Everyone has some gas now and then, but Boston's really got it going on.
Imagine driving all 784 miles of roadway within Boston's city limits. Writing in Environmental Pollution, Nathan Phillips of Boston University and co-authors did just that. (Full disclosure, four of the authors - Adrian Down, Jon Karr, Kaiguang Zhao and Rob Jackson - are at Duke.). But there was a method to their madness. They were looking for natural gas leaking up from distribution piping buried beneath the streets of Boston. And why would they do that? The story starts with everyone's favorite divisive subject.
Fracking for shale gas has changed the energy landscape for the US and perhaps the world. With falling prices and predictions of plentiful supplies of natural gas for decades to come, coal-fired power plants are looking more and more to be so 20th century. At the same time America's energy future is looking more and more secure.
Fracking has the potential to be an environmental boon. After all burning natural gas leads to far less pollution (e.g., nitrogen oxides, sulfur oxides, mercury) than burning coal and it doesn't leave a bunch of post combustion toxic waste to deal with. From a climate point-of-view, natural gas also appears to be a winner, at least at first blush. On a BTU basis, burning natural gas emits 30% less carbon dioxide than burning oil and 45% less than burning coal.
Win-win, right? Maybe not, at least when it comes to the environment. First of all there's all the hoopla about water contamination from fracking. And a number of scientists question whether natural gas really provides a climate benefit. Methane is the major component of natural gas and it is a potent greenhouse gas; 23 times more powerful of a greenhouse gas than carbon dioxide. Any natural gas that is vented to the atmosphere during drilling and from leaking pipelines will add to the greenhouse gas load in the atmosphere and the warming that results.
How serious is natural gas leakage? At the moment there is no consensus. If the fraction of unaccounted gas is only about 1.4%, as reported by industry, this is essentially a non-issue where climate is concerned. If EPA's estimate of 2.4% is correct it is a small but not negligible issue. However if it is as large as up to 7.9% as Howarth et al of Cornell University argue, it is a huge issue. So large in fact, that it might be better for the climate if we stuck with coal instead of natural gas.
It is unlikely that this debate will be settled soon but there is a straightforward way for the industry to make it moot. Find out where natural gas is escaping and shut those leaks down. And this is where Phillips et al come in--they took it upon themselves to search out and document the locations and sizes of major leaks in one of America's major cities - Boston.
Driving and Measuring
In the late summer to fall of 2011, Phillips et al conducted a total of 31 surveys, covering all Boston's roads. As they drove the city streets they measured methane levels at the same time that they mapped the locations using GPS. (See top figure.) The also recorded the carbon isotopic composition of a subset of leaks. Their results include:
- The discovery of more than 3,000 leaks under Boston's roads and sidewalks.
- The leaks cut across both rich and poor neighborhoods.
- Most of the leaks were linked to cast-iron pipes (some of which are more than a 100 years old) in the gas distribution system.
- Some leaks were up to 15 times background levels and six locations had levels in manholes that approached explosive conditions.
Making the Win-Win More of a Win-Win
The natural gas boom has often been characterized as a win-win. A win for the economy, our energy security and for the environment--with that last "win" being the less certain of the three. Phillips et al provide a path that could lead to a more realistic win-win: by finding and patching leaking natural gas pipes, gas companies could save money while benefiting the environment by using gas more efficiently at the same time that it reduces the greenhouse gas emissions from growing natural gas production.
Think of it a dose of beano for the nation's natural gas pipeline infrastructure.