Methane happens: Why uncaptured emissions are a wasted opportunity

Friday 01 May 2015

At Blue Spruce Farm in Bridport, Vt., the black-and-white dairy cows are used to the routine. In what looks like a choreographed dance, 1,400 milk cows delicately step over the scrapers that run along the concrete floors and collect their manure, which goes into a huge digester capable of holding 21 days’ worth of waste. Inside, highly flammable methane gas is built up under low pressure and then burned in a 600-kilowatt generator, with the capacity of powering 400 homes.

Blue Spruce doesn’t have to capture the methane, but taking that approach has turned waste into a profit center, bringing in a premium price for energy. Ernie Audet , one of the owners, said “cow power” has become an integral part of the dairy operation. “We wouldn’t run the farm without it,” he said, adding that after six years in place the $1.5 million digester was close to paying for itself. At least a dozen other Vermont farms are also selling cow power to eager buyers.

Stories like this are increasingly important in a warming world because methane is a bad climate actor. Produced by ruminants, energy production and rotting organic material, and the main ingredient in natural gas, methane is a far more powerful greenhouse gas than carbon dioxide. “It packs a heck of a wallop,” said David Doniger, director of the climate and clean air program at the Natural Resources Defense Council.

Although methane comprises only about 14 percent of total climate emissions and has a lifespan in the atmosphere of only about 12 years — compared to roughly 100 years for CO2 — it is many times more potent than CO2 in the short term, according to the Intergovernmental Panel on Climate Change. And global methane release has shown significant increases since 2007.

Methane is produced naturally by forest fires, permafrost, wild animals, rivers, lakes and wetlands. But more than half of the methane entering the atmosphere comes from human activities. According to the Global Methane Initiative, anthropogenic sources worldwide include the digestive process of ruminant animals (29 percent), oil and gas systems (20 percent), landfills (11 percent), rice paddies (10 percent, with other agricultural production at 7 percent), wastewater (9 percent), coal mining (6 percent) and manure from farmed animals (4 percent).

The good news is that there are fairly easy ways to dramatically slow our methane emissions — if we make the commitment to do so.

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