Research at the University of California, Berkeley, has shown that proper use of compost on rangelands can sequester very large quantities of carbon dioxide.
The researchers have found that if a quarter-inch to one-half inch layer of compost were applied to 5 percent of California’s rangelands, it would sequester 28 million tons of carbon from the atmosphere—the equivalent to the annual emissions of 6 million cars. California’s grasslands evolved under the influence of with great herds of ungulates, tule elk among them. These herbivores would typically graze an area intensely, then move on. This pattern resulted in the periodic “harrowing” (with hooves) and fertilizing (with dung) of the land, encouraging the lush growth of native grasses which sequester carbon more effectively than the dense weeds that grow on vacant lands.
One study compared soil carbon levels at 35 sites on beef cattle and dairy operations in Marin County, California. They found a range of carbon levels, but the sites that registered a lot of carbon had one thing in common: Ranchers and farmers had spread raw manure on the land. Even though raw manure is known to emit prodigious quantities of greenhouse gases into the atmosphere, somehow carbon was getting down into the soil—and staying there. A study using compost found that four years after application, 90 percent of the compost’s carbon was still in the soil. Computer models indicated carbon levels would remain high for 30 to 100 years as a result of a single application of compost. Surprisingly most of the carbon did not come from the compost, it came from the atmosphere. The compost, it turned out, was a catalyst for a cycle of sequestration of atmospheric carbon.
Now the American Carbon Registry has certified application of compost to rangelands as a technology appropriate for production of saleable carbon credits to the voluntary carbon credit market. This means that, in an economic framework known as ‘carbon farming’, ranch owners can earn income by applying compost to their land.
An interesting article on this research is available at http://alumni.berkeley.edu/california-magazine/just-in/2014-11-19/new-global-warming-remedy-turning-rangelands-carbon-sucking
While this research comes from California it is quite possible that similar results could be obtained in Canada, especially on the prairies where large herds of bison were once common but have now almost completely disappeared. The presence of the bison maintained much higher soil carbon levels, and more ecologically sound and productive plant communities, than modern day agriculture. The California researchers note that their findings run counter to conventional wisdom among some climate change activists who tend to view cattle – major producers of methane – as a part of the problem. Their research suggests that rangelands, essential to cattle production, could be a major tool for addressing climate change. Businesses that send food waste to compost facilities instead of to landfill, with the compost subsequently going to agricultural land, could be making a more significant contribution to mitigation of climate change than previously recognized.