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?

15 thoughts on “Creating a carbon vacuum: turn MSW into charcoal and bury it”

  1. Nobody in that article refers to it as a silver bullet. They have great hope for its potential, which is a big difference.

  2. Eco cement has higher potential to sequester CO2 and doesn’t take extra energy to do it. In fact the kilns fire at half the temperature as portland cement and it sequesters CO2 while it cures. You can also use municipal solid waste as the aggregate. Killing 3 birds with 1 stone is always lovely.

    Japan is all over this. The strength still needs more testing for buildings is still good for slurry walls and foundations for MURBs and houses. Classic chemistry using MgO.

  3. Charcoal has a high heat value… burning it completely to genrate electricity and hence displace coal based generation would further reduce the volume in the landfill, and allow more coal to be left where it is.

    As you say, “it’s the rough equivalent of making coal, but doing it in a few hours instead of a million or so years. ” So why not burn the charcoal and leave the real coal where it is?

  4. Sure, you could do that, but then it wouldn’t be carbon negative. As Lovelock said, it’s not enough to just reduce emissions, we have to remove them as well. But certainly, if it’s something that would make it more economical then it’s a good way to demonstrate the approach.

  5. The basic theory of biocharing seems simple. It could prevent some carbon from getting to the atmosphere but I foresee much conflict and controversy. There will be great pressures to burn the char as a carbon neutral fuel source to produce heat or electricity. The char would burn much cleaner than fossil fuels and even biomass for that matter and the latter is also touted to be carbon neutral. Even if reuse of the char could be effectively prohibited, would the process not qualify for carbon credits which would then be sold to others so they can continue to burn fossil fuels? It seems somehow the approach would be fraught with complicated regulations, ripe for misuse, conflicts and criticism. This could be a vicious circle, an exercise in futility, which in the end would be totally ineffective in reducing CO2 build up. At the very best it might slow down the accelerating accumulation of CO2. I suggest the best way to slow the rate of acceleration is to wind down the use of fossil fuels. Remember that fossil fuels not only add to the CO2 but are a major source of pollution. The health impacts are likely a more immediate concern than global warming and reducing fossil fuel use will help on both fronts.

  6. I think some people (including Harper, Canada’s PM) view sequestration as the silver bullet because we have seen that after 20+ years of trying to curb global GHG emissions, they are rising faster then ever. Lovelock is not showing the light at the end of the tunnel. He’s saying that in addition to drastically reducing GHG emissions worldwide in the very near future, we now also need to have a global effort to sequester GHGs as we have exceeded safe atmospheric levels. The challenge is double what it was before.
    Before we start burying biochar, we need to stop digging coal out of the ground, if not it seems like a hypocritical measure. If we can’t shut coal plants down altogether, then use carbon neutral biochar. Once we are no longer burning dirty coal then we can start burying biochar. Although, in theory this sounds good, but in practice I can’t see how this can be done on the required scale without impacting food supplies, and with over 1 billion people hungry already, how do we proceed? Possibly ban meat production?

  7. Tom,

    You wrote: “So why not burn the charcoal and leave the real coal where it is?”

    Because you would be wasting 50% of the energy of the original biomass used to produce charcoal. It’s twice as efficient energy-wise to burn raw biomass. The only reason that charcoal is used in steel production (eg. Brazil) is because charcoal burns cleaner and hotter than raw biomass.

    Why even use charcoal (@>$1.00/lb. in barbecue grills, if you can use wood chips (free from the municipality) in Chip Energy’s new grill?

  8. Biochar is a good way, but not the only way, to start thinking in terms of net emissions – ie not just in terms of what we emit, but what we take back from the atmostphere. It has two obvioius mass-handling challenges- getting the feedstock, and the hassle of disposing of the product underground. Both could impose a lot of energy and cost. Check out what Klaus Lackner is doing with direct capture (via Marathon B, a resin now used for water filtration). It has its own challenges but certainly mass-handling is not one of them.

    The first policy question about net emissions is to compensate for missing emissions-reduction targets- if we fall short by %10, can we take up that ‘missing’ carbon? the second question is, if we can reach zero net emissions, can we go beyond that to go negative? Biochar is one way, direct capture a la Lackner is another. I expect that a consistent economic incentive would uncover others.

    By any method, it offers the prospect of measurable and indisputable carbon offsets, without any of the opportunities for ambiguity over ‘additionality’ (or opportunities for fraud). Suppose that your smokestack can meet %90 of its emission-reduction target for a supportable cost, but going %100 will be unsupportably expensive. Can you buy a “real”, ie negative, carbon offet for the rest at a lower cost? Not a silver bullet but a new tool in the kit.

  9. I’m a little concerned by some of these plans.

    for one, plastic char is bound to be toxic, as will the exhaust. Also, the benefit from biochar comes from putting it into a biologically active region. The soil microbes that tolerate/thrive with the char are also sequestering MORE carbon.

  10. I’m not advocating burning charcoal so much as leaving the real coal where it is… My point is that the priority should be not mining coal… if charcoal can actas a substitute, then that’s probably the best use.

    Gerald: I agree completely… I’m a woodworker, and I use my wood scrap to BBQ my burgers.

  11. Tyler, I’d like to mention another promising approach for extracting CO2 from the air in a benign way. It’s called mineral sequestration, probably olivine. There are many benefits of this technique:
    – it is chemically benign
    – it is already occuring at large scale in processes of erosion
    – it is affordable
    – there are enough olivine deposits to sequester all of our CO2 emissions for many decades if necessary, and much is situated near the sea to help reduce ocean acidification

  12. I just stumbled on this thread (I live in Europe). One of the problems we (collectively) have in dealing with the reality and immediacy of climate change is our conditioning. We are raised and educated to see the world in simplistic and limited ways, and this is where the silver bullet idea comes from.

    Of course there are no silver bullets, but a constellation of strategies might just succeed, if we can stop arguing over whether carbon capture is meaningful when someone else is still burning coal, or if high tech is better than obvious-tech. or if goverment or industry or individuals need to do more. We are all equally fried if we do nothing.

    We are buried alive in our own waste, and if we can return some of that to repair soil quality in a way that also locks in carbon, it’s worth doing. I’ve been following and promoting biochar for the past two years, and I have to say, it’s possibly the most promising development I have come across in the past 20 years.

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