Biochar is a well-established technology that Swedish botanist Carl von Linné described as long ago as the 18th century. Properly produced, biochar is stable for several hundred years and can be bound in the soil, while increasing the growth of other biomass by improving soil quality.
In collaboration with Stockholm Vatten och Avfall and the City of Stockholm, we operate a biochar plant in Stockholm. The site includes a state-of-the-art charcoal kiln where biomass in the form of garden waste is heated without oxygen, which means that the charcoal remains instead of being fully burnt and forming carbon dioxide. The process generates heat which we recycle into the district heating network and distribute to Stockholmers.
The project is partly funded by Bloomberg Philanthropies through prize money in the Mayors Challenge innovation competition.
Garden waste is obtained from Stockholmers who leave it at one of Stockholm Vatten och Avfall’s recycling centres. Biochar is then buried in parks and gardens to improve the quality of the soil and bind carbon in it. This currently creates a very small carbon sink, but the technology is now in place and can be scaled up.
Our existing plant can handle around 15 per cent of Stockholm’s garden waste. We are working on expanding this anount with more biochar facilities.
Currently, biochar is mainly seen as a way of improving soil quality, but extensive research is being conducted into biochar internationally, for example because it can, among other things, reduce emissions caused by meat production, while at the same time becoming a component of natural fertilizer. There are several other possible uses, including filler in concrete, as filter materials, or as additives in animal feed.