The Biochar debate

EnvironmentalResearchWeb.org
Posted by Dave Elliott on October 3, 2009 12:28 AM

“There is one way we could save ourselves, and that is through the massive burial of charcoal” James Lovelock

Converting biomass into charcoal type char which can be used to improve soil fertility, while also trapping carbon dioxide, certainly has major attractions. Some energy is generated too. But a key issue is whether, in net climate terms, the loss of (some) biomass for direct conversion to energy is balanced by the gain from CO2 entrapment and extra CO2 absorption by more fertile soils- especially if the combustion route also used geo-sequestration i.e. CCS?

A parametric study of bio-sequestration by Malcolm Fowles at the Open University, suggested that from a global warming perspective we should displace coal with biomass if the latter’s conversion efficiency is much over 30%. Otherwise we should sequester carbon from biomass rather than generate energy.

However, this was only a preliminary study and he felt that a more comprehensive analysis might shift the balance more towards bio- sequestration. He did not include carbon savings from hydrogen and other pyrolysis products, or crucially from reduced soil emissions- that’s hard to assess after all. And costs were not included in his model, although qualitatively and intuitively he felt bio-sequestration should be cheaper than geo-sequestration by CO2 capture and storage. (Fowles, M. (2007), “Black carbon sequestration as an alternative to bio-energy’, Biomass and Bioenergy 31: 426-432, doi:10.1016/j.biombioe.2007.01.012)

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