California Proposes Forest Thinning for Biomass Energy, But is it a Good Idea?

A Sierra Nevada beaver took a couple watt-hours' worth of biomass from this aspen trunk. | Photo: Miguel Viera/Flickr/Creative Commons License

A report released today by a consortium of state agencies recommends ramping up California's forest thinning program so that the resulting biomass can be burned to produce energy, but doing so may actually make the state's carbon footprint worse instead of better.

The state's 2012 Bioenergy Action Plan calls for increasing "community-scale, forest-based biomass facilities" that would take leftover biomass from forest thinning and commercial logging operations and burn it to produce electricity.

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The plan recommends that vegetation removed from transmission line corridors as a fire control measure also be burned to produce power. It also discusses options for using urban and agricultural biomass waste as a power source. All in all, says the plan, California creates enough biomass waste to generate at least 4,000 megawatts of power, but just 15% of that waste currently makes its way to energy production.

The California Energy Commission estimated in 2005 that the state could burn 10 million tons of forest waste each year on a sustainable basis. Forest waste includes debris from logging operations, trees cut in "forest thinning" operations, residue from sawmills, and what the Energy Commission referred to as "shrubland biomass" -- often meaning mature stands of chaparral.

Authors of the Bioenergy Action Plan point out that forest thinning is used to reduce the risk of wildfire by reducing the amount of fuel in vulnerable forests, and that:

Forest fires ... cause unproductive loss of biomass, large emissions of criteria pollutants and GHGs [greenhouse gases], property destruction, adverse public health consequences, and sometimes, permanent loss of ecosystem structure and function. These changes in turn lead to increased soil erosion, sedimentation in dams, declining water quality and quantity, and habitat and species loss.

According to the plan, Placer County's Air Pollution Control District has estimated that each 31,000 acres of that county's forest land could support 50 megawatts of biomass power production if forest thinning were done annually on the acreage in question.

Thinning California forests for biomass power generation may not be an easy sell. "Forest thinning" has long been seen by many environmentalists as a cover for increased logging of public lands, and reframing it as a renewable power source doesn't seem to have helped. According to the Natural Resources Defense Council (NRDC), renewable energy could even be seen as a "Trojan Horse" to promote clearcutting. In the NRDC's words:

The market and some government incentives -- for example, state renewable portfolio standards that require a certain proportion of power to be produced from renewable sources -- currently favor converting forests to intensively-managed, single-age and single-species plantations that resemble a natural forest only on the surface, providing little wildlife habitat and few other "ecosystem services." Converting forests to these types of tree plantations is an environmental disaster, given how much we depend on our natural forests for biodiversity, clean water, and many other important values. No matter how efficient and clean power plants get, they cannot turn unsustainable forest biomass into sustainable energy.

A study published last year by researchers at Oregon State University adds metaphorical fuel to the fire. Researchers Joshua Clark, John Sessions, Olga Krankina, and Thomas Maness measured the amount of carbon sequestered by forest ecosystems in the Pacific Northwest. They found that forests that had been thinned for biomass energy lost more carbon to the atmosphere than was saved by replacing fossil fuels with the theoretically carbon-neutral biomass.

In other words, cutting down young forest trees disrupts the ecosystem's ability to keep CO2 out of the environment, thus augmenting climate change, and the amount of carbon saved by burning that wood instead of coal isn't enough to make up the difference. If the Oregon State researchers' findings apply in California's somewhat drier forests, the conclusions will be somewhat daunting for forest biomass advocates.

The 2012 Bioenergy Action Plan was prepared by the state's Bioenergy Interagency Working Group, which included representation from the Natural Resources Agency, Department of Food and Agriculture, California Environmental Protection Agency, California Public Utilities Commission, California Energy Commission, Department of Forestry and Fire Protection (CAL FIRE), CalRecycle, and the State Water Resources Control Board.

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