Creating a carbon vacuum: turn MSW into charcoal and bury it
During a recent round-table session I attended with British scientist and Gaia author James Lovelock, it was easy to walk away feeling helpless about the climate problems humanity faces. But when pressed, Lovelock said he does believe there’s potential in “biochar” — that is, converting some of the world’s biomass (e.g. forest slash, agricultural residues, fast-growing grasses grown on depleted soils, farmed algae) into charcoal and sequestering the black mass in soil or under the ocean. This is done through a process called pyrolysis, which when creating the charcoal locks in about 60 per cent of the biomass’s carbon. Charcoal stays inert and chemically stable for hundreds of years. Best to turn some of the world’s biomass into charcoal instead of letting the biomass rot and release methane into the atmosphere. At least that’s the thinking.
In the end, it’s the rough equivalent of making coal, but doing it in a few hours instead of a million or so years. It’s considered better — and likely cheaper — than the capture and sequestering of fossil-fuel CO2 emissions because it doesn’t just avoid the release of emissions; so-called charcoal sequestration can lead to the extraction of CO2 from the atmosphere. This makes it carbon negative. Turning some of the biomass into charcoal prevents new emissions, but the new generation of biomass that grows also absorbs CO2 from the atmosphere. Over time, the cycle of charring biomass and growing new biomass can act like a big global carbon vacuum.
The trick is doing it on a large enough scale to matter. EnCana researcher Subodh Gupta, a big believer in charcoal sequestration, recently argued at the Canadian International Petroleum Conference in Calgary that the best way to demonstrate that the approach works is to start with the organics and even some plastics collected from municipal solid waste. It solves many problems. For one, you can leverage an existing municipal MSW collection network, so no extra costs there. Second, pyrolysis systems can be economically set up at central MSW collection points. Third, a municipality can better manage its waste by reducing how much of it goes to landfill. The charcoal produced is essentially crushed and stored in existing landfills, where it will sit inert for centuries. (A good way for municipalities to earn carbon credits, too).
Gupta argues that if it works well with MSW, and at scale, then it can expand to other areas over time. He even did a comparison to using MSW for other purposes — such as electricity-from-waste and ethanol-from-waste — and concluded that sequestration of MSW-based charcoal is cheaper to implement and, with the benefit of carbon credits, more economical overall. That said, we’re already seeing huge competition for biomass resources driven by the quest for carbon-neutral fuels and power.
Gupta’s enthusiasm for charcoal sequestration is shared by more than just James Lovelock, who says that if he was a betting man he’d put all his money on biochar. The Weather Makers author Tim Flannery supports it, as does NASA scientist James Hansen. Sure, you’ve got skeptics like Heat author George Monbiot, who recently slammed the approach in a column for the U.K. Guardian. But nobody is calling charcoal sequestration a silver bullet, as Monbiot suggests. It’s one promising option in the climate mitigation toolbox. Nobody is suggesting that we use prime agricultural lands to grow crops that we would then turn into charcoal. By making that connection Monbiot is doing his readers a disservice.
Would Monbiot be against turning all the dead and decaying pine trees in B.C. — victims of pine beatle infestation — into charcoal? Municipal solid waste? Would he be against farmers choosing to turn their own crop residue into charcoal, which can be used as a soil enhancer for their own land?