This news from the Spokane Spokesman-Review caught my eye:
Tons of slash from a 250-acre logging site north of Loon Lake, Wash., could have gone up in smoke.
Instead, the woody debris will be chipped and hauled to Avista Corp’s biomass facility in Kettle Falls, where it will produce enough electricity to meet 37,500 homes’ needs for about eight hours.
I’m the very first to admit that I know very little about forest management. No, strike that—I effectively know nothing. So I have no idea if carting away all of that debris could deprive the soil of necessary nutrients over the long haul—or if burning slash is even a reasonable forest management technique. (Can anyone out there in blog-land help me out?)
Still, from a novice’s point of view, this doesn’t seem crazy: if the “waste” wood is going to be burned anyway, why not try to use the heat to generate some electricity?
Well, that’s fine as far as it goes. But what caught my eye was the numbers: 250 acres, for 8 hours of power, for 37,500 homes. Could that possibly scale up? Could wood waste offset a significant amount of fossil fuels in the generation mix?
Short answer: probably not.
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Just running the numbers a bit—and remember, these are order-of magnitude estimates, so use them at your own risk…
- First off, let’s assume that the slash in those 250 acres is fairly representative of yield across the state. That’s a huge assumption, obviously, and it’s probably wrong. But we’re just playing around, right?
- To power 37,500 homes for a full year, rather than just 8 hours, would require the slash from 3 x 365 x 250 acres = 273,750 acres of land. (In comparison, Mt. Rainier National Park is about 236,000 acres.)
- Excluding wilderness, parks, and other protected areas, there are about 18 million acres of forest land in the state of Washington. (See here for more precise estimates.)
- Assuming 50 year rotations, that makes about 360,000 acres of logged forest per year. (Remember, I’m a forestry newbie, so I have no idea if 50 years is a reasonable estimate for the average rotation length of the average forest in the state.)
- If we used all of the slash from those 360,000 acres to generate electricity, it would power about 50,000 homes for a year, give or take.
- The census says that there are about 2.6 million housing units in Washington State—meaning that if the forest slash from all logged land in the state were burned for electricity, it could provide about 2 percent of the state’s residential power needs. Note that this doesn’t include the use of electricity in office buildings, factories, and smelters—all of which are substantial.
So it looks like forest slash is small beans. That’s not an argument that burning slash for power is a bad idea; I have no opinion on the matter, really. But it does suggest that it’s a bit unrealistic to hope that slash will play more than a bit part in our energy future. Still, it’s a worthwhile experiment; as long as forest soils don’t suffer, every little bit of non-fossil energy can help.