The Science of Biomass
Biomass refers to burning wood or other solid, organic materials for heat or to generate electricity. About 17% of Vermont homes heat with wood, and Vermont also has two major biomass generating stations, McNeil and Ryegate. Biomass has been favored in Vermont energy policy as a "green" alternative to fossil fuels, despite the clear science that it worsens climate change, harms forest ecosystems, and causes serious health problems.
Biomass Worsens Climate Change
Burning biomass for heat or electricity is a potent contributor to climate change. In fact, biomass emits more CO2 per unit energy produced than even coal, the dirtiest fossil fuel (Sterman, 2022). Biomass also emits more black carbon than fossil fuels, which is a primary cause of lowered albedo on snow and ice and associated warming.
Supporters of biomass claim that carbon emissions from biomass do not need to be counted because they are "biogenic" emissions, i.e. emissions that are already part of the natural aboveground carbon cycle. The forest that (ideally) grows back after trees are cut and burned, they claim, will reabsorb the carbon emitted by combustion. This logic has seeped into most mainstream greenhouse gas accounting metrics, like those used by the EU, IPCC, and US EPA. Emissions from biomass combustion are considered "land use" emissions, and only counted if forest is permanently cleared and converted to another land use.
The fundamental problem with this argument is that there is a critical time delay between when wood is burned and emits a pulse of carbon into the atmosphere, and when a forest (putatively) grows back to reabsorb that carbon. The exact magnitude of time delay is very difficult to measure or generalize, but studies have been clear that the time it takes for wood to reach "carbon neutrality" is far longer than the 7-10 years we have to meaningfully act on climate change (Gunn et al). Holtsmark (2013) found that "the climate impact per unit of CO2 emitted seems to be even higher for the combustion of slow-growing biomass [like the forests of Vermont] than for the combustion of fossil carbon in a 100-year time frame." Another study modeling hardwood forests in the Southeast estimated that burning wood for electricity brought no net reduction in CO2 emissions for over 110 years, even when compared to coal, the dirtiest fossil fuel (Sterman, 2022). An analysis of wood pellet heat specific to the Northeast US found that wood pellet heat had modestly better climate impacts compared to the regions current thermal energy only when no additional harvests were undertaken to make the pellets. Even in the most favorable scenarios, pellet heat was far from carbon-neutral and compared poorly to using even natural gas for heat (Buchholz 2017).
Whatever the specific parameters and estimates of each individual study, their implications are clear: forests need to be minimally disturbed to serve as the most effective carbon sinks possible, not harvested and burned on a wide scale.
Additional complications arise from the fact that heavy logging degrades forest ecosystems and impairs their ability to regenerate to a level comparable to their health before logging (see following section). The pests, diseases, fires and weather extremes associated with climate change will further jeopardize a forest's ability to regenerate.
Buchholz et al., 2017. Greenhouse gas emissions of local wood pellet heat from northeastern US forests
Holtsmark et al., 2013. Quantifying the global warming potential of CO2 emissions from wood fuels
Sterman et al., 2022. Does wood bioenergy help or harm the climate?
Biomass Harms Forest Health
updates coming soon!
Biomass has Serious Health Impacts
updates coming soon!
The Science of Biofuels
The Science of "Renewable" Natural Gas
Robert Howarth, professor of ecology & environmental biology at Cornell University testified in front of the Vermont Senate Natural Resources & Energy Committee on February 8th, 2023. He testified to request the removal of incentives for renewable natural gas that appear in the current version of the Affordable Heat Act (working its way through the Vermont Legislature this legislative session). His written testimony included the following statement:
"RNG is made by processing biogas, making a fuel that is composed mostly of methane and that can be mixed with fossil natural gas in gas pipeline systems. Biogas is a mixture of methane and carbon dioxide as well as other impurities that is produced from anaerobic digesters (including some wastewater treatment plans as well as farm-based systems using manure) and can be captured from landfills. The biogas can itself be used as a fuel, for instance to 2 generate electricity or heating, but biogas is not suitable for use in pipeline distribution systems. In the final Scoping Plan for the New York Climate Action Council, we specified that whenever possible, biogas should be used directly at the site of production, and preferably used in fuel cells rather burned to generate electricity. Our plan further stated that the use of biogas as biogas was to be preferred to processing it into RNG. There are two reasons for this: 1) it takes energy to process biogas into RNG, and so this is inherently inefficient and increases greenhouse gas emissions; and 2) the latest peerreviewed science shows that methane emissions from processing biogas into RNG can be substantial, as shown in a review paper published last year (see: Bakkaloglu, Cooper, and Hawkes. 2022. Methane emissions along biomethane and biogas supply chains are underestimated. One Earth 5: 724-736, doi:10.1016/j.oneear.2022.05.012). Converting biogas into renewable natural gas is wasteful and further contributes to greenhouse gas emissions, with no benefit other than to allow the gas to be pumped into the traditional fossil gas distribution systems."
Professor Howarth's full testimony can be found here: Sen. Natural Resources & Energy 02-08-2023 10:15AM - YouTube. This link will take you to his full written testimony: November 11, 2004 (vermont.gov) .