Are biobased materials the key to a more sustainable construction industry?

Besides its significant demand for energy, the built environment is also a large consumer of material resources.

These are mostly minerals (rocks, gravel, and sand), metals, and fossil oils used for plastic manufacturing. In developed economies such as the EU27, the construction sector is the largest single consumer of metals and uses more minerals than all other industrial sectors combined.[1] Indeed, minerals are essential for the modern building: from concrete, to bricks and stones, to glass, plaster and ceramics. But although they are abundant materials, they are not renewable and often require invasive and polluting processes for their extraction.

In the effort to reduce the environmental impact of construction, researchers and designers have turned their attention to biobased alternatives. Biobased materials are organic resources produced by plants and animals, such as timber or sheep’s wool. In the context of construction, biobased materials can have several benefits over conventional ones:

• They are renewable and can be sustainably produced over the long-term;
  
• They can naturally absorb carbon from the atmosphere during cultivation, thus positively contributing to climate change mitigation;
  
• They promise performance gains in terms of moisture absorption and breathability;
  
• They are generally less harmful to people and the natural environment in terms of pollutant emissions;
  
• They can be disposed of more easily and sustainably at their end of life.
  

Traditional and vernacular architecture across the world has always made large use of biobased materials available in the local environment. Nomadic peoples often relied on shelters made entirely of biobased materials, such as the Native American tepee or the Mongolian yurt. As humans adopted a more settled and sedentary way of life with the development of cities, architecture came to favour a wider range of minerals. Culturally, we have learned to associate bricks and mortar with stability, safety and prestige.

As the environmental impact of minerals, metals and plastic usage in the industry becomes clear, vernacular architecture can inspire us to re-evaluate the use of biobased materials. “Biobased” does not necessarily mean old-fashioned; building material research is increasingly focused on the development of innovative combinations of traditional materials. For example, lime, industrial hemp shives, cotton fibres and timber studs can be assembled into cladding panels[2] that have comparable performance to their conventional counterparts. Researchers are also developing new materials from non-conventional natural resources. Bioplastics can be produced from a variety of plants and are increasingly favoured by the packaging industry as well as in construction.[3]

With so many examples from nature to be inspired from, the potential for new products appears limitless. Mycelium – the vegetative part of fungi – is a particularly promising material. It only takes five days to grow mycelium boards and bricks in a mould filled with organic waste and infused with fungal spores.[4] The process happens naturally, and the only energy needed is a little heat to stop mycelium growth at the right moment. While mycelium bricks have lower compressive strength than conventional bricks, they are much lighter, and thus ideal for non-structural uses such as insulation and internal partitions.

Timber is probably the most commonly used biobased material in construction projects. Having left behind the typical modernist enthusiasm for concrete and steel, contemporary designers often choose timber for iconic architecture pieces – such as the Metropol Parasol in Seville, Spain. But the use of timber structure does not need to be confined to landmark buildings. Across the world, examples of medium-rise buildings with timber structures are increasing. In Paris, the Office in Wood building provides 17,000 m2 of space over nine storeys.[5] Designed by Baumschlager Eberle and SCAPE, the building rests on a bridge platform spanning over several railway lines. Given the need to limit the load on the bridge, a timber frame, 30% lighter than conventional concrete or steel, was the obvious choice. So far, the tallest timber-framed structure ever built is the Mjøstårnet office in Brumunddal, Norway, designed by Voll Arkitekter.[6] The building uses glued laminated timber to reach 85 meters of height, corresponding to 18 storeys.