In the hunt for alternative fuels, biomass burning has become a popular way to swap out fossil fuels. Some industry leaders tout these plant-based fuels as carbon neutral, but many scientists say that’s not really the case.
This year, the US enacted a federal tax credit to provide a discount to home-owners who install wood burners to heat their homes because they are frequently seen as “clean” and renewable alternatives to fossil fuels. . One of these wood fuels that has been gaining popularity globally over the last decade is pellets made from compressed wood. Wood pellets are a type of biofuel made from compressed sawdust and wood scraps, and sometimes chopped down full trees, that can be used both to warm up a home and in a residential setting and on a large scale for electricity generation in lieu of fossil fuels like coal.
The biomass fuel industry has labeled pellets and wood a “renewable, reliable, local” fuel source, but that’s not necessarily the full story. Just last month, over 500 scientists from around the world signed on to a letter to President Biden and other world leaders warning that burning trees and forests for fuel seriously undermine climate goals because burning wood pellets considerably increases carbon emissions in the short term. While wood pellets are used for domestic home heating, only a small percentage of US homes use wood for heat. The main threat of wood pellets to carbon emissions and forests is when they are used on a massive scale to power electricity generation outside of the US.
“It’s just a physical fact that burning wood emits more carbon dioxide per unit energy than burning fossil fuels,” says Mary Booth, the director of Partnership for Policy Integrity. According to a report by the National Resource Defense Council, since wood is less dense than fossil fuel, a greater amount needs to be burned to generate the same amount of energy. This becomes a major emissions issue when wood pellets are used for large-scale electricity generation at power plants that once used coal, but have now been converted to use wood fuel because it was considered better for the climate.
Beyond just the inefficiency of trees as a fuel, we desperately need them for carbon capture purposes. The idea is that trees are renewable and can capture the carbon emitted from wood that is burned, but this only works on long timescales. The NRDC report details that it will take at least 50 years until enough carbon is captured by new trees that cumulative emissions from burning wood biomass will be reduced and could be considered carbon neutral. Add on the transport of materials and the production facilities themselves (that sometimes are powered by not-so renewable methods) and you’ve got even higher carbon emissions to contend with.
“You have an accumulating carbon debt every year that you run the facility” because trees take decades to grow back to their full carbon-capturing potential, Booth says. “So this is obviously not compatible with aggressive targets to reduce emissions.”
But not all wood pellets are made equal. If the pellets powering your home or business really are waste wood scraps that would otherwise decompose, using up those scraps is significantly less ethically murky than chopping down whole trees to do the same job. Typically only premium stock is used to make products such as furniture and building products, leaving many forests of less desirable wood untouched, but because wood pellets can be made out of any quality of wood, that could change. There is the possibility whole trees that would have otherwise not been logged could be used to make wood pellets. And for pellet companies like Enviva, meeting production capacity for their facilities requires logging 50,000 acres of oftentimes native hardwood forest yearly across the southeast US.
Sam Davis, a conservation scientist focused on the international export of wood pellets at the Dogwood Alliance, a nonprofit that works to protect forests, says they are skeptical that the pile of otherwise useless wood scraps from the lumber industry is enough to support the rapidly expanding wood pellet industry. “In 2011, [the US] exported one million tons of wood pellets and in 2019, we exported seven and a half million tons…that is not coming from byproducts.” According to the Dogwood Alliance, 60,000 acres of North Carolina forests are clear cut each year by the wood pellet industry.
The US exports wood pellets that are mainly manufactured in southeastern states such as North Carolina and Georgia. Last year, the U.S. exported 7.26 million metric tons of wood pellets to destinations like the United Kingdom and European Union.
Countries in the EU use wood pellets for electricity generation, which is frankly a concern, Davis says, considering the most efficient way to use up wood pellets—waste wood or otherwise—is to heat a home. “When you’re using wood pellets for heat, it’s actually pretty efficient…but when you’re using them for electricity, the efficiency is very, very low.”
Partnership for Policy Integrity and others are working to get the EU to overhaul their renewable energy strategy and end subsidies for forest biomass burning. In February, the Dutch Parliament ended some subsidies for the fuel after importing over 79,000 metric tons of wood pellets from the U.S. in 2020.
Scientists and conservationists are reluctant to promote any form of fuel that involves increasing logging, even if it helps move electricity generation away from fossil fuels. While we still have a fair amount of forest left in the United States, Davis says, forestry-related activities account for 85 percent of carbon emissions in forests in the country. “The Paris Agreement, which calls for close to net climate neutrality by 2050,” Booth says. ”And we’re just not going to get there by burning wood.”
Correction 3/18/21: The U.S. exported 7.26 million metric tons of wood pellets to destinations like the United Kingdom and European Union last year, not billion.