The Worldwatch Institute, for decades a leading player in sustainability research, has issued a report with startling findings about recent changes in the U.S. fossil fuel mix and their implications for the country's greenhouse gas emissions. From 2007 to 2009, the share of natural gas in U.S. electricity generation increased from 20 to 23 percent, while the share of coal dropped from 52 to 45 percent. That may not look like much at first glance but in fact may be the beginning of a sea change in U.S. energy. The decrease in coal generation accounted for half the decline in carbon emissions from 2007 to 2007, which dropped a jaw-dropping 10 percent.
"In just two years, we wiped out half the increase in U.S. greenhouse gas emissions that had taken place during the previous 15 years," observes Christopher Flavin, president of Worldwatch and principal author of the report, "The Role of Natural Gas in a Low-Carbon Energy Economy." Could that dramatic decrease in U.S. carbon suggest that the U.S. goal of cutting greenhouse gas emissions 17.5 percent by 2020 is unduly unambitious? "It could," says Flavin.
Easily the most important factor enabling U.S. coal generation and carbon emissions to fall so dramatically has been the fast-growing role of natural gas in electricity generation. That in turn is attributable to the revolution in "unconventional gas," that is, natural gas extracted from deep shale formations by means of horizontal drilling and hydraulic fracturing. But almost important, arguably, is the bear hug that prominent organizations in the environmental community--Worldwatch and Sierra Club, among them--are giving gas.
Gas, after all, is a nonrenewable fossil fuel. So why do a lot of environmentalists like it so much?
If you go to a place like Dimock, in northeast Pennsylvania, where Marcellus Shale gas drilling is going on great guns, you'll see huge trucks carrying drill pipe through the middle of what used to be a sleepy rural town. Methane has contaminated drinking water wells and must now be vented; everywhere around town there are huge unsightly tanks (see photo above), some holding water for injection into wells, some holding the flowback water which contains all manner of chemicals--some put into the injection water to expedite gas extraction, some picked up from the ground on the way back to the surface.
So how can national environmental leaders be for gas? Actually, the advantages, as enumerated by Flavin and his coauthor Saya Kitasei, are overwhelming. First: "Burning natural gas produces virtually none of the sulfur, mercury, or particulates that are among the most health-threatening of pollutants that result from coal combustion," they explain," citing a study that found the environmental cost of gas-generated electricity was one-twentieth--yes, one twentieth!--that of coal.
Second, electricity from natural gas results on average in about half the carbon emissions resulting from coal-fired power. And that's the average: the ratio is much worse for the older, dirtiest coal plants and best gas-fired ones."New combined-cycle gas plants produce 55 percent less carbon dioxide that new coal plants do and 62 percent less than the average U.S. coal plant," say Flavin and Kitasei.
Because of dispatch rules favoring coal and nuclear baseload plants ahead of gas, and because gas often is used in peaking plants that only come onstream intermittently, gas-fired plants represent a much larger share of U.S. generating capacity than they do of actual generation. This implies that changes in rules and policy could induce an even more rapid conversion of coal to gas, if prices stabilize. Flavin thinks it's now conceivable that in the next 10 or 12 years we could cut coal's share in electricity generation to about a 25 percent share in U.S. generation, to yield roughly a 12.5 percent cut in U.S. carbon emissions.
But prices and policies are the wildcards. Traditionally gas prices have fluctuated drastically; their stabilization will depend on finding ways to develop shale gas consistent with meeting local concerns, which are serious. Needed policies include more uniform Federal and state regulation of gas development, revised electricity dispatch rules, tighter air quality regulation, and--above all--a strong cap-and-trade climate bill that discourages coal generation instead of "locking it in," as Flavin puts it.