The Christian Science Monitor Weekly

November 26, 2018

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SCIENCE & NATURE BOULDER, COLO. C limate mitigation strategies tend to focus on emissions reduction. But carbon capture is becoming an equally vital prong of climate action. And the technology to do it is rapidly catching up. Many experts say it's a necessary part of any plan to keep global temperature rise below 1.5 degrees C, or even 2 degrees C. "The first rule of holes is to stop digging," says Noah Deich, executive director of Carbon180, referring to the need to lower emissions. "But we can't just stay down in the hole; we've got to climb our way out.... We have to figure out how strategies on the removal side can complement what we're doing on mitigation." Some of the means to do that are entirely natural: Forests and farms, managed the right way, can both be carbon sinks. Others are technological: Bioenergy with carbon capture and storage – better known as BECCS – converts biomass into outputs like heat or biofuel and captures and stores the carbon dioxide emitted in the process either underground or in products like concrete or plastics. Direct air capture and storage scrubs carbon dioxide out of ambient air, often using a chemical adsorbent to separate the carbon dioxide before storing or using it. And a suite of other nascent technologies is slowly emerging: A technique known as enhanced weathering accelerates natural reactions between CO 2 and certain minerals. Seawater capture extracts CO 2 from the oceans. Plant engi- neering involves selectively breed- ing certain plants for traits that in- crease carbon storage in soils. All those options have potential as well as significant challenges, says James Mulligan, an associate at the World Resources Institute and lead author on a series of papers on carbon removal. It's one rea- son he and others favor a portfolio approach: pursuing each of those options at a scale and a manner that make sense, investing in research and development to further our understanding or drive down costs, and not seeing any one carbon- removal strategy as a silver bullet. Some of the biological means of removing carbon – reforestation and managing forests to maximize their use as carbon sinks, planting some trees on agricultural and graz- ing lands, and managing farms to capture more carbon in the soils – are an obvious place to focus efforts first, says Mr. Mulligan. "They're easier to do now, and they generally have very good co-benefits," says Mulligan. One big downside is that the carbon storage isn't necessarily permanent: Forests can burn down; soils can release their carbon with changes in climate. But many of the cli- mate-friendly practices also boost soil health, aid in conservation, and Once a pipe dream, the ability to remove CO 2 from the atmosphere is gaining ground. STORY BY AMANDA PAULSON / STAFF WRITER GRAPHICS BY JACOB TURCOTTE / STAFF Carbon capture rises as a battlefront 2 Natural carbon removal Forests and farms both have the capacity to remove carbon from the atmosphere – while providing significant co-benefits, such as cleaner air and healthier soils. Each acre of forested land can store about 3 metric tons of CO 2 per year at a relatively low cost. Planting cover crops and crops with deeper roots can increase soil's carbon content – sequestering about half a metric ton of CO 2 per acre per year. Forestry Farming -20 20 40 60 80 0 2010 '20 '30 '40 '50 '60 '70 '80 '90 2100 Greenhouse gas emissions (Gigatons of CO 2 per year) CO 2 Other greenhouse gases Mitigated greenhouse gas emissions Gross negative CO 2 emissions Net negative greenhouse gas emissions B u s i n e s s - a s - u s u a l s c e n a r i o W a r m i n g l e s s t h a n 2 ° C s c e n a r i o Conventional mitigation techniques Carbon-removal technologies In addition to cutting carbon emissions, removing CO from the atmosphere will be essential to mitigating the effects of climate change This hypothetical scenario laid out by the United Nations Environment Program shows that emission reductions may not be enough to keep global warming below 2°C. Carbon-removal technologies may be needed to achieve that goal and to reach net-negative greenhouse gas emissions. SOURCE: United Nations Environment Program BREAKTHROUGHS 16 THE CHRISTIAN SCIENCE MONITOR WEEKLY | NOVEMBER 26, 2018

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