Power plants that burn wood: Renewable energy or major polluters?

In the north of England, surrounded by villages and farmland, lies a vast complex of concrete cooling towers that dominate the landscape.

These gray and somber structures might give the impression of traditional power generation, feeding on a feast of fossil fuels, but no longer. Instead of consuming copious amounts of coal, most of the boilers at the Drax power station now rely on a different menu: wood pellets, sourced from North American forests and shipped to the United Kingdom to keep the fires burning 24 hours a day.

This is bioenergy, and it’s classed as a clean source of energy by both the U.K. and the European Union, among others – playing a crucial role in their targets of renewable energy generation. Supporters see bioenergy as a critical asset in the transition to a cleaner future, even part of the longer-term mix, but critics are aghast that the felling of forests could ever be considered sustainable.

In tacit acknowledgment of this apparent paradox, the EU is currently in the midst of negotiations to classify what exactly can be counted as sustainable biofuel – with the added complication, now, of the war in Ukraine and efforts to pivot away from Russian fossil fuels as quickly as possible.

“Bioenergy – if it’s done sustainably – can really contribute,” says Andrew Welfle, a research fellow at the Tyndall Centre for Climate Change Research at The University of Manchester. “We have carried out much research working with industry, government, and academic partners scrutinizing its sustainability. In the vast majority of scenarios, bioenergy can provide energy with emissions far below those of coal or natural gas.”

Drax would certainly agree. And the power station in North Yorkshire accounts for 12% of the country’s renewable energy.

Others, however, are less convinced. A group of conservation organizations filed a complaint to the Organization for Economic Cooperation and Development last October, challenging many of Drax’s claims on sustainability. Just a few days earlier, Drax and 14 other firms were kicked off a global investment index of clean energy companies, as criteria for inclusion were tightened up.

Over in the European Union, where some of the other booted-out companies are based, the subject is no less controversial. Various EU bodies are hammering out their positions on revising what can be classed as “green” biomass, qualifying for subsidies. In a place where fully 60% of renewable energy is generated by the burning of organic matter, this is no trivial issue. And while biomass can refer to sources other than trees – crops grown to provide biofuel, for example – forest biomass is the most controversial, and it accounts for 70% of the EU’s bioenergy.

“Biomass, in all its different forms, is an integral part of our energy needs,” says Irene di Padua, policy director at Bioenergy Europe, a trade association that describes itself as the voice of European bioenergy. “When it comes to sustainability, we already have to respect quite strict requirements – how it’s harvested, where it comes from, what is the carbon footprint.” 

But herein lies one of the key points of contention: Proponents of bioenergy argue that burning wood can be a carbon-neutral process because the carbon released into the atmosphere will be reabsorbed by new trees growing where the old ones were logged. 

They also point out that the carbon released has been sequestered only as long as a tree has been growing, whereas the burning of fossil fuels is pumping carbon into the atmosphere that’s been locked away for millions of years. 

The problem, however, is that it will take decades of growth before the new trees will have reabsorbed the same amount of carbon released by the combustion of their predecessors – time, say climate activists, that we simply don’t have. Moreover, because of the nature of wood, you have to burn more of it than you would of coal to produce a given amount of energy, thus releasing a greater quantity of carbon into the atmosphere in the interim. 

“At the moment, it’s the worst of both worlds, because you’re using an energy source that adds the most carbon to the atmosphere, at the same time as cutting into your carbon sink,” says Martin Pigeon, forest and climate campaigner, and the focus person for bioenergy, at Fern, a forest advocacy group based in the EU.

“If you had asked me even two years ago if burning trees was better than burning coal I would have said, ‘Of course,’” continues Mr. Pigeon. “But now we are living in a situation where the climate crisis is becoming very visible for all to see; we’ve already entered an emergency phase.” 

For now, the debate is less about whether to use bioenergy and more on how to make it as sustainable as possible. One particular concern: what parts of the trees are being used to fuel the bioenergy boom. The industry insists that it uses only waste products from other activities, tree parts that can find no other use and would otherwise be sent to landfill or left on the forest floor.

Various investigations, however, have questioned these assertions. A CBS report in April 2022 captured footage of mountains of logs at a pellet-producing plant in the United States. Photographic evidence showing a similar story was compiled from sites all over the EU by the Forest Defenders Alliance in the same month. In both cases, they query whether such quantities of hefty tree parts could not have found uses other than burning.

The concern is that rising bioenergy demand may be leading to logging that would not otherwise occur. In a letter sent to world leaders last year, hundreds of scientists, describing this very scenario, put their name to a plea not to “undermine both climate goals and the world’s biodiversity by shifting from burning fossil fuels to burning trees to generate energy.”

To alleviate some of these potential pressures, one EU proposal is to exclude from its definition of green biomass any wood that comes from “primary forests” – areas little disturbed by human activity to date.

“The effects of using biomass for energy have impacts on the natural environment and other environmental objectives, which deserve society’s attention, in addition to just climate,” says Ben Allen, executive director at the Institute for European Environmental Policy, in an email exchange. 

The bioenergy industry, however, is lobbying to water down these proposals. In addition, at the end of January, 10 EU nations signed a letter to the European Commission, arguing that it was “too early” to strengthen the sustainability criteria for bioenergy. While it is not yet officially in the public domain, a spokesperson for the Commission confirms receipt of the letter.

The EU is expected to reach a conclusion on the matter no later than September, when a final vote is expected to take place. Amid the debate, many experts are wary of dismissing bioenergy out of hand. 

One paper, for example, co-written by more than 20 scientists from institutions around the globe, argues that “narrow perspectives obscure the significant role that bioenergy can play by displacing fossil fuels now, and supporting energy system transition.”

“If you look at bioenergy over the years, it’s a dynamic picture,” says Dr. Welfle, whose work focuses on bioenergy, sustainability, and climate change. “In the U.K., it’s used in a big way for power generation, but power is likely to be decarbonized in a big way.”

He predicts that “in the future it’ll be much more targeted to niche sectors such as providing low carbon fuel options for aviation and shipping.”