The sun peeks through a canopy of trees on Skyline Drive in Shenandoah Park, Va., in October 2008. (Karen Bleier/AFP/Getty Images)

Along with 196 other countries around the world, the United States has made a number of ambitious climate commitments that experts say will depend heavily on the expansion of renewable energy and the increasingly stringent regulation of carbon output. But some potential new legislation, which critics claim relies on scientifically questionable assumptions, has scientists and environmentalists worried about taking a step backward when it comes to climate goals.

The controversy centers on a specific provision in the House appropriations bill for fiscal year 2017 regarding the burning of biomass (typically wood and other plant material) for energy. The bill proposes that the Environmental Protection Agency treat biomass energy as carbon neutral —that is, the agency would assume the practice does not contribute any extra greenhouse gas emissions to the atmosphere — under certain conditions.  

Biomass is, in fact, generally regarded as a renewable energy source, since more trees can be grown after the old ones have been harvested for energy. However, renewable energy and clean energy are not always one and the same. Burning biomass for energy actually releases substantial amounts of carbon into the air — in fact, some research has suggested that it may even be worse for the climate than burning coal.  

The proposed legislation suggests that biomass energy be treated as carbon neutral as long as national forest stocks are stable or increasing. The rationale is that trees serve as a carbon sink, taking up carbon from the atmosphere and storing it away — so if more trees are growing, they’ll cancel out the carbon emissions released by burning other plant matter.  

Scientifically, though, the argument has a lot of problems, experts say.

“It takes decades to centuries for carbon to accumulate in what I call the forest carbon bank,” said Beverly Law, a professor of global change biology and terrestrial systems science at Oregon State University. On the other hand, burning trees for energy releases all their carbon into the atmosphere immediately. This means that biomass energy has an immediate effect on the climate, one that would take years of tree-growing to reverse.

The Senate is considering its own version of the appropriations bill as well, although it’s unclear for now how the language regarding biomass energy differs from the House version. An earlier draft of the Senate bill, obtained by The Washington Post, contained nearly identical language, although it suggested evaluating stocks on a regional basis instead, a move intended to account for differences in forest ecosystems throughout the country. However, people familiar with the matter have indicated that the language may have since changed. The draft is expected to be reviewed by the full Senate appropriations committee on Thursday.

The House bill also indicates that the same carbon-neutral treatment should apply if the biomass in question comes from residual matter leftover from mills, harvests or other forest management activities — in other words, if the biomass was dead and considered waste in the first place. It’s true that these bits of matter would eventually decompose and lose their carbon to the atmosphere anyway — but Law pointed out that, occurring naturally, this process would take long periods of time, whereas burning the plant matter would release all its carbon immediately.

In fact, she and colleague Mark Harmon, another forest expert at Oregon State, recently submitted a letter to Democratic Sens. Ron Wyden and Jeff Merkley of Oregon, expressing their concern about the language, which they claimed “is very likely to be extremely counterproductive to the goal of reducing greenhouse gas emissions to the atmosphere.”  

In a separate letter to members of the Senate Appropriations Committee, who will soon be reviewing the Senate’s version of the bill, nearly 50 environmental groups expressed similar concerns.  

If such legislation were to go into effect, many biomass energy facilities would not be subject to the carbon-cutting regulations proposed for other industries in the Clean Power Plan. Rather, they would be regarded in much the same way as solar or wind farms. Critics worry that this treatment could slow the ability to meet domestic climate goals, particularly now that the practice is gaining popularity and some coal-fired power plants in the country are being re-outfitted to burn biomass as well.

This is not the first time this controversy has arisen. Earlier this year, the Senate passed a sweeping energy bill addressing everything from advancing the electric grid to researching clean coal technologies. But environmentalists largely decried an aspect of the bill involving biomass energy. 

Similar to the legislation proposed in the appropriations bills, the energy bill proposed that the EPA recognize biomass burning as a carbon-neutral energy source. This provision received comparable backlash at the time, including a letter signed by dozens of scientists.

“This amendment puts forest carbon in the atmosphere contributing to climate change instead of keeping it in living, productive forests that provide multiple benefits of water and wetland protection, flood control, soils protection, wildlife habitat, improved air quality and recreational benefits for hunters and all who enjoy being in the great out-of-doors,” they wrote. “Legislating scientific facts is never a good idea, but is especially bad when the ‘facts’ are incorrect.”  

Granted, there’s another side to this issue. It’s true that forests do serve as a valuable source of carbon storage — so over a long enough period of time, enough new trees could actually end up absorbing the same amount of carbon emitted by burning biomass. In fact, a 2014 letter to the EPA, signed by more than 100 university experts, praised the advantages of biomass burning and noted that “most debates regarding the carbon benefits of forest biomass energy are about the timing of the benefits rather than whether they exist.”

It remains to be seen whether the current protests will trigger change in either the energy bill (which has yet to be signed into law) or the appropriations bill. But scientists and activists remain concerned about the possibilities.  

“Our global target is to keep temperatures from getting above 2 degrees Celsius by reducing greenhouse gas emissions, and so with that agreement we need to be tracking the carbon closely — and this would simply be adding it to the atmosphere,” Law said. “It’s a problem in our international agreements. It goes against what we’re trying to do.”

Read more at Energy & Environment:

30 years ago scientists warned Congress on global warming. What they said sounds eerily familiar

Poison ivory? Scientists say the sale of legally collected elephant ivory was a disaster

The atmosphere has hit a grim milestone, and scientists say we’ll never go back ‘within our lifetimes’

For more, you can sign up for our weekly newsletter here, and follow us on Twitter here.