Landfill Pumps for Gas Well Dewatering

AutoPumps keep the power on for thousands of Florida homes

Waste Management's Springhill Regional Landfill near Campbellton, Florida generates "green" energy by extracting and burning the methane in landfill gas. Its $7 million landfill gas energy (LFGE) plant, with six large Caterpillar engines running 24 hours a day, 7 days a week, is capable of producing 4.8 million watts of power.

Most of the energy goes to the Alabama Electric Cooperative for distribution to customers, enough to supply the electrical energy needs of 4,000 homes. In May of 2006, the plant was receiving only enough gas to run two of the six engines. Consulting engineers determined that many of the landfill gas extraction wells were "watered in." High levels of liquid, primarily condensed water vapor, flooded most of the wells' available surface area, reducing gas extraction efficiency drastically.

The excess liquid had to be pumped down; it was not a job for ordinary electric submersible pumps. Temperatures in the wells exceed 140 degrees Fahrenheit, and the condensate is highly corrosive because of dissolved sulphur dioxide, another waste decomposition by-product. In essence, the pumps must survive operating in hot sulfuric acid. With their rugged, high-clearance design and unique range of corrosion-resistant materials, air-powered AutoPumps from QED Environmental Systems deliver the durable, reliable performance demanded by challenging applications like this one. In August, six AutoPump® AP4 units were ordered, followed by another six in October. By November, the landfill's gas supply was back to nominal levels and all six engines were running at capacity, generating the full 4.8 megawatts.

AutoPumps were developed specifically for difficult pumping applications at landfills and petroleum and solvent spill remediation sites and are in use in these applications worldwide. These pumps provide a unique combination of safety, simplicity, and long service life under conditions that challenge other submersible pumps, such as elevated temperatures, high solids levels, high viscosity fluids and corrosive fluids.

Nationwide, approximately 400 of the 2,300 existing landfills are extracting methane for green energy, either burning it to produce electricity or piping the gas to industrial consumers who use it to heat and power their facilities. Another 600 or so are reasonable candidates for energy projects; the rest are too small or too old to produce enough methane for the process to be economically viable. According to the EPA website (2003 and 2005 figures), benefits of the operating LFGE efforts include:

• About 9 billion kilowatt-hours of electricity produced by 2/3 of the projects
• 5 billion cubic feet of gas for direct use in boilers, engines, greenhouses etc.
• Equivalent energy for electricity for 725,000 homes or heat for 1.2 million homes
• Reduced greenhouse gas emission equivalent to 13 million cars
• Saved 140 million barrels of oil or 295,000 rail cars of coal
• Prevented release of 75 million pounds of sulphur dioxide, 18 million pounds of nitrogen oxides, and 300 pounds of mercury into the atmosphere.

Installing landfill gas energy plants at the remaining landfill candidates would more than double these contributions to the public good. To bring it closer to home, the average American produces about 4.5 pounds of trash per day. This amount of trash in an LFGE process would produce enough energy to run a stereo for half an hour or light a 60-watt bulb for 15 minutes.