Feb 08 2010

One Step Forward for Biomass Power

Posted by: Jonathan Marshall

Like Rodney Dangerfield, electric power plants that burn biomass don't get much respect in this age of high-tech solar and wind energy. But the conditional approval last week by the California Public Utilities Commission of a deal between PG&E and the owners of a small cogeneration plant near Bakersfield bodes well for the future contribution of biomass to a cleaner environment.

The Mt. Poso Cogeneration Company has operated a coal-fired cogeneration facility (combined power plant and industrial heat source) since 1989. Now it plans to convert the facility to burn agricultural and urban wood waste--everything from orchard prunings to clean demolition wood--to generate 44 megawatts of power, enough to meet the needs of about 47,000 average homes. Unless engineering or economic obstacles emerge, the plant should begin feeding biomass power into PG&E's grid by 2012.

The plant will divert woody biomass, which would have been burned in the open, to a combustion facility with modern emissions control equipment. And it will reduce carbon pollution by substituting biomass--which might otherwise have decayed, releasing greenhouse gases--in place of coal.

The retrofitting of old coal plants to run with at least some biomass won a ringing endorsement in a new study published by the Journal of Environmental Science and Technology. Substituting wood pellets for just 10 percent of the coal used in power plants in the United States and Canada would reduce greenhouse gas emissions by 170 million metric tons each year, it concluded.

The idea is catching on. In December 2006, Public Service of New Hampshire began running a 50 MW former coal-fired plant entirely on wood chips. Portland General Electric is now seriously considering converting Oregon's only coal-fired plant to burning wood pellets. And several other cogeneration plants in PG&E's service area are considering similar conversions.

California likely could do even more. Currently, biomass accounts for only about two percent of the state's power (comparable to wind and small hydro). David Bischel, president of the California Forestry Association, has argued that dead trees, scrub brush and other wood waste are abundantly available as fuel for additional power generation.

Biomass generation isn't a cure-all, but it's an important part of the clean-energy solution, even for transportation. As noted previously in NEXT100, some scientists have determined that in most cases it's better for the environment to burn biomass to generate electricity for plug-in vehicles rather than converting it to biofuel to run in traditional engines.

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