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Landfills Become Engines of Electricity

Dumps are becoming exemplary citizens

Our sport-utility vehicle slowly climbs a substantial mound, one of several hills on 248 acres dotting the North Texas flatlands at the City of Denton Landfill off South Mayhill Road. Heat-hardy sunflowers are the primary vegetation. There’s nothing else to see except an occasional pipe or conduit sticking out of the ground.

The pipes are methane gas wellheads. Considered a greenhouse gas, methane accumulates as organic matter disintegrates in the mounds of garbage now covered by compacted earth. Methane can be a pollutant like car exhaust, and it can even cause explosions in the quantities generated by a dump. Although it’s bad news when released into the environment, methane can be tapped and converted into electricity.

After cresting a mound, we wend our way down to a 1-acre clearing with several outbuildings. Our attention is on a piece of equipment somewhat bigger than a house trailer that emits a muffled woosh of clean exhaust. Vance Kemler, the City of Denton’s solid waste department general manager, says if we were to open the door, the sound of the electricity generation from even this tiny unit would be deafening. The juice is transmitted to an on-site Denton Municipal Electric substation, which supplies power for some 1,000 to 1,200 homes a year.

The Environmental Protection Agency (EPA) promotes the four “Rs”— reduce, reuse, recycle and rebuy. In this case, a dangerous pollutant—methane —is converted into a product that utilities purchase. 

Approximately half the gas generated by a landfill is methane, and most of the rest is carbon dioxide. Methane has 20 times the global warming potential of carbon dioxide and approximately half the energy potential of natural gas, according to the EPA.

Kemler said Denton speeds the production of methane by recirculating storm water and leachate, which is produced when water trickles, or filters, down through packed waste to the bottom. The liquid is collected and pumped back to the upper levels of the waste, and the process is repeated. Many advanced landfills do this.

Texas Comptroller Susan Combs reported in June 2009 that Texas had 24 landfill gas energy projects and at least 57 more sites suitable for such projects.

Whether cities, counties or for-profit services run them, large regional landfills are the future of the business, even in co-op country.

Texas Disposal Systems (TDS) in southeast Travis County, for example, takes solid waste from nine counties partially served by cooperatives. The contracts may be with cities—Austin is one of them—counties or private entities. The company may offer home pickup or simply gather garbage at rural transfer stations.

TDS is planning to provide electricity from methane to Pedernales Electric Cooperative, but it won’t generate as much power as many landfills because the waste is already recycled so efficiently at the site.

Bob Gregory, CEO of TDS, says the reduce, reuse, recycle and rebuy philosophy works well for his company. Counties, for example, pay TDS to pick up trash, and his workers repair and resell what is salvageable at the Travis County site. Gregory said under his business concept, customers pay to send what they don’t want to the dump, where everything usable has a recycled life. So he is paid when the junk comes in and again when it is converted to something useful.

The companies with the largest number of regional landfills in Texas, Republic Services/Allied Waste and Waste Management, serve 13 North Texas counties, most of which include cooperatives. Houston-based Waste Management has several methane gas-to-energy plants in Texas.

Coal, natural gas and nuclear power will continue to provide major amounts of power. Wind and solar will do their part. But in addition, thousands of different initiatives, such as harnessing methane, will supply a little energy here and a little energy there. And eventually it will all add up.

Kaye Northcott is the retired editor of Texas Co-op Power.