Harvest Carbon from the Air
Soil stewards can impact a changing climate by rebuilding soil to sequester carbon from the atmosphere.
Author: Raylene Nickel | Published: December 22, 2017
Carbon is as precious as gold to plants. Working with water and sunlight, carbon makes plants grow. Plants assimilate carbon in the form of carbon dioxide, extracting it from the air to make roots, shoots, and leaves. With the help of soil microbes, the plants then transfer the carbon to the soil through roots and decomposing residue.
The stable storage of this carbon below ground not only builds soil organic matter and improves future crops but also, like a pressure valve, relieves the atmospheric carbon buildup.
CARBON BENEFITS
The benefits of this plant-driven harvesting of carbon from the air extend far beyond the farm and ranch gate.
“If we were able to increase the carbon in the soils of the world by sequestering 3.6 gigaton of carbon per year [1 gigaton equals 1 billion tons], we could offset or negate the additional effects of climate change that will be caused by future increases in carbon dioxide released by the fossil fuel use of a growing world population,” says Rattan Lal. Lal directs the Carbon Management and Sequestration Center at Ohio State University.
“It is this assumption that was the basis of the 4 per Thousand program initiated at the Climate Summit in Paris in December 2015,” he says. “The strategy of this program is to sequester carbon in soils of the world at the rate of 0.4% per year in the top 16 inches of soil. Implementing such a program would require appropriate policies to encourage farmers to adopt the recommended management practices.
“Globally, the release of carbon into the atmosphere from fossil fuel use is 10 gigaton, and it goes up annually,” says Lal. “The U.S. accounts for about 18% to 20% of that amount. In the U.S., the per-capita rate of release of carbon into the atmosphere is going down but rising globally. Global warming has resulted from the increasing levels of carbon in the atmosphere. This is causing an increased frequency and intensity of extreme weather events such as floods, droughts, and hurricanes.
“Estimates of the total potential of carbon sequestration in world soils vary widely, and this potential is finite in capacity and time,” says Lal. “Nonetheless, soil carbon sequestration buys us time over the next 20 to 50 years until the low-carbon or no-carbon alternatives to fossil fuel take effect.”
The capacity for soil to sequester carbon is finite, because it’s limited to the soil’s original capacity to store carbon. Agricultural use over time has caused soil to lose carbon. Restoring soils to their original states accounts for the global potential for carbon sequestration.
“The potential soil carbon sink capacity of managed ecosystems approximately equals the cumulative historic carbon loss estimated at 55 to 78 gigaton,” says Lal. “Some recent estimates indicate the historic loss as high as 130 gigaton. Restoring carbon stock in world soils by 130 gigaton would be equivalent to a drawdown of atmospheric carbon dioxide by about 65 parts per million. Such an achievement could happen in 50 to 100 years.”