<P> Carbon dioxide, a greenhouse gas, is emitted during fermentation and combustion . This is canceled out by the greater uptake of carbon dioxide by the plants as they grow to produce the biomass . When compared to gasoline, depending on the production method, ethanol releases less greenhouse gases . </P> <P> Compared with conventional unleaded gasoline, ethanol is a particulate - free burning fuel source that combusts with oxygen to form carbon dioxide, carbon monoxide, water and aldehydes . The Clean Air Act requires the addition of oxygenates to reduce carbon monoxide emissions in the United States . The additive MTBE is currently being phased out due to ground water contamination, hence ethanol becomes an attractive alternative additive . Current production methods include air pollution from the manufacturer of macronutrient fertilizers such as ammonia . </P> <P> A study by atmospheric scientists at Stanford University found that E85 fuel would increase the risk of air pollution deaths relative to gasoline by 9% in Los Angeles, US: a very large, urban, car - based metropolis that is a worst - case scenario . Ozone levels are significantly increased, thereby increasing photochemical smog and aggravating medical problems such as asthma . </P> <P> Brazil burns significant amounts of ethanol biofuel . Gas chromatograph studies were performed of ambient air in São Paulo, Brazil, and compared to Osaka, Japan, which does not burn ethanol fuel . Atmospheric Formaldehyde was 160% higher in Brazil, and Acetaldehyde was 260% higher . </P>

How can ethanol be used as a source of energy for powering plants