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CO? removal to halt warming soon would be a gargantuan undertaking


BECCS
DAC
DOI
PNAS
the Ars Orbital Transmission
CNMN Collection WIRED Media Group
Condé Nast


Scott K. Johnson
Ars

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Earth
the Global South

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US

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Positivity     36.00%   
   Negativity   64.00%
The New York Times
SOURCE: https://arstechnica.com/science/2020/08/proposals-to-suck-up-co%e2%82%82-have-their-limits/
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Summary

But if you’re looking at the first 30 years, a number of sites would fail to overcome their initial debt.So sticking with the suitable locations—and leaving cropland untouched—could BECCS supply all the carbon capture needed to make a 1.5°C warming scenario work? It also included scenarios for improved switchgrass crops and fuel-making processes, as well as the possibility of capturing the carbon emitted during fuel production.Unsurprisingly, the study found that using cropland or former pasture produced a much clearer carbon benefit than converting forest for switchgrass agriculture. So there is a positive path here, in the right circumstances.The authors write, “While climate and other ecosystem service benefits cannot be taken for granted from cellulosic biofuel deployment, our scenarios illustrate how conventional and carbon-negative biofuel systems could make a near-term, robust, and distinctive contribution to the climate challenge.”The third study looked at an entirely different technology—“direct air capture” (DAC) of CO2 from ambient air, after which it can be stored underground. With things like BECCS allowed to take over cropland, they simulated pretty extreme increases in staple crop prices, particularly in the Global South.Direct air capture doesn’t contribute to that problem, but water use in the two scenarios is actually similar. And the heat required in the DAC process—provided by natural gas with capture of the emitted CO2 in some pilots—could be equivalent to two-thirds of current natural gas production or more.But even with the current state of this young technology, the economic model shows that DAC could play a substantial role, removing enough CO2 by 2035 to equal 7 percent of current-day emissions, if we’re willing to go that route.The authors of this study emphasize a take-away message that applies to all three: “These results  highlight that delays in aggressive global mitigation action greatly increase the requirement for DAC to meet climate targets, and correspondingly, energy and water impacts.” The sooner we start reducing our emissions, the less of a need there will be for these carbon-removal techniques, allowing us to minimize the scale of the trade-offs they come with.Nature Climate Change, 2020.

As said here by Scott K. Johnson