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Granite Geek: Burning wood for power makes sense – or so I thought

  • A truckload of wood chips is dumped into the Northern Wood Project power plant in Portsmouth. Courtesy of Eversource



Monitor staff
Tuesday, September 26, 2017

It’s no fun to realize that you’ve been wrong, so this isn’t a fun column.

For years I’ve supported the idea that whenever possible, Northern New England should swap fossil-fuel power and heat for wood-fired power, taking advantage of our tree-laden status as the “Saudi Arabia of biomass” to boost the logging industry while also doing environmental good. It’s a pretty obvious position.

But over the years I’ve come to realize that surprisingly often, this isn’t a good idea from the environmental point of view. Quite the opposite.

That doesn’t mean it’s okay to burn coal and oil for power, which should be curtailed as quickly as possible, or that using more natural gas is always better. But it does mean that my simplistic “just switch to burning wood” argument needs to go.

One consolation: I’m not alone.

“When we took on this in 2010, I thought this was an easy question – they’re growing much more than they’re harvesting, what’s the big deal if you take a little more and burn it?” said John Gunn, research assistant professor of forest management at UNH, looking back at a study on biomass power in Massachusetts. “When we sat down and mapped it out and modeled it, it became clear that this wasn’t the case.”

Gunn just wrote a commentary on this issue, cautioning that “unconstrained production of biomass energy ... can lead to emissions in excess of the fossil fuels being replaced” for reasons we’ll talk about in a moment. This, combined with a study last week from the Harvard Forest in Massachusetts that showed that New England is starting to use up its woodlands again after decades of forest regeneration, were the events that prodded this column.

First, note that the value of burning biomass for power has been debated for years.

Often the debate has financial implications. The Biomass Power Association, which represents various folks who own plants that burn wood to produce electricity, has released a number of studies arguing that burning wood is carbon-positive. Gunn’s commentary cited above was written in response to the most recent study.

But the debate exists for environmental reasons, too, which used to surprise me.

In a climate-change world, switching from fossil fuels to wood seems a no-brainer. Burning coal and oil releases carbon that would have otherwise stayed hidden and can’t be recycled (we’re not making new coal, you know). Burning wood releases carbon that would have been released within a century anyway as the tree died, and which can be recycled by growing new trees.

The poster child for this policy is the decade-old Northern Wood Biomass Project, under which Eversource (then PSNH) refurbished one of the three 50-megawatt boilers at Schiller Power Plant in Portsmouth. Instead of consuming coal brought up the Piscatquog River on a barge or oil from tankers, it now slurps down wood chips by the truckload to produce electricity.

I applauded this transition and have written many a glowing story about it, and assumed I would be writing more as other power stations switched over.

Since then however, evidence has accumulated that the environmental benefits of this switch are much less than I thought.

There are times the change makes environmental sense, such as creating combined heat and power systems at the level of a hospital, or swapping your elementary school’s oil boiler for a pellet boiler. Gunn, in fact, is co-author of a not-yet-published analysis that says state-of-the-art wood pellet boilers for heat, burning pellets from Northeastern forests with good harvest practices, cut greenhouse gas emissions by more than half over lifetime usage compared to oil or gas boilers.

The calculation goes awry when you burn wood just to create electricity, without using the excess heat to also offset fossil fuels, or if the biomass-fuel market is boosted to the point that it starts to really affect forests.

There are many reasons for this. Wood is less energy-dense than fossil fuels, so it takes more volume to generate the same amount of power. Harvesting timber also releases carbon from the soil, which skews calculations. Finally, the alarming speed at which climate change is happening makes the century-ish time scale for carbon replacement via growing new trees much less valuable.

If biomass power and heat occurred only by burning wood that is unused in lumber or land-clearning operations – tops and limbs – it would be all right. But the mechanics and economics of wood harvesting mean this often isn’t the case, and the industry leads to harvesting that wouldn’t happen otherwise.

“These details matter,” Gunn wrote in his commentary, published in the latest issue of a publication called the Forestry Source. “Although biomass energy carries many benefits, assessment of these benefits should be based on sound science. In many cases, the greenhouse gas emissions are uncertain and often based on an inappropriate or unlikely set of assumptions.”

Part of my reluctance to embrace this position, I’ll admit, is that I want biomass-is-always-better to be true. Logging is cool and an important part of what makes Northern New England what it is, so I want the power market to be there to support loggers. Life would be easier if I could say that biomass is always environmentally positive without having to think too hard about it.

But facing reality is part of being a grownup, darn it.

“Counting from Infinty” with discussion

Don’t miss a unique opportunity tonight to see and discuss a documentary about the most surprising mathematics breakthrough in New Hampshire history.

Dave Brooks and UNH professor Edward Hinson will lead the talk after a showing of “Counting from Infinity,” a film about UNH lecturer Yitang Zhang’s breakthrough in the twin-prime conjecture, which so astonished the science world that it, among other things, won him a MacArthur “genius grant.”

The movie starts at 6 p.m. tonight in Red River Theatres, 11 S. Main St., Concord. There’s a $12 charge ($10 for members).

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)