I have been familiar with biochar as mainly an agricultural soil amendment that helps provide habitat for beneficial microbes and sequesters carbon in the ground. It hadn’t occurred to me that it could also be used as a building material, until a reader suggested that I check out this article at www.biochar-journal.org
Biochar is a highly porous material produced by heating biomass to a temperature of 400 – 800°C under the absence of oxygen, a process called pyrolysis. The resultant material has countless tiny pores which have the ability to store water or trap large quantities of air, which makes it one of the best natural insulation materials. Biochar also allows buildings to be turned into carbon sinks.
In combination with clay or lime, biochar can be used as an additive for plaster or for bricks at a ratio of up to 80%. This blending creates walls with excellent insulation and breathing properties, able to maintain humidity levels in a room at 45 – 70% in both summer and winter. This prevents inside air from becoming too dry or condensation from forming around thermal bridges and on outside walls which could lead to the formation of mold.
Should such a house be demolished later, the biochar-clay or biochar-lime plaster can be directly used as a compost supplement, thus continuing the carbon cycle in a natural way.
Biochar-clay plasters adsorb smells and toxins and are very efficient absorbents of electromagnetic radiation resulting from the use of both wireless technology and mains electricity.The biochar-clay mixture is not irritating to the skin of those applying it, meaning that gloves and protective clothing are not needed.
Tests to produce biochar bricks using cement, lime or mud as a binder are very promising. Sand can be completely replaced by biochar reducing the weight of the material by factor 5, allowing the bricks to actually float in water.
With al of these positive qualities I predict that biochar will find increasing uses as a building material.