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Trees Are Not the Solution to Our Electricity Needs

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- 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.

Comments

Just a note that the term "megawatt" is a measurement of power not energy. Power plants generate electricity (a form of energy) in the form of megawatt hours. That's a basic tenate of energy economics and the fact u don't know the difference makes me question if u have a competent grasp on the other fundamentals claimed in this article.

Power plants are never rated in megawatt hours. They are rated in megawatts. We are using the same terms as the energy industry.

Yes, plants have a name plate capacity stated in megawatts, BUT you explicitly stated it takes "250 acres a year to generate 1 megawatt". That's an utterly ridiculous statement. You're basically saying that it takes 250 acres of biomass to generate the amount of instantaneous power equivalent to one MW which means it takes 900,000 acres to produce one MWH (250 acres x 60 seconds x 60 minutes). Assuming that it runs 24 hours a day, that means this one plant will consume about 21,600,000 acres every day!

Then in the second to last paragraph that the Presque Isle coal plant in Marquette "generates 450 MW annually". That's a mistake. Annual generation rates are based on MWH since you're implying generating electricity over a given time and the basic tenate of energy is POWER multiplied by TIME (here you use a year as your time frame). Since commercial energy (not power) is measured in MWH, your statement is a mistake. The plant rated capacity is MW the energy it generates is MWH. Sorry but you need to get this figured about before throwing all sources of biomass impacts around. It makes it difficult for people who understand the basic concepts of energy production to find any merit in your argument.

"To replace even a modest-size electric plant would require clear-cutting about 5 square miles of forest each year."

But.... if they're thinning the forests, and removed only a third of the forest on each acre, that's 15 square miles to be thinned each year or roughly 10,000 acres per year-- a trivial percentage of the forest in your state. But, much will come from arborist work, land clearing for homes, etc.

"Trees are simply too expensive to use as fuel. But that doesn’t matter, either." Of course it matters, and you can be sure, no logger is going to send sawlogs to a biomass plant to be burned. Don't presume forest workers are THAT stupid.

"large-scale replacement of coal-fired plants with timber-based biomass generation is simply not possible"- well, of course not, and I doubt anyone said it could--- but all sources of energy have their problems.... ALL--- and if you think solar and wind are pure as the driven snow, I'll elaborate why they often are NOT- especially large scale solar and wind "farms"
Joe Zorzin
MA Lic. Forester #261

You are right. The author of the article (who isn't a member of our organization) is wrong about that. Replace "MW" with MW multiplied by the number of hours in a year and multiplied by the percent of time that the generator is online to get MWH.

I don't think we make this mistake in our organization's writing on the subject. But if we do, we will fix it.

I think some of the comments ignore the main point of the article which is still valid. It is absurd to consider cutting down valuable trees to supply electricity on ANY community-wide scale. Let's use the trees to supply oxygen, which apparently we need to breath, and to build housing, etc. and stop promoting these silly ideas about burning trees for power...... Thank you Mr. Roberson for your valuable and inciteful article. Thanks!