Biomass Can Displace Coal
- Posted on May 12, 2011
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Dominion Virginia Power is converting three of its coal plants to those that can use biomass, or in this case, wood chips that it says will result in less pollution. If approved by local regulators, the project could get going in two years -- and become a harbinger of things to come in the utility sector.
It’s all part of Dominion’s plan to meet Virginia’s voluntary Renewable Portfolio Standard that calls on the state’s investor-owned utilities to provide 15 percent of its power from green sources by 2025. Wood chips, in fact, are part of the biomass family. But unlike its agricultural brethren, they do not result in food shortages and those wood chips could be mixed in with coal before it is combusted.
"Our proposal to convert these units from coal to biomass provides customers with economical electricity, delivers environmental benefits and takes advantage of a renewable, low-cost fuel source,” say Dominion Generation CEO David Christian.
Each of these units can currently generate 63 megawatts of electricity of peaking power, running only when demand is at its highest, the utility says. When converted, they would crank out 50 megawatts each, but operate essentially all of the time. Together, these stations would provide electricity to about 37,500 homes.
Dominion goes on to say that the fuel switch would reduce nitrogen oxides, sulfur dioxide, mercury and particulate emissions, and all of the stations would meet stringent new emissions standards established by the U.S. Environmental Protection Agency. While some disagree, it maintains that wood fuel is “carbon neutral.”
The three power stations to be affected are Altavista, Hopewell and Southampton County. They would work similarly to another of Dominion’s facilities that uses the concept: Pittsylvania. That 80 megawatt plant is one of the largest on the East Coast with more than 90 percent of its fuel stock coming from waste wood that would otherwise be burned off or dumped in landfills.
As is the case with any biomass facility, there must be a continuous supply of wood chips. Take Pittsylvania: Dominion says that 3,300 tons of waste wood are loaded on to 150 trucks each day.
Building a biomass plant from scratch is a hugely expensive undertaking. Estimates are that it cost twice as much as a coal plant. Further, coal produces about twice the oomph -- BTUs -- as wood chips, meaning power plants have to burn twice the amount of wood chips as they would with coal.
That has led the Manomet Center for Conservation Sciences to say that the net effect on greenhouse gas emissions is higher. Generally, if more trees are cut down and then there would be fewer of them to absorb the carbon emissions. Newly planted trees, meanwhile, are unable to absorb that carbon at the same rate as older trees. A more practical solution may be to co-fire the wood and coal together.
About 20 utilities in North America are now using wood chips to replace 5-25 percent of the needed coal or natural gas. Biomass plays a key role today with 7,000 megawatts of installed capacity, says the U.S. Department of Energy. It also says that the co-firing of biomass and fossil fuels is the most immediate step that utilities can take to cut their carbon dioxide emissions.
Consider WE Energies, Wisconsin’s largest utility: It is building a 50-megawatt wood-burning power plants that is expected to be operational in 2013. That is a $250 million effort intended to settle a coal plant-related lawsuit. It’s similar to a situation to that of FirstEnergy, which had planned to convert two of its coal units to would run on wood chips and produce 312 megawatts, although that has been put off because of the economic downturn.
“The most economical means of generating electricity using these wood chips is the technology of co-firing,” writes Southern Co., which is using the technology at one of its Alabama facilities. “The high capital and operating costs involved with a new stand-alone power plant are avoided. It is a renewable technology most likely to directly displace coal. And there are tens of millions of acres of forests in Alabama, Georgia, Mississippi, and Florida, many located within reasonable transportation distance of Southern Company power plants.”
Utilities are under pressure to reduce their emissions. And while the cutting down of trees to make electricity would come under fire from opponents, the using of biomass from wood waste is a more plausible option. It’s not a panacea but it is one way to lessen the nation’s dependence on coal.
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