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A carbon-negative fuel source

May 4th, 2007 (10:29 am)

current mood: hopeful

I just read an article on Truthout about "agrichar". You take agricultural waste (e.g., corn husks) and put it through pyrolysis. You get clean-burning gases such as methane, which you can use as fuel, plus charcoal. You then bury the charcoal in your fields, which makes them more fertile and sequesters the carbon in the charcoal, keeping it from going into the atmosphere. Since the plants took CO2 out of the atmosphere in the first place, the whole cycle is not just carbon-neutral, but carbon-negative.

There are some open questions, of course; for one thing, nobody knows for sure how long the carbon would stay sequestered. Ordinary compost doesn't count as carbon-negative for just that reason: the carbon returns to the atmosphere within about 10 years or so. However, there is reason to think that Amazonian terra preta was created this way in the first place, and it seems to have lasted for 7,000 years or so.

If agrichar works out, it could be great news: a technique to clean up the atmosphere which is profitable in its own right. (One reservation in my mind is whether third-world people living on the edge would actually bury the charcoal—which they know is useful fuel—or just go ahead and burn it.)