Lawmakers are once again pushing U.S. EPA and other federal agencies to recognize the burning of biomass as a carbon-neutral energy source. But scientists say that could be a bad move for the climate.

A massive fiscal 2018 federal spending bill unveiled by congressional leaders Wednesday night includes a provision urging the heads of EPA, the Energy Department and the Agriculture Department to adopt policies that “reflect the carbon-neutrality of forest bioenergy and recognize biomass as a renewable energy source.”

The language has appeared in similar forms in previous spending bills the last few years, due to pressure from lawmakers in forest-heavy states. This latest version follows recent comments by EPA Administrator Scott Pruitt declaring biomass a carbon-neutral energy source. He has billed the change as part of the administration’s broader efforts at “energy dominance.”

In a letter to New Hampshire Gov. Chris Sununu (R) last month, Pruitt stated the agency’s decision was partly in response to concerns articulated by the forest and forest products industry (Climatewire, Feb. 14).

But scientists have been expressing concern for years about the emissions produced by burning biomass. Many experts suggest that declaring wood burning a carbon-neutral form of energy is not only inaccurate, but a potential step backward for global climate change mitigation efforts.

Renewable, yes. But carbon neutral?

William Schlesinger, a biogeochemist and former president of the Cary Institute of Ecosystem Studies, was among the latest to weigh in with commentary published in Science yesterday. He said that “recent evidence shows that the use of wood as fuel is likely to result in net CO2 emissions.”

Biomass is technically a “renewable” energy source, in that trees can be replanted after they’re harvested. And some lawmakers have argued that because trees store carbon as they grow, replacement forests will gradually remove the carbon dioxide emitted when the previous trees were burned for energy, making the whole process carbon neutral—that is, putting no net emissions into the atmosphere.

But there are some serious flaws in that argument, many scientists suggest. One of the biggest issues is the matter of timing.

Burning biomass for energy releases large amounts of carbon into the atmosphere all at once. But depending on the type of tree, forests may take decades or even a century to draw the same amount of carbon back out of the air.

“We call it ‘slow in,’ as in it takes a long time for the carbon to accumulate in the forest, and ‘fast out’—you’re burning it so it goes into the atmosphere rapidly,” said Beverly Law, an expert in forest science and management from Oregon State University.

One could argue that the process has the potential to be carbon neutral over very long time scales but not in the short term. And that means it’s not a useful strategy when world leaders are working to reduce global carbon emissions immediately.

Even for the process to be considered carbon neutral on long time scales, Schlesinger noted, forest managers would have to be certain that replacement trees were given enough time to store the same amount of carbon that their predecessors contained when they were harvested. Especially if older, more carbon-rich forests are cleared to make room for faster-growing, easier-to-harvest trees, then even more carbon must be stored away to make up the difference.

The language in the spending bill does indicate that forest biomass for energy should only be considered carbon neutral if it “does not cause conversion of forests to non-forest use.”

Schlesinger also pointed out that much of the wood raised and harvested in the United States for energy purposes is actually shipped to the European Union, where biomass is currently treated as a carbon-neutral energy source. Processing the biomass for energy use (converting trees into wood pellets, for instance) and shipping it overseas only adds to the total emissions produced by the industry, he noted.

According to Law, a more climate-friendly approach would be to simply preserve or add to existing forests without harvesting them—a process that would enhance the nation’s natural carbon sinks—and focus instead on truly carbon-neutral sources of energy, like wind and solar. Adopting policies that equate biomass with these cleaner energy sources could be “devastating,” she said. “It does exactly the opposite of what we need to do: reduce emissions.”

It’s hardly the first time scientists and environmentalists have raised the alarm. In 2016, dozens of environmental groups submitted a letter to the Senate Appropriations Committee urging members to reject any language in an upcoming appropriations bill that might deem biomass a carbon-neutral energy source. An energy bill also passed by the Senate in 2016 contained similar language, and more than 60 scientists responded with a letter outlining their concerns. Controversy arose over similar language in spending bills announced in 2017, as well.

Scientific discussions ‘left hanging’

The House and Senate have until tonight to pass the 2018 spending bill to avoid another government shutdown. In the meantime, EPA appears primed to follow through with some of the forest product industry’s recommendations.

Pruitt said in his letter to Sununu last month that EPA was considering “a range of options consistent with a carbon neutral policy for biomass from forests and other lands and sectors” for Clean Air Act permitting programs. Pruitt described the move as a way to increase the “economic potential” of the nation’s forests under an “all of the above" energy policy.

“Unquestionably, by providing certainty for the treatment of biomass throughout the agency’s permitting decisions, the use of biomass energy will be bolstered, to the benefit not only to the forest products industry but to the environment as well, while furthering the Administration’s goal of energy dominance,” he wrote.

EPA is also reviewing certification standards for its federal procurement recommendations. Pruitt’s letter noted that current standards excluded products from managed forests such as those certified by the Sustainable Forestry Initiative and the American Tree Farm System.

The agency did not elaborate when asked for more information about how the agency was progressing toward classifying biomass as carbon neutral.

Pruitt’s statements also came as EPA’s Science Advisory Board remains deadlocked after years of debate on the best way to advise regulators on how to account for emissions from burning biomass. Schlesinger, himself a member of the advisory board, noted that the group has not met since August and that discussions about the designation of biomass energy were “kind of left hanging as to what was happening.”

“If he’s made that decision, it was done without the input of the Science Advisory Board,” he added.

Steven Hamburg, chief scientist at the Environmental Defense Fund and an advisory board member, criticized Pruitt’s position during an interview last month.

“The science isn’t done,” he said. “The administration is not in a position to make a science-based determination in absence of scientific assessment, and this is a science question.”

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.