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Concentration of CO2 in the Atmosphere

Reforestation Versus Biomass

Hapgood Pond Recreation Area of the Green Mountain National Forest. USDA photo.

George Harvey

Through reforestation, we can draw down atmospheric carbon dioxide (CO₂). We can also use wood from the forests to heat our homes. The question is, can we do both of these things at the same time?

One of my favorite events of the year is the VECAN conference. This year, we saw some extraordinary people give some really great presentations. One of those was “The Role of Vermont’s Forests in Climate Action – Heating and Sequestering,” presented by Jamey Fidel, Vermont Natural Resources Council; Emma Hanson, Department of Forests, Parks and Recreation; Adam Sherman, Biomass Energy Research Center; and Bill Keeton, University of Vermont.

The question of forests and biofuel is not something that can be settled by armchair speculation; it needs studying, testing, and careful calculation. According to the presenters at VECAN, however, through sustainable forestry practice and use of clean stove technology, Vermonters can get about 35% of their heat from the state’s forests, without compromising their ability to sequester CO₂.

The issues are complex, partly because of the many uses we have for forest products. High quality wood is used for fine carpentry, lumber for construction, and lower quality wood for making paper. Our maple industry is based in forests, and though fruit orchards are considerably less wild, they also should be considered as part of the overall question. There is low quality wood left over from all of these, and forest falls add to the amount.

Another consideration is that trees in the forests do not sequester CO₂ forever; eventually they die. Given the issue of climate change, that might happen sooner rather than later for most species. The Vermont Agency of Natural Resources produced a series of papers on climate change about ten years ago, and their conclusions were that most types of trees in our forests are vulnerable to invasive species. Two species of wooly adelgids will attack firs and hemlocks. A virus targets pines. Maples are being attacked by fungus. We have emerald ash borers coming for our ash trees. Most other trees have similar issues. In the end, it may be that only our oaks and hickories are safe.

Clearly, careful forestry, based on planning that considers the problems, is required. And if there is infected dead wood in the forests, it has to be removed.

We might consider, if forest waste is not burned, what will become of it? And how is that different from burning it? While termites are not on lists of invasive species in Vermont, with increasing temperatures from climate change, they are getting more active. I bring this up because when wood rots, it is often decomposed by fungus, with chemical reactions giving off CO₂, just as though the wood had been burned. If the wood is eaten by termites instead, a fair amount of methane is produced, which is many more times as powerful as a greenhouse gas than CO₂. Allowing a tree to decompose naturally may be worse than burning it, though we might do well to return the minerals in the ash to the land.

This brings us to the question of pollution from burning wood. Dirty wood-burning appliances can cause pollution, but energy-efficient ones can be quite clean. Very often, the difference can be seen clearly by everyone in the neighborhood. A clean wood fire should not produce any smoke.

The VECAN presenters made another issue clear. Though the use of wood for heating is a comparatively straightforward matter, in terms of pollution and efficiency, using wood for generating electricity is more problematic. All combustion systems need to meet EPA standards, but the wood fuel for generating electricity often comes, in huge quantities, from forests a long way off. This tends to lead to poor forestry practice, and the required transportation adds to the carbon footprint. Care must be taken anywhere wood is used as fuel.

There are other reasons to be careful to use wood from local sources. Not only does transporting wood over long distances add to the climate costs, wood that has been brought in from a distance can bring invasive species with it.

One other point is that there was a time in the late 19th century when only 20% of Vermont’s forests remained. Today, with forest reforestation, 80% of Vermont is woodland. While that restoration was taking place, Vermonters continued to cut wood for fuel, and the restoration proceeded anyway.

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