Concentration of CO2 in the Atmosphere

Sustainable Forestry for Biomass, Building, and Products

What would happen if we left all the trees standing? Hemlock woolly adelgids can quickly destroy large stands of hemlocks. Shown is damage in Linville Gorge, North Carolina. (Steve Norman, U.S. Forest Service)

Personal opinion by George Harvey, not necessarily the opinion of Green Energy Times

Biomass is a very controversial subject. Before we discuss it, however, we need to review the context.

1. Forests naturally change, even without human activity. We might take comfort in the thought that they could remain as they are, but that will not happen without intentional human action. In fact, in many cases it might prove impossible to achieve, and in a time of climate change, forests can change quickly in ways people might not like. To have our forests in the best possible health, we will have to be actively engaged in stewardship.

For example, here in the Northeast, invasive species are killing whole stands of trees. Hemlock woolly adelgids have already shown how destructive they can be in southern New England. A survey in 2018 found numbers of them in three counties in Vermont and all but one of the counties in New Hampshire. This, however, is just one of the many threats our forests face from climate change.

2. There are many kinds of biomass used for energy, and the issue of biomass cannot be limited to forest biomass. Agricultural waste of various kinds, municipal waste, and landfills are all possible sources of energy, and they have to be managed to prevent their own problems from arising. For example, farm waste can be fermented in bio-digesters to produce methane, which can be burned for energy; the alternative is to let nature take its course, which releases the methane into the atmosphere where it is a powerful greenhouse gas.

3. There are many ways to use biomass to produce energy, and their use has different consequences. If we burn cord wood in an old model stove, for example, we will make a lot of smoke, contributing to air pollution. By contrast, a rocket mass heater burns wood with enough air that there should be no smoke or creosote, but the extraction of heat is so efficient that the exhaust gases are below the boiling point of water as they leave the flue system, averaging 60°C to 90°C. This means even most of the heat from the water vapor created in combustion is extracted. This can be seen in the Wikipedia article on the rocket mass heater ().

4. There are many ways to use the energy from biomass. We can use it for heat in a home or for a large building. We can use it for combined heat and power. We can use it for electricity. The efficiencies and results of use are different.

5. There are many reasons aside from biomass for energy to harvest wood from forests. These include for buildings, making furniture, paper, and a number of other uses. One by-product of most or all of these is biomass.

One of our readers, Mr. Tim Maker, contacted us after our last issue about our addressing the issues concerning the biomass issues. With a background in biomass energy, he wanted to be sure we included discussions of issues we might otherwise miss. He pointed out that while we really need to practice sustainable forestry, that will be nearly impossible to do without some market for low-grade wood. He said of this, “Look at a forest as a garden with lots of weeds in it. Take out the weeds.”

We asked Vermont’s professional Forest Climatologist, Dr. Alexandra Kosiba, for her thoughts, and she provided a number of insights. One thing she said was, “Our forests produce some of the best wood around, and they are very productive – often tending to the forest and culling trees not only provides firewood, but also leaves the stand healthier and more productive.”

Dr. Kosiba said she does not support forest plantations, “because they do not provide all of the services that a natural forest does and are very vulnerable to stressors.” She added, “Along these lines, also important is making sure biomass harvested comes from well managed and sustainable harvests.”

Tim Maker stressed in our conversation that the use of biomass should be limited to circumstances in which it is most efficient. He gave the example of a new plant using forest biomass for generating electricity as one that would be likely to have unacceptably low efficiency. “You have to run the numbers,” he said.

Dr. Kosiba also made the interesting statement, “I do wish that there was more of a focus from the public on the value of local wood for heat and materials as there is for local food.”

I might sum up my position on biomass by pointing out that it is a complicated issue. I would not want to use biomass for new facilities that generate electricity exclusively, and I believe that clear-cutting forests for fuel is not a solution, but I would encourage people to use local wood or locally produced wood pellets to heat their homes. Most of all, I would stress a need to engage in sustainable forestry, tending all forests in the state, not to preserve them in their current state, which may be unhealthy or unsustainable, but to keep them in best possible health.

Please watch for more about the controversial issues surrounding biomass in the next issue of Green Energy Times.

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