Greenhouse gas emissions from high demand, natural gas-intensive energy scenarios

Since coal and oil emit 70% and 30% more CO2 per unit of energy than natural gas (methane), fuel switching to natural gas is an obvious pathway to lower CO2 emissions and reduced theorized greenhouse warming. However, methane is, itself, a strong greenhouse gas so the CO2 advantages of natural gas may be offset by leaks in the natural gas recovery and supply system. Simple models of atmospheric CO2 and methane are used to test this hypothesis for several natural gas-intensive energy scenarios, including the work of Ausubel et al (1988). It is found that the methane leaks are significant and may increase the total 'greenhouse effect' from natural gas-intensive energy scenarios by 10%. Furthermore, because methane is short-lived in the atmosphere, leaking methane from natural gas-intensive, high energy growth scenarios effectively recharges the concentration of atmospheric methane continuously. For such scenarios, the problem of methane leaks is even more serious. A second objective is to explore some high demand scenarios that describe the role of methane leaks in the greenhouse tradeoff between gas and coal as energy sources. It is found that the uncertainty in the methane leaks from the natural gas system are large enough to consume the CO2 advantages from using natural gas instead of coal for 20% of the market share. (author)