Cement and steel are very carbon-intensive materials. Cement, the key ingredient of concrete, is responsible for 8% of global greenhouse gas (GHG) emissions. The production of cement also contributes to the emissions of nitrogen oxides, sulphur oxide and heavy metals. Cement industries have been linked to increases in respiratory diseases resulting from particle emission during production, as well as during construction itself. Meanwhile, the extraction of sand, gravel and limestone for concrete, and iron ores for construction metals, have a major landscape impact and lead to loss of biodiversity. In The Gambia, 20% of all material use relates to construction, and over 50% of construction materials stem from finite extraction. The import of construction materials and metals constitute 24% of imported embodied carbon—as demonstrated in a metabolic analysis by UNDP and Shifting Paradigms. Additionally, the extraction of sand and gravel to produce concrete threatens forest stock, including community-managed forests on which valuable livelihoods depend.

Soil is a very old construction material and, by integrating clay and natural fibres as stabilisers, soil-based building can last for centuries. Earthwork Construction is a construction company in The Gambia which uses compressed earth bricks. Historically, The Gambia relied on mud, stone, thatch and compressed earth for building construction, which have a low carbon footprint. To date, 51% of buildings in The Gambia are still built from mud, stone and compressed earth. To make them water resistant and stable, these materials are often mixed with cement, lime bitumen or fibres. While some of these materials are natural and sustainable, others are not.

Similar initiatives have emerged in nearby Senegal where Worofila, a design collective, uses modern design to revive earth-based construction methods, often applying a combination of clay and reed. Elementerre is a Senegalese construction company, which also relies primarily on locally sourced construction materials, such as earth.

According to ARUP, a global collective of designers and sustainability consultants working towards sustainable development, sustainable materials and circular material flows can help reduce the impact of construction on eight of the nine planetary boundaries. This highlights how the linear use of carbon-intensive construction materials plays a huge role in our transgression of planetary boundaries. Another benefit of locally sourced, sustainable construction is that it can make comfortable housing affordable and accessible to more people. The extent to which earth- and bio-based construction can lower concrete and steel related emissions depends on how often these materials can be substituted. For some applications, the material qualities of concrete are hard to match—in infrastructure, for example. However, for many less demanding applications, like buildings, local alternatives exist. Prioritising locally sourced construction materials can help reduce the impact of production and transport of construction materials, and construction itself.

Photo by Mufid Majnun from Unsplash.