ROCKLAND, Maine — A long-planned system to burn off gas emitted from the city’s quarry landfill is working great, according to city officials.
The city turned on the flare Oct. 19 and it has been burning efficiently since that day, according to Solid Waste Director David St. Laurent.
“This not only burns off gases that are responsible for odors but it reduces greenhouse gas emissions and is good for the environment,” St. Laurent said.
He said while not all odors have or will disappear with the flare system that burns off the landfill gas, it has made a significant reduction. He said a neighbor even came over and commented about the difference.
Rockland has used former lime quarries for more than five decades to dispose of its wastes. For 24 years, household trash has been shipped to the Penobscot Energy Recovery Corporation in Orrington with only demolition debris being dumped in the quarry.
But the decades of prior use for household wastes, demolition debris, and sludge from the sewer plant has built up an environment underground that produces gases such as methane, hydrogen sulfide, carbon dioxide and nitrogen.
Dump odors have been the focus point of complaints on and off by residential neighbors for the past quarter century.
Beginning in the summer of 2010, the city installed a series of pipes throughout the quarry that would capture the gas. That piping is now covered with additional debris and soil covering. The visible part of the system is a tall pipe with a flare at the top. A roughly one square foot solar panel powers a battery that sparks the flare to keep the flame burning.
The hydrogen sulfide accounts for the smallest amount of gas being burned, but it is that gas that creates the odors, St. Laurent noted. More than half the gas is methane, which the solid waste director said traps 20 times more heat in the atmosphere than carbon dioxide.
The entire system cost about $40,000, he said.
The city is not using the gas to power anything because the current projections are that the amount of gas to come out of the quarry will peak between now and 2017 and then decline dramatically, St. Laurent explained. Investing in equipment to convert the gases for energy would not make sense financially because of the short-term returns, he said.
Another project to control odors involves the installation of a computer-automated system to inject hydrogen peroxide into water pumped from the quarry to the city’s wastewater treatment plant. The city is required by the Maine Department of Environmental Protection to keep water levels in the quarry low enough so that the water does not flow into adjacent groundwater.
St. Laurent said the city has cut in half its hydrogen peroxide use at the landfill. He said in addition to the cost saving, the automated system knows when to inject more chemical into the water to curb any odor from hydrogen sulfide.