Rattan Lau (another page of his here), director of the Ohio State University Carbon Management and Sequestration Center, argues that no-till farming could pull a substantial portion of carbon out of the atmosphere as an anti-global warming strategy.
Traditional plowing, or tilling, turns over the top layer of soil. Farmers use it for, among other reasons, to get rid of weeds, make it easier to use fertilizers and pesticides and to plant crops. Tilling also enriches the soil as it hastens the decomposition of crop residue, weeds and other organic matter.
Still, the benefits of switching to no-till farming practices outweigh those of traditional planting.
Since the mechanization of agriculture began a few hundred years ago, scientists estimate that some 78 billion metric tons – more than 171 trillion pounds – of carbon once trapped in the soil have been lost to the atmosphere in the form of CO2.
Lal and his colleagues estimate that no-till farming is practiced on only 5 percent of all the world's cultivated cropland. Farmers in the United States use no-till methods on 37 percent of the nation's cropland, which results in saving an estimated 60 million metric tons of soil CO2 annually.
"If every farmer who grows crops in the United States would use no-till and adopt management practices such as crop rotation and planting cover crops, we could sequester about 300 million tons of soil carbon each year," said Lal, who is also a professor of soil science at Ohio State.
"Each year, 6 billion tons of carbon is released into the planet's atmosphere as fossil fuels are burned, and plants can absorb 20 times that amount in that period of time," he said. "The problem is that as organisms decompose and plants breathe, CO2 returns to the atmosphere. None of it accumulates in the soil."
Out of that 6 billion tons of carbon that is released into the atmosphere the United States probably accounts for approximately a quarter since the US accounts for about a quarter of all energy use. Those are rough figures. But compare that approximately 1.5 billion tons released with the 300 million tons Lau says we could capture in the soil. About 20% of our current carbon release could be captured in the soil with changed farming practices. Of course, as population and the per capita GDP grow energy consumption will grow. The amount of carbon captured by changed farming practices would likely not increase along with the population and energy consumption increases.
Keep in mind that we may not want to reverse all the carbon dioxide increase caused by farming and the burning of fossil fuels. First of all, release of carbon dioxide caused by the human development of farming may already have prevented onset of an ice age. Also, higher carbon dioxide appears to be allowing plants to grow into the Negev Desert and other deserts. We may be able to genetically engineer crop plants to grow faster in the presence of higher atmospheric carbon dioxide and those plants may be more drought resistant.
Still, some carbon sequestration may eventually become desirable and changing of farming practices might be a cheap way to accomplish it. A friend points out that sequestration in soil even has the advantage over deep ocean sequestration in that the soil carbon is more easily accessible should we need it again in the much longer term to use as a warming gas. Given that the interglacial warming periods like the one we are living in now are the exceptions to the average colder periods that have characterized Earth's history keeping carbon accessible seems prudent.
On the other hand, for planet warming we could make a small amount of carbon go a much longer way. Methane is a more potent warming gas than carbon dioxide. If thousands of years from now it ever became necessary to release hot house warming gasses into the atmosphere we could run nuclear fusion power plants to generate power to reduce carbon with hydrogen to produce methane. Then we could release the methane gas into the atmosphere to have it serve as a warming gas.
Also see my previous post Iron Enriching Southern Ocean Pulls Carbon Dioxide From Atmosphere.
|Share |||Randall Parker, 2004 April 21 02:20 PM Engineering Environmental|