March 27, 2007 11:11 AM PDT
Manure power goes live in Texas
Six of the eight digesters--large silos that effectively employ heat and microbes to transform the manure into gas--are up and running. When the facility is fully operational, it is expected to be capable of producing 650,000 million cubic feet of gas, or BTUs of heat, a year. That's the equivalent of 4.6 million gallons of heating oil. (About 1,000 cubic feet of natural gas can produce 1 million BTUs.)
The gas is being bought by the Lower Colorado River Authority, which will also get carbon-trading credits in the transaction.
The shipment, which was delayed, marks another milestone in the pursuit of making alternative sources of energy more mainstream. Farmers, mostly in Europe, have been using digesters that turn manure into gas for a few years. The farmers, however, consume the gas for their own purposes.
By contrast, Microgy, a division of Environmental Power, takes the manure from thousands of cows at different dairy farms, processes it and then ships the gas over commercial pipelines.
It's a small amount, compared with the overall consumption of natural gas. In 2003, the world used 95 trillion cubic feet of natural gas.
Getting natural gas from manure has commercial and environmental benefits, according to Microgy. Harvesting manure efficiently could help reduce natural gas exploration and imports. The carbon dioxide produced in the process is also considered renewable: alfalfa sucks up carbon dioxide from the atmosphere; cows eat it; and when it gets released from the biogas, some portion gets reabsorbed by plants. The process doesn't add additional carbon from the middle of Earth to the environmental cycle taking place on the surface.
Manure is also nobody's friend. It can cause algal blooms--an increase in algae in aquatic systems--and other problems. The stems and other solid matter left over after the gas is produced can also be used for cow beds.
Demand for energy and mandates to cut emissions are expected to drive the alternative-energy markets.
Microgy originally hoped to start shipping gas last fall. The company, however, experienced difficulties in getting the machinery that cleans and compresses the gas for commercial shipments.
Manure doesn't directly turn into gas. First, it gets turned into a substance called biogas, which is a mixture of methane (natural gas), carbon dioxide and sulfur compounds. The machinery removes the carbon dioxide, sulfur and any water vapor that happens to get into the mix.
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