Even prior to the final EPA gas drilling air rule, compared to coal or oil, natural gas is already much cleaner. It emits virtually no soot, mercury, or lead and less sulfur dioxide, carbon dioxide, and other pollutants.
Now with the EPA gas drilling air rule promulgated, the environmental advantages of natural gas just grew. The EPA final rule makes natural gas even cleaner by slashing by 95% emissions of volatile organic compounds during gas production. It also cuts methane emissions. http://www.epa.gov/airquality/oilandgas/actions.html. This rule means that substituting natural gas for coal or oil will deliver bigger environmental benefits than ever before.
The rule also means that shale gas may have more climate benefits than other sources of natural gas. Here is why.
The rule requires green completions/reduced emission completions must be used at high pressure wells like shale gas wells. Virtually all shale gas wells will be green completed by January 1, 2015. Yet, the rule does not require green completions at low-pressure wells (87% of coal bed methane gas wells are low-pressure).
Shale gas development also typically has newer gathering systems and newer equipment generally, because it is the most recent. Newer pipelines and equipment reduce methane leakage, compared to older systems that serve typically conventional gas fields.
The combination of the newer infrastructure serving shale gas wells and the requirement of green completions for shale gas wells means that shale gas may have the biggest climate benefits of all gas.
Compared to coal, using gas reduces by approximately 50% global warming emissions, even prior to the EPA gas drilling air rule. After the rule, the climate advantage of gas is going up.