In 2009, great swathes of the environmental world were wildly enthusiastic about biochar. This charcoal-like material, produced by burning plants, trees and crops at a high temperature in low oxygen conditions, was hailed by some as a miracle product that, when added to soil, could both lower carbon in the atmosphere and improve crop yields. If sustainably produced (by converting agricultural waste or trees killed by pests), its proponents argued that it represented the cleanest way of fixing CO2. Since then, a mass roll-out of biochar has failed to materialise, but many scientists continue to investigate its potential.
Hamze Dokoohaki, a researcher at Boston University, is one of these people. He explains that biochar is a carbon-negative substance. Unlike normal organic matter which leaks carbon into the atmosphere as it is decomposed by microorganisms, biochar is resistant to decomposition. Its carbon atoms are so strongly bound together that they can’t be broken down, thereby locking carbon in the soil. ‘It would take the microbes thousands and thousands of years to decompose the biochar and put the carbon back in the atmosphere, so it’s a very effective way of mitigating climate change,’ says Dokoohaki. Estimates as to how much carbon could be sequestered in this way vary. The researchers predict that at its maximum sustainable output, biochar could reduce US net greenhouse gas emissions by ten to 15 per cent.
Biochar’s second useful application is as a soil ‘conditioner’ which helps with the storage of nutrients and water. It’s this second property that the scientists at Boston University are working to better understand in the hope that highlighting the yield-enhancing capacity of biochar will eventually increase use by farmers across the US. The team has produced a model which aims to help farmers answer the question of how and where to apply biochar for maximum benefit. In general, the researchers conclude that average yield increase by applying biochar is around five per cent, though this varies greatly across different terrains. They also note that biochar is most effective in poor soil conditions and add that biochar could be valuable in countries with arid soil.
However, despite this apparent win-win situation, biochar has a major pitfall. ‘It’s not economically feasible given the price in the US right now,’ admits Dokoohaki. Because biochar is still mostly produced on a very small scale it remains expensive and the benefits in crop yield do not yet outweigh the cost. For biochar detractors, this is just one of many practical problems that limit its potential. In addition, some commentators argue that sustainable biochar could never be produced in large enough quantities to achieve sufficient carbon-saving benefits.
Dokoohaki and his colleagues disagree. They think that biochar has been underestimated as a mitigator of climate change. Their main hope is that in the future, carbon credit markets, in which businesses receive financial benefits for saving carbon, will be developed, allowing biochar to become a viable choice. Until then, it’s a case of fine-tuning its application and trying hard to keep it in the limelight.
This was published in the June 2019 edition of Geographical magazine
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