Monday, November 7, 2011

Biomass In Vermont: It Won't Replace Vermont Yankee

Biomass In Vermont's Future

On September 14, The Department of Public Service (DPS) released a 600 page Comprehensive Energy Plan (CEP) for Vermont. The plan was long, vague, and internally inconsistent.

Instead of tacking the whole thing, environmentalist Chris Matera studied a defined chunk: the plan's recommendations for increased use of biomass for electricity production. Matera wrote an opinion for the Bennington Banner titled Vermont's Plan Misses the Forest. He describes how burning wood for electricity causes air pollution, generates carbon dioxide, and causes deforestation. He asks: So how did increased cutting and burning of forests (called "deforestation" and "pollution" when it occurs in other countries) get re-branded as "green" energy..?."

The CEP sections on woody biomass were confusing. On some pages, the CEP seems to expect only about a 30% increase in electricity from woody biomass in the near future. On nearby pages, the CEP describes "25 x'25", a plan to produce 25% of Vermont's energy by biomass fuels by 2025.

Ignoring the Working Group

Two years ago, the state legislature convened a biomass working group. The group is supposed to report its results on biomass utilization to the legislature in 2012. It is typical of this administration that it is rushing to adopt the Comprehensive Energy Plan before receiving that report.

Is There Enough Biomass, Anyway?

Instead of trying to decipher the CEP statements on biomass, let's look at real examples of biomass plants, and what it would take to expand this type of electricity production in Vermont.

The Springfield Power LLC biomass plant in Springfield New Hampshire is visible to people who drive south on Interstate 89. It is located at exit 12A, not far from New London. The plant makes 19 MW of power, and runs most of the time, only shutting down for maintenance. It sells its power at about 5 cents per kWh, while paying around 4 cents per kWh for its wood. The Springfield plant is well-equipped with NOx and particulate control, and sells its fly ash as a garden amendment.

It also sells Renewable Energy Certificates, and therefore is profitable to run. I visited it with the Energy Safari class. Bob Hargraves wrote a very comprehensive blog post on our visit.

The Springfield plant burns 200,000 tons of wood to make 20 MW of electricity. This about 100,000 cords of wet wood (2 tons per cord).). Chuck Theall, the plant manager, says that the plant calls the grid operator daily, and promises to supply energy. The grid counts on his energy, and if the plant does not operate, it has to pay for replacement power.

Wood-burning plants are heat engines, which means they can be reliable baseload plants, like Springfield Power. The ability of a wood-burning plant to supply baseload power is in sharp contrast to solar and wind renewables, and makes expansion of wood-burning very attractive for an all-renewable energy plan.

How Much Forest Per Megawatt?

In terms of power production, the Springfield plant is tiny. Vermont Yankee makes 620 MW of power. It would require 31 Springfield Power plants to replace Vermont Yankee on the grid. How much forest would this require?

I did research on sustainable forest yields. I could not find answers in a book, so I asked local foresters: "What is the sustainable yield of firewood for an acre of Vermont forest?"

I learned that foresters hate to answer general questions about "Vermont forests" because "Every bit of forest is different." Eventually, I found an approximate consensus: One-half cord per acre is a sustainable yield for most of our forests. As a child, I learned the mantra that you could harvest a cord of wood each year from an acre of forest. Vermont foresters agree that that number was too high.

Half of the Green Mountain Forest for 20 MW

A quick calculation (100,000 cords per year, half a cord per acre) shows that the yield from 200,000 acres is required for a 20 MW plant. To give some context to this number, the entire Green Mountain National Forest is 400,000 acres, and the state of Vermont is 6,000,000 acres. It takes the equivalent of half the harvest of the Green Mountain Forest to make 20 MW of electricity. To make 31 times this amount of electricity, to replace 620 MW of Vermont Yankee with woody biomass power plants--this would mean the entire state would be devoted to raising wood to burn. Six million acres wouldn't even be quite enough.

Expanding our current wood-fired electricity production will be difficult, but not impossible. Replacing Vermont Yankee with wood-fired plants is impossible. Going "25% by 2025" for electricity through woody biomass is close to impossible, especially since power plants must compete with homes and schools for firewood.

The Bigger Picture in the Woods

In the long run, our forests are our joy. Our forests are our foliage season. Our forests eat carbon dioxide from the air, and even sustainable harvest will affect this to some extent. We can add some wood-fired electricity in Vermont, but not much. We cannot get one-fourth of our electricity from our forests. We need to be mindful of competing uses for our woodlands.

And so, we return at last what Matera said in his op-ed: So how did increased cutting and burning of forests (called "deforestation" and "pollution" when it occurs in other countries) get re-branded as "green" energy..?"

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Picture of Chuck Theall of Springfield Power, and Neil Daniels, retired engineer, courtesy of Bob Hargraves, from his post on the ILEAD visit to the Springfield plant.

True North Reports published a more complete version of this article. I thank Rob Roper and True North Reports for the opportunity to reprint the article on my blog.

Picture at upper left is part of the wood pile: approximately two weeks worth of logs, and logs are approximately 1/3 of the wood used. The rest of the wood is delivered as chips.

This post also grew out of an earlier Yes VY post about the biomass plant, specifically from the comment section of that post.

4 comments:

Anonymous said...

Plus only 4.6M acres of Vermont are forested (http://www.vtfpr.org/util/vt_forest.pdf, p2)

JonE

Jeff Schmidt said...

Wood has been traditionally used for heating small homes and small buildings, and it seems to me like that's a good role for it play, perhaps better than for electricity generation.

I only know the basics of thermodynamics, but I know that when you burn wood to heat your home, you can benefit from close to 100% of the energy released (at least, if you have a good stove/furnace - in a fireplace, much of the heat goes up and out the chimney).

When you burn wood to produce electricity you convert a somewhat small fraction of that heat energy to useable electricity - I think the efficiency is somewhere in the ballpark of 25-30%?

It stands to reason when you have a very limited resource, like wood, that efficiency becomes a pretty important concern, no?

Jeff Schmidt said...

Meredith, I was reviewing that op-ed piece you linked from the Bennington Banner, and noticed a great quote I missed the first time I read that piece a month back when you posted it originally:

"According to the Cary
Institute for Ecosystem Studies, Vermont is already
cutting 67 percent of its annual forest growth, and if
inaccessible areas like steep slopes are taken into
consideration, Vermont is already cutting about all
of its available growth."

That seems to paint an even bleaker picture than your estimates, so it seems that there are multiple voices coming to the same conclusion - there's not much room for "growth" in tree-wood energy production.

Meredith Angwin said...

JonE. Thank you for the link! Yes, we aren't all forest up here, and our forests are basically in recovery mode. This state was virtually de-forested about 100 years ago, as were many areas of the country.

Jeff. Yes, it is pretty bleak. The problem is that it takes a lot of wood to make electricity. Also, wood is naturally wet and doesn't burn hot without a lot of staging (the Springfield plant has elaborate staging of air to get the temperature up so they can have decent thermodynamic efficiency.) Plus, if you begin thinking about the diesel fuel the logging trucks burn, delivering wood from a hundred-mile radius, it all begins to look pretty darn bad.