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Could the garbage heap help save us from global warming?

By Hugh Price
Saturday, September 18, 2010; A13

In New Haven, W.Va., the Mountaineer Power Plant is using a complicated chemical process to capture about 1.5 percent of the carbon dioxide it produces. The gas is cooled to a liquid at a pressure of about 95 atmospheres and pumped 2,375 meters down to a sandstone formation, where it is meant to remain indefinitely. The objective is to reduce the amount of carbon dioxide being added to the atmosphere from the coal burning at the plant.

This certainly seems to be doing it the hard way. Extracting just this 1.5 percent of the CO2 from the plant's flue requires a $100 million investment, and whether the gas will remain underground or bubble to the surface is in question.

Fortunately, there is a way to capture and store excess carbon from the atmosphere that is cheap, efficient and environmentally friendly. It relies on two technologies that have been in use for more than 8,000 years: agriculture and the garbage heap.

Some basics: Plants absorb carbon dioxide from the atmosphere and convert it to sugars and other organic compounds. Some of this carbon is burned by the plant, and the rest is used to increase the plant's mass. If the plant or its components are eaten by an animal, some of that carbon will be burned by the animal, with the remainder used to increase the animal's mass. When the plant or animal dies, the remains are generally consumed by bacteria, which burn some of the carbon and use the remainder to create more bacteria.

When this process is in equilibrium, living things return as much carbon to the atmosphere as plants take out of it. And the CO2 generated by these organic processes is exactly the same as the CO2 released by burning coal or oil.

With an overabundance of carbon dioxide in the atmosphere, it is reasonable to ask, "Where are the plants?" Why hasn't the Earth's vegetation grown larger and faster to absorb the additional CO2? The answer is that it probably has. Some of the 20th century's improvement in crop yields may be due to higher concentrations of CO2 in the atmosphere. Nevertheless, eventually those plants die or are eaten, returning their carbon to the atmosphere. To remove CO2 from the atmosphere, the plant material has to be prevented from decomposing.

Any gardener knows that compost heaps must be turned regularly. Without access to oxygen, bacteria cannot break down plant material. The principle can be harnessed for carbon capture: All that is necessary is to pile the plants high enough, and the carbon at the bottom will stay put indefinitely. After all, this is how all that coal and oil formed in the first place.

Piles of plant material are not like ordinary landfills, of course. There is no need to worry about toxins leaching into the water supply. No elaborate liner or monitoring is required. Plant material need not be transported to distant sites or pumped underground but can be piled up where it grows. It is not even necessary to cover the heap with soil.

The most obvious target for such a technique is agricultural waste. Worldwide carbon dioxide emissions in 2006 were estimated at about 28 billion metric tons, of which the United States was responsible for 5.8 billion. That represents about 1.6 billion tons of carbon.

In 2009, the combined U.S. production of corn, wheat and soybeans was 487 million metric tons. That production measures the usable part of the plants. It is reasonable to believe that there is at least as much material in unused stalks and leaves. If just this material were stored rather than burned or plowed under, it could compensate for almost a quarter of the U.S. carbon footprint. The Mountaineer Power Plant could match the captured carbon of its high-tech approach by piling up the plant waste from 12,000 acres of farmland, at a tiny fraction of the cost.

Other land could be managed to maximize carbon capture. There are millions of acres of woodlands in North America where trees are grown for paper and lumber. Can leaves, bark and branches that are now discarded or burned be piled up instead? Is it more beneficial to recycle paper or to collect it?

Instead of trying to manufacture ethanol from switchgrass, would it be more effective to burn oil and bury the switchgrass? We sometimes pay farmers not to grow crops to sustain prices; should we pay them to grow otherwise useless crops and stockpile them?

The biggest problem with this approach may be that it's so low-tech. No green-technology subsidies are required, so there may not be a natural constituency for it. On the other hand, environmentalists should love it. What could be greener than growing plants? And for those concerned about the economy, this approach provides a low-cost method of reducing the country's carbon footprint without increasing the cost of energy. It is also reversible. If current concerns about CO2 concentrations turn out to be unwarranted, the stockpiled material will be readily available for use. What could be simpler?

The writer is the director of production planning at The Post.

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