Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 86

Alternate fuels (renewable fuels, advanced fuels, synthetic fuels which include liquid and gaseous fuels, as well as clean solid fuels) are any materials or substances that can be used as fuels, other than conventional fuels. Alternate fuels are derived from resources such as coal, oil shale, or tar sands, and various forms of biomass – in the last case the erm that is more appropriate is renewable fuels. Renewable fuels are making headway into the fuel balance by reducing dependence on imported oil. Often, renewable fuels produce less pollution than crude oil-derived gasoline or crude oil-derived diesel fuel.

Examples of renewable fuels and renewable energy sources are: (i) biodiesel, which is diesel fuel derived from vegetable oils and animal fats. It usually produces less air pollutants than crude oil-based diesel, (ii) biogas which is produced from the anaerobic digestion of diverse organic waste sources using various methods, (iii) biomass liquids: produced by biomass-to-gas-to-liquid conversion and by pyrolysis processes which involve the conversion of biomass, such as wood and agricultural residues, (iv) ethanol or other alcohols produced domestically from corn and other crops and produces less greenhouse gas emissions than conventional fuels, and (v) hydrogen which is produced from biomass, (vi) nuclear power, or (vii) other sources such as solar energy, tidal energy, and wind energy and hydroelectric power.

Biodiesel from plant sources is similar to diesel, but has differences that include higher cetane rating (45 to 60 compared to 45 to 50 for crude oil-derived diesel fuel), and it acts as a cleaning agent to get rid of dirt and deposits. As with alcohols and gasoline engines, taking advantage of the high cetane number of biodiesel potentially overcomes the energy deficit compared to ordinary number 2 diesel.

See also: Biodiesel, Biogas, Hydrogen, Synthetic Fuel.