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6 December 2012

The new dash for gas should be good for the environment, but there is a complication…

Measures to promote Britain’s embryonic shale gas industry were a big feature of this week’s Autumn Statement. Shale gas (and natural gas generally) is good news for those worried about energy costs, but is it good news for the environment?

In an article for National Geographic, Marianne Lavelle explains why it could be:

  • “Unlike coal, natural gas burns without spewing sulfur dioxide, mercury, or particulates into the air or leaving ash behind. And it emits only half as much carbon dioxide. The greenhouse gas inventory compiled by the U.S. Environmental Protection Agency (EPA) shows that the nation’s CO₂ emissions in 2010 were lower than in 2005 by just over 400 million metric tons, or 7 percent… Reduced emissions from power plants, mostly because many have switched from coal to gas, accounted for a bit over a third of that.”

In fact, Lavelle understates the environmental case for gas in that, as well as having a lower carbon content than coal per unit of fuel, gas-fired power stations are also more efficient than their coal-fired rivals – meaning that fewer units of fuel need to be burned to produce each unit of power.

There is a catch, though. Natural gas is mostly methane – and methane is a much more potent greenhouse gas than carbon dioxide:

  • “Carbon dioxide is the main [greenhouse gas], because the atmosphere holds 200 times as much of it. But a given amount of methane traps at least 25 times as much heat—unless you burn it first. Then it enters the atmosphere as CO₂.”

Of course, most of the natural gas we produce is burned. However, in the process of getting from the well to the power station (or your boiler) some of it leaks.

  • “The atmospheric methane concentration has risen nearly 160 percent since preindustrial times, to 1.8 parts per million…
  • “As U.S. CO₂ emissions fell between 2005 and 2010, methane emissions rose. By 2010, [the Environmental Protection Agency] says, the rise was equivalent in global warming potential to around 40 million metric tons of CO₂annually, which means it offset 10 percent of the CO₂ decline. More than half of that methane increase, says EPA, came from the natural gas industry—the country’s biggest emitter.”

This is a problem, but it could also be an opportunity:

  • “Some experts consider methane capture… an easier way than controlling CO₂to slow global warming, at least in the short term, because small amounts of methane make a big difference and because it’s a valuable fuel. China, for instance, the world’s largest coal producer, vents huge amounts of methane from its mines to prevent explosions…”
  • “Drew Shindell, a climate scientist at NASA’s Goddard Institute for Space Studies, recently led a global team of scientists in analyzing seven methane-reduction strategies, from draining rice fields to capturing the gas that escapes from landfills and gas wells. Unlike CO₂methane affects human health, because it’s a precursor of smog. When health impacts are included, Shindell’s group found, the benefits of methane controls outweigh the costs by at least 3 to 1, and in some cases by as much as 20 to 1.”

Perhaps, instead of trying to solve the climate change problem all in one go, we should start with the easy stuff and work our way up?


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