US Must Cut CO2 Emissions By 800 Percent

A new report authored by researchers at the University of Michigan shows that the US must cut its CO2 emissions by 800 percent if the nation is to achieve its goal of stabilizing atmospheric CO2 levels at 450 parts per million by 2050. The study concentrated on what must be done to automobiles to achieve this kind of reduction.

Currently, automobiles deposit about 160 grams of carbon into the atmosphere every mile. To achieve the US greenhouse gas emission goal, vehicles can produce no more than 20 grams of carbon per mile. The study was authored by Greg Keoleian of the University of Michigan's School of Natural Resources and will appear in the Feb 1 issue of Environmental Sciences and Technology.

According to Keoleian, achieving those targets won't be easy and will take a number of strategies to accomplish. Simply improving fuel efficiency isn't enough, although cleaner, more efficient vehicles are part of the equation. In addition, Keoleian says that low-carbon fuel formulations and a reduction in the number of miles driven each year must also factor into the plan.

According to computer models developed at UM, a single-strategy approach is destined to fail. To achieve carbon emission goals by improving fuel economy alone would mean that vehicles in 2050 must achieve an average fuel economy of 136 miles per gallon. Reducing carbon emissions to acceptable levels strictly through the use of low-carbon ethanol would mean an almost exclusive use of the ethanol fuel formulation. Reducing overall miles traveled would require a cut of more than 50 % in the overall number of miles traveled each year.

Keleoian says that none of the single-strategy approaches are viable. Instead, the US must adopt an aggressive, multi-pronged approach to carbon emission reductions that includes the development of renewable, nonfossil-based fuels, and a sharp reduction in the number of miles traveled each year. Keleoian says that switching to electric and hybrid electric vehicles may not be enough. In many areas, power is generated by coal-fired plants. While a PHEV does reduce the tailpipe CO2 emissions, the net emissions reduction is much smaller if the electricity to charge the vehicle was generated at a coal-fired plant. Keleoian says that the country must look at solar, wind and nuclear energy sources to make the needed reductions in atmospheric greenhouse gases.

Keleoian's study can be found at http://pubs.acs.org/doi/abs/10.1021/es801032b.

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