Biomass, Renewables

Uncertainties lead to biomass-fired unit shutdown

Issue 10 and Volume 99.

Uncertainties lead to biomass-fired unit shutdown

According to the National BioEnergy Industries Association (NBIA), Washington, D.C., the biomass power industry in California grew at an annual rate of 28 percent during the 1980s. California`s biomass-fired capacity was 807 MW in 1990.

However, from 1990 through 1993 only 1.3 percent of the State`s new electric capacity was added by biomass fuels. A peak of 838 MW was reached in 1993.

Today, only 584 MW of biomass-fired capacity is operational in California, a loss of 30 percent of the total capacity in operation in 1990. In the opinion of the NBIA, the plants that have been shut down were operating efficiently and reliably and were profitable. All of the plants taken out of service have been the targets of electric utility buyouts.

Electric utilities in the state are making the buyout of projects very attractive even to operators of profitable projects, said the NBIA. However, some people in the biomass industry believe the biomass power plant owners are selling out because of the uncertainty caused by the restructuring of the electric utility industry presently under way in California.

Research continues

Although California`s biomass-fired electric power capacity is shrinking, research is being conducted into biomass gasification. In 1994, researchers at Battelle, a research and development facility in Columbus, Ohio, successfully integrated a gas turbine with a biomass gasification pilot plant. In the opinion of the researchers, this was the first known operation of a gas turbine, fired with biomass-derived gas.

According to Mark Paisaley, Battelle`s program manager, the pilot plant demonstration is significant because sawdust, bark, wood wastes and other forms of renewable waste resources were used to produce electricity economically and efficiently.

Biomass-derived gas, produced by the gasification of renewable resources such as wood, crop residue, lawn scraps and residue from food manufacturing can also be used in the production of chemicals. In the opinion of Battelle, biomass fuels have the potential to make a significant im pact on the U.S.`s energy supplies by reducing our dependence on the import of foreign oil.

Similarly, crops grown specifically for biomass fuel can provide sustainable supplies of economical, environmentally attractive, renewable energy, said Paisley.

During the operation of Battelle`s pilot plant the researchers fed 10 tons of wood per day into the gasifier together with a mixture of steam and hot sand. On leaving the gasifier the gas has to be scrubbed (cleaned) before it can be used in the gas turbine. Sand removed in the scrubbing process is recycled back into the gasifier while the small amounts of charred wood, also removed during the scrubbing process, are captured and sent to a combustor. The combustor reheats the sand and produces steam used in the gasifier and for drying the wood.

“There are big advantages to being able to generate electric power from biomass,” said Paisley. Two major advantages are that it is a completely renewable fuel and that no carbon dioxide is added to the environment during combustion.

Biomass-produced gas is also more efficient than burning the wood without gasification because the process takes advantage of the high reactivity of the biomass, said Paisley. Battelle is continuing its research in this area and is now experimenting with using shredded municipal waste in the gasifier.

Together with their partners, Future Energy Resources Corp. of Atlanta, Battelle has just broken ground for a commercial-sized plant at the McNeil generating station in Burlington, Va. The schedule calls for the plant to be in commercial operation in early 1997. In operation, the McNeil plant will gasify 200 tons per day of dry biomass material. z