Biochar

Biochar is charcoal created by pyrolysis of biomass, and differs from charcoal only in the sense that its primary use is not for fuel, but for biosequestration or atmospheric carbon capture and storage.

Pyrolysis is a process involving the heating of waste biomass at low temperatures with very little oxygen to produce a char. The biochar is a stable form of carbon that can sequester the CO2 that plant biomass would normally release when decomposing.

Uses

Biochar has been proposed as a means of carbon capture and storage, to draw carbon from the atmosphere and reduce the global impact of industrial farming and agricultural waste. Biochar can potentially sequester carbon in the soil for hundreds to thousands of years, thus storing carbon in the ground from plants that would have decomposed into the atmosphere, reducing atmospheric GHG levels while also increasing the soil fertility of carbon-depleted fields, thus reducing water pollution through fewer nitrogen inputs and improving agricultural productivity.

Current biochar projects are small scale and make no significant impact on the overall global carbon budget, although expansion of this technique has been advocated as a natural geoengineering approach. Further research is in progress, notably by the University of Georgia, which has a dedicated research unit. Agrichar is produced by Best Industries in Australia. In May 2009, the Biochar Fund received a grant from the Congo Basin Forest Fund to implement its concept in Central Africa.

Research

The March/April 2011 issue of the Journal of Environmental Quality published a study funded by the Foundation for Research Science and Technology involving scientists at Lincoln University in New Zealand, who determined the effect of incorporating biochar into the soil on nitrous oxide emissions from the urine patches produced by cattle. Biochar was added to the soil during pasture renovation and gas samples were taken on 33 different occasions over an 86-day spring/summer period. They found that addition of biochar to the soil allowed for a 70% reduction in nitrous oxide fluxes over the course of the study. Nitrogen contribution from livestock urine to the emitted nitrous oxide decreased as well. The incorporation of biochar into the soil had no detrimental effects on dry matter yield or total nitrogen content in the pasture.

A study published in August 2010 in Nature Communications found that biochar could reduce up to 12 percent of CO2 emissions. The process involves capturing CO2 that would have made its way into the atmosphere, and using the biochar as a soil amendment to enrich soils lacking in nutrients for food production.

Criticisms

Proponents of biochar have been accused of overhyping its potential to address the severity of global warming. In March 2009 George Monbiot wrote:

"Sorry, not charcoal. We don't call it that any more. Now we say biochar. The idea is that wood and crop wastes are cooked to release the volatile components (which can be used as fuel), then the residue - the charcoal - is buried in the soil. According to the magical thinkers who promote it, the new miracle stops climate breakdown, replaces gas and petroleum, improves the fertility of the soil, reduces deforestation, cuts labour, creates employment, prevents respiratory disease and ensures that when you drop your toast it always lands butter side up. (I invented the last one, but give them time).

"They point out that the indigenous people of the Amazon created terras pretas (black soils) by burying charcoal over hundreds of years. These are more fertile than the surrounding soils, and the carbon has stayed where they put it. All we need to do is to roll this out worldwide and the world's problems - except, for the time being, the toast conundrum - are solved. It takes carbon out of circulation, reducing atmospheric concentrations. It raises crop yields. If some of the carbon is produced in efficient cooking stoves, it reduces the smoke in people's homes and means they have to gather less fuel, curtailing deforestation(2).

"This miracle solution has suckered people who ought to know better, including the earth systems scientist James Lovelock(3), the eminent climate scientist James Hansen(4), the author Chris Goodall and the climate campaigner Tim Flannery(5). At the UN climate negotiations beginning in Bonn on Sunday, several national governments will demand that biochar is eligible for carbon credits, providing the financial stimulus required to turn this into a global industry(6). Their proposal boils down to this: we must destroy the biosphere in order to save it."

Resources and articles

Related GEM.wiki articles

• Biofuels

External articles

• George Monbiot, "Woodchips With Everything", Znet, March, 29 2009.

External Resources

• "A critical review of biochar science and policy" Biofuels watch, 2011