The state of California, wracked by drought, has 66 million dead trees across its landscape. They’ve been killed by both the drought itself and by voracious bark beetles, and now they’re just sitting there — destined to either decompose, burn in a wildfire, or be incinerated, for safety reasons, by state fire managers before the next blaze comes along.
And it isn’t just California. Raging bark beetle infestations, fanned by warmer temperatures and droughts, have also struck forests in Colorado, Wyoming, Montana, and Idaho in recent years. “About 100,000 beetle-kill trees fall every day in Wyoming and northern Colorado, to give you an idea of the order of magnitude,” says Erica Belmont, a professor of mechanical engineering at the University of Wyoming.
Belmont is studying an intriguing solution for what to do with all these dangerous dead trees — namely, burn them for energy. In a recent study in Energy Policy, Belmont and colleague Emily Beagle do the math on whether it would make sense to use the timber in existing coal plants, which can be “co-fired” with wood.
In isolation, it probably costs coal plants too much money to go around rounding up dead trees, carting them back, and then burning them — a big endeavor, Belmont explained. But there are sources of possible funds. For instance, the U.S. Forest Service is currently spending considerable money to treat forests and rid them of these dangerous trees — money that, maybe, could be given to the companies that burn them for energy instead, the study suggests.
Moreover, coal plants are facing strong climate regulations, in the form of the pending Clean Power Plan. In this regulatory context, burning trees that are already destined to decompose, catch fire, or be incinerated — and thus, give off greenhouse gases to the atmosphere no matter what — could conceivably supplant some of coal’s voluminous emissions.
“We see the real incentive for them to do this as being the upcoming regulations,” said Belmont of coal plants that may be considering co-firing. “Without those regulations, there would have to be some incentive for them to want to do this, because it is additional complexity to them.”
It’s not just co-firing — there are also specialized biomass plants that could burn dead trees. And a different group of researchers with the U.S. Forest Service, several California Universities, and other institutions have already experimented with the economics of taking trees from the Sierra Nevada region, which would otherwise have been burned to reduce wildfire hazards, and burning them in one of these facilities instead.
Such studies represent a hard-to-categorize contribution to an increasingly pitched debate over the burning of trees, or biomass, for electricity.
Large numbers of scientists have loudly protested recent legislative attempts to decree that biomass burning is “carbon neutral” based on the logic that, even though it gives off greenhouse gas emissions just as coal does (releasing the carbon that had been stored in the tree as it grew), future tree regrowth will one day sequester those emissions once again.
A leading critique of this assertion is that it takes a long time for a tree to grow back, meaning that the biomass burning is still adding carbon dioxide to the atmosphere for, at least, decades — a time period that can make a real difference for the climate and for climate policy. Moreover, there is not necessarily any guarantee that for every tree chopped down to provide electricity, another corresponding tree will regrow someday. Changing decisions about land use, for instance, could upset that assumption.
But Belmont argues trees that have already been killed by pests, like bark beetles, are a different story. First, they’re a hazard, because they can fall or provide fuel to wildfires. So there’s a benefit of getting them out of the way and getting something out of that, like energy.
She also points out the carbon in these dead trees is already destined for the atmosphere anyway, either through decomposition, release through combustion in a wildfire, or release in a controlled or planned burn that’s seeks to prevent one. “Quite often, it is being burned, and that carbon is being released, frequently without any emissions controls,” Belmont says.
That’s why the study suggests that under the Clean Power Plan, using a coal plant to burn some already dead trees could be a solution that presents a lot of wins.
It’s not clear, though, that even the particular situation of dead trees caused by drought and bark beetles is enough to quell the raging debate over biomass energy.
“The commonly-made claim that burning wood for energy is ‘carbon neutral’ is at best an exaggeration and at worst completely wrong,” said Phil Duffy, president of the Woods Hole Research Center and a prominent critic of biomass energy, after reviewing the study for the Post. “Because beetle-kill wood will decompose anyway, however, this case comes closer to being carbon neutral than others.”
But Duffy also added by email that the research may have missed some key points that complicate the analysis, such as the amount of carbon that would be required to transport dead trees to coal plants before they are even burned.
He also pointed out by email that “it is not clear if they accounted for the greater emissions from wood versus coal per unit of energy produced.” Ultimately, Duffy suggested, the research might be “pretty overoptimistic about the amount of emissions saved compared to the baseline scenario (letting the wood decompose and burning pure coal).”
The study identified four Colorado plants and one Wyoming coal plant that were reasonably close to large tree kill areas (within a roughly 100-mile radius), close enough to think that the trees could actually be culled.
But the opportunities probably aren’t just in these states. California, for instance, recently passed a bill that favors the burning of wood from “high fire hazard zones” for energy.
There is, any way you look at it, an irony in all of this. Tree-killing droughts and bark-beetle infestations are likely being exacerbated by a warming climate. To use the resulting dead trees to try to offset the emissions that are causing that warming — well, that’s sort of bizarre.
But in the strange world in which we find ourselves, it still may just be a policy that makes sense in some instances.