WorldWide Drilling Resource

31 WorldWide Drilling Resource ® FEBRUARY 2016 Trash to Treasure Compiled by Amy White, Associate Editor WorldWide Drilling Resource ® Every person in the U.S. produces an average 4.5 pounds of waste each day. Most of it is managed in municipal solid waste (MSW) landfills across the country. When MSW is initially deposited in a landfill, it mixes with oxygen in the first de- composition stage, generating a relatively small amount of methane. Within a year’s time, an oxygen-free environment is normally established and bacteria starts to decompose the waste, generating more methane. Landfills often burn off produced methane in a flare system, but some use the gas to create energy. By drilling a well into the trash dump to extract methane, land- fills have an option to sell it as fuel, or landfill gas (LFG). LFG collection typically begins after a portion of the landfill (known as a “cell”) is closed to additional waste. The sensitive extraction process requires drilling wells into landfill cells for methane removal and transport. The most common method of LFG collection involves drilling vertical wells. A drill rig creates boreholes - at least 24 inches in diameter in most instances - in a landfill to remove trash and make way for a well screen and casing to be installed. Older trash is located at the bottom of the landfill; thus, increased depth equates to increased methane concentrations. It is not uncommon for boreholes in landfills to be drilled greater than 100 feet deep. Crews must monitor the depth closely to make sure the landfill’s lower liner or bottom seal is not punctured. The installed well includes a slotted or perforated well screen with a cap on the bottom and solid casing to the surface. Total depth of the well and length of the well screen are determined by the location of the methane accumulation. Organic content of the MSW is a significant consideration. Waste composed of high organic content will generate more LFG than waste with lower organic con- tent. For example, construction and demolition landfills are not expected to create large amounts of LFG, and are usually not viable for an energy generation system. The U.S. Environmental Protection Agency (EPA) has identified close to 2400 active or closed MSW landfills in a national database. Approximately 595 of these have one or more LFG projects in operation, resulting in a total of 645 active sites. Over the last 20 years, more than 1800 megawatts of electricity have been gener- ated by LFG in the U.S. EPA suggests as many as 440 additional landfills could convert methane to an energy resource in a cost-effective manner to power nearly 512,000 homes across the country. An estimated 75% of currently operational LFG projects in the United States use methane to generate electricity. Power for on-site use or sale to the grid can be produced with a range of technologies, including internal combustion engines, turbines, microturbines, and fuel cells. Most projects use internal combustion engines or turbines, with microturbine technology being used at smaller landfills and in niche applications. An estimated one third of LFG projects directly use landfill gas in boilers, dryers, and kilns, among other uses. Industries such as auto manufacturing, wastewater treatment, consumer electronics and products, paper and steel production, prisons, and hospitals use energy from landfill gas. Companies currently utilizing this energy include BMW, SC Johnson, Tropicana, Ford, Dupont, Honeywell, Sunoco, General Motors, Fujifilm, Stouffers, Anheuser Busch, Frito-Lay, and many more. One million tons of MSW can produce 432,000 cubic feet per day of LFG, and continues producing LFG up to 20 or 30 years. Currently, Houston-based Waste Management and Arizona-based waste disposal firm Republic Services own the majority of the nation’s LFG facilities. An EPA proposal to govern emissions at existing landfills will be released in August 2016. This chart from the EPA shows the number of operational LFG projects in the U.S., as well as candidate landfills by state.