Could the Southeast create a 50-year debt of greenhouse gases by burning wood?

02-15-2012 // Tiffany Stecker - E&E News

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Burning wood from whole trees and residues to generate electricity in the southeastern United States may cut greenhouse gas emissions in the long run, but in the next 35 to 50 years, it will only hasten the consequences of climate change, environmental groups say.

The Southern Environmental Law Center, Forest Guild, National Wildlife Federation and Biomass Energy Resource Center released a study yesterday, composed of a literature review on the supply of biomass and an atmospheric study of greenhouse gas emissions from 22 biomass-burning facilities in seven Southeastern states -- Alabama, Florida, Georgia, North Carolina, South Carolina, Tennessee and Virginia.

Burning biomass is not likely to be carbon-neutral before 2053, the study finds.

"The short-term implications for climate change are especially critical," said Julie Sibbing, director of global warming, agriculture and wildlife for the National Wildlife Federation's National Advocacy Center in Washington, D.C.

To lower the negative impacts of a booming biomass market, the study makes three recommendations for the Southeast: Favor the use of forestry and paper mill waste, increase the efficiency of biomass plants, and burn biomass for thermal power rather than electricity.

Repaying the debt

Biomass energy is becoming an increasingly attractive option as a quick solution for transitioning from fossil fuel electricity to renewable energy. Forest-rich Southeastern states that have adopted a renewable energy standard could easily turn to biomass energy. North Carolina is the only state in the region with a legally mandated renewable energy standard. Virginia has a voluntary standard.

The supply review found that there is likely to be enough wood to satisfy a roughly 15 percent renewable energy portfolio for six of the seven states in the study, with the exception of Florida. In this scenario, woody biomass from the study region would power no more than 20 percent of the overall renewable target.

Although burning wood and plants for energy -- like burning fossil fuels -- releases carbon dioxide into the atmosphere, proponents of biomass energy said this is simply a carbon "debt" to be repaid. As trees are grown to satisfy a steady stream of biomass, they absorb carbon through photosynthesis, thus helping avert climate change.

Critics has said that this payback time is too long to really make a difference. A study released last year by the Manomet Center found that Massachusetts forests needed about 50 years to repay the carbon debt from expending carbon dioxide to generate electricity. This would increase the state's carbon emissions by 3 percent by 2050 (Greenwire, June 11, 2010).

Biomass supporters have criticized the Manomet study for being too local to Massachussetts. Bob Perschel, Eastern forests director for the Forest Guild, said the Southeast survey confirms the same idea as its predecessor, released in June 2010.

"The patterns were the same in that you get a short-term debt with a long-term benefit," said Perschel. "What it confirms is the general pattern stays the same." In Massachusetts forests, however, the payback is longer than in Southeastern forests.

Proponents have said that the use of waste wood from timber, pulp and paper industries would lower the carbon footprint of biomass power, as the residues would be burned or disposed of regardless. However, the study's literature review suggests that future biomass will come from whole trees as mill residues are used up in expanding markets, said Andrea Colnes, policy director for the Biomass Energy Resource Center.

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