More broadly, the desirability or undesirability of gas is a major issue in environmental politics. On the basis that electricity produced using gas produces fewer emissions per kilowatt-hour than electricity from coal (or that natural gas vehicles pollute less per kilometre than gasoline or diesel ones), some have argued that more widespread use of natural gas can be part of a transition to a low-carbon future, with some identifying it specifically as a “bridge fuel”.
The case against gas is multi-faceted. First, there is an argument about fossil fuel dependence. Gas may be less polluting per unit of output than other fossil fuels, but building new infrastructure to extract, transport, and burn gas arguably perpetuates fossil fuel dependence. In part, this could be by crowding out investment in options which are better from a climate change perspective including renewables and, possibly, nuclear. A second major argument is that natural gas, which is primarily composed of methane, is a powerful greenhouse gas itself. One estimate recently cited in The Economist is that 2-2.5% of all the methane produced in America leaks into the atmosphere (“fugitive emissions” – “much higher, and that would endanger the argument that natural gas is over all time periods cleaner than coal”. A third argument centres on how most new gas production in North America comes from hydraulic fracturing (fracking), which in turn contaminates ground water and causes health and environmental problems. On this basis, numerous environmental groups have called gas “a bridge to nowhere”. A paper by Robert Howarth concludes:
Using these new, best available data and a 20-year time period for comparing the warming potential of methane to carbon dioxide, the conclusion stands that both shale gas and conventional natural gas have a larger GHG than do coal or oil, for any possible use of natural gas and particularly for the primary uses of residential and commercial heating. The 20-year time period is appropriate because of the urgent need to reduce methane emissions over the coming 15–35 years.
A last argument might be that since the fossil fuel industry is implacably opposed to the kind of government action which would keep temperatures to less than 2 ˚C or 1.5 ˚C of warming, the profits they derive from gas maintains financial and political strength which will continue to make climate action impossible.
Perhaps the most plausible argument in favour of gas doesn’t concern rich states like Canada and the U.S. but rapidly developing states like India, China, and Brazil which continue to deploy new coal-fired generation. If the choice really is between coal and gas, and methane leaks can be controlled, then gas may be an improvement in some situations. Rich states that are looking to build energy systems which can be counted on indefinitely, however, need to be working to move beyond fossil fuels entirely, reducing the policy-blocking power of the fossil fuel industry and avoiding the imposition of new forms of social injury through fracking.