The concept of upcycling refers to taking an item that would be considered waste and improving it in order to make it useful again, adding value and new functionality to it. This is a common word in several industries, such as fashion and furniture. In civil construction, this concept can also be incorporated, making the waste generated by the industry itself recirculate or even bringing what would be discarded from other industries to be processed and incorporated into constructions. This is the case of transforming agricultural waste into building materials, bringing a new use to discards, reducing the use of raw materials and creating products with excellent characteristics.
Rethinking the current linear economic model - where production is directly linked to the extraction of natural resources and disposal at the end of its useful life - has been a prominent topic among the debates around a more sustainable future. According to the principles of the Circular Economy, organic waste from cities and the countryside could be diverted from landfills, irregular disposal or incineration to become raw material for the creation of products before being fed back into the biological cycle at the end of their useful life.
This includes the reuse of corn cobs, sugarcane bagasse, rice straw, wheat and soy, peanut husks, bananas, sunflower seeds, cellulose, and many others, depending on the culture of the place. Constructions using straw have already been explored in this article, where leftover grain production, usually wheat, rice or barley, can be bundled together to create highly efficient seals and insulators. Several studies and experiments have been carried out with this agricultural residue, qualifying it as a potential material for the construction of walls, with good thermal, acoustic and even structural characteristics.
In regions closer to the tropics, for example, a product whose waste occupies a significant space is coconut. Its fibers, whether ripe or unripe, have several uses. They can be added to concrete mixes or, in some cases, become cement soil brick reinforcement. This is the case of this scientific research in the northeast region of Brazil, whose purpose is to meet the demand for new constructions in low-income communities and increase the production of an alternative brick reinforced with coconut fibers, capable of contributing mainly to the recycling of green and ripe coconuts in urban and rural landfills. Coconut fiber can also be used as a thermal insulator, as at Casa Parasita, by El Sindicato Arquitectura, where a 12-centimeter layer was used between the external metal sheets and the OSB interior finish.
But waste doesn't have to come just from the earth in order to be upcycled. Waste from mariculture in southern Brazil has the potential to be used as an aggregate in the production of concrete, to avoid depositing it in sandbanks and by the sea or on any piece of land. The material replaces a large part of the sand and concrete used to produce the blocks, making them lighter than the common ones and with better acoustic results. Another example comes from Mexico, where trials of using the agave left over from tequila production to produce wood substitutes have been conducted.
The Filipino-Ghanaian architect Mae-Ling Lokko developed comprehensive research on the concept of Agrowaste design or “design with agro-waste” and the use of these biomaterials in architecture. As Marília Matoso writes in her article on the topic, “This has the potential not only to close gaps in the product lifecycle, but also to boost forms of generative citizenship through upcycling.”
In addition, there is several academic researches that demonstrate that the reuse of agricultural-based waste helps not only to face the problem of pollution caused by the exploitation of conventional construction materials, such as cement, but also the environmental concern of disposing of waste in landfills. These created materials can also have commercial viability and characteristics that allow them to be compared to any other traditional product. In 2017, the global engineering company ARUP developed a comprehensive survey of the possibilities of processing agricultural waste as efficient construction materials. Titled “The Urban Bio-Loop: Growing, Making and Regenerating”, it lists the main uses as:
- Partitions and internal finishes: flat plates - with decorative layers when necessary. Various organic waste streams can be used for applications, such as bagasse, pulp, seeds, stalks or peanut shells. These products are generally characterized by low specific weight - therefore, they are easy to handle - and are sufficiently rigid to guarantee adequate resistance to impacts.
- Furniture: Natural fibers and small residual particles can be molded into complex shapes for chairs, tables and more generally for any interior application. A variety of surface finishes provide strong aesthetic appeal.
- Sound absorption: materials with high porosity – such as biofoams – can be obtained from soybean residues. In addition, fibers of different types can be combined to create insulation material with good sound-absorbing properties.
- Thermal insulation: various natural fibers obtained from agricultural harvest can be used. These provide low thermal conductivity and some of them are characterized by the good performance of spruce and are water repellent, such as potato skins and cork.
- Rugs and carpets: based on a wide variety of natural fibers, such as those obtained from banana or pineapple harvest residues, and other flexible, strong and light fibers.
- Envelope Systems: To some extent, natural fibers can be combined with biopolymers to obtain rigid end products that can be used for both indoor and outdoor applications.
The materials can be used almost raw, with little processing, as is the case with the sugar cane straw that covers the roof of The Green Island Community Center in Thailand. In the project by LCA Architetti and luca compri architetti, ecological materials play a leading role. According to the responsible architects, “nature guides the choice of construction materials: wood for the basic structure, rice straw and cork as insulation; the interior finishes and furniture are in stone and oak wood.”
Flax, for example, can be used to create thermal insulation, as in the case of the Hemma House, by stek architecten, but it can also form boards, such as those used in the construction of the Vasterival Case Study Houses.
The Biological House project in Denmark brought attention to the waste products of the agricultural industry such as sheep's wool, grass, straw and seaweed, transforming them into valuable building materials. The house is almost completely biodegradable and has minimal environmental impact. Its main function, however, is to demonstrate how the incorporation of waste can create aesthetically interesting and, above all, high-performance buildings.
Considering the possibilities and supporting research and experiments on Circular Economy and the reuse of waste to an industry as large and voracious for natural resources as civil construction can be a good way to meet global sustainability goals and seek a more environmentally friendly future.
