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Biomass Power
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Biomass refers to a group of organic materials that can be used to generate electricity. Sources of biomass are: herbaceous and woody plants, agriculture and forestry wastes and residues, landfill gases, animal wastes, municipal wastes, and other organic material.
Because of the variety of sources, there are a variety of ways that electricity can be generated using biomass.
Direct combustion is a process that involves burning biomass, such as wood and solid waste from forestry and agriculture. The burning biomass creates heat that is used to boil water and make steam. The steam turns a turbine to generate electricity.
Anaerobic digestion makes use of the microorganisms living in wastes that break down organic matter and produce biogas. The biogas that is created is a combustible fuel that can be used in an electricity generation plant.
Co-firing refers to adding biomass to coal-fired electricity generation plants. Burning biomass and coal together means less coal is used, minimizing the overall consumption of coal and its environmental impact.
Pyrolysis is a process that converts solid biomass into a liquid fuel. This is achieved through heating biomass in an oxygen-free tank to produce a gas. The gas is quickly cooled to create an oil-like liquid rich in hydrocarbons. This liquid fuel can be used to generate electricity.
Gasification is a form of pyrolysis that uses more air during the heating process. It creates a producer gas, which is burned to heat water and make steam. The steam turns turbines and generates electricity.
Biomass power makes up only a small fraction of Canada's total electricity generation, but its use in Ontario is expected to increase with Provincial incentives to make the price of biomass power comparable to traditional sources of electricity (fossil fuels and hydro). The use of biomass will increase as Ontario works to phase out coal: there are plans to co-fire biomass and coal, and to convert some coal-fired plants to biomass-fired plants.
What are the benefits of biomass? What are its drawbacks and environmental impact?
Biomass is a carbon-neutral source- The amount of carbon dioxide (a greenhouse gas) released when biomass is burned to generate electricity is less than the amount it captured through photosynthesis when it was a living plant. For this reason, it's considered carbon-neutral.
- Biomass power uses organic wastes and residues from the forestry and agriculture industries, as well as gases produced by landfills, and animal and human wastes to generate electricity.
- Organic materials are replenished by natural plant growth cycles. Meanwhile, the forestry and agriculture industries continue to produce organic wastes and municipalities generate their own wastes. All can be used for biomass power.
Drawbacks and Environmental Impact
Biomass power needs a constant supply of organic materials- There are worries that tracts of land will be used to grow biomass rather than food, and that natural environments will be converted to monoculture biomass crops, destroying habitats and biodiversity in order to meet the supply needs of biomass electricity generation.
It involves collection and transportation challenges
- It is difficult to collect enough biomass to generate electricity. Large quantities are needed, and they typically come from a variety of places.
- Although biomass is considered carbon-neutral, it still releases GHGs and other air pollutants when burned to generate electricity. Its emissions are far less than those caused by burning fossil fuels, but they are still harmful.
- Ash is created by burning biomass and can contain the same metals and other harmful substances present in the original waste.
For more information:
Centre for Energy (2010). What is biomass energy? Available here.
David Suzuki Foundation (2010). Biomass. Available here.
The Pembina Institute. Bioenergy. Available here.
Pollution Probe (2003). Primer on the Technologies of Renewable Energy. Available here.
U.S. Energy Information Administration. Energy Kids: Biomass. Available here.
U.S. Environmental Protection Agency (2010). Biomass. Available here.
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