Interest in extracting woody biomass—usually the limbs, tops, needles, logging slash and other low-value wood—has increased because of rising fossil fuel costs, concerns about carbon emissions from fossil fuels and the risk of wildfires. Environmentalists are concerned about tapping into available forest biomass, but officials say it can be done in ways that meet the country’s energy needs while maintaining crucial forestlands.
How Much is Available and Where is It?
Forestlands make up about one-third of the nation’s total land area and could supply about 368 million dry tons of biomass annually, according to “Biomass as a feedstock for a bio-energy and bioproducts industry: the technical feasibility of a billion-ton annual supply,” a joint study sponsored by the U.S. DOE and USDA. Several factors including environmentally sensitive areas were taken into consideration when calculating the figure, which included forest and agricultural biomass potential. To displace 30 percent or more of the nation’s petroleum consumption would require 1 billion tons of dry biomass annually, the report says.
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In 2008, 2.9 million green tons of biomass was removed from national forests, according to Ed Gee, chair of the USDA Woody Biomass Utilization Group. It is possible that more will be used in the future, he said, and more biomass is available on private lands than federal because of timber residue. The USDA alone manages 193 million acres of forestland, including grasslands, and the Bureau of Land Management manages another 263 million acres.
Nearly 70 percent of the existing biomass feedstock comes from forest products industries, the billion-ton report says. Although 368 million tons are available, estimates of what the workforce is capable of harvesting have not been nailed down, Gee says.
Gee says he believes forest woody biomass could meet America’s renewable energy needs, but the forests need to be sustained for future generations. “It’s very difficult to balance that,” Gee says. “Folks need to work together and find common ground.”
The most biomass-dense forests are in the southeast portion of the country. The “Southern Bioenergy Roadmap,” a report by the Southeast Agriculture and Forestry Energy Resources Alliance and the University of Florida, found that 12 southern states—Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee and Virginia—contain 30 percent of the nation’s bioenergy potential in their agricultural and forestry resources.
In California, about 20 percent of the total 4.5 million bone-dry tons of biomass used annually to fuel the state’s 27 biomass power plants comes from forests, according to John Shelly, woody biomass utilization specialist at the University of California-Berkeley, and Forest Products Society president-elect. Biomass plants produce about 2 percent of California’s power, or 640 megawatts, he said, and forest-based biomass makes up 7 percent of the estimated 50 million tons of biomass available in the state per year. “It’s estimated we could probably double that without negative effects on the forests,” he says.
Pennsylvania’s 17 million acres of forestland also have generated interest from the biomass industry, but the current estimate of available low-grade wood for biomass harvest in the state—6 million tons—is overly optimistic and doesn’t adequately consider several ecological, social and practical concerns, according to the Pennsylvania Department of Conservation and Natural Resources.
Differences also exist among forests east and west of the Mississippi River because of fire susceptibility relating to weather, density and insect infestations, Shelly says. Wildfires are common in the west, where forests are dense and fuel availability for fires is high. “If you’re going to remove it, a good place to put it is into the biomass sector,” he says.
The primary short-term benefit of biomass harvest for wildlife in a forest is to create clearings that provide the habitat needed by a variety of species, according to the DCNR report.
The long-term benefit lies in the potential for biomass markets to provide economic incentives to cut low-value wood and promote the regeneration of a new, healthier and more diverse forest, it adds.
“From my point of view, it’s positive because we’re using residue,” Shelly says. It would end up in landfills if it wasn’t used, he adds.
The Flip Side
Harvesting biomass from forests, if not done properly, can expose soil to drying and erosion, reduce biodiversity, negatively impact the food supply for beneficial insects and wood-boring species, reduce organic matter, eliminate habitats and denning sites, and limit flowers that support declining species of pollinators like bees, bats, butterflies and hummingbirds, among other adverse effects.
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