Bye trash, hello gas: The Puente Hills Landfill is still active

Even though the landfill is closed, the facility continues to generate power.

Even though the landfill is closed, the facility continues to generate power.

By Karla Robinson

Driving along the CA 60 just 20 miles east of downtown Los Angeles, a large grassy hill full of trees comes into view. Most drivers wouldn’t look twice. But what seems to be a pleasant park is actually the collection of roughly 120 million tons of municipal solid waste that has piled up to the height of a 50-story building. This is the Puente Hills landfill.

Once the largest landfill in the United States, Puente Hills closed October 31, 2013 after 56 years in operation. The mass of refuse has since been covered with dirt and vegetation. Walking around the property you might never guess it was a landfill.

“You notice what we call our trash companies: They’re waste ‘management,’” Edward Humes, a Pulitzer Prize-winning journalist and author of Garbology: Our Dirty Love Affair with Trash, told NPR. “They’re managing our waste; they’re not reducing our waste, they’re not disappearing our waste. And what that means is they’re really good at picking it up and getting it out of sight [and] making garbage mountains out of it.”

Post-closure, Puente Hills remains an active gas-to-energy (GTE) facility where methane captured from decomposition of waste is converted to energy. The site produces 50 megawatts (MW) of electricity daily – enough to power 70,000 homes – and will continue to do so for the next 20 to 30 years, according to Basil Hewitt, senior engineer at the Los Angeles County Sanitation Districts (LACSD).

“We use about 30 megawatts of that electricity – or a little less than 30 – to power our offices, one of our wastewater treatment plants, and then the rest we sell,” Hewitt said in a phone interview. He explained that microorganisms break down the refuse, releasing methane and carbon dioxide, which is then trapped and transported to the energy plant.

“Historically you flared [methane] gas because you don’t want it escaping to the atmosphere or migrating to other people’s property…our first goal is to make sure we’re protecting public health and the environment. And while doing that, we generate electricity.”

Gas-to-energy plants are not an efficient power source, however. According to a 2009 EPA study, waste-to-energy (WTE) plants that simply burn garbage produce nine times the energy of GTE facilities for the same mass of waste. WTE plants also produce fewer pollutants than landfills, and they emit about half the amount of greenhouse gases.

“Moreover, if all [municipal solid waste] (excluding the recycled and composted portion) is utilized for electricity generation, the WTE alternative could have a generation capacity of 14,000 MW, which could potentially replace ∼4.5% of the 313,000 MW of current coal-fired generation capacity,” the EPA report found.

Despite the EPA’s support of waste-to-energy plants, the technology retains a strong negative connotation among Americans. More than half of the garbage in the United States goes to landfills; only 13 percent of waste is incinerated with energy recovery, according to the New York Times.

Now that Puente Hills is closed, Los Angeles County relies on other landfills, which may expire in a matter of years. Hewitt says the LACSD has established another facility, called the Mesquite Regional landfill, 210 miles east of Puente Hills, and is preparing to ship L.A.’s garbage out on trains. The transportation costs would be steep, but with WTE alternatives still undesirable to many, landfills will continue to be built up, covered up and driven by while few people actually take notice.

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