Closing the Waste Management Loop: Creating Fuel From Landfill Gas

Video credit:Waste Management

Each day each person throws out about 4.7 pounds of garbage that is often taken to a landfill to be processed where it eventually decomposes. But what many people don't know is that the waste process doesn't necessarily end there. When organic waste decomposes through natural means, it emits gases that can be collected and used to generate renewable energy and fuels. In fact, the fuels created can even power the same waste collection and recycling trucks that picked up the trash in the first place. At Waste Management's Altamont Landfill near Livermore, California, landfill gases are being collected and processed to create clean, renewable fuels to "close the loop" on waste collection.

This week, Waste Management (WM) announced that its joint venture company with Linde North America, part of The Linde Group, a leading global gases and engineering company, has begun producing fuel from landfill gas at the facility. Currently, Altamont is the world's largest landfill gas (LFG) to liquefied natural gas (LNG) plant, in which Linde purifies and liquefies the landfill gas collected by Waste Management.

Here's how the process works. The landfill gas that is collected is fed into a gas purification system. This multi-step process includes compression, chilling, adsorption and membranes to remove impurities - such as sulfur, carbon dioxide, nitrogen and alcohols - from the gas stream. The purified stream is then fed into a natural gas liquefier where the gas stream is cooled to below the natural gas boiling point of -260 F to produce LNG.

Liquefaction occurs in an aluminum heat exchanger - refrigerants flow through one side while natural gas flows through the other side. The refrigerants are used to cool the natural gas into a liquid state. The resulting LNG is stored in a tank, which acts like a giant thermos to keep the LNG at liquid temperatures until a truck picks it up to transport it to an LNG filling station. At the filling station, WM's waste collection and recycling vehicles have full access to this clean fuel.

When the Altamont facility is operating at full capacity, it is expected to process about 3 million cubic feet of landfill gas per day, which is equal to producing up to 13,000 gallons a day, or over 4 million gallons per year of LNG. This is enough to fuel 300 of Waste Management's 485 LNG waste and recycling collection vehicles in twenty California communities. Since September 2009, when the commissioning process began, the plant has produced 200,000 gallons of LNG. You can learn more about how this joint venture came to be by watching this video.

Depending on logistical and operational considerations, several Waste Management landfills across North America could be candidates for LFG-to-LNG technology, offering another alternative energy option to improve air quality and environmental sustainability.

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