Environmental impacts of biomass
Last updated 12/24/2019
Bioenergy is a unique type of renewable electricity: unlike solar, wind, and hydropower, generating power from biomass emits greenhouse gases and pollutants into the air. However, because of the renewable nature of biomass, many consider it to be a carbon-neutral source of electricity.
Is biomass/bioenergy carbon-neutral?
When we burn biomass for heat or electricity, it releases carbon dioxide into the atmosphere. However, sources of biomass, such as agricultural crops and trees, also capture carbon dioxide during the process of photosynthesis and sequester said carbon dioxide. If trees and other plants absorb as much carbon dioxide as they emitted during the biomass combustion process, then the carbon cycle remains in balance.
However, in real-life practice, it’s not that simple: the carbon impact of bioenergy depends on the combustion technology, how the biomass is harvested, any re-growing efforts, the type of biomass used, timing, and the energy resource it’s displacing.
For example, consider electricity from woody biomass: burning wood to produce electricity emits carbon dioxide into the atmosphere, but trees will re-grow and capture the emitted carbon dioxide. However, forests can take decades to regrow and sequester carbon, so the carbon neutrality of that source of bioenergy depends on the time frame you’re looking at. If companies burn trees at a faster rate than they’re being re-planted and grown or burning trees that would otherwise be left untouched in a forest, the carbon neutrality is compromised. Trees and other plants also capture differing amounts of carbon depending on their age, which makes carbon accounting for woody biomass even more complicated.
Now, compare woody biomass to biogas generated from animal waste in anaerobic digesters: burning biogas for electricity also emits carbon dioxide into the atmosphere. However, this process often results in net negative greenhouse gas emissions because of the potency of methane. Biogas is made mostly of methane which, if not burned as biogas, has a more negative impact on the greenhouse effect.
If you’re being offered “green” electricity from biomass energy plants, it’s important to remember that it’s not necessarily clean like other types of renewable energy.
Additional environmental consequences of biomass energy
Outside of the greenhouse gas emission implications of using bioenergy, there are a number of additional environmental consequences to consider:
There are plenty of bioenergy plants that use waste –whether that be agricultural or animal– as a fuel source. However, many energy companies use forest timber for fuel and clear-cut mature trees that, if left untouched, remove carbon dioxide emissions from the atmosphere. Actions like these lead to deforestation, causing habitat loss, soil erosion, destruction of natural beauty, and more.
Outside of contributing carbon dioxide emissions, burning biomass in a solid, liquid, or gaseous state can also emit other pollutants and particulate matter into the air, including carbon monoxide, volatile organic compounds, and nitrogen oxides. In some instances, the biomass burned can emit more pollution than fossil fuels. Unlike carbon dioxide emissions, many of these pollutants cannot be sequestered by new plants. These compounds can lead to a number of environmental and human health issues if not properly contained.
Plants require water to grow; when energy companies grow trees and other crops for a bioenergy plant, they use a lot of water for irrigation. On a large scale, this exacerbates drought conditions, impacting aquatic habitats and the amount of water supply available for other purposes (food crops, drinking, hydropower, etc.).
Making biomass more environmentally friendly
Not all biomass energy solutions are created equal; some of the environmental downsides of bioenergy can be mitigated through more sustainable forest management, and making careful choices about the type of biomass we harvest for fuel and how we harvest it. Advancements in research and technology, along with policy development, can help ensure that future investments in bioenergy are more environmentally friendly.