By Nicole Montesano • Staff Writer • 

Riverbend installs 44 new gas wells

Believing more gas is being generated in the early stages than in later stages of the process, it has made the new wells much shallower, he said. They are boring into garbage no more than 6 months old, instead of into deeper layers.

Wilson made the presentation during one of the semi-annual community meetings required under the landfill’s state Department of Environmental Quality air quality permit, held Tuesday night. The landfill is committed to capturing methane because it has been identified as a leading contributor to global warming.

Unfortunately, he said, the gas captured by the new wells will be burned off, because the gas turbines the landfill uses to generate electricity are already maxed out.

The burning process produces carbon dioxide, a greenhouse gas that also contributes to climate change, according to DEQ air quality specialist Gary Andes. However, he said, it is much less potent than the methane emanating from the decomposition process.

Under terms of its permit, the landfill is allowed to release 303,000 tons of carbon dioxide a year.

In past years, Andes said, landfills were one of the planet’s largest emitters of methane. Regulation, however, has dramatically decreased that, he said.

The DEQ requires the landfill to capture at least 75 percent of the gas it generates. But Andes said there is no real way to know how much that is.

The DEQ uses a model generated by the federal Environmental Protection Agency, but there are so many variables that it isn’t considered very accurate.

To meet the requirement, the landfill relies on sensors measuring the amount of methane escaping into the air directly above the garbage. If it measures less than 500,000 parts per million, the landfill is assumed to be successfully meeting its 75 percent collection requirement.

In fact, both Andes and members of the landfill staff told interested citizens attending the meeting, the sensors are detecting far less than 500,000 parts per million.

In addition to installing the new collection wells, the landfill has been working with Florida State University to test how well different types of covers prevent odorous gases from being emitted, with a particular emphasis on hydrogen sulfide, known for its rotten egg smell.

The partners tested a 50-50 mixture of peat moss and compost, and found that it cut hydrogen sulfide emission by 85 percent. However, the landfill staff said a soil cover of 18 inches works almost as well, as it breaks down the gas into its sulfur and hydrogen components and captures the sulfur.