Biomass energy, or bioenergy, is the energy stored in biomass — that is, nonfossil organic materials such as wood, straw, vegetable oils and wastes from forestry, agriculture and industry, as well as municipal solid waste. Like the energy in fossil fuels (e.g., coal), bioenergy is derived from solar energy stored in plants through the process of photosynthesis. The principal difference is that fossil fuels require thousands of years to be converted into usable forms, while properly managed biomass energy can be used in an ongoing, renewable fashion. In Canada, biomass is the second-largest source of renewable energy (following hydroelectricity).
Sources of Biomass
Biomass energy may be in solid, liquid or gaseous form, permitting a wide range of applications. At present, the majority of Canada's biomass energy is supplied in solid form (e.g., hog chips, sawdust, pellets, charcoal, garbage), and in liquid form (e.g., pulping liquors and ethanol). Other liquid forms of biomass energy include methanol (i.e., wood alcohol) and vegetable oils. Landfill gas (i.e., methane) from the anaerobic digestion of municipal solid waste in refuse sites is becoming more widespread. Energy-from-waste projects include steam production for industrial or commercial use or electricity generation in several major metropolitan centres in Canada.
Biomass Energy in Canada
Bioenergy comprises about 4 per cent of Canada’s total energy supply, and is the country’s second largest source of renewable energy after hydroelectricity. Historically, consumption of bioenergy was very important for home energy use, as Canadians burned wood for heating and cooking. While some households still use wood as a primary or secondary source of heat, the percentage has declined to less than 5 per cent, as other sources of energy have taken precedence (namely oil, hydroelectricity and natural gas).
In Canada, the pulp and paper industry is the largest industrial consumer of bioenergy. Forest industries have been increasing their use of wood wastes that otherwise would be burned, buried or landfilled. Principal uses include firing boilers in pulp and paper mills for process heat and providing energy for lumber drying.
Biofuels, such as methanol and ethanol, are liquid fuels produced from biomass. methanol, produced from wood and forest waste by a distillation process, may provide an alternative fuel for transportation and industry at prices competitive with fuels from bitumen and coal liquefaction. Ethanol, although it is also a viable transportation fuel, is more expensive to produce when potential food supplies such as corn and wheat are used. However, ethanol made from biomass sources such as food and agricultural wastes has the potential to be cost competitive with methanol and gasoline. The emphasis of much current research is in the conversion of biomass to alcohol for use as a transport fuel (to extend or replace gasoline and diesel oil).
Forest Biomass: Possibilities
Harvesting energy from forest biomass could be an economic boon for new industries: all cellulosic material now thrown away (i.e., branches, bark, trunks and stumps, and crooked, diseased, insect-infested, fire-damaged, dying and dead trees) could become valuable energy products. Use of forest biomass for energy also affords the opportunity to liquidate low-grade forest stands and replace them with productive stands of more valuable species. In some areas (e.g., British Columbia), it has been estimated that forest-industry wastes alone could provide enough solid and liquid fuels to replace much of the current oil consumption, once the energy conversion technologies are proven to be economic.
In other parts of Canada (e.g., the Prairies and Eastern Canada) energy plantations would be needed to provide enough biomass for significant oil displacement. Energy plantations are farms created specifically to grow trees used for bioenergy. Marginal and sub-marginal agricultural land, as well as non-agricultural land (e.g., wetlands), could be used for high-yield "forest farming" with rotations of less than 10 years between harvests (see Silviculture). The tree species under trial in Canada are primarily poplar and willow hybrids and include larch, green ash, willow, alder and soft maples.
Agricultural Biomass: Possibilities
Agricultural biomass includes animal manure, cellulosic crop residues (i.e., grain production “waste,” such as corn stalks, wheat straw, etc.), fruit and vegetable culls and food-processing waste water. Potential energy crops include high-yielding, high-carbohydrate crops such as switchgrass and vegetable oil crops such as canola and sunflower, and hydrocarbon plants such as milkweed and gumweed. In Canada, the potential for agriculturally derived biomass is less than that of forest-derived biomass. Most agricultural residues have alternative uses as animal fodder or soil conditioners and typically have much lower energy intensities than wood.
Typically, agricultural biomass is only available at one time of year, while forests can be harvested year-round. The average inventory of biomass on forested land is about 20 times the annual yield from cropland. However, agricultural biomass does have a place in farm-scale or localized operations. Biogas from animal manures can be used to heat farm buildings or, if scrubbed and compressed, to power farm vehicles. The use of animal and food-processing wastes can abate pollution and reduce disposal problems as well as produce energy. Straw can be burned in a specially designed furnace to dry grain and to heat farm buildings, and converted to ethanol for transportation fuel. The development of vegetable oils as fuels in farm diesel engines is undergoing continual development.
The main problems facing the expansion of biomass energy production are the relatively high costs of new facilities and the need to make the industry truly renewable. The cost barrier may be overcome by government policy and rising prices of conventional energy sources. However, careful attention is also needed in order to confront problems of reforestation, land use, water use, soil quality, erosion and pollution. Producing energy, in addition to lumber and paper, could put new stress on the sustainability of a forest resource base that is already endangered by past practices of the forest industries. Biomass energy must be farmed, not mined; otherwise it will merely join coal, oil and natural gas as yet another non-renewable energy source.