Fuels to Drive Our Future (1990) / Chapter Skim
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5. Environmental Impacts of Alternative Fuels
5. Environmental Impacts of Alternative Fuels
Pages 105-114
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From page 105... ...
local, state, and federal governments are interested in reducing emissions from motor vehicles and stationary sources in those regions that fail to meet ambient ozone standards. One proposed strategy to reduce ozone is to decrease emissions from gasoline-powered vehicles of volatile organic carbon (VOC)
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From page 106... ...
to achieve greater fuel efficiency, then for moderately lean mixtures the NOx levels would be higher and carbon monoxide and hydrocarbon emissions and engine power would be lower than those of engines operating at stoichiometric ratios, as do most of today's gasoline engines. However, almost all automobiles now (and for the foreseeable future)
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From page 107... ...
The ozone formation process is highly complex; even the most sophisticated photochemical air quality models have error margins of 30 percent or more in predicting hourly averaged ozone concentrations (Russell, 1988; Tesche, 198X)
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From page 108... ...
The conclusions on spark ignition engines are roughly the same for compression ignition engines. Use of methanol or CNG instead of diesel fuel dramatically reduces particulates emissions and, because there is no sulfur in these fuels, sulfur oxide emissions; methanol may also significantly reduce NOX emissions depending on the engine design (Arson et al., 1989; Unnasch et al., 19861.
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From page 109... ...
For example, leakage of natural gas from pressurized tanks in closed spaces creates the potential for explosions. Pure methanol burns with an invisible flame in daylight, although adding 15 percent gasoline makes the flame visible.
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From page 110... ...
Conclusions and Recommendations Because of different assumptions about vehicle emissions, vehicle replacement rates, and ratios of RHCs to NOx ambient levels, air quality models incorporating substitution of gasoline-powered vehicles by methanol-fueled vehicles vary widely in predictions of tropospheric ozone reduction. Using optimistic assumptions for the California South Coast Air Basin and some other areas, significant potential improvements are predicted if formaldehyde emissions can be controlled adequately.
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From page 111... ...
CNG vehicles using fossil methane have a lower production of greenhouse gases than gasoline-powered vehicles, although this result depends on assumptions about the relative contributions of CH4 and CO2 to global warming and on CH4 emissions from production and use (DeLuchi, 1989; Ember et al., 1986~. In this particular analysis, CNG is 19 percent better
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From page 112... ...
This is true only for biomass processes that do not use fossil fuel, that do not displace land from forest that would otherwise sequester carbon in its biomass, and that are grown every year so that carbon dioxide from fuel use is talcen up by the crops. bShould be increased by 25 to 33 percent for thermally enhanced oil recovery.
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From page 113... ...
In any long-term evaluation of greenhouse gas strategies, consideration of the contribution of the entire transportation sector to the global effect and the various trade-offs involved in fuel manufacturing and in switching to alternative fuels, vehicles, or transportation systems is needed. Conclusion Because manufacture of transportation fuels from coal and oil shale resources produces more CO2 than processes based on oil, natural gas, or non
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From page 114... ...
Since biomass supply will probably limit its use, system studies of the optimum use of biomass for reduction of CO2 emissions from fossil fuel conversion are recommended. In the longer term other nonfossil energy sources for heat and hydrogen production should also be investigated.
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