A couple of weeks ago, we discussed the possibilities of biochar – burning organic waste, such as wood chips, left-over crop residue or even manure at extremely low oxygen levels and high temperatures in order to produce charcoal and biogas. The charcoal would go into the ground, increasing soil fertility, while the gas would be an effective energy source, making good use of detritus that would otherwise decompose, returning its carbon to the atmosphere.
I suggested that although the technology was still distant from full-scale implementation, it had considerable promise as a way to draw-down carbon from the atmosphere.
Well, environmental writer George Monbiot has demurred. He wrote in the Guardian yesterday that biochar advocates have been "suckered." They promote "an even crazier use of woodchips." They wish to "turn the planet's surface into charcoal." They are a wild band of "magical thinkers" who wish to "destroy the biosphere in order to save it."
Remember, this is Monbiot, a serious analyst of anthropogenic global warming, not Bjorn Lomborg or a mercenary from the Heartland Institute. This man isn't "supposedly" in the coalition to avert disastrous warming – he's part of it, through and through.
So what's he in a tizzy about? A lot of nothing, it turns out, since he's battling with a straw-man that most biochar researchers don't take even remotely seriously.
Monbiot states that the idea that "biochar is a universal solution that can be safely deployed on a vast scale is as misguided as Mao Zedong's Great Leap Backwards," adding that its "hazards" outweigh it benefits, that it's unclear if it even promotes soil fertility.
After so much huffing-and-puffing, he finally notes, "Nor does this mean that charcoal can't be made on a small scale, from material that would otherwise go to waste."
Monbiot is right to tear into those who propose industrial tree-farming as a way to create biomass for biochar. And of course he is right to point out that there would be problems in planting 1.4 billion hectares of trees and sugar to produce biomass for biochar, as Peter Read suggests, since the world's arable land is 1.36 billion hectares.
But beyond that, he's quite lost his way.
Contradicting Monbiot's worry that it isn't clear if biochar can increase land's fecundity, Johannes Lemann's research project at Cornell University has shown that biochar has tremendous effects on soil fertility.
And Jim Hansen, one target of Monbiot's polemic, adds that serious scientists aren't suggesting trash-forest plantations but are advocating pryolizing farm waste: turning some into charcoal—biochar—that can be buried to increase soil fertility, turning the rest, which would normally decompose, bleeding carbon into the atmosphere, into a biogas that can be used as fuel in lieu of fossil energies.
One peer-reviewed paper published by Lemann and a team of researchers in Mitigation and Adaptation Strategies for Global Change advocates replacing slash-and-burn with slash-and-char in tropical areas.
Slash-and-burn leaves a residue of 3 percent of the biomass's carbon in the soil. Pyrolysis leaves up to 50 percent. Meanwhile, deforestation could only continue until it is taxed as a carbon emission. The biochar strategy would mitigate carbon emissions while deforestation decreases. Monbiot is against this?
In another paper, published by the Goddard Institute for Space Studies, the authors, including Hansen, observe that
Waste-derived biochar application will be phased in linearly over the period 2010-2020, by which time it will reach a maximum uptake rate of 0.16 GtC/yr.
They add that this could draw down about 8 ppm of carbon from the atmosphere. They derive the number from the Lemann paper I cite above, which suggests that there is an adequate supply of waste biomass—rice husks, forest and mill residue, urban debris—to fuel this process. Does Monbiot seriously wish to ignore such a figure?
Finally, even the most optimistic figures scientists bandy about are based explicitly on converting biomass into charcoal and energy in the places where it is grown. Otherwise, the transportation costs would be enormous, negating the benefits. Indeed, agronomist David Laird writes explicitly of the benefits to be gained from a distributed, as opposed to centralized, network.
Monbiot is right to pillory the latter, as well as vast plantations of socially and ecologically disruptive fast-growing monoculture trees. But that doesn't mean biochar isn't a good idea, even if it makes for good copy to attack its and its proponents in the harshest terms.