About a dozen years ago, the town where I live was trying to figure out what was wrong with their five-year-old bus barn. The foundation was cracking, the roof deforming, and doors couldn't close. The building wasn't settling. Quite the opposite: it was RISING.
It turned out that the bus barn and servicing area had been built on top of an old landfill that was closed in the mid-1960s. When the bus barn and service center was built, the asphalt and concrete sealed the ground over the site. That meant that no methane gas, a natural by-product of anaerobic decomposition, could excape into the atmosphere. As gas generated, pressure built over time. Eventually, pressure lifted this 45-vehicle-capacity bus barn and about an acre of land several inches.
The bus barn was sitting on a huge potential bomb.
Engineers sank a number of wells to bleed off the gas. After a few months, the building settled back down. The town thought it would soon have an energy surplus. Unfortunately, the amount of piping required to successfully capture enough gas to make the scheme viable also required the town to demolish the bus barn. As such, only a fraction of natural gas could be recovered. So, the effort was abandoned. The gas vents into the atmosphere.
Originally, landfills were just very big holes in the ground that were filled with trash, buried and forgotten. During the 1970's, it was discovered that toxic metals and other compounds were migrating from the bottoms of landfills and contaminating groundwater. This finding helped lead to a re-structuring of how landfills are designed and utilitized. 
Landfills are now contstructed using dense rubber membrane-barriers and layers of clay to prevent liquids (leachate) from passing into the groundwater. Leachate is now collected at the bottom of landfills and pumped into treatment facilities. For decades, it was also known that landfill methane could migrate underground for several kilometers and cause fires far away from the dump site. Now, when a landfill closes, gas collection pipes are buried and the landiflll is capped with layers of clay (usually bentonite). Over time as the garbage decomposes, methane gas is released and captured by the collection system. The result is low-cost gas that can be conditioned for heat and generating electricity.
"Preparing a 1 million-ton landfill for energy production can entail initial capital costs of $600,000 to $750,000 or more and operating costs of $40,000 to $50,000 a year. Other costs include legal fees, permitting, environmental impact studies and other costs associated with maintaining the landfill."
According to an EPA landfill database, Texas has 24 landfill gas energy projects and at least 57 more sites suitable for such projects. Texas landfill and municipal waste projects produced just 230 million kilowatt-hours (kWh) in 2006. With 186 active landfills accepting waste and an estimated 50-plus sites with landfill gas potiential, Texas has an opportunity to convert much of its waste into an energy efficient and cost-saving fuel.
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