Biochar as a Building Material
Two of biochar’s key properties are its low thermal conductivity and its ability to absorb water up to 5 times its weight. These properties mean that biochar is just the right material for insulating buildings and regulating humidity. In combination with clay, but also with lime and cement mortar, biochar can be used as an additive for plaster or for bricks and concrete elements at a ratio of up to 80%. This blending creates inside walls with excellent insulation and breathing properties, able to maintain humidity levels in a room at 45 – 70% in both summer and winter. Not only does this prevent the air inside the rooms from becoming too dry which is a potential cause of respiratory problems and allergies, but it also prevents condensation from forming around thermal bridges and on outside walls which could lead to the formation of mold.
Biochar-clay plasters adsorb smells and toxins, a welcome property in kitchens and for smokers. Alongside their use in housing, biochar-mud plasters are particularly well-suited for warehouses, factories and agricultural buildings as well as in schools, universities, hospitals and other buildings frequented by many people. Improved indoor climate, it can be assumed, has a positive effect on one’s ability to concentrate, a welcome property in meeting rooms, libraries, offices and classrooms. In addition, biochar is a very efficient absorber of electromagnetic radiation resulting from the use of both wireless technology and electricity.
Through the use of biochar-based insulation material, houses can become very long-term carbon sinks, while at the same time providing healthier indoor climate. And should such a house be demolished at a later date, the biochar-clay or biochar-lime plaster can be directly used as a compost supplement, thus continuing the carbon cycle in a natural way.
At the Ithaka Institute and with several partners like the Hochschule Rapperswil or the Swiss Federal Laboratories for Material Science, we are currently working on measuring and improving the material properties of biochar based building materials including lightweight biochar-concrete panels, biochar-lime bricks, indoor and outside insulating plasters or wall paper and tile adhesives. With wet bulk densities under 1.2 g/cm3 and partly under 1 g/cm3 and a compressive strengths around 20 N/mm2, this very exciting, highly functional lightweight material will soon be making its appearance! When using cement and lime, sand can be completely replaced by biochar reducing the weight of the material by factor 5.
We continue to work on optimizing both the product and the application methods and are developing different demonstration projects in Europe, North American and the developing world. Our intention is to identify partners in the green building materials industry to help deploy this exciting new material and to pair them with local or regional biochar producers to ensure appropriate biochar quality and to support the biochar industry as a whole in a sustainable manner. For enquiries about partnering on demonstration projects or rolling out our biochar based construction materials and methods, please contact the Ithaka Institute.
For more information see the articles in the Ithaka Journal: The use of biochar as building material and Biochar as building material for optimal indoor climate.