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About a month and a half ago, I blogged about a no-till, cover-crop, monoculture-phobic farming technique called regenerative or restorative agriculture, which has proponents who make some — to say the least — rather remarkable claims regarding its environmental benefits. I expressed my skepticism in the post, and I promised a follow-up where I would check some of the numbers. Let's take a look at one of the more astounding assertions made by David C. Johnson of New Mexico State University.
Johnson claims that by combining no-till farming with a composting process he developed, which changes the soil microbe mix from one that is mostly bacterial to one that is mostly fungal, it may only take 11% of the world's cropland to offset total anthropogenic CO2 emissions (~34 Gt/yr).
If you're not aware, that, ladies and gentlemen, is quite a staggering declaration, and here's why...
The world has somewhere near 1,396,200,000 hectares, or 13,962,000 square kilometers, or 3.5 billion acres of arable land.
11% of 3,500,000,000 acres is 385,000,000 acres. In order for that amount of land to offset 34 Gt of CO2 annually, each acre would have to sequester about 88 metric tons each year.
That's around the mass of a herd of 10-15 African elephants getting stuffed into an approximate 200' by 200' area of ground every year.
While admitting uncertainties, Eve et al. 2002, the USDA, and the National Farmers Union all put the best sequestration rates for strict no-till farming practices at about 0.6 metric tons of CO2 per acre per year more than popular conventional tillage practices. At that improved rate, if we converted all 3.5 billion acres of viable cropland (not just 11%) to no-till agriculture, we would take about an additional 2,100,000,000 metric tons or 2.1 Gt of CO2 out of the atmosphere annually, which is nice, but quite a departure from Johnson's numbers.
Therefore this composting technique, whatever it is, would have to improve no-till's sequestration potential by 146 times (88/0.6=~146).
146 times.
That's some fairly impressive decaying biological material, lemme tell ya. Now, I must admit I have not read Kristin Ohlson's book, nor have I delved fully into Johnson's research at NMSU/WERC, and Sandia Labs, so I cannot even pretend to understand the entire process he is proposing, but 0.6 metric tons of sequestered CO2 versus 88 metric tons? I feel pretty comfortable at this point reinforcing my initial skepticism, while welcoming any corrections at the same time. In other words, lemme have it, regenerative agriculture fans, because right now I am anything but convinced. ;)
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