Strategies to deal with climate change have focused largely on reducing emissions of CO2 and other planet-warming compounds from industry, transportation and agriculture. The news isn’t particularly heartening on that front. After three years of leveling off, CO2 levels are expected to rise by two percent by the end of 2017, due largely to increased coal-burning in China. For all the talk of solar, wind, carbon-neutral biofuels and fourth-generation nuclear, the world will continue to rely on fossil fuels for a long time.
And even in the best-case scenario, reducing emissions may not be enough to avoid the worst consequences of global warming such as melting ice caps and dramatic sea level rise. It’s likely we’ll need a complementary strategy such as carbon capture, the active removal and storage of atmospheric CO2.
As covered in a recent New Yorker story by Elizabeth Kolbert, carbon capture may not only be possible—it could become an immensely profitable enterprise, paying its own way and making people rich (or at least employed) even as it saves the planet. Kolbert cited the efforts of the Berkeley-based Center for Carbon Removal as a prime mover in the carbon capture quest.
Over the past century, two trillion tons of carbon have been pumped into the atmosphere through human activity, says Noah Deich, the executive director of the Center who has an MBA from Berkeley-Haas.
Any preliminary evaluation of the current situation may induce clinical depression in the highly sensitive. Over the past century, two trillion tons of carbon have been pumped into the atmosphere through human activity, says Noah Deich, the executive director of the Center who has an MBA from Berkeley-Haas. Add that to the roughly 40 billion tons still going into the air each year, and we have to play a lot of catch-up just to stay at the current baseline, let alone cool things down.
And yet, says Deich, it’s by no means impossible. Assuming we have the will (a big assumption), a combination of natural and artificial approaches could do the trick. More about the artificial approach later. As for natural approach, well, we’re mainly talking trees.
All plants capture CO2 from the air and use it to store carbon in the form of vascular tissue. But trees are particularly apt for carbon storage because they’re big and long-lived. Carbon is wood’s building block, and forests can store large quantities of carbon.
So why not just plant lots of trees everywhere? That’s a good idea as far as it goes, says Deich. It just doesn’t go far enough. “We couldn’t sequester all the carbon released over the past century by planting trees because there’s simply not enough available land,” Deich says.
Still, by replanting and protecting extant forests, reclaiming carbon-hoarding wetlands and grasslands, and following certain sustainable agricultural practices that sequester carbon in the soil, it could be possible to capture and store up to 10 billion tons of carbon a year, or about one-quarter of annual emissions.
As noted earlier, that’s not just a lot of carbon—it’s also, potentially, a lot of money.
For such an ambitious scheme to be practical, it would have to be founded on some form of cap-and-trade carbon markets, which are based on carbon limits assigned to CO2-producing economic sectors—everything from car manufacturers to farms. A cap on allowable carbon emissions is decreed, and then credits representing those emissions are issued, sold and purchased. A company that doesn’t need all its credits can sell them to another firm that has higher carbon emissions. At the same time, companies that exceed their carbon limits are severely penalized. Further, those limits tighten over time as the planet moves toward a carbon neutral—or ideally, carbon negative–future.
“A paper produced by Nature Conservancy researchers for [the journal] Science determined that it would be economically feasible to achieve 10 billion tons of carbon mitigation with carbon credits selling for less than $100 a ton,” Deich says.
That’s because that 10 billion tons of carbon translates to an ungodly amount of money. If carbon prices are pegged at $100 a ton, we’re talking about a trillion dollars—more than enough to excite any eco-entrepreneur.
Carbon markets are growing, but they’ve had a fairly bumpy ride so far, and there’s no clear indication if or when they’ll be linked into a smooth and effective mechanism that addresses emissions on a global scale. But Deich thinks there’s an inevitability to carbon pricing; the dire effects of climate change demand it, and policy makers, willingly or not, are acknowledging the necessity of action. Further, says Deich, a lot of progress can be made even without a rigorous worldwide regulatory system.
“You don’t necessarily need a [large and coordinated market] to make progress,” Deich says. “There are a lot of niche opportunities for marketing carbon that we can pursue now. It’s a good opportunity for people to get involved and get positioned for broader regulation when it happens.”
Those opportunities not only include earning carbon sequestration revenues for such things as planting trees, but marketing products that can be created from captured CO2, says Deich, including wood obtained by thinning forests that are managed for carbon sequestration.
It’s not just wood from trees; other products can be derived from the aforementioned artificial approach to carbon sequestration, or so-called direct air capture, says Deich—a method he likens to “mechanical trees.” You use sustainable energy such as solar or wind to blow air over devices that extract CO2 via chemical processes. You can then use the captured CO2 for concrete or plastics or inject it deep underground into saline aquifers, where it eventually transmutes into solid and stable minerals.
Or it’s possible that hybrid approaches might be apropos for certain areas, says Gina Amador, the Center’s managing director, citing an experiment conducted by the U.S. Department of Energy and Archer Daniels Midland that involves a direct capture facility powered by biofuels.
“In this case, the fuel was ethanol,” says Amador. “The carbon capture end worked very well, but the ethanol was an issue because the way it’s currently derived from corn doesn’t meet carbon reduction goals. There are a lot of challenges involved in growing sustainable bioenergy crops, but it’s clear there are great opportunities as well. Ideally, a single piece of [cropland or range land] could have multiple carbon removal benefits; say a tract supports a direct air capture project while growing a specific type of grass that both sequesters carbon in the soil and provides biofuels.”
Ultimately, says Deich, there will be no killer app for carbon removal. The idea is to foster and perfect a multitude of systems, customizing programs for specific locales.
Other approaches that sound promising might not pencil out because they pump out more carbon than they ultimately store. Amador cites certain types of rocks that suck up atmospheric carbon and lock them up as stable carbonates. If you ground up such rocks and spread them widely, you could have a massive—and passive—landscape-scale carbon storage system. The problem is the carbon output resulting from the energy spent processing and spreading the rocks might negate the benefits; it’s simply not clear if biofuels, solar or wind could be harnessed to operate the necessary machinery in an efficient carbon-neutral or carbon-negative manner.
And some carbon-reduction ideas that were once heralded with great fanfare have sunk into oblivion. That includes ocean fertilization, a scheme to seed the oceans with minute iron pellets that would stimulate massive algae blooms. The algae would lock up CO2 from the atmosphere and eventually—it was hoped—settle to the seabed.
“It’s unclear, though, what would happen to local marine ecosystems if you produced that much algae,” says Amador. “It’s likely there would be major impacts. In any ambitious project like carbon capture, you want to minimize unintended consequences, and all the systems we’re studying have very low risk factors.”
Ultimately, says Deich, there will be no killer app for carbon removal. The idea is to foster and perfect a multitude of systems, customizing programs for specific locales.
“Our approach is to offer a lot of approaches that communities can choose from, implementing the ones that are best suited for them,” Deich says. “For example, we know that applying compost to rangelands can have a positive effect on increased carbon storage. Some experiments on Marin County rangeland demonstrated that. But Marin is close to major sources of compost made from garbage produced by Bay Area cities, including San Francisco. It might make sense from a carbon storage perspective to expend some carbon by trucking it there—the distances aren’t that great. But what about rangeland that’s really remote, that’s a long distance from a compost source? In terms of carbon storage gains, it may not make sense.”
