Do people (including business and political leaders) realize that claims about agricultural soils being able to sequester “one trillion tons of CO2” from the atmosphere are not realistic? At least not to this scientist, and not to others who have worked on this for decades.pic.twitter.com/3aWOkSqKph
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Here’s why. Since the dawn of agriculture, humans have maybe released 350-450 billion tons of carbon dioxide from Earth’s natural soils. One good study on this is: https://www.pnas.org/content/114/36/9575 … There are many others going back to Houghton’s work in the 1980s and 1990s.
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That means to store a trillion tons, we would have to put back 2-3x this amount — restoring soils back to natural carbon levels, and then multiplying by 200-300%. This means going above levels of soil carbon seen in *recent geological history*. While still feeding the world.
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I see no evidence showing how this would be possible. (And, no, a few years of data from a handful of field plots aren’t going to hold up in my book. We are talking about centuries-to-millennial processes over continental scales.)
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Yes, soils *can* definitely sequester carbon out of the atmosphere. And we should definitely work on this with better farming practices. A win-win solution. But we need to bound these expectations with data and common sense. Please.
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The NAS report on negative emissions estimated a practically achievable capacity of at most 6 GtCO2/year worldwide for agricultural soil enrichment. It would take 150 years or so to get to a Terraton at those rates. Still, large.
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