By George Harvey
The question of the sustainability of forest biomass is perplexing, especially in the northeast, where it is used for much of our heating. There has long been the assumption that forest biomass is carbon neutral, because the carbon atoms in it were recently taken from the atmosphere, and the trees cut would be replaced by fresh growth, which would also take carbon from the air.
This idea has been challenged in recent years for a number of reasons. Questions arise about the amount of carbon in the soil, the amount of carbon emitted in fossil fuels harvesting and transporting wood, how clean-burning wood is, and more. These questions were amplified by a statement from the White House and a report by the Manomet Center commissioned by the Massachusetts Department of Energy Resources. While both of these sources appear to be clear, appearances can be deceptive.
The White House statement related to a bill, HR 2822, before the House of Representatives, which defined “biomass” as carbon-neutral. The statement from the White House said, in part, “The Administration objects to the bill’s representation of forest biomass as categorically ‘carbon-neutral.'” We should note that this statement cannot be properly understood without taking into account the word “categorically.” What is being said should not be represented as “Biomass is not carbon-neutral,” which it was by many who commented on it. A sentence with a much closer meaning would be, “The fact that it is biomass does not automatically mean that burning it is carbon-neutral.”
The report from the Manomet Center was similarly misconstrued by some in the media. Part of the problem with it is that it was rather narrowly focused in a way that reflected some current realities, in terms of wood harvest and use, but reflected neither all currently available methods nor all foreseeable systems. The study might have been good as far as it went, but to consider it definitive for all forms of biomass development and use is a big mistake.
Addressing this issue, Andrew Perchlik, the Director of the Vermont Clean Energy Development Fund (CEDF) said in an email, “The CEDF believes that wood can be used as a carbon neutral heating fuel if harvested and burned with practices that are based on carbon neutrality as the goal. This requires harvesting wood used for energy locally and following certain harvesting principles. It also requires burning the wood as efficiently as possible, which to the CEDF, means only using it for heat or [combined heat and power primarily for heat].”
He continued, “The CEDF believes that by engaging the wood heat industry and stakeholders through collaboration as well as with market incentives it can have the greatest impact on securing a carbon neutral or carbon positive wood energy future.
“It’s important to realize that the White House/EPA position is focused on (and is largely a response to) using wood for electric power in inefficient power plants. This was also the focus of the [Manomet Center] study. I don’t think we should use any wood for power if it can’t reach the high efficiency levels of using it for space heating (>85%) as a fossil fuel substitute.”
The bottom line here is that while it is certainly possible to grow, harvest, transport, and use biomass in such a way that it is very dirty, it is also possible to do so in such a way as to be both very clean and carbon-neutral. Clear-cutting an old-growth forest so it can be pelletized, shipped overseas, and burned to make electricity is very different from sustainably growing and harvesting biomass and using it locally in a very clean and efficient energy system. Such a system could be a large, utility-scale installation, but it could also be a really good, efficient home wood stove.
We should mention other emissions from burning wood. Particulates are especially damaging to health but are nearly eliminated in modern, EPA-approved equipment that is properly run. Older stoves are heavy polluters, and this is especially true of the so-called air-tight stoves of the 1970s and 1980s. The EPA advises that these stoves be replaced. If in doubt, check the smoke. It should never be black.
Those who are engaged in the science and ecology of biomass include many who consider these matters, and there is much science that may be developed. It will be interesting to see what they can do in the future.