Chicago is not the first American city to use CNG taxi cabs, but it is by far the largest and most influential to do so. The timing of this partnership comes as a result of a $1.5 million dollar grant package from the City of Chicago and the US Department of Energy (through the Clean Cities Coalition program).
The City of Chicago is convinced that the CNG taxi cab program will both reduce greenhouse gas emissions and save cab operators money, according to a story posted to Inhabitat:
CNG isn’t a zero emission technology, but according to the Environmental Protection Agency, it emits 80 percent fewer ozone precursors and over 95 percent fewer particulates than conventional gasoline-powered vehicles. In addition to being cleaner, compressed natural gas is also 30 to 40 percent cheaper than gasoline or diesel on a mileage basis.
Although these estimates of emissions and cost reductions may be accurate, it is important to analyze new investments in alternative fuel technology from a life cycle analysis perspective. In short, this new CNG taxi cab partnership should be assessed based on whether its total aggregate emissions from every stage of its operations - construction of the filling stations, station maintenance, fuel production, procurement, and logistics, purchase of new CNG-compatible cabs, and the increased distances cabs must travel to fuel up - constitute a significant reduction from conventional petroleum fuel emissions. The City of Seattle recently suspended its own 1992 experiment with CNG vehicles for this very reason: the predicted emissions reductions did not materialize when the life cycle costs were factored in.