VIDEO: our experiments with biochar The biology team look at using charcoal to improve soil and sequester carbon
Contact: Alex Randall / alex.randall@cat.org.uk / 01654 705953 (Email)
Date: 23/07/2009
Report by Lewis Winks, Biology Department
The charcoal industry has had an interesting history, once being the staple commerce of woodlands in the British Isles, it provided work for many and was a quintessential part of our landscape. Soon after the discovery of coal as a fuel source in the early 1700s charcoal became an unprofitable venture, and the woodsmen who made it became a part of history, lost to the beginnings of the industrial revolution.
So who would have thought, that 250 years after the first use of fossil fuels we would be turning back to charcoal as a means of undoing the damage of those emissions. Poetic it may seem, but to those who are studying the capacity for Biochar to sequester CO2 from the atmosphere, this is an all too real opportunity. And it doesn't stop at mopping up emissions; Biochar has the potential to improve degraded agricultural land and reduce fertiliser dependency while creating rural jobs, providing a use for organic waste and becoming an integrated part of our biomass energy systems.
Biochar is made using a process called pyrolysis, during which organic matter is heated to temperatures below 700 C in the absence of oxygen. This leaves a compound consisting mostly of carbon, which we would call charcoal. The inert character of this carbon means that it is not prone to decomposition unlike most organic matter which eventually rots down and releases its carbon into the atmosphere. By charring plant waste material in this way, carbon is transferred from the relatively fast carbon cycle into carbon storage where it is able to remain for thousands of years in the soils of terrestrial ecosystems. Scientists say that only a small percentage of atmospheric carbon dioxide needs to be captured and stored in order to mitigate our emissions.
Biochar has also been seen, albeit mostly in the tropics, to have a positive effect on crop yields when applied to some soils. This is because it acts essentially as a nutrient sponge, holding on to minerals in the soil for plants to access, and preventing them from being washed out. Research in this area is not conclusive and much more work is needed to ascertain the true potential for Biochar to improve soil quality in other regions. At CAT we are running our own trials to address the use of Biochar as a soil conditioner with urine as a fertiliser. Indeed, it does seem that charcoal has a role to play in future environmental management, although the magnitude that it could be applied is unknown.
On paper it looks good land can be converted to biomass production, feeding the energy industry which profits from electricity production and again from the sale and distribution of Biochar as an industrial waste product. It is also expected that under the clean development mechanism (or whatever replaces it at Copenhagen later this year) Biochar will eventually benefit form tradable carbon credits as a way of buying and selling emissions rights globally. So whats the catch? Amongst the enthusiasts you will find those who urge caution to our optimism. In order to achieve such magnitude of sequestration, vast areas of land would be required- far outstripping the demand of bio fuels and threatening food security globally. We risk displacing current land use practices and people for energy crops and plantations.
We must check our enthusiasm and be sure not to fall for the magic bullet scenario which so many reports claim for Biochar. Most importantly, we cannot hope to have a stable global climate while emissions from the burning of fossil fuels remain so great. Initiatives such as biochar hold some promise in terms of reducing the worst of climate change, and certainly in providing higher food yields and better soil quality, but only if we recognise this will have to come as part of a range of approaches, including a large scale reduction in direct emissions.
