaks and diaper rash

2. Chlorine

3. Plastic, latex, TBT, polyurethane/polypropolene

4. Biodegradability (vs. flushability)

5. gDiaper hands-on aspects

6. Price

7. SAP or Sodium polyacrylate

After receiving suggestions from readers and replies to queries from the companies, I decided to revisit some of these issues. Below you can find more detailed information about these diapers, and an investigation of some of the claims that are made on their behalf:

1. by the companies: "this diaper is chlorine-free and that is how we differ from other disposables."

2. by the consumers: "it's green so if I throw it in the trash, or flush it down the toilet, it will biodegrade in the landfill or sewage."

It is easy to take these claims at face value, but a conscientious consumer will question and weigh them against one another: is one green diaper better than another? Are green diapers better than non-green disposables? are disposables better than cloth diapers?

{Correction} in my previous review I mistakenly wrote that Seventh Generation claims that their diapers are plastic-free. This is not the case, that is, they do not claim this, and their diapers do contains plastics ("poly," see later). Mea culpa! I've removed the faulty claim from the review

SAP (super absorbent polymer, a.k.a., sodium polyacrylate)

In the old review my two main concerns - the ones that separate the cloth from the disposable from the flushable people - are SAP and biodegradability. These two turn out to be intricately related.

If you have a problem with SAP, it is probably a health-related concern (see previous review). If you can't stand them, then cloth is your choice, because all the diapers I reviewed use them.

Seventh Generation, gDiapers, as well as the Whole Foods 365 brand have SAP. As do TenderCareDiapers, rumored not to use SAP. Cf. Jolene at TenderCareDiapers (email 24 May 2007):

The superabsorbent in TenderCareDiapers Plus is the same as in Huggies, Seventh Generation, Luvs, etc. Our supplier has informed us that the super absorbent polymer in TenderCareDiapers Plus contains a partially neutralized cross lined sodium polyacrylate that has been found to be safe for use in diapers through extensive testing internally as well as by external sources.

In a fantastic Grist interview (from which I will quote more), Jason and Kimberley Graham-Nye, the inventors and founders of gDiapers, address the issue of SAP (bolds mine):

Sodium polyacrylate has been rigorously tested both in the U.S. and abroad, and the predominant conclusions are that it is completely safe and non-toxic. MBDC is a leading U.S.-based design chemistry firm that has assessed SAP as GREEN, which is the safest assessment a chemical or material can receive. The FDA has approved SAP as a food additive, and the EPA considers SAP "harmless" when ingested. A 10 pound baby would have to eat about 200 grams of SAP - or 50 gDiapers! - to be at risk. Also, to put this in perspective, SAP is less toxic than table sugar. We appreciate that no matter what arguments we put forth there will be parents who are still not comfortable with SAP in their diapers. Fair enough. For us, the plastic in disposables is a much bigger issue for both our sons' health and comfort.

A food-additive: there's food for thought! Here is, by the way, another application of those SAPs: we're even sticking it into farmland and using it to raise whole countries.

In my previous review I wondered why Seventh Generation uses SAP in their diapers, but make such a big deal about not using it in their feminine care Maxi Pads. Here is their response to this question (email from Louis Chapdelaine, May 24, 2007):

The natural super absorbent material that we use in the design of our feminine hygiene products lend themselves well for that particular application but not so much for diaper design applications. That has to do with the material capacity to absorb but also with the characteristics of the fluid that needs to be contained. The good news is that new generations of super absorbent polymers technologies are emerging. I believe these materials are promising in terms of opening the door to using more sustainable absorbent polymers in the design of baby diapers. As you would presume, sustainability is a very important part of the design equation at Seventh Generation.

But SAP is also at the center of the biodegradability-issue, about which next.

Diaper buyers believe that by using "ecological" diapers, we contribute less to waste. Yes, we dump them in the trash and they end up in the landfill, but there they will miraculously biodegrade, no? No. That they are "biodegradable" or "designed to biodegrade" doesn't mean that they actually do. It turns out that even the organic, truly biodegradable stuff in them does not degrade in a landfill.

In fact, each of the diaper companies I wrote to admit to this (you have to do some asking and digging to get to that fact, though).

In response to my query about this, Jason Hays, Guest Services Content Administrator of the WF 365 Private Label, emailed me the following (on 24 May 2007, bolds mine):

Although wood pulp is a 100% biodegradable material, there have been 100 year old newspapers (made of wood pulp) found intact in landfills. US landfills are anaerobic (no air) and [have] no water or light facilities - all key elements necessary for biodegradability. We know of no commercial composting facilities for disposable diapers and temperature could never be high enough to decompose a disposable diaper. We do not advocate home composting disposable diapers because of possible feces contamination of ground water. We understand Australia is having some good results using tiger worms decomposing our diapers.

Also Seventh Generation volunteers this information on their website (in the FAQ, my bolds):

Just like most disposable diaper designs in the marketplace, Seventh Generation diapers are not readily biodegradable, nor can they be composted. Many of the materials used are synthetic, and do not readily biodegrade. The inner pulp of the diaper is made of 100% total chlorine-free whitened wood pulp fibers. This pulp is mixed with a super absorbent polymer (SAP) that does not biodegrade. Most diapers end up in a landfill where they will not biodegrade, even if they were designed to do so.

And to clarify even further, Louis Chapdelaine, of Seventh Generation, emailed me the following (25 May 2007, bolds mine):

I am not aware of any disposable diaper designs out there that could claim 100% biodegradability. 80% is about the max that I have seen in a design and this is by far a leading design. Everybody else is quite a bit behind that. That design can be found in the European market where access to biopolymers tends to be easier. Now, that does not mean that because a material going into a diaper design is said to be biodegradable that it will in fact readily biodegrade. That depends on the conditions and the conditions do not lend themselves well for biodegradability in a landfill which is where the vast majority of disposable baby diapers end up at. This is why caution must be exercised when evaluating the sustainability aspect of a baby diaper design; biodegradability alone can be somewhat misleading.

Seventh Generation lists "poly" among the ingredients of their diapers. I assumed it was polyurethane, and left it at that, but in a comment, Annika suggests: "It is still plastic; in fact, it's the same polypropolene used to line landfills (that's how water-tight and air-tight they are!)."

I've written to Seventh Generation for clarification and am waiting for a reply, and indeed, it is polypropolene (L. Chapdelaine), which is used to enclose landfills.

Also the Whole Foods 365 diapers contain polypropolene, more specifically:

The diaper covers contain polymerized propylene spun bound non-woven material. The absorbency gel is a non-toxic Super absorbent Polymer consisting of partial sodium salt of cross linked polypropenoic acid. [Jason Hays, email of 31 May 2007]

There is an interesting thread about how poly's - polyurethane (PE), polypropylene (PP) - behave in landfills here.

Biodegradability of gDiapers: SAP again

At this point gDiapers comes in with two promises.

1. the disposable part of their diapers is fully biodegradable (with the exception of the SAP). There are no "poly"'s to worry about. "The outer material of the flushable refill is viscose rayon, a natural material that comes from trees. It is the only polymer used in the textile industry that comes from a natural, renewable, and non-fossil-fuel source."

2. this biodegradable material won't end up in the landfill, where it can't (actually) degrade, because you can either (a) flush them, or (b) compost them or (c) throw them in the septic tank.

That the gDiaper refill goes down the drain with such a majestic swirl doesn't of course mean it miraculously disappears. The concern about the diaper-in-the-landfills applies to the diaper-in-the-sewage as well. So what happens with it?

The sewage system brings the diaper to a wastewater processing facility, which separates potable water from sewage sludge. Many of these facilities produce "biosolids" out of the sludge. In the Grist interview, Jason and Kimberley Graham-Nye fill us in (bolds mine):

The EPA estimates that 16,000 publicly owned treatment facilities generate approximately 7 million tons of sewage sludge. About 80 percent of all sewage sludge is biosolids that is used as a fertilizer on farmland following treatment. It appears that at the North Bend, Wash., facility, 1.2 million gallons of biosolids were applied to forestland and grazing land last year.

They add that "the gDiapers flushable is complimentary to the wastewater facility's production of biosolids".

Great, but what about the SAP, the non-biodegradable part? It won't break down, but there is very little of it in a diaper. Seventh Generation ( on their FAQ) specifies that the ratio is 30-50 grams of wood pulp to 5-15 grams of SAP per diaper. gDiapers use even less: less than 4 grams per diaper.

The promise is that this little bit of stuff "is inert and will settle out" (the Graham-Nyes in the Grist interview). It will get separated from the organic compost/biosolid-sludge and be washed away, and "if the septic is working properly, [the flushable] will break down completely and be discharged with the effluent".

But discharged whereto? And how "inert" is it? Does it matter that it is such a small amount? ... There you have it: the issue of biodegradability too comes down to SAP.

"Chlorine free": ECF and TCF, and does it matter?

Here's another interesting fact. All the green diapers are "chlorine free". Indeed, that is their main selling point. But what does that mean?

There is a difference between ECF (Elemental Chlorine-Free) and TCF (Totally Chlorine-Free).

1. ECF pulp is bleached with chlorine dioxide instead of elemental chlorine.

2. TCF pulp is bleached using any chemical other than chlorine, chlorine dioxide and hypochlorite.

The Alliance of Environmental Technology points out the following (bolds mine):

Research has shown the environmental risks to aquatic ecosystems from ECF bleaching are negligible and there is no toxicological difference between wastewaters generated from ECF-based or TCF-based bleaching.

But " more trees are required to make paper with TCF compared to ECF. With TCF, 3-4% less paper is produced from the same amount of wood compared to ECF."

The AET also writes that (bolds mine):

In North America, ECF pulp production for papermaking increased to 53.1 million tonnes, totaling more than two thirds of the world market share. The balance is produced with some elemental chlorine. [...] In the U.S., ECF has taken off, reaching 20 million tonnes in 2000 - accounting for 75% of U.S. production. TCF production lags far behind at less than 250,000 tonnes per year. [...] In summary, with internationally acknowledged environmental parity between effluents from ECF-based and TCF-based bleaching processes established in 1994, the initial driving force for market demand for TCF was eliminated. Further growth of either product from 1994 forward depended on the traditional values of product quality and manufacturing cost. ECF-based bleaching produces higher quality with at lower costs. The market has spoken.

gDiapers ' Jason and Kimberley Graham-Nye want to make a difference (bolds mine):

We find it most frustrating that in the pulp industry, there is only one complete chlorine-free mill in the world, and they weren't willing to supply us. As we grow, we would like to be an agent of change in the industry, and we hope to be able to source both FSC [ Forest Stewardship Council] and completely chlorine-free fluff pulp. [ Grist interview]

But why, if there is no difference between ECF and TCF? Forgive me my skeptical nature, but could it be because "non-Green" diapers such as Huggies are also using, for the main part, EFC wood pulp? Read, for instance, the 2006 sustainability report of Kimberly-Clark (which makes Huggies). It states (for all their products, not just diapers, bolds mine):

Our preference is to purchase elemental chlorine-free (ECF) bleached pulp for use in our consumer products. This process uses chlorine dioxide rather than pure chlorine, reducing toxicity. During 2006, 89 percent of total pulp purchased was ECF and a further 7 percent was totally chlorine-free (TCF). Some of our South American and Mexican suppliers still use chlorine bleaching, accounting for around 4 percent of fiber use in 2006. We are no longer sourcing from one of these suppliers, are looking for an alternative to another and a third is installing a new ECF bleaching plant. Our own two pulp facilities, in Tantanoola, Australia, and Everett, Washington, U.S., use TCF and ECF bleaching technology, respectively.

So in the end, the question becomes: where does the wood pulp come from? If your child's diaper has pulp that comes from a mill in China, can we be assured that it is ECF? And even if it is, has it been harvested with sustainability in mind? And how many miles has it traveled (how many barrels of oil has it soaked up) by the time it reaches your home?

The Seventh Generation wood pulp comes from Europe, mainly Finland, and the diapers are assembled in the US (L. Chapdelaine, email 25 May 2007).

gDiapers' Jason and Kimberley Graham-Nye in the Grist interview:

The inner core of the flushable is made of soft, fluffed wood pulp and super absorber. Like the outer material, the inside of the flushable comes from sustainably managed forests using an elemental-chlorine-free process. Our pulp supplier is actually certified by the Sustainable Forestry Initiative.

And gDiapers' kim comments (on Diaperjungle.com) on the fact that the little gDiaper outer pants are "Made in China":

As for the China issue...we certainly understand and respect where you are coming from. We work closely with China Labour Watch and in a few months will be opening the Happy Planet Mill. By increasing the standards of employment, compensation, conditions and respect, we hope we are contributing to a better China. If you prefer however, you can always buy the covers/pants from our Australian company at eenee.com (made in Australia). I did want to point out however, that parents only need 12 pairs of little gs for the lifetime of diapering their child, but you will need 6,000 flushables....all made here in the USA.

I gather that the pulp for gDiapers comes partially from China, but that they are assembled in the U.S. I've asked them for clarification and will update as soon as I hear from them.

Also, a reader left a comment calling into question the credentials of the Sustainable Forestry Initiative (SFI) - the certifiers of sustainable practices that gDiapers so proudly mentions. It is certainly disconcerting to read that "The SFI is funded primarily by AF&PA members and other timber companies it certifies. Timber companies and industry allies also continue to dominate the SFI's governing board, which controls the SFI standards and other aspects of the system"... Read more about that here.

Lastly, Jason Hays at WF 365:

Our diapers contain wood pulp, sourced primarily from family farmed and sustainable managed forests, as part of the absorption materials. The product contains no recycled materials nor TBT, a common wood treatment agent. / The wood pulp comes from Scandinavia. [email of 24 May 2007 / email of 31 May 2007]

TushiesDiapers, by the way,

are assembled in the U.S.A. With Domestic Materials & Scandinavian Certified 100% TCF-Totally CHLORINE-FREE Woodpulp from Renewable, Sustainable Family Owned Forests!

If your choice of the right diaper for your child is also an ecological choice, then it pays off to look into the claims made by the companies, our culture, and our own assumptions. Once you start doing this, you may find that the issue is a complex one that grows with each newly learned bit of information. That's ecology for you! An ecological decision is one that fits into that intricate web of life. Even if the above does not conclude which is the best choice, hopefully it leads you to some considerations that are helpful to you on your quest for the "right diaper".

Comments? Suggestions? Please leave them here.

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Green Diapers: SAP, biodegradability, chlorine, woodpulp

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The choice of a "green" or "ecological" diaper is not straightforward. In my previous review of Seventh Generation diapers, Whole Foods Private Label 365 diapers and gDiapers, I tackled the following issues: Comfort, leaks and diaper rash Chlorine Plastic, latex, TBT, polyurethane/polypropolene Biodegradability (vs.

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Recycling of disposable nappies and their effect on the environment

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Recycling of disposable nappies and their effect on the environment

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Key Topics：Safeguarding the Well-being of Our Planet | Sustainability-Unicharm Company Information

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Presents the Unicharm Group's key topic: Safeguarding the Well-being of Our Planet.

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Current disposable nappy recycling plants

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Current disposable nappy recycling plants

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- To clean, hot water and steam are applied to nappies. Sewage drains away waste. Clean materials then separated.

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Recycling used nappies/diapers to reduce/reuse plastic waste (Italy) BBC News - 23rd April 2019

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A method for recycling diaper waste pulp was developed. Super-absorbent polymer (SAP) in diapers was dehydrated by oxidizing it using ozone, then the pulp in the diaper waste was recycled. The diaper waste was washed and centrifugally separated, then the SAP and pulp mixture was oxidized using ozone to separate the SAP and pulp to allow the pulp to be recycled.

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Highlights

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SAP used in disposable diapers was dehydrated by ozone treatment.

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Mw and Mn of SAP decreased with increasing ozone treatment time.

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Water-insoluble SAP was converted to water-soluble sodium polyacrylate polymer.

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FT-IR peaks of SAP treated with ozone was the same as sodium acrylate polymer film.

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The absorptivity of pulp used to absorb urine was not affected by ozone.

Abstract

A method for recycling diaper waste pulp was developed. Super-absorbent polymer (SAP) in diapers was dehydrated by oxidizing it using ozone, then the pulp in the diaper waste was recycled. The diaper waste was washed and centrifugally separated, then the SAP and pulp mixture was oxidized using ozone to separate the SAP and pulp to allow the pulp to be recycled. A sample of SAP that had absorbed either 400 mL of distilled water or 80 mL of a 0.9% NaCl solution was placed in 2000 mL of a 45 g/m ³ ozone solution produced by passing ozone through the solution at a flow rate of 1.0 mL/min. The SAP concentration decreased as the reaction time increased. Oxidation by ozone destroyed the cross-linked SAP structure and therefore eliminated the ability of the SAP to retain water. Ozone treatment also broke the ether bonds of the cross-linking agent in the SAP. This caused the water-insoluble SAP to be converted into a water-soluble sodium acrylate polymer. The molecular weight and degree of dispersion of the SAP also decreased as the reaction time increased. The water-absorptivity of the recovered pulp was almost the same as the water-absorptivity of virgin pulp and was higher than the standard value of 10 g/g. The water-absorptivity of the recovered pulp was not affected by the ozone treatment. We concluded that the method can be used to recycle disposable diaper pulp.

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Recycling disposable diaper waste pulp after dehydrating the superabsorbent polymer through oxidation using ozone

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SAP used in disposable diapers was dehydrated by ozone treatment. * Mw and Mn of SAP decreased with increasing ozone treatment time. * Water-insoluble SAP was converted to water-soluble sodium polyacrylate polymer. * FT-IR peaks of SAP treated with ozone was the same as sodium acrylate polymer film.

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Acquiring and experimenting on sample: fast fashion 

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Acquiring and experimenting on sample: fast fashion 

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From Matalan
Body is 57% cotton, 43% polyester

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Tried paper and CD shredder

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Material too soft and stretchy for shredder. Got jammed and tore minimally.

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Sander shaved off soft fluff and then tore fabric

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Time and energy consuming but seemed to be the only way to break the material down productively

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Produced soft, felt-like clumps that can be picked apart into single threads

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This process was time consuming and caused wear on the fabric but only produced soft fluff and single threads

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Pieces easily clump together into soft bouncy ball. When compressed, they hold their shape in a flexible sheet.

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Original panel of fabric not very absorbent

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When separated into smaller pieces absorbency was greatly improved

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Fabric is extremely flammable

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Fabric mainly turned to ash

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Acquiring and experimenting on sample: disposable nappy

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Acquiring and experimenting on sample: disposable nappy

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The first step of recycling nappies is to wash and separate the materials. To mimic this I put the disposable nappy in a tote bag and into the washing machine. This disintegrated the absorbent cushioning and I was left with the waterproof outer layer.

At a real recycling unit, the cleaned materials can then be separated but I don't have the equipment to do this. Some of the recycled material after this process (like the pulp) would be of a slightly lower quality but as I could not simulate this I had to accept this as a limitation in my experiments.

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The SAP crystals were distributed in the pulp like fine granules with the occasional chunk. This meant separating out the SAP was extremely intricate and time consuming and it was impossible to remove all the SAP from the pulp

Eventually I figured out I could remove most of the SAP crystals by putting the pulp into a plastic bag and shaking it.

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Pulp layer (containing SAP crystals) from one nappy

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Pulp layer (containing SAP crystals) from one nappy

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SAP is known for its extremely high absorbency. To test this I used a pipette to drop water on this small amount of SAP crystals and observed the changes as I tried to completely saturate the sample.

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The particles expanded dramatically from sugar-like particles to what looked like water beads.

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Continuing to add water the gel expanded so much I had to move it to a larger container

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The substance continued to expand as more water was added and began to resemble jelly.

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The pulp was difficult to experiment on because it was basically impossible to remove all the SAP.

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The pulp was difficult to experiment on because it was basically impossible to remove all the SAP.

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I then wanted to test how heating the layers would affect the materials, and see if by melting the plastic, I could mould or combine it with different materials. First I heated the waterproof bottom sheet (polyethylene)

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I then wanted to test how heating the layers would affect the materials, and see if by melting the plastic, I could mould or combine it with different materials. First I heated the waterproof bottom sheet (polyethylene)

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In 200 degree fan oven for 8 minutes, the plastic shrunk dramatically, becoming thick and fairly rigid

Unlike the SAP and cotton and polyester samples, this did not elicit an extreme reaction. The most interesting thing about this sample being the "shrinkage".

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Heating the pulp in the oven like the plastic had no effect, this is unsurprising considering pulp is often used for insulation

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Attempting the same experiment with the cotton and polyester layer

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After only 5 minutes at the same temperature, the plastic had nearly disappeared, all that was left was hard yellow melted chunks and burnt fluff

According to user feedback, this sample was the worst. Aesthetically it looked "dirty" and "crusty" and reminded one indivdual of "burnt hair and rotten teeth".

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2nd attempt heating polyester+cotton layer

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2nd attempt heating polyester+cotton layer

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This time I compressed the material into an aluminium coffee capsule and grilled it over fire.
In this case the sample seemed to evaporate leaving only dust.

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I also tried heating the pulp over fire hoping that the more intense heat would have a result.

The pulp was slightly singed but again proved indestructible.

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Of all the samples this proved to be the favourite, reminding people of "gelli baffs" it seemed like a toy.

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After sharing my findings so far the group voted that the issue of recycling disposable nappies was more interesting

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After sharing my findings so far the group voted that the issue of recycling disposable nappies was more interesting

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Creating samples

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I struggled to come up with a way to make new samples from the materials that make up a nappy. Breaking down the nappy into its separate materials was time consuming and yielded small amounts of thin plastic, which would shrink and harden when heated, pulp, which also did not react well to heat and SAP crystals.

So in order to combine the materials without heating, I used a paper making screen

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To create each sample I blended the nappy materials I wanted to include with water and food colouring

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Once blended, the mixture was poured over the screen  and shaken as it sat at the surface of a pool of water. This allowed the mixture to disperse and left a flat sheet of material on the screen.

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The screen was then compressed to squeeze out as much water as possible.

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The finished screen would then be left to dry for a couple days until the sheet of material was dry enough to be peeled off.

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This sample was made from a thin mixture of pulp, shredded newspaper and blue food colouring to differentiate the sample. This sample was compressed as much as possible on the screen and as a result was thin and card-like but still soft and bendy.

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This sample was made of a thin layer of pulp. The sample was extremely soft and had a lot of holes

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Similar to sample 1, this was also made of pulp, shredded newspaper and blue food colouring. However this sample was much thicker and so was very thick and rigid, similar to an egg carton. The drying process for this sample took much longer than for sample 1. Like sample 1, it had an almost fluffy exterior.

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Similar to sample 2, this material is made exclusively from pulp but with added blue food colouring. In contrast to sample 2, this layer was made very thick and not compressed, this drying process took a few days, longer than any other sample. This sample was very soft but fell apart easily.

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Sample 4 was originally the same size as sample 2 but shrunk dramatically while drying.

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This sample was made from pulp, red food colouring and shredded polyethylene from the outer layer of the nappy. The sample was still flexible but had a crunchy feel due to the added plastic. The red food colouring only caused a slight pink tint in this sample.

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For consistency, sample pieces were cut from each material 2cm wide and 4cm long.

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For this experiment I secured the samples in a clamp up to the midpoint, leaving a 2cm length free. I then flexed the sample 90 degrees upwards or downwards and counted how many bends before the sample broke.

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Fatigue/flex to failure testing: Results

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Fatigue/flex to failure testing: Results

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(TOP)
Sample 1: thin blue pulp and newspaper
=88 bends to fail

Sample 2: white whispy pulp
=12 bends to fail

Sample 3: thick blue pulp and newspaper
=125 bends to fail

Sample 4: thick blue pulp
=10 bends to fail

(BOTTOM)
Sample 5: pulp and plastic
=27 bends to fail

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Fatigue/flex to failure testing: before and after

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Fatigue/flex to failure testing: before and after

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From top to bottom:
Sample 1: thin blue pulp and newspaper
Sample 2: white whispy pulp
Sample 3: thick blue pulp and newspaper
Sample 4: thick blue pulp
Sample 5: pulp and plastic

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The samples that contained newspaper were much more durable than those without. I had expected the other 3 samples to break almost immediately and was surprised by their strength. These samples had much more holes than the newspaper based samples and the tears originated from these gaps. I suspect that if these samples were more uniform they would have been quite durable in this experiment due to their flexibility.

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To test the affect of torsion on the samples I again clamped down the sample up to the midpoint, leaving a 2cm length free. I then used wire cutters to grip the free end of the sample and rotated each 180 degrees, photographing the effect.

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From top to bottom:
Sample 1: thin blue pulp and newspaper
Sample 2: white whispy pulp
Sample 3: thick blue pulp and newspaper
Sample 4: thick blue pulp
Sample 5: pulp and plastic

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The samples containing newspaper ripped much more easily than the other 3 due to their flexibility. The white samples had very little damage from twisting and therefore much more durable under torsion.

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To test the absorbency of each sample I used a moisture meter to measure the moisture levels before and after soaking and then removing each sample from 50ml of water.

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As the moisture meter only measured up to 33%, some samples do not have an accurate result but instead have a minimum increase in moisture levels.

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(TOP)
Sample 1: thin blue pulp and newspaper
= +12.8% moisture

Sample 2: white whispy pulp
= +18.2% moisture

Sample 3: thick blue pulp and newspaper
= +15.5% moisture

Sample 4: thick blue pulp
= at least +19.5%        moisture

(BOTTOM)
Sample 5: pulp and plastic
= at least +24.5% moisture

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From top to bottom:
Sample 1: thin blue pulp and newspaper
Sample 2: white whispy pulp
Sample 3: thick blue pulp and newspaper
Sample 4: thick blue pulp
Sample 5: pulp and plastic

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The pure pulp and pulp with plastic samples were the most absorbent. However, the results may have been affected by leftover SAP crystals in the samples. This is evident from the swelling of some samples which is likely caused by expansion of the crystals.

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To test the tensile strength of the samples, I duct taped the bottom and top centimeter, leaving a length of 2cm free. String was taped within this centimeter on both sides to get an even grip along the sample. The string was then thread through a plastic bag which I filled with nails of uniform weight until the sample broke.

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(TOP)
Sample 1: thin blue pulp and newspaper
=1.106kg to break

Sample 2: white whispy pulp
=130g to break

Sample 3: thick blue pulp and newspaper
=1.665kg to break

Sample 4: thick blue pulp
=156g to break

(BOTTOM)
Sample 5: pulp and plastic
=225g to break

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From top to bottom:
Sample 1: thin blue pulp and newspaper
Sample 2: white whispy pulp
Sample 3: thick blue pulp and newspaper
Sample 4: thick blue pulp
Sample 5: pulp and plastic

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The strength of the samples was surprising to me. The samples reinforced with newspaper were extremely strong. Again, I suspect that the samples not reinforced with newspaper would have been quite strong if it weren't for the holes that breaks originated from.

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To measure the thermal insulation  of the samples, I first filled a small Tupperware container with boiling water and made a hole in the lid to measure the decrease in temperature of the water every 10 minutes for an hour. I then repeated this experiment for each sample, covering the walls and bottom of the container with the sample material.

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From this experiment, it is clear that pulp had the most beneficial impact on thermal insulation as the samples with a higher proportion of pulp retained heat much more efficiently. The addition of plastic also increased the insulation of the sample.

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To get firsthand feedback on the samples, I gave them to my family and flatmates.