This chapter explores a strategy for mitigating climate change for coal-derived synthetic fuels both by CCS and by choosing an energy carrier that facilitates a shift to more-efficient energy end-use technology. The focus is on dimethyl ether (DME). Its high cetane number makes DME a suitable candidate fuel for compression ignition engine vehicles, which are more energy efficient than spark-ignition engine vehicles. Compression ignition engine vehicles are not more widely used in part because of difficulties in realizing simultaneously low levels of emissions of both NOx and particulate matter (PM), which are being sought in tightening air pollutant emission regulations throughout the world, driven by public health concerns. The tradeoffs that make simultaneous NOx and PM control difficult for diesel fuel do not exist for DME, the combustion of which generates essentially no PM because of the absence of C-C bonds and of sulfur. Low NOx emissions can be realized with much less complicated tailpipe emission control technologies. These pollution control advantages can facilitate a transition to fuel-efficient vehicles such as compression ignition engine/hybrid electric vehicles, although the pollution control advantages offered by DME are offset in part by the refueling infrastructure challenges that arise because at atmospheric pressure. DME is a gas that must be stored in mildly pressurized canisters. It also illustrates the potential DME offers for reducing emissions by facilitating a shift to more energy-efficient vehicles.
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