WYTOPITLOCK — Sens. Susan Collins and Angus King have proposed an amendment to the Senate clean energy bill that would officially classify biomass energy as “carbon neutral.” This designation would mean that all uses of biomass for energy would be considered to add no net carbon to the atmosphere; thus, they would qualify for renewable energy credits and other favored treatments.

The science, however, does not support such congressional designation. Indeed, 65 scientists with backgrounds in energy, soils, forest ecosystems and climate change sent a letter to the Senate arguing that it is not a good idea to declare all biomass energy as “carbon neutral.” “Legislating scientific facts,” they wrote, “is never a good idea, but is especially bad when the ‘facts’ are incorrect.”

The argument for biomass being carbon neutral assumes that the amount of carbon being emitted by harvesting and burning is balanced by the carbon being sequestered and stored by trees, regardless of what is cut, how it is cut, what is left behind, what is the rate of cutting, what is used for biomass, how much energy goes into processing and transportation or even how efficiently the biomass is used.

These factors, however, can determine whether biomass is part of the solution to global climate change, or part of the problem. Calling biomass “carbon neutral” does not make it so.

Most of the carbon in forest ecosystems is stored in the soil. Recent studies have shown that heavy cutting, especially whole-tree removals that expose or disturb the soil, can lead to soil carbon losses that can last for decades. Those arguing for the carbon neutral status of biomass are not accounting for such ecosystem losses from intensive cutting.

There are no regulations in Maine to prevent such heavy cutting. There are no regulations to prevent landowners from cutting more than growth. And there are no regulations to prevent conversion of extensive areas from mature to immature stands.

It takes decades to grow a mature tree. It takes minutes to burn that same tree. We need to start reducing carbon emissions in the atmosphere now. If a landowner cuts heavily on short rotations, the stand, and ultimately the ownership landscape, will not be able to recover the original ecosystem carbon storage even after a century.

If climate change is truly a concern, then the dual goals should be to increase carbon sequestration and reduce carbon emissions. To increase carbon sequestration, it would be better to manage for higher-volume forests with bigger trees. To reduce carbon emissions, it would be better to reduce burning both wood and fossil fuels; but if they are burned, that should be done in the most efficient way.

The biggest market for biomass in Maine is for wood-fired electric generators. Current commercial biomass electric power plants in Maine, are, in general, less than 25 percent efficient – less efficient than fossil fuel electric power generators. The stack emissions of carbon dioxide (as well as pollutants such as aromatic hydrocarbons or particulates) from these biomass electric plants are greater per megawatt of electricity than the emissions from fossil fuel-fired plants, including coal-fired plants.

It is far more efficient to use the heat generated from burning biomass to heat buildings than it is to use it to supply electricity. It is possible to have close to 90 percent efficiency if the wood is burned primarily for heat – with electricity as an added benefit. This dual use is called “co-generation,” or combined heat and power.

Low-grade wood does not have to be burned. There are other possible markets that could be encouraged in Maine, such as cross-laminated timbers, which isolate the wood’s carbon from the atmosphere for decades. These products can replace steel and concrete, which have more embodied energy in production.

Declaring all uses of wood for energy “carbon neutral,” therefore, can reward both climate-unfriendly forest practices and climate-unfriendly biomass burning. But the impacts are also inefficient economically. Burning wood to create electricity is not competitive, unless it’s subsidized. In 2016, Central Maine Power testified that over the last 20 years, biomass power plants in Maine have received $2.6 billion in ratepayer subsidies.

These subsidies haven’t been enough to prevent plants from shutting down anyway. The Maine Legislature voted last year in favor of an additional $13.4 million in subsidies to prevent further biomass energy plant shutdowns. Subsidizing higher-cost electricity will, according to CMP, lead to $23.4 million in higher electricity costs in just the first year. Making the public pay with tax money and higher utility rates adds economic insult to the allowable ecological injuries.