ARUN RATH, HOST:
If you're just joining us, this is ALL THINGS CONSIDERED from NPR West. I'm Arun Rath.
Right now, east of downtown Los Angeles, the closing of America's largest landfill is nearly complete. The Puente Hills Landfill took in trash from all over L.A. County. It became the go-to repository for most of L.A.'s garbage. And for more than 50 years, the landfill grew to over 500 feet high. That got reporter Liyna Anwar wondering, after a half-century-old landfill closes, what happens to all that trash?
LIYNA ANWAR, BYLINE: The trash will stay here. All those years and years' worth of garbage will be covered up and remain underneath the ground.
BILL GROSS: Right now, this is the top deck of Puente Hills Landfill. It has been closed to receive the refuse since the first of November now. And we are putting the final cap on it. We're putting five feet of cover soil over the entire thing to basically seal in the refuse.
ANWAR: That's Bill Gross, one of the supervising engineers of the now closed facility. Closed landfills are often treated this way, covered up and turned eventually into something else once it's deemed inactive. The National Tennis Center in Queens is built on a landfill. Even Wall Street sits on top of an old landfill.
Puente Hills was never meant to be open forever. In fact, in 2002, L.A. County issued the landfill its last permit. So the Sanitation District knew back then that the end of 2013 meant the end of the landfill. Officials had to figure out where new trash would go and what to ultimately do with Puente Hills. Now, the site will one day transition into a park where its true identity will just be a memory.
Edward Humes is an expert on trash and author of the book "Garbology." He says constantly covering up our trash means we never fully understand how much garbage we generate.
EDWARD HUMES: You notice what we call our trash companies, they're waste management. That is the term of (unintelligible). And think about that. They're managing our waste, they're not reducing our waste, they're not disappearing our waste. They're managing it. And what that means is they're really good at picking it up and getting it out of sight, making garbage mountains out of it.
ANWAR: The average American makes seven pounds of trash per day. That's about 50 percent more than what we made back in the '60s. And we're running out of space. In fact, we make so much garbage that trash is our largest export by volume. And who buys it from us?
SAM PEDROZA: The countries that build the most things. So that's China.
ANWAR: That's Sam Pedroza, environmental planner at Puente Hills.
PEDROZA: And it makes sense, you know, they come in with these huge ships to the port filled with goods. And rather than going back empty, they go back filled with recyclables.
ANWAR: When China became a manufacturing powerhouse, they turned to America's trash as raw material to build cardboard and packaging. Maybe even the same box your laptop came in. Sounds like smart globalization, but China gets the better deal here: They pay very little for items that cost us a lot. And the environmental impact of long-distance shipping isn't great. So what other options do we have to deal with our trash?
The folks at Puente Hills decided that if they couldn't significantly decrease the trash, at least tap into an important resource - the methane gas that emits from the decomposing trash. That gas goes to an onsite building called the Puente Hills Energy Recovery Facility.
PEDROZA: This is where we're taking the landfill gas, and we're using it as a heat source for the creation of steam. The steam then is used to turn a turbine, and then from there we produce 50 megawatts of electricity.
ANWAR: That's enough to power about 70,000 homes in Southern California. The facility even became a model for other landfills across the country. But Edward Humes has his reservations.
HUMES: The problem is, is that's still a lousy way to make energy, because you are ending up spending hundreds of times more energy to produce the fuel - the trash - than you're getting back from it.
ANWAR: But the quest to convert trash to energy is constant. Tim Portz is the executive editor of BioMass magazine, a trade journal that looks into new energy sources. He says national legislation gives incentives to companies who can make liquid fuel from renewable sources. That's why more and more companies are looking for ways to do that directly from waste.
TIM PORTZ: Plasma gasification is using intense heat to essentially explode the molecules that make up a potato chip wrapper into carbon monoxide and hydrogen into its very basic molecular components.
ANWAR: And those atoms get transformed into synthetic gas, which can then be used for fuel. But Portz says the technology is expensive and still being developed. And even with new technologies, many experts say it will be tough to get to zero landfills. Back at Puente Hills Landfill, with the mountain of garbage now enclosed, it's hard not to think of the compacted layers of history. The site includes burned-down storefronts from the riots after the Rodney King verdict and building rubble from major earthquakes. It makes Puente Hills engineer Bill Gross reflective.
GROSS: It's just, I don't know, to me, just a little bit of a letdown. I guess I'm still getting used to it. It just really felt different closing this place.
ANWAR: But perhaps there's no need to be too nostalgic. The future of trash may be looking quite familiar. The Sanitation District already has plans underway for a new and even larger landfill in a remote area of the desert. Liyna Anwar, NPR News.