Growing evidence for anthropogenic climate change has forced industries to work to reduce their greenhouse gas emissions. Several strategies have been explored in the construction industry of late, including making increased use of renewable energy, green manufacturing processes, and green building materials.
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The rapid increase in the world population and urbanization has led to the need for an unprecedented amount of building materials to construct domestic, commercial, and industrial buildings, and infrastructure such as roads, tunnels, and power stations. Concrete, steel, and glass are ubiquitous building materials in the modern era, but their manufacture uses vast amounts of raw materials and water and emits copious amounts of greenhouse gases per year.
Cement manufacture alone produces 622 kg of carbon dioxide per tonne of cement produced, with around four billion tons of cement produced annually. A staggering 8% of total global carbon dioxide emissions come from cement manufacture alone. Moreover, embodied carbon, which is carbon released over the entire life cycle of a building, including end-of-life material disposal, is responsible for 11% of total global carbon emissions. The impact of these “hidden” emissions is vast.
Several conventional and innovative green building materials are increasingly being explored to reduce the impact on the construction industry. Here are some traditional and state-of-the-art green building materials that are helping to improve sustainability in the construction industry and reduce its carbon footprint.
Wood has been used for millennia as a construction material. The use of reclaimed wood utilizes waste streams and can be easily sourced from construction sites, retired barns, pallets, and salvage yards. This material saves virgin resources and reduces landfill usage. Reclaimed wood is useful for structural framing, flooring, and cabinetry. Reclaimed wood is lightweight but has drawbacks, including reduced strength and treatment and reinforcement needs.
Bamboo is an incredibly fast-growing and carbon-neutral building material. This perennial grass grows in many parts of the world and continues to proliferate without the need for replanting. Bamboo possesses a high strength-to-weight ratio, is long-lasting, and has greater compressive strength than concrete or brick. Useful for flooring and cabinetry, one drawback is the need for treatment to avoid rot, water absorption, and insect infestation.
Another ancient material, rammed earth, is a long-lasting green material. It has benefits for use in foundations, floors, walls, and can be pressed into wooden frames to produce a building material similar to concrete. Walls and floors constructed from rammed earth can be used as natural thermal storage, being warmed by the sun in the daytime and releasing their heat in the evening when it is cooler.
Rammed earth buildings contain vastly reduced amounts of embodied carbon than traditional concrete buildings and can be strengthened by the use of bamboo or rebar.
Recycled plastic can be used for several purposes in building projects, such as flooring, roofing, and windows. Utilizing plastic waste reduces the environmental impact of both the construction industry and the plastics industry, reducing landfilling and helping to mitigate greenhouse gas emissions. Recently, several innovative studies have explored the incorporation of polymeric materials into concrete as aggregates, reducing carbon emissions and improving its mechanical and chemical properties.
Reclaimed and Recycled Steel
Steel has the advantage of being 100% recyclable, and the use of reclaimed and recycled steel significantly reduces energy demands and carbon emissions. Possessing sufficient mechanical and physical properties even after re-processing, recycled and reclaimed steel can be used for structural framework, roofing, facades, and foundations and is an incredibly long-lasting construction material.
HempCrete is an innovative green material that uses hemp, a natural and sustainable resource and carbon sink, to construct a concrete-like material. The hemp plant’s woody inner fibers are combined with lime to construct renewable, carbon-neutral, strong, and lightweight blocks that reduce transportation costs and energy. The material is fire-resistant and has good acoustic and thermal insulation properties.
Similar to Hempcrete, Timbercete makes use of renewable and CO2-neutral resources to produce a green concrete-like material. Timbercrete uses sawdust, a valuable waste material produced by the construction and carpentry industries, to replace a proportion of the energy-intensive materials used in traditional concrete manufacture. It can be used to create bricks, blocks, and paving slabs.
Mycelium is the root structure of fungi. This natural material makes use of a valuable waste stream from the agricultural and food industries to create a green, sustainable, and low-carbon building material. Composites of mycelium and pasteurized sawdust are strong and lightweight and can be shaped into a multitude of shaped bricks for different construction purposes. Able to withstand extreme temperatures, mycelium-based composites can be used as green insulation and fire-resistant concrete alternatives.
Another innovative green building material, Ferrock is a relatively new addition to the sustainable toolkit of the construction industry. Waste industrial materials such as ferrous rock and steel dust, which would otherwise be sent to landfills, are used to manufacture a concrete-like building material with superior strength.
In the drying and hardening process during production, carbon dioxide is trapped and absorbed, making the material carbon neutral. This innovative green material can be mixed and poured like traditional concrete to produce structures, pathways, flooring, and construction elements like staircases. Research has indicated that Ferrock is extremely weather-resistant, making it a hard-wearing construction material.
With the environmental impact of the construction industry becoming clearer, the drive toward net zero in the sector is accelerating. Green building materials are becoming a hot button topic in the construction industry and provide an innovative, forward-thinking solution to reducing the carbon footprint of the industry whilst providing new materials that perform as well as or better than traditional building materials.
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References and Further Reading
International Code Council (2022) Embodied Carbon in Buildings and Building Materials [online] iccsafe.org. Available at: https://www.iccsafe.org/advocacy/embodied-carbon/
Kukreja, R (2022) 15 Sustainable and Green Building Construction Materials [online] conserve-energy-future.com. Available at: https://www.conserve-energy-future.com/sustainable-construction-materials.php
Clark, T (2021) Cement: how its carbon impact can be reduced [online] constructionnews.co.uk. Available at: https://www.constructionnews.co.uk/sustainability/carbon-cementing-net-zero-22-11-2021/