In a time of increased awareness of the need for a circular economy, both environmental and economic impact of material has been raising. According to a Nielsen report, '66% of global consumers say they’re willing to pay more for sustainable brands'. In the meantime, the increasing demand for environmentally friendly production with low emissions can be leveraged into a profitable business strategy. This is evident in the rampant method of ‘greenwashing’, which uses public sentiment about the environment to create an environmentally friendly brand for marketing purposes.

‘Being 100% sustainable is often still a challenge' [1], however. In the furniture design industry, construction materials such as timber, steel, concrete, stone, and synthetics are widely used because of their durability and ubiquity. With the exception of wood, however, it is not easy to adapt these natural alternatives in ways that would satisfy the qualities of durability and ease of working. While many designers increasingly use sustainable materials, including recycled materials, natural alternatives and biomaterials still require mixing with synthetic binders and reinforcing agents, such as epoxy resin, plasticizers, and alginate. In addition, biomaterials, which spoil easily, are not suitable for products intended for day-to-day use.

Mollusk industry is advocated as a highly sustainable food source and may play an important role in future food security globally. With the increasing demands worldwide, it is timely to appraise all aspects of this industry when considering its expanding role as a food source [2].

Contamination of the ecosystem by waste shells is one of the major problems. Statistical data shows that mollusk shells contribute more than 7 million tons of ‘nuisance waste’ discarded every year, most of which is dumped in landfills or the ocean. For instance, in the UK, landfill disposal costs up to £100 per ton, but this is unavoidable way to deal the bulky waste. The rock-state shell waste does not corrode, and over time, during microbial decomposition, this waste develops very toxic gases, such as NH3 and H2S [3] (fig1).

(fig1)

The world’s first reported public health case related to oyster residues was made known by the South Korean oyster farming process in the early 1980s. The government, alarmed with the state of public health, financed a project to define new strategies for recycling oyster shells. As part of this program, factories for calcium and fertilizers production were created to increase the number of recycled oyster shells [4]. Moreover, European Union has vigorously enforced the development of new technologies that exploit shell waste as resources and contribute to the concept of sustainable development. However, only 30% of waste oyster shells are reused by companies globally. In this regard, recent trends in shell waste applications have been reviewed, as creative ideas for reducing the waste [5].

The 30% oyster shell recycling system also has problems. The largest proportion is reused for substantial fertilizer and lime and the method has its own difficulties as well. First, it is not easy to develop a reuse system because of the enormous number of shells generated every year. Second, customers often return the fertilizers recycled from oyster shells because, after recycling, the fertilizer still contains salt. (The shells are fired at a relatively low temperature of under 900 degrees.) Third, the high cost of firing seashells for making calcium (lime) exceeds its sold price, which causes continuous financial deficit. The annual deficit for reprocessing shells into 'limestone substitutes' totals about £1,322,796.

If the problem with recycling oyster shells is the method’s high processing cost and its comparatively low profits, one may expect that the system could create fair profits by adapting new value for the material, used for high value-added industries. The contemporary design furniture industry could be a significant part of this approach.

Most of shell valorization strategies are established in areas that generate large amounts of shell waste, i.e., where mutually beneficial partnerships have been established between shell producers and other industries (Morris et al., 2019). This project aims to create the new value for oyster shells as well as a circular system of waste in London by collaborating with local restaurant 'Wright Brothers Ltd.', a seafood restaurant with five locations across London, which donates their waste oyster shells (fig 2).

(fig 2)

Knowledge of natural processes dictate that oyster shells can be transformed into calcium carbonate [CaCO3], calcium oxide [CaO], calcium acetate [Ca(C₂H₃O₂)₂], and calcium hydroxide [Ca(OH)₂]. In terms of design methodology, some experiments have proven the value of this material as a.) light weight, b.) durable, c.) waterproof, d.) preservable and versatile, e.) colourless and odourless, and f.) alkali.

To enable the shells to obtain higher durability and waterproof surfaces with only natural methods (fig 3), I adopted a traditional technique called Tadelakt, which Moroccan artisans have practiced and taught to young apprentices as an ecological job. This method enables An experiment conducted with three different shell conditions—normal oyster shell piece (rock state), polished shell Tadelakt (calcium acetate), and unpolished shell Tadelakt has proven its waterproofing property in seawater pH levels. In the test, the clay, which was not treated with the Tadelakt method, was biodegradable in water, unlike the material in the other two conditions, while Tadelakt-treated material was completely waterproof during the 1-month test period.

(fig 3)

The property of shell Tadelakt can be used to reduce soil and water acidification. Compared with general oyster shell reuse fertilizers, which contain residual saltiness due to low fire temperatures, this shell Tadelakt is without saltiness as long as it is fired at more than 1,100 degrees. These experiments have proven that this material is durable, long-lasting, yet lightweight and can be utilized in a wide variety of applications, such as accessories and furniture. Moreover, once it is artificially broken or sanded, exposing an unpolished inner surface to strong moisture, the shell material naturally begins to degrade. Lastly, when it returns to nature, it acts as a useful substance to neutralize acidified soil.

[1] Marieke Eyskoot (2019) ‘This is A Good Design: for A Sustainable Lifestyle’, BIS Publishers, Amsterdam, the Netherlands

[2] James P. Morris (2018) ’Shells from aquaculture: a valuable biomaterial, not a nuisance waste product’, Reviews in Aquaculture / Volume 11, Issue 1

[3] Thamyres H. Silva et al. (2019) ’The Potential Use of Oyster Shell Waste in New Value-Added By-Product’, Resources 2019 v.8 no.1, ISSN: 2079-9276

[4] Yang, E.-I.; Yi, S.-T.; Leem, Y.-M. (2005) ‘Effect of oyster shell substituted for fine aggregate on concrete characteristics: Part I. Fundamental properties’. Cem. Concr. Res. 2005, 35, 2175–2182. [CrossRef]

[5] Mihajlo JOVIĆ et al. (2019) ’Recent trends in application of shell waste from mariculture’, Studia Marina 2019, 32 (1): 47-62

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