Sustainable, Carbon-Neutral Construction Using Biobased Materials

The construction industry plays a significant role in global carbon emissions. This issue has led to a growing interest in sustainable, carbon-neutral building materials. This paper reviews the potential of biobased materials such as hempcrete, biochar-enhanced concrete, timber, clay, cork, etc. in lowering the environmental footprint of construction. Hempcrete, a composite of hemp shiv, lime binder, and water, offers excellent insulation, thermal efficiency, and breathability. Its ability to absorb CO<sub>2</sub> during its life cycle makes it a carbon- negative material. However, it requires a structural frame due to its low mechanical strength. Biochar, derived from biomass through pyrolysis, is another sustainable material. It enhances concrete’s mechanical strength, durability, and thermal performance while significantly reducing its carbon footprint. By using biochar in appropriate amounts, concrete can store CO<sub>2</sub>, making it a more sustainable alternative to traditional cement-based construction. A case study of a four-story CO<sub>2</sub>-neutral residential building in Windau, Switzerland, demonstrates the successful application of these materials. Biochar-enhanced concrete, prefabricated timber structures filled with hempcrete, alongside with other biobased materials such as clay, cork, and straw are used for constructing this building. This innovative hybrid construction reduces carbon emissions and enhances energy efficiency. The building follows a plus-energy concept which means it generates more energy than it consumes through passive solar heating, smart ventilation, and intelligent energy management. The combination of high thermal mass materials and strategic design choices minimizes heating and cooling demands. Material reuse and sustainable energy solutions ensure a net-zero carbon emission over its 60-year lifespan. Additionally, the building’s energy-efficient design significantly decreases energy costs for its residents.