Biochar

Biochar is seen by many scientists and policy makers as a promising solution for climate change mitigation and adaptation. Some even argue that biochar is a so-called fast mitigation measure – one that can achieve deep, early reductions of greenhouse gases. Biochar is a fine grained, charcoal-like product obtained when biomass is heated in a closed container with limited supply of air. The method is called pyrolysis.

The biochar is then applied to soils. This becomes a climate mitigation measure since the carbon will stay in the soil for hundreds to thousands of years. New plants will grow and absorb CO₂ and one can speak of a carbon negative cycle; removing CO₂ from the atmosphere and putting it in the soil. Adding carbon to soil has several benefits; it retains water and nutrients which leads to increased yields and plant growth. It also reduces emissions of nitrous oxide - a greenhouse gas that is released from farmland, and some trials show that the use of biochar in agriculture could reduce the need for artificial fertilizer. Adding carbon to soil is nothing new, deep in the Amazon there are layers of very fertile, carbon rich soils that were produced by ancient human settlements dating back thousands of years. It seems that these settlements lived off the land by “slashing and charring” biomass out of the forest as opposed to the “slash and burn” method which is not sustainable but damages the forest and climate. Today there are pilot projects in Africa that produce biochar from agricultural waste that would otherwise release greenhouse gases when it decomposes. 16 African and Latin-American countries, as well as Australia, have made submissions to the UN’s climate panel to include biochar in a post-2012 climate agreement. Biochar may hold a huge potential; some scientists have estimated as much as one gigatonne of carbon can be stored in soil annually. However, many unanswered questions remain, like for example how long the carbon remains in the soil.