Renewable resources of energy are constantly replenished and will never run out.

Biomass can be transformed into liquid fuels for transportation, called biofuels. The use of biofuels will reduce pollution and reduce a country’s dependence on non-renewable oil.

Figure 2.2 Feedstock for biofuels (yield per hectare in liters). Source: Agriculture and Agri­Food Canada; www4.agr. gc. ca.

Biomass is material that comes from plants. Organic waste is also considered to be biomass, because it began as plant matter. Plants use the light energy from the sun to convert water and carbon dioxide to sugars that can be stored, through a process called photosynthesis. Some plants, like sugarcane and sugarbeet, store the energy as simple sugars. Other plants store the energy as more complex sugars, called starches. These plants include grains like corn and are also used for food. The problem here is that sugar and corn are used for food as well.

Another type of plant matter, called cellulosic biomass, is made up of very complex sugar polymers and is not generally used as a food source. This type of biomass is under consideration as a feedstock for bioethanol production. Specific feedstocks under consideration include:

• Agricultural residues: leftover material from crops, such as the stalks, leaves, and husks of corn plants. The residue from sugarcane, called bagasse, is becoming a very important biomass. Other types of plant mass traded as biomass are tea leaves, coconut shelves, olive oil seedcake, and palm kernel shells.

• Forestry waste (chips and sawdust from lumber mills, dead trees, and tree branches).

• Municipal solid waste (household garbage and paper products).

• Food processing, feedlot waste, and other industrial wastes.

• Energy crops (fast-growing trees and grasses) developed just for this purpose like Jatropha and Camelina. Hybrid eucalyptus trees and Miscanthus or Elephantgrass plantations are also being developed and sold as biofuel and biomass. A basic requirement for the production of grass-based biofuels is a sufficiently large area that permits the economic production ofthis raw material. The use of marginal land does not necessarily stand in competition with worldwide food production, as is often feared. Grass for biofuels can thus also be grown on soils and in climates that are entirely unsuitable for the cultivation of food crops. More than half of today’s global demand for liquid fuels could be covered by biofuels produced from raw materials grown in such areas.

Cellulose is the most common form of carbon in biomass, accounting for 40­60% by weight of the biomass, depending on the biomass source. It is a complex sugar polymer (“polysaccharide”).

Lignin is a complex polymer that provides structural integrity in plants. It makes up 10-24% by weight of biomass. It remains as residual material after the sugars in the biomass have been converted to ethanol. It contains a lot of energy, and can be burned to produce steam and electricity for the biomass-to-ethanol process.

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