Bio-char: fighting climate change with… charcoal?

An interesting approach to offsetting the world’s carbon emissions may pre-date civilization itself.  Traditionally, agricultural waste was incompletely burned to produce charcoal, a useful fuel itself, but also a potent additive to improve soil fertility, allowing ancient Indians to survive on low-quality land. Through new processes, woody biomass, from grass clippings to peanut shells to wood shavings, may be pyrolyzed (heated in the absence of oxygen) to produce bio-oil, syngas (a mixture of combustible gases) and bio-char which locks up much of the plants carbon for possibly thousands of years as stable charcoal.

The oil and syngas may be burned to provide energy in excess of that required by the process, thus creating a novel energy source renewed by bio-production (agriculture).  The carbon-rich bio-char is buried to act as a pH balancer, soil stabilizer and, in order to offset carbon emissions, a new sequestration method of carbon that would have otherwise been burned and completely released into the air.  As the farmland is enriched by the addition of bio-char, further plant growth captures more carbon from the atmosphere, which may be cycled back into the process in order to sequester more carbon.

Bio-char production may be practiced by even the poorest of countries, creating a means for even the most undeveloped countries to combat climate change.  Slow pyrolysis of woody feed has reported a 50% of original feed dry weight bio-char output after a few hours of cooking while a recently developed microwave pyrolysis can achieve a conversion of 20% to bio-char is mere minutes.  But some doubts exist: could land change caused by char-destined agriculture release more carbon than could be sequestered?  Also, some evidence exists that microbes attracted to the rich char-infused soil release much of the carbon back into the atmosphere.  Regardless, much work needs to be done to determine the value of bio-char production in combating climate change worldwide.

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