Editor’s note: This op-ed is by Lawrence “Rip” Kirby, an electrical engineer who works for Central Vermont Public Service. He lives in Rutland.
A good friend of mine, an attorney, once told me that that in swearing to tell “…the truth, the whole truth, and nothing but the truth”, the hardest part is that middle one, the pledge to tell “the whole truth.” Josh Schlossberg’s recent article criticizing biomass power production illustrates why.
He insists that producing power by means of burning biomass (wood, in particular) is environmentally irresponsible. Let’s consider two of his chief arguments in support of this premise (paraphrased below to the best of my ability):
- Using trees as fuel prevents their continued absorption and sequestration of excess carbon dioxide (a green house gas) in the atmosphere.
- Burning wood releases more carbon dioxide than burning coal (presumably based on an amount of each fuel that is sufficient to produce equal amounts of energy).
Both of the above statements are true, in the strictest sense, yet are misleading. So let me try to fill in some of the “whole truth” that is missing.
Let’s begin with Josh’s first premise. As we all know, trees follow a natural cycle of birth, growth, death and decay — much as we humans do. From the moment that seedlings first poke through the ground, they begin absorbing carbon dioxide. Their rate of absorption accelerates as they grow and mature. But upon their death, they begin to decay. This decay process reverses the trees’ absorption of carbon dioxide and begins re-releasing it into the atmosphere. At any given moment, there are many living trees absorbing carbon dioxide and many dead trees re-releasing it.
In this day and age, at the rate forests are being destroyed in some parts of the world, there is undoubtedly a gradual, net movement toward fewer trees and therefore a release of carbon dioxide from decaying trees that outpaces its absorption by new trees. But that net change is not caused by biomass power production; it is largely caused by poor environmental and forest management practices in developing nations that over-harvest their wood and wish to open up their forested land for crops or for urban expansion.
In this country we generally cut only mature trees and then replant new trees after the wood has been harvested for power production. As those new seedlings grow, they re-absorb the carbon dioxide that was released by burning their predecessors. Also, the mature trees that are harvested for power are generally either dead or within a few years of death and would soon re-release their carbon dioxide anyway. The bottom line is that trees are not a particularly good way of sequestering carbon because they tend to do so only temporarily. Burning them merely releases carbon dioxide that would have eventually been released anyway as part of their natural life/death cycle.
Now let’s consider Josh’s second premise. I have not fact-checked the comparison between coal-fired carbon dioxide release and wood-fired carbon dioxide release, but his statement seems credible enough.
The hidden catch is that coal is truly “sequestered” carbon, that is, carbon which has been locked in the Earth’s crust for many millions of years and would never be released into the atmosphere were it not for its use as a power source by humans. Unlike trees, when coal is burned, it releases carbon dioxide that would not have eventually been released naturally, and there are no new coal deposits being formed (at least not in the time frame relevant to climate change, which is the next few decades or centuries) to reabsorb it. Coal is a very different and much more damaging source of carbon dioxide than that released by biomass, because, unlike biomass, its carbon dioxide emissions accumulate in our atmosphere over a long period of time.
Partisans are generally careful to tell you the truth and nothing but the truth. But the whole truth? Well, that middle one is the hardest.
