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How 'Green' Are Wood Pellets as a Fuel Source?

In the search for a clean source of energy, a contender has emerged: little pellets of compressed wood. Harvested from forests in the American South, pine and hardwood trees are dried, compressed, and turned into inch-long pellets that are burned as fuel in electric power plants, mainly in the United Kingdom and Europe, to power homes and businesses.Under rules grandfathered into the Paris Climate Agreement and reaffirmed this summer by European regulators, burning trees for electric power is considered a carbon-neutral energy source—as long as the trees are replanted. The wood pellet industry argues that it provides an alternative to coal and relies on a sustainable resource: forests that will regrow in the future and remove carbon from the atmosphere .

But many scientists and conservation groups say the opposite: that burning wood is as dirty as coal, and the claim of carbon neutrality is an error that will boost emissions and make it impossible to keep the planet from warming further. What’s more, trees that are cut down take anywhere from several decades to half a century to regrow, time that many climate scientists say the planet doesn’t have.

“It's really simple,” says John Sterman, professor of management and director of the sustainability initiative at the MIT Sloan School of Business. “You put carbon into the air right now, today. But regrowth takes time and is not certain. Maybe you'll remove it in decades to come, or a century from now. That's a terrible deal.”In 2018, Sterman and two colleagues published a study in the journal Environmental Research Letters calculating that carbon dioxide emissions from burning wood are actually higher than burning coal because wood contains more water—even when dried and compressed into a pellet—and is a less efficient source of energy. The study stated that it would take 44 to 104 years for new growths of trees to soak up that excess CO2 and make wood a greener fuel source than coal. (The wide range in the study indicates that some forests regrow faster than others.)In Washington, provisions to boost the wood pellet industry were included in the massive $1.2 trillion infrastructure bill signed Monday by President Joe Biden, as well as the $1.75 trillion Build Back Better spending bill being negotiated by Congress. On November 4, a group of 100 forest ecologists, climate scientists, and ecosystem experts, including Sterman, signed an open letter to Biden and Congress urging them to remove these provisions in both pieces of legislation.The infrastructure bill, which is now law, approves an additional 30 million acres of logging on federal public lands over the next 15 years. It also exempts logging for wood pellet plants from the National Environmental Policy Act, which requires the US Forest Service to study the environmental effects of its own proposed actions before it makes a decision. That new law also adds subsidies to promote carbon capture and storage (CCS) technology at plants that both manufacture and burn wood pellets.