Biochar — a serious carbon-negative option?

My Clean Break column/feature today takes a look at growing interest in the use of pyrolysis technology to covert wood, agricultural and municipal solid waste into gas (methane/hydrogen), bio “oil”, and char. The idea is that the gas and bio oil produced could be used as a renewable source of carbon-neutral energy, while the char or “biochar” could be buried in topsoil as a form of carbon sequestration that’s also carbon negative.

Using the char in soil goes back hundreds of years to the Amazon Basin, where pockets of carbon-rich black earth known as terra preta can be found throughout the region. Scientists have long studied the benefits that char brings to soil, such as enhanced water retention and nutrient absorption. It has also been shown that char can revive depleted soils and improve the growth of crops. But another benefit is that the char itself is packed with carbon and is resistant to chemical breakdown (i.e. decay), meaning it acts as a form of carbon storage for hundreds, potentially thousands of years. Scientists are now looking at this secondary benefit in the context of Kyoto and perhaps as a way to sequester carbon for carbon credits and at the same time improve soil so that reforestation and new agriculture can be more easily pursued (thus expanding the world’s carbon sink).

I’ll let you read the article for more details. The bottom line is that this could be more affordable than geological sequestration, easier to implement (particularly on a local scale), could prove an easier way to calculate carbon credits, and has the added benefit of improving the world’s soils. Last month scientists gathered in Australia for the first International Agrichar Initiative conference to discuss ways of advancing this approach. Tim Flannery, author of The Weather Makers, was a keynote speaker at the conference and is reportedly a big supporter of biochar sequestration.

It’s certainly an area worth more study, particularly by the handful of Canadian companies that have become experts in pyrolysis, including Dynamotive, Advanced Biorefinery and Agri-THERM.

For a great overview, Prof. Johannes Lehmann of Cornell University has this excellent commentary in a recent issue of Nature.