A growing number of farmers are exploring the potential of capturing and storing greater amounts of carbon dioxide in soil as a way to combat climate change.<\/p>\n
Soil naturally stores some amount of carbon, much of it from decaying plants and animal matter. The National Academy of Sciences\u00a0estimated in a study last year<\/a>\u00a0that global farmland could capture and store as much as 3 billion tons of additional carbon dioxide if farmers adopted a number of improved practices, including adding organic matter like manure or compost, shifting cultivation to favor crops that contribute more of their carbon to the soil, or using off seasons to plant cover crops that will then break down. (See \u201cOne man\u2019s two-decade quest to suck greenhouse gas out of the sky<\/a>.\u201d)<\/p>\n California has started\u00a0providing small grants<\/a>\u00a0from the state\u2019s carbon cap-and-trade fund to farmers who employ techniques that promise to store more carbon. Meanwhile, a Boston startup known as Indigo AG\u00a0recently announced<\/a>\u00a0a plan to pay farmers to pursue similar practices and then sell carbon credits to companies or individuals looking for ways to offset their climate impacts.<\/p>\n But there is still huge uncertainty concerning how much of a climate benefit these efforts provide, what practices work best under different soil and climate conditions, and whether there are\u00a0more reliable ways to balance out the industry\u2019s greenhouse-gas emissions<\/a>, according to panelists at a session on \u201ccarbon farming\u201d at the Breakthrough Institute\u2019s annual conference in Sausalito, California, on Thursday.<\/p>\n Noah Deich, executive director of Carbon180, a think tank promoting carbon removal and recycling, said that since the onset of agriculture, the planet has released\u00a0about 500 billion tons<\/a>\u00a0of carbon dioxide from soil\u2014about 14 times the\u00a0amount released<\/a>\u00a0from all fossil-fuel energy sources globally last year. It\u2019s a huge pool that could potentially be refilled, if those ecosystems can be made to take up higher levels of carbon dioxide.<\/p>\n \u201cBut from that basic premise it gets much, much more complicated,\u201d he said.<\/p>\n There are still a lot of unknowns about how soil microbe ecosystems actually work and what practices are most effective at capturing and storing carbon dioxide, Deich said. He added that what we most need right now is a lot of field experiments in a lot of places exploring these things in greater detail.<\/p>\n Tim Searchinger, a researcher at Princeton who closely studied the potential of carbon farming for an upcoming World Resources Institute report, took an even more skeptical stance.<\/p>\n He said there are limits on how much farmers can change their soil management practices, and other restrictions on how much more carbon we can reliably store in soils that we continue to farm. In addition, some efforts that could be credited as carbon farming might have taken place anyway.<\/p>\n \u201cOur view generally is that it\u2019s been a huge diversion,\u201d he said. \u201cWe have \u2026 an enormous number of things that need to done to be solve agriculture and climate change, and soil carbon ain\u2019t it, at least from a mitigation standpoint.\u201d<\/p>\n The first and most important priority for minimizing the climate impact of agriculture is to stop clearing more land for it, Searchinger stressed.<\/p>\n \u201cThere\u2019s no scientific uncertainty about that,\u201d he said. \u201cYou clear a forest and you lose a lot of carbon.\u201d<\/p>\n In particular, he said, we need to make extra efforts to conserve or restore peatlands, a type of wetland that releases vast amounts of carbon dioxide when it\u2019s dried out and converted to agricultural uses.<\/p>\n Boosting productivity on grazing and croplands\u2014through, say, better processes, nutrients, crops, or seeds\u2014can deliver bigger benefits, he argued, by easing pressure to expand agricultural operations. Better still would be for farmers to convert some fields back to grasslands and forests, which store far more carbon in their leaves, trunks, roots, and soil.<\/p>\n