Biomass and the Environment
Biomass is plant matter such as trees, grasses, agricultural crops and other biological material. It can be used as a solid fuel, or converted into liquid or gas forms for the production of electricity, heat, chemicals or for use in vehicles.
There are three primary ways to convert biomass to energy:
- thermal —The oldest and most common way is to burn biomass to create heat. This can be used directly for heating, cooking and industrial processes, or indirectly to generate electricity. At biomass power plants, biomass is burned in a boiler to produce high-pressure steam, which, in turn drives a turbine to generate electricity.
- thermochemical —By heating (but not burning) plant matter, it is possible to break down biomass into gases, liquids and solids, which can be further processed into gas and liquid fuels like methane and alcohol. Biomass reactors heat biomass in a low-oxygen environment to produce a fuel gas (mostly methane), which can then fuel steam generators, combustion turbines, combined cycle technologies or fuel cells.
- biochemical —Adding bacteria, yeasts and enzymes to biomass liquids causes biomass materials to ferment and change into alcohol. A similar process is used to turn agricultural products into ethanol (grain alcohol), which is then mixed with gasoline to make an ethanol-gasoline blend. And when bacteria are used to break down biomass, methane is produced and can be captured from landfills and sewage treatment plants to produce fuel for heat and power.
Biomass energy can be produced from plants or “energy crops” grown specifically for this use. Energy crops include corn, grasses and fast-growing poplar and willow trees.
Biomass fuel sources can also be found in left-over materials in other industrial processes such as forestry, agriculture and manufacturing. These materials can include straw, wood residues and paper trash and yard clippings in municipal waste. Also, municipal sewage, animal manure, resourant and vegetable wastes.
Currently the forest products and pulp and paper industries produce most of our country’s biomass materials. By burning bark, wood chips, sawdust and “pulp liquor” (a mixture of pulping chemicals and organic material), these industries create heat for drying kilns and produce steam and electricity to meet their needs or to sell to others. The pulp and paper industry has about 1,500 megawatts of electricity generating capacity, fuelled in part from the burning of wood residues.
To a lesser extent, biomass energy is produced from wood burned for residential heating. According to Natural Resources Canada, about 1.5 million Canadians use wood for home heating.
Biomass is also used as a feedstock to create fuels. For more than 20 years, government and industry researchers in Canada have studied technology to produce ethanol from biomass feedstock such as grains, trees, grasses and agricultural wastes. Ethanol can be either blended with gasoline and burned in regular automobile engines, or used straight in modified engines.
Canada produces about 238 million litres of ethanol each year, mainly from corn and other grains, for fuel use and industrial applications. About 1,000 retail stations across Canada offer ethanol-blended fuels that provide important environmental benefits. Independent analysis by the U.S.-based Centre for Transportation indicates that ethanol-enhanced gasolines reduce emissions of greenhouse gases and carbon monoxide through improved combustion.
Using landfill gas, which results from the decay of municipal solid waste, is becoming more widespread in use. In 2000, about 13 sites across Canada captured roughly 200,000 tonnes of methane annually for energy purposes. These sites are primarily located in Ontario, Quebec and British Columbia.
There is significant potential to increase the use of biomass energy, because of Canada’s enormous forest resources and large agricultural sector. Government and industry are exploring the potential of quick-growing plant crops, such as poplars and willows, that can be planted and harvested as energy crops. They are also collaborating on technology projects to improve the combustion efficiencies of biomass furnaces and wood fireplaces.
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