Biochar Plaster and Biochar Bricks

Biochar, a highly porous material produced from plant waste, is mostly used in agriculture as a soil conditioner, in livestock farming as a feed supplement, and in metalworking as a reducing agent. The latest developments at the Ithaka Institute are now focusing on its use as a building material.

Why? As well as having excellent insulating properties, improving air quality, being able to soak up moisture and protect from radiation, biochar also allows buildings to be turned into carbon sinks. Every tonne of biochar used in a building’s envelope means that the equivalent of more or less one tonne of CO2 is prevented from re-entering the atmosphere.

Biochar plaster can be applied to walls of a building using standard plaster spraying or rendering equipment. Applied at a thickness of up to 20 cm, it can be a substitute for Styrofoam insulation. Through the use of biochar-based insulation material, houses can become very long-term carbon sinks, while at the same time providing a 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.

Such 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 suited for warehouses, factories and agricultural buildings as well as in schools, universities, hospitals and other rooms frequented by many people. It can also be assumed that an improved indoor climate has a positive effect on one’s ability to concentrate, for instance 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 mains electricity.

How to make biochar-clay plaster
The biochar-mud mixture contains 50% biochar, 30% sand and 20% clay. This mixture can be used both for spray plastering and for conventional throw-on techniques. For the bottom and intermediate plaster layers it is recommended to also use larger-dimensioned pieces of biochar (diameter < 25mm), as this makes the plaster less likely to crack. To a great extent on account of the char, such plaster dries evenly and relatively quickly, with the result that – depending on a layer’s thickness – a further layer can be applied within 12 – 24 hours. Biochar bricks and concrete First tests to produce biochar bricks using cement, lime or mud as a binder are very promising. With wet bulk densities under 1.2 g/cm3 and partly under 1 g/cm3 and a compressive strengths around 20 N/mm2, it would seem that a 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 (samples float in water). Read the full article at the Biochar Journal
The Ithaka Institute is an international open source network for carbon strategies. It is a non-profit research foundation with the Headquarter in Europe having independent offices in the USA, Nepal and Australia. In the last decade, Ithaka became a leading research collaboration for carbon sequestration and cycling through agronomic methods. The Institute is known for its expertise in production, post-production treatment and use of biochar. Ithaka established the European Biochar Certificate and developed numerous biochar based products. We are engaged in several food security, soil fertility and reforestation projects in Eastern Asia.

The Ithaka Institute offers carbon intelligent solutions including the use of carbon-positive building materials, increased biomass production in the urban environment, fostering biodiversity, improving green water cycles and promoting carbon recycling.

Thanks to Aaron for this tip.