– by Marvin Roberson, April 27, 2014. Source: Detroit Free Press
There is a lot of concern in Michigan, especially the Upper Peninsula, about meeting future electrical needs. Many aging, polluting coal plants are soon to go offline, as they should. New coal plants are unlikely to replace them, and would be a poor choice even if feasible.
There is, and should be, significant focus on energy efficiency and renewable sources of electricity. A portion of our future needs is likely to be met through biomass electricity generation. Biomass electricity is generated by burning plants.
Biomass can come from a variety of sources. Switch grass, waste wood, corn stalk residues and the like all may be burned to generate electricity. Standing timber (live trees cut down for the purpose of burning them) can also be used — and in our state, that’s the primary form of biomass available. In Michigan, with its vast forests, many people naturally think of this resource as an opportunity to generate green, renewable power.
This is a mistake. Power derived from cutting and burning standing timber cannot be any significant part of the solution to electrical needs because there simply aren’t enough trees in Michigan. To replace even a modest-size electric plant would require clear-cutting about 5 square miles of forest each year.
Some proponents suggest burning wood on the grounds that it is “carbon neutral,” causing no net increase of carbon dioxide into the atmosphere, and thus does not contribute to global warming. This is false. Every other use of wood (paper, furniture, even letting it fall over and rot) keeps more carbon out of the atmosphere than burning it. But that doesn’t matter.
Some claim that it will provide economic activity and badly needed jobs in rural areas. But the reality is every other use of harvested timber creates more jobs than burning it does. Trees are simply too expensive to use as fuel. But that doesn’t matter, either.
Some claim that using trees for power generation will help the forest by providing incentives for sustainable forest management. It won’t. Supplying biomass electricity plants with standing timber will only leave ever younger forests in Michigan, even though our current forests are wildly younger than naturally balanced forests. But that also doesn’t matter.
Why don’t these things matter, and what does?
It’s simple: Even with 20 million acres of forest,there is not enough wood growing in our state to provide a significant portion of our electricity generation. Period. Nothing else in the debate over biomass electricity generation is relevant.
If we used all the forest growth from all of Michigan’s forests for biomass, including state parks, all private, protected and public lands, and closed down all current consumers of timber (lumber, paper, etc.), we would generate less than 7% of Michigan’s electrical needs.
It’s simple math. It takes about 13,000 tons of live wood to generate 1 megawatt of electricity, which can power 240-400 households a year.
A generous estimate is that Michigan averages forest growth of about 1.3 tons of wood on each forested acre each year. This means that we need the “annual growth” (the amount of new wood grown each year) from 10,000 acres to generate a single megawatt of electricity. Or, to put it another way, if we grow wood and cut it on a 40-year cycle, we need to clear-cut, chip, haul away and use every bit of wood from 250 acres a year to generate 1 megawatt.
A few years ago, Traverse City was considering building a 10-megawatt biomass plant. If sourced from green timber, as planned, this would have required using the entire annual growth from 100,000 acres, or clear-cutting 2,500 acres (4 square miles) each year.
How about in the UP, where we surely have lots of wood? The Presque Isle coal plant in Marquette needs replacement. It generates 450 megawatts annually. Replacing that coal with standing timber would require the annual growth of 4.5 million acres of forest land, or clear-cutting 112,500 acres (180 square miles) a year.
So, while small, local biomass electric generation — using mill wastes and other forest byproducts — may be a useful and practical part of meeting our power needs, large-scale replacement of coal-fired plants with timber-based biomass generation is simply not possible.
Marvin Roberson is a forest ecologist for the Michigan Sierra Club.