Friday's compound: carbofuran

Carbofuran in the news:

A short time after a Lincoln County farmer sprayed the insecticide carbofuran on his 95-acre sunflower field on the Colorado plains in 2006, birds started turning up dead. [...]

Now, the U.S. Environmental Protection Agency is trying to ban the pesticide — a first in 20 years — after determining that even legal uses are likely to kill birds.

But the agency, which banned DDT in 1972, is facing resistance from the one company that produces carbofuran and from congressional champions in agricultural states.

- from the Denver Post.

Methane: From Landfills to Greenhouse Gas

The Background:
Larimer County is hoping to make money off of its landfills. Methane gas forms within the massive piles of trash, and the county began venting and burning methane from the county landfill last year.

Instead of simply burning the gas to get rid of it, county commissioners this week approved a contrast with Timberline Energy to build a methane collection system at the Larimer County Landfill. The methane may be converted to natural gas or burned in order to generate electricity, and Timberline will compensate the county for the methane they collect.

The Science:
Much of the waste that ends up in landfills -- food scraps, paper, and yard waste, for instance -- contains carbon. After the waste is buried, bacteria begin to digest the waste in much the same way that our bodies digest carbon-containing food -- turning it into the many different compounds make up cells. But just like our bodies, these aerobic bacteria require oxygen to work, and the compounds they create, such as sugars, have a high oxygen content.

After several years, most of the oxygen buried within the landfill has been used up, and a different set of bacteria -- anaerobic bacteria -- begin to work. Because of the scarcity of oxygen, the primary compound produced by these bacteria doesn't contain oxygen.

Methane, with the chemical formula CH₄, is the simplest compound that contains only carbon and hydrogen and no oxygen. It comprises half of the gases produced by these anaerobic -- sometimes called methanogenic bacteria. The Environmental Protection Agency estimates that a quarter of all methane produced as a result of human activity comes from landfills.

The Misconceptions:
The Loveland Reporter-Herald stated that methane "has more than 20 times the heat-trapping power of carbon dioxide." What they're referring to is methane's global warming potential. Global warming potential depends both on how much energy each molecule of methane absorbs, but also the length of time the compound stays in the atmosphere.

Without specifying a length of time, the Reporter-Herald's statement is about as meaningful as measuring speed in miles. The length of time matters because the longer a compound stays in the atmosphere, the more energy it can absorb. Methane decomposes in the air after roughly a decade, so the global warming potential -- as compared to carbon dioxide, which sticks around for a century or more -- will vary depending on what length of time you consider.

The 2001 Intergovernmental Panel on Climate Change estimated that methane has 62 times the GWP of carbon dioxide when measured over 20 years, but a GWP of only 7 times carbon dioxide when measured over 500 years. The Reporter-Herald's statement probably referred to global warming potential calculated over 100 years, which is the most common value used in these calculations.

Friday's compound: methane

Methane in the news:

The Larimer County Solid Waste Department will, for the first time, sell methane gas released from the landfill to a Colorado based energy company. [...]

Because the county landfill emits relatively little methane, no company has expressed interest in the gas before, said Stephen Gillette, director of the county waste department.

“The solid waste department has been on a quest to find uses for the methane at the landfill,” Gillette said this morning. “It is now advantageous for this to happen.”

- from the Fort Collins Coloradoan.