As I was trying to cram a greasy pizza box down my apartment building’s garbage chute yesterday, I couldn’t help but wonder: How much room can we possibly have for garbage in this country? When will the United States run out of landfill space?

Not for centuries. There are plenty of reasons to cut down on waste, but the amount of space left in the ground isn’t a pressing concern. Won’t you join the Lantern on a brief tour of American trash?

From the 1920s until the mid-1970s, most of our household garbage ended up in dumps—nothing more than manmade craters scattered across the country. They were, in many ways, an environmental disaster. All the liquids in the decomposing trash filtered down to the bottom of the hole and, from there, into the soil and groundwater. This gloop, known as “leachate“, could have contained any number of hazardous chemicals, especially in an era when few people thought much about what they tossed. The rotting garbage also released significant amounts of methane, a greenhouse gas 20 times more potent than carbon dioxide, straight into the atmosphere.

When Congress passed the Resource Conservation and Recovery Act in 1976, it fundamentally changed the way we store trash. The law and its subsequent amendments require disposal facilities to line their gigantic trash holes with layers of either plastic or clay, or both. These liners, and a subterranean piping system, collect the leachate, which is then hauled to sewage treatment plants. Landfill operators must also install pipes to vent the methane gas, which is burned off—reducing the superpotent greenhouse gas to mere carbon dioxide. (Some facilities take advantage of the heat created in the process, using it to power turbines or turn the methane directly into liquid natural gas.)

Though the 1976 law was a huge win for the soil and groundwater, there are drawbacks. Technologically advanced landfills—the word dump now applies only to old-school holes in the ground—are more expensive to design and operate. To make up for these costs, landfill operators began to emphasize economies of scale. Rather than having lots of tiny dumps scattered everywhere, we now have a small number of mega-landfills. In 1986, there were 7,683 dumps in the United States. By 2009, there were just 1,908 landfills (PDF) nationwide—a 75 percent decline in disposal facilities in less than 25 years.

Which brings us to the problem with the new system: Trash now has to travel farther from your kitchen to its final resting place, and longer trips mean more greenhouse gas emissions. Thirty years ago, a bag of garbage dropped down a chute in Manhattan would have traveled just a few miles by barge to the aptly named Fresh Kills facility on Staten Island. (Until 1931, the city dumped most of its trash in the Atlantic Ocean.) Today, it would likely make an overland journey to Ohio, Pennsylvania, or West Virginia. One ton of garbage traveling 500 miles by train from New York to the Mountain State would generate 115 pounds of carbon dioxide. If New York City shipped all of its trash to West Virginia the commute would produce 760,000 tons of CO2 each year.

How does that compare with throwing it in a dump and letting it vent methane into the atmosphere? It’s hard to say. The train trips to West Virginia generate about 40 percent more carbon-dioxide equivalents than the methane the garbage would have released in its first year at an old-school, in-state dump. In the following years, however, the garbage would continue to release methane—though less of it—complicating the calculation.

Analysts from the Environmental Protection Agency and the landfill industry assure us that, despite having fewer landfills, total capacity has increased. That is, landfills are getting bigger, on average, faster than their brethren have disappeared.

Of course, not all states are equally endowed. And a landfill deficit in any region means that the nation’s trash will, overall, have to travel farther. The industry publication BioCycle conducts a biennial assessment of America’s trash capacity called “The State of Garbage in America.” The variation between states is startling. Arkansas reported enough capacity to go more than 600 years without opening another facility. Massachusetts and Rhode Island, on the other hand, have just 12 years of capacity remaining. New York state, despite shipping most of the Big Apple’s trash across state lines, has only 25 years of capacity left.

In landfill-strapped states, the problem is more political than geological or geographical. Landfill operators can build a new site from nearly any piece of land (apart from sensitive ecological areas) in six to eight years. But many voters and bureaucrats in the Northeast, for example, would rather ship their trash across state lines than have a landfill near their homes.

Like prisoners, trash shipments can be big business for states willing to accept them. Kentucky, for example, has room for 212 million tons of waste. At the going rate of $29 per ton, that’s a $6 billion economic opportunity. Ohio has $21 billion of available landfill space. Because of political opposition to local landfills, most Northeastern states’ trash will probably be riding the rails for a long time to come.

The Lantern thanks Nora Goldstein and Dan Sullivan of BioCycle, Scott Kaufman of Columbia University, and Chaz Miller of the National Solid Wastes Management Association.

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