Biochar is defined as the black carbon material produced from the thermal decomposition of biomass in a low or zero oxygen environment (i.e. pyrolysis or gasification). When biomass is converted to biochar, it is much more stable than uncharred organic matter, having a potential soil residence time in the order of thousands of years. Consequently, biochar is considered a method of long term storage of carbon in soils.
Importantly, the addition of biochar to soils can bring many potential co-benefits. Biochar incorporation can act as a soil enhancer, improving agricultural productivity, particularly in low-fertility and degraded soils. It can improve soil water and nutrient holding capacity, which means less dependence on artificial fertilizers. The production of biochar via pyrolysis or gasification also means the production of bioenergy as electricity and/or heat, which can be translated as further potential for carbon abatement from avoided fossil fuel use. This combination of factors means that biochar has been labeled as carbon negative mitigation technology by many.
Interest in the benefits of adding biochar to soils has arisen through studies of terra preta (Portuguese for dark earth) soils found in the central Amazon basin, where soils amended with, among other things, charred animal and plant remains, show much higher fertility and more water and nutrient retention than adjacent soils. Subsequent studies have shown that addition of biochar can increase crop yield, on average by 10% but more in the case of addition to very poor depleted tropical soils. Application of biochar to agricultural soils could therefore decrease dependency on fertilizers. There is also emerging evidence that biochar can suppress emissions of methane and nitrous oxide from soils, in addition to reducing nitrate leaching (a major problem in heavily fertilized agricultural regions).
Although biochar has huge potential for carbon sequestration, there remain many uncertainties regarding its long-term storage, and how to control production conditions to maximize specific properties. Current research has shown that biochar soil residence time differs with different biochar and soil types. It is also important to fully understand how it enhances soil quality. According to a recent study, biochar could offset 1.8 billion tonnes of annual carbon emissions by its most optimistic scenario without endangering food security, habitat or soil conservation. This would equate to a potential 12% of global greenhouse gas emissions that could be offset by the use of biochar.
Biochar research is still in its infancy and the 15-person strong UKBRC team based at the University of Edinburgh is tackling these fundamental questions. The UKBRC has recently published the first UK report on biochar for DEFRA and DECC which outlines the potential benefits and uncertainties. Current research is focused on the soil science for biochar (i.e. biochar-soil-plant interactions, as well as understanding the longevity and nutrient value of biochar), systems and policy analysis (Life Cycle Assessment, techno-economic modeling, spatial analysis and land-use modeling, policy development, etc.) and engineering assessment (i.e. understanding the production conditions of biochar and scale-up of technology). The centre was opened in early 2009, and now has its own dedicated laboratories and equipment that can produce varying amounts of specific biochar from different feedstocks, under highly controlled conditions. Three facilities are available for producing biochar (capacity ranges from 10g to 100kg per day) and we welcome enquiries regarding provision of biochar for research and deployment in field trials.