Building with waste: transforming excavated earth into architecture

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  • Nowadays, the understanding of our building culture and the application of local construction methods may seem like a distant and obsolete concept given the role of industrialization and globalization in the construction industry.
  • We can now obtain almost any material from around the globe just by searching the internet for a distributor in our region.
  • But this practice has important implications for our society, from the loss of architectural identity to environmental costs related to high CO₂ emissions associated with the processes of extraction, manufacturing, transportation, and disposal of these materials.

The increasing global need to reduce our carbon emissions and use materials in more efficient ways has led us to research and learn about the origin of our region’s resources, eventually leading to better understanding their applications within a circular economy approach. But why not look right under our feet? Soil is one of the most common materials on the planet, and when it is locally sourced, it does not generate considerable amounts of embodied CO₂.

It seems that after industrialization, we have forgotten that building with earth was for many years a viable construction method for our ancestors in different parts of the world. We spoke with Nicolas Coeckelberghs, one of the four founders of BC Materials, a worker cooperative based in Brussels that has been working with earth, rediscovering its use, and sharing its knowledge on a global scale while working with a local conscience.

Building with earth in different regions

Using local materials has a clear ecological but also economic purpose. In countries where industrialization took place with reduced intensity, this practice makes sense given the high costs of industrialized materials such as concrete, cement, and steel, which usually have to come from abroad. An example is the Library of Muyinga project developed in the Eastern Africa region by BC Architects —a parallel practice to BC Materials— where a construction process involving both end-users and second-hand economies was conceived. The library was built with a participatory approach using locally sourced compressed earth blocks and local labor.

Onsite brick making for the construction of the library of Muyinga. Image Courtesy of BC Architects

The fieldwork in the region and the surrounding provinces allowed the team to learn about local materials, techniques, and construction typologies to subsequently build the first library in Muyinga, part of a future inclusive school for deaf children. This approach of studying local techniques and typologies was also applied in the North African region, where locally sourced natural stone foundations, adobe walls, and a flat roof of wood and earth were used to build a Bioclimatic Preschool.

Although the use of earth may seem similar in different contexts, according to Coeckelberghs, “you need to understand your building’s culture.” The approach to earthen construction changes depending on the region where it is developed. In contrast to the examples from Africa, it highlights BC Materials’ work in Brussels that, like other European capitals such as Paris and Geneva, has large amounts of soil extracted from excavations, which are seen as waste.

These massive amounts of “waste” represent an opportunity considering that, according to Nicolas, “70% of the soil in Brussels is usable, and the remaining 30% is not because it is mixed with other materials.” The vastness of materials available in Brussels shows that building with soil is not only viable in less industrialized countries but also in regions with large amounts of resources that are seen as waste.

Regional House Edeghem. Image Courtesy of BC Architects

An example is the Regional House in the city of Edeghem, which used only two construction techniques for the building’s superstructure: compressed earth blocks from local clay and an insulating façade and roof system of apparent hemp concrete as a finish, making the building CO₂ negative.

For this project, 19,000 blocks were manufactured in a 3-week workshop, and 312 m² of hemp concrete was installed in a 2-week workshop. In total, more than 150 volunteers learned with this project, making the Regional House reflect an educational and ecological approach through a radically sustainable and participatory architecture.

Adapting the technique to the context

The vastness of the materials available in cities like Brussels is nevertheless faced with the challenge of labor costs. In contrast with the lower price of labor in other regions, building this way in Europe means that even if ecologically wasteful construction makes sense, economically, it might not. But the reality is that with the right processes, earth can be an environmentally friendly and economically viable material when working with local actors and adapting the technique to the context.

Under the premise of adapting contextual characteristics, BC Materials collaborates with a factory that normally focuses on the mass production of concrete blocks to allocate a fraction of their production time to the manufacture of Brickett, a compressed earth block (CEB) used for masonry walls. The impact of this collaboration is enormous, as according to Coeckelberghs, “In one day of production through this process, it is possible to produce the same amount of blocks that could be produced in a year with small machines.”

Brickette. Image Courtesy of BC Materials

By combining knowledge of earth-building material production techniques and the advantages of mass production, “It was possible to reduce the price of CEB by 200%, making it economically competitive versus concrete blocks and the traditional fired bricks that are widely used in Belgium,” notes Nicolas. Regardless of whether the earth is treated by manual techniques, as in Burundi, or locally approached industrial processes as in Belgium, building with earth represents a social-economic impact and an environmental impact on carbon emissions.

Earth itself is not the solution to everything

If building with earth represents diverse and vast benefits, why isn’t it being used to erect entire buildings? One of the keys is “using the right material in the right spot,” says Coeckelberghs. Contemporary needs require diverse materialities that combine wood and reused materials, and given the nature of earth, it performs best when it is not outdoors, so it is used extensively in interiors in the form of walls, cladding, or flooring.

Library of Muyinga. Image Courtesy of BC Architects

The reality is that even though earth-based materials have diverse applications and can reduce the impact on the environment by up to 5 times, there is no real demand for earth-building materials. That is why BC Materials is working on different fronts: training students and contractors on earth-based materials, studying standards and codes on earth construction, researching new products, and applying existing ones in BC Architects’ projects, to create a real demand that competes with traditional materials.

The need to continue building to accommodate the world’s growing population will probably not cease, but what may change the paradigm is our way of collaborating with the industry and our conception of good architecture, thinking first about the benefits that a particular material can bring, rather than purely prioritizing aesthetics. Otherwise, as Nicolas points out, “We will need another planet before we can provide a roof for everyone.”


This article was first published in ArchDaily and is republished with permission.


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