Wood grown in the United States is being ground up, dried out, pressed into pellets, and shipped to Europe, where power plants burn it to make electricity.
Is this good for the planet?
The answer is yes, according to the wood pellet industry and policymakers in the European Union and the United Kingdom, which consider wood energy carbon neutral and encourage it as climate-friendly alternatives to coal and natural gas.
But many climate scientists and environmentalists disagree, arguing that trees should be left alive so they can continue to suck carbon out of the atmosphere and store it as wood.
The fight is heating up in the US, as both sides try to influence the Biden administration, which thus far has taken no stance on the issue. Both the New York Times and Politico have recently examined the pellet industry in lengthy articles.
“As the industry keeps expanding, the battle lines have hardened,” says Dr. Thomas Buchholz, who leads the Forest and Agriculture Team at Spatial Informatics Group (SIG).
Buchholz, however, is carving out some middle ground.
In a new case study of three wood pellet mills in the Southeast US, Buchholz and colleagues show that the presence of pellet plants drives tree harvests that otherwise wouldn’t have happened, therefore reducing carbon stocks. The paper, published in the journal Frontiers in Forests and Global Change, concludes that biomass energy from these plants is not carbon neutral and offers no climate benefits compared to fossil fuels over the next 40 years.
Despite the results of this research, Buchholz has no interest in condemning the entire industry.
“Biomass can be beneficial for the climate, or it can be horrible,” Buccholz says. “You have to evaluate these systems on a case-by-case basis.”
Today’s booming wood pellet industry has its origins in a regulatory decision. In 2009 European officials ruled that biomass energy—electricity generated by burning wood or other plant material—should be considered carbon neutral.
Since that decision, wood pellet manufacturers have built 23 plants in the Southeast US—the global center of pellet production—that can produce more than 10 million metric tons of pellets each year. Most of that output is exported to the UK, where biomass energy plants receive large government subsidies. British coal plants are being converted to burn biomass, which now accounts for nearly 15 percent of all electricity generated there.
The industry touts pellets as a green alternative to fossil fuels, a concept that seems counterintuitive. After all, trees are one of our best tools for fighting climate change because they’re so good at pulling carbon out of the atmosphere and storing it as wood. Burning wood releases that carbon back into the atmosphere.
But as European regulators see it, land where trees are harvested will be replanted. As those new trees grow, they reabsorb the carbon dioxide emitted by biomass power plants, achieving carbon neutrality.
What’s more, the industry claims that pellets are made from residues—tops and branches—of trees cut down to make lumber or paper. Such waste, they argue, is usually piled on the ground in forests, where it slowly rots. Turning this waste into pellets and burning them for energy, they say, releases no more carbon than the natural process of decay—while also producing electricity that otherwise would have required burning fossil fuels.
Many pellets, however, are made not from waste wood but from whole trees.
The industry claims that even this is good for the planet, because pellet demand creates an incentive for landowners to plant trees instead of agricultural crops, thereby sequestering more carbon.
The critics respond that it will take decades for these newly planted trees to absorb the amount of carbon that is being emitted by burning pellets now. And those are decades that we don’t have, given the rate of warming and the scientific consensus that emissions need to be cut now to avert catastrophic climate change.
“With all the urgency around climate mitigation action, you frequently hear that we really need to change things in the next 20 years to have a meaningful impact on climate change,” Buchholz says. “If a system doesn’t promise any benefits in the next 20 years, then it’s questionable whether that’s an approach we should take.”
According to Buchholz, the value of biomass depends on the type of wood you use and what factors you include in your carbon accounting.
Imagine, he says, that you measure the carbon stored in a forest once in 2010 and then a second time in 2020. During that decade you harvest some trees for pellet production, but the remaining trees continue to grow, keeping the overall level of carbon steady.
“If there’s no change to the amount of carbon in those ten years, then you can label any pellets produced from that forest during that decade as carbon neutral,” Buccholz says. “That’s the view endorsed by the pellet industry and European policymakers.”
But there are other ways of looking at it, such as estimating the amount of carbon the forest would have contained in 2020 if there had been no harvest for pellet production. Under that scenario, more trees would have continued to grow, so the forest in 2020 would have contained more carbon than in 2010. As a result, the pellets produced cannot be considered carbon neutral.
New Research from SIG
This missed opportunity for further carbon sequestration is central Buchholz’s new paper, “When Biomass Electricity Demand Prompts Thinnings in Southern US Pine Plantations: A Forest Sector Greenhouse Gas Emissions Case Study,” coauthored with his SIG colleagues John S. Gunn and Benktesh Sharma.
The paper examines three mills in the Southeast US that make pellets destined for electricity generation in the UK.
The plants use wood from non-industrial, privately owned pine plantations originally established to provide timber and pulp. Such plants traditionally have been managed with one thinning midway through the production cycle and then one final clearcut harvest. Small trees cut during thinning were intended for the pulp market, while the final harvest would be turned into lumber.
In recent years, however, the pulp market has not been lucrative enough to justify these thinnings, which means that entire stands were being left to grow.
The pellet market, however, has changed the market, creating a demand for thinned trees.
“The presence of the pellet industry triggers additional harvests that otherwise wouldn’t have happened,” Buchholz says. “That impacts carbon stocks in the US in a way that’s not accounted for in the European policies.”
When such factors are counted, “switching to biomass from fossil fuels offers no near-term carbon benefits or climate benefits,” Buccholz says.
Better Types of Biomass
Buchholz is careful to point out that the results pertain only to this particular system, where trees that otherwise would have been left standing are harvested to create pellets. Other types of biomass can offer carbon benefits, including:
- Forest residues that otherwise would have been disposed of by burning at the harvest site.
- Biomass from forest health restoration projects that use selective cutting to increase a forest’s resilience to drought, insects, or wildfire.
- Wood from dedicated fuelwood plantations growing short-rotation woody crops such as willow, poplar, or eucalyptus. Because such plantations are established with bioenergy use in mind, the carbon they sequester can legitimately offset future emissions from industrial processes, as long as they do not replace other vegetation that is high in carbon. (For two articles from Buchholz and colleagues on this topic, click here and here.)
The other key to making wood pellets climate-friendly is to use them in high-efficiency applications that produce both heat and power or heat alone. These systems can use up to 90% of the energy embodied in the biomass, compared to only 20%–40% for electricity-only systems.
Getting the Science Right
The future of biomass depends heavily on regulatory decisions.
During the Trump administration, the Environmental Protection Agency (EPA) declared biomass power carbon neutral but never established a formal rule on the issue.
It’s not yet clear where the Biden administration will come down on the issue. An EPA agency spokeswoman recently told the New York Times that the agency was not considering adding most wood pellets to its renewable fuel standard. On the other hand, Secretary of Agriculture Tom Vilsack was a strong supporter of biomass power when he served in the same position under President Obama.
The European example shows how important it is to carefully consider such regulatory decisions.
“The European Union and the UK endorsed biomass as a carbon-neutral fuel without looking too much into the details,” Buchholz says. Now, some European countries are taking a harder look at their commitments to biomass.
That suggests the US should proceed with a more nuanced approach.
“Biomass energy is not black and white—there’s a large gray zone,” Buchholz says. “The carbon accounting has to be thorough. You have to get the science right.”