The carbon dioxide produced during ethanol production and gasoline combustion is extracted from the atmosphere by plants for starch and sugar formation during photosynthesis. It is assimilated by the crop in its roots, stalks and leaves, which usually return to the soil to maintain organic matter, or to the grain, the portion currently used to produce ethanol. Only about 40 percent or less of the organic matter is actually removed from farm fields for ethanol production. The rest is returned to the soil as organic matter, increasing fertility and reducing soil erosion. With modern conservation farming practices, this soil organic-matter will build up, representing a net removal of carbon dioxide from the atmosphere. An increase of only 1% in the soil organic matter level means an atmospheric reduction of over 40 tonnes of CO2 per hectare of farmland. http://www.comalc.com/fuel ethanol.htm
Canada has vast areas of agricultural cropland. Most of these soils could benefit from increasing soil organic matter by several percentage points. Ethanol use in gasoline has tremendous potential for a net reduction in atmospheric carbon dioxide levels.
6.1.2 Carbon Monoxide
Carbon monoxide, formed by the incomplete combustion of fuels, is produced most readily from petroleum fuels, which contain no oxygen in their molecular structure. Because ethanol and other “oxygenated” compounds contain oxygen, their combustion in automobile engines is more complete. The result is a substantial reduction in carbon monoxide emissions. Research shows that reductions range up to 30%, depending on type and age of automobile, the automobile emission system used, and the atmospheric conditions in which the automobile operates. http://www.greenfuels.org/ethaques.html
Because of health concerns over carbon monoxide, the 1990 amendments to the U.S. Clean Air Act mandate the use of oxygenated gasolines in many major urban centres during the winter (when atmospheric carbon monoxide levels are highest) to reduce this pollution.
6.1.3 Nitrous Oxide (N2O)
Agricultural grain production for ethanol may generate a slight increase in nitrous oxide (N2O) emissions resulting from heavy fertilizer use. However, research and advances in agricultural technology in grain production are resulting in a reduction of these emissions, often to levels below other common crops. (http://www.greenfuels.org/globalwarm.html)
6.1.4 Other Octane Additives
Because of its high octane rating, adding ethanol to gasoline can permit the reduction or removal of aromatic hydrocarbons (such as benzene), and other hazardous high-octane additives commonly used to replace tetra-ethyl lead in Canadian gasoline.