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BURNING WOOD to make electricity? There’s enough controversy in this concept to keep us occupied for awhile, so let’s begin by considering several aspects of the matter, as discussed in Science, January 6, 2017, published by the American Association for the Advancement of Science.
“The Burning Question,” by Warren Cornwall, is a summary of this controversial wood-to-electricity concept. At its core is the question of wood being a “carbon-neutral” fuel.
That is, as they grow, plants take in CO2, just as we expel CO2 with each breath. And when wood is burned, one of its combustion products is CO2 returned to the atmosphere.
Does this make wood a carbon-neutral energy source?
The European Union has a goal of producing 20 percent of its electricity through renewable sources by 2020. And, for the purposes of emissions accounting, the EU has designated wood as a carbon-neutral fuel. This gives wood the same beneficial treatment under tax, trade and environmental regulations as that given to wind or solar energy.
Yet, in some cases, wood-burning facilities put out more CO2 per unit of electricity than their coal- or natural gas-fueled counterparts. Among other factors, it depends on the water content of the wood being combusted.
Another important aspect of renewability is the total life cycle of an energy source. As a reductio ad absurdum, even coal and petroleum are renewables: All we have to do start with the right stuff and wait for millennia.
Proponents of wood-to-electricity point to reforestation as a reasonable cycle. One tree is cut down, part of it ends up as lumber, part as pulp, and part as wood pellets destined to an electric power plant. Another tree replaces this one and, as it grows, it will again sequester, i.e., store up, CO2. It’s just a matter of time.
In fact, the U.S. Environmental Protection Agency has a panel studying this. According to Science, “In its latest draft, the group recommends doing carbon accounting over a 100-year time frame…. Such long tallies give new forests plenty of time to mature and recapture carbon, making wood appear closer to carbon neutral.”
“But some scientists,” the magazine notes, “object that such long time scales gloss over the risk that the near-term spike in emissions produced by large-scale wood burning will cause damage that can’t be undone.”
Another aspect is the type of tree: Softwood pines evidently repopulate a forest more quickly than hardwoods. Also politics enter the picture: Notes Science, “Unlike forests in the western U.S., which are mostly owned by the U.S. government, more than 80 percent of southeastern forests are in private hands.”
Commerce enters as well: “At one extreme, logged forest might be converted into farmland or housing lots, never getting a chance to regrow and soak up carbon. Or a booming pellet trade could have the opposite effect: encouraging farmers to plant trees where crops or pasture grasses once grew, amplifying the carbon benefits.”
A specialist noted, “You can’t just tell the biological story. My thesis is that ignoring markets gives you more of a wrong answer.”
The southeastern U.S. has been a growing source of wood pellets for European power plants. Britain’s 4000-megawatt Drax power station in Yorkshire, the largest one in the country, has converted half of its facility to burning wood pellets.
According to Science, “U.S. exports, nearly all from the southeast, grew from zero in 2005 to more than 6.5 million metric tons in 2016…. Pellet exports are expected to grow to 9 million metric tons by 2021.”
To put this in perspective, Science reports, “Overall, pellets consumed three percent of the wood cut in the southeast in 2013, far less than what goes in pulp or lumber. Still, at least seven new pellet plants are expected to start operating in the region over the next five years….”
Science reports that environmental groups are alarmed and scientists are divided: “This past February, 65 scientists, many from major universities, penned a letter to Senate leaders warning that the carbon-neutral label would encourage deforestation and drive up greenhouse gas emissions. But a month later, more than 100 scientists took the opposite view in a letter to EPA, stating the ‘the carbon benefits of sustainable forest biomass energy are well established.’ ”
As I’ve noted here before, science, of any sort, is never really over. And it’s important that we all keep informed. ds
© Dennis Simanaitis, SimanaitisSays.com, 2017