About half of all municipal solid waste in the United States ends up in a landfill. In 2018, that amounted to more than 146 million tons of trash buried in engineered disposal sites across the country. But the journey from your curbside bin to its final resting place involves several stops, and what happens to waste once it’s buried is more complex than most people realize.
From Curb to Transfer Station
After a collection truck picks up your trash, it typically doesn’t head straight to a landfill. Most waste first travels to a transfer station, a large facility where trucks from neighborhood routes unload their contents. At the transfer station, waste is organized, sorted, and compacted before being loaded onto larger, long-haul vehicles that carry it to the landfill itself. This step exists because landfills are often located far from populated areas. Consolidating waste into fewer, bigger shipments cuts down on fuel costs and truck traffic.
Some recyclable or hazardous materials get pulled out at this stage. Items like lead-acid batteries, medical waste, bulk liquids from businesses, and low-level radioactive materials are legally prohibited from entering standard municipal landfills. These get diverted to specialized facilities. Household hazardous waste like solvents and pesticides isn’t technically banned, but many municipalities collect it separately because it’s poorly suited for landfill disposal.
What a Modern Landfill Looks Like Inside
A modern landfill is not just a hole in the ground. It’s a heavily engineered structure designed to isolate waste from the surrounding environment, particularly groundwater. At the bottom sits a composite liner system. Federal regulations under the Resource Conservation and Recovery Act require municipal landfills to use these liners along with leachate collection systems to protect groundwater.
The liner typically includes a thick plastic sheet called a geomembrane, which is impervious to liquid, layered with processed bentonite clay (an extremely absorbent material formed from volcanic ash). These layers sit between protective fabric sheets that resist puncture damage. Together, they form a barrier that prevents contaminated liquid from seeping into the soil below.
Waste gets deposited in sections called “cells.” Each day’s load is spread, compacted by heavy machinery, and covered with a layer of soil or other material to reduce odors, discourage pests, and limit rainwater from soaking in. Over months and years, these cells stack up until the landfill reaches its permitted height.
What Happens to the Liquid
When rain percolates through buried waste, it picks up dissolved chemicals, heavy metals, and organic compounds, creating a toxic soup called leachate. Left unchecked, leachate can seep into groundwater and contaminate drinking water sources, aquatic ecosystems, and surrounding soil.
To prevent this, landfills use drainage systems built into the liner to collect leachate before it can escape. Pipes channel the liquid to holding tanks, where it undergoes treatment. The process varies by facility but generally combines physical filtration, chemical neutralization, and biological treatment to break down or remove harmful components. Some advanced facilities use membrane filtration and reverse osmosis to clean the liquid thoroughly enough for safe discharge or even reuse within the facility.
Gas Collection and Energy Recovery
As organic material in the landfill breaks down, it produces landfill gas: roughly 50 percent methane and 50 percent carbon dioxide, with small amounts of other organic compounds. Methane is a potent greenhouse gas, but it’s also the primary component of natural gas, which makes it a usable fuel.
Landfills extract this gas through networks of vertical wells and horizontal trenches buried throughout the waste mass. A vacuum system pulls the gas through piping to a processing facility on site. At a minimum, the gas passes through moisture removal and filtration before being flared (burned off) to prevent it from entering the atmosphere as raw methane.
Many landfills go further. About 17 percent of operational landfill gas projects use the gas directly as fuel for boilers, kilns, or industrial dryers. Others feed it into engines or turbines to generate electricity for the local grid. The most advanced treatment upgrades landfill gas into renewable natural gas by stripping out the carbon dioxide and impurities, producing fuel clean enough to inject into commercial gas pipelines or compress for use in vehicles.
How Fast Waste Breaks Down
One of the most surprising things about landfills is how slowly waste decomposes. Modern landfills are sometimes called “dry tombs” because the liner systems and daily soil covers limit the moisture and oxygen that microorganisms need to break things down. A banana peel that would compost in a month in your backyard can persist far longer in a sealed landfill cell.
Plastic bottles take an estimated 450 years to fully decompose. Aluminum cans last 80 to 200 years. Even food scraps like orange peels, which break down in about six months under normal conditions, decompose much more slowly when sealed away from air and water. Researchers have excavated landfills and found readable newspapers and recognizable food items decades after burial. The rate depends heavily on local conditions, but the general principle holds: landfills preserve waste far more than they transform it.
When a Landfill Reaches Capacity
Once a landfill is full, it doesn’t just get abandoned. Closure involves installing a cap system over the entire site, essentially a mirror image of the bottom liner. A typical cap includes, from top to bottom: six to twelve inches of topsoil for vegetation, a layer of compacted earthen material, protective fabric, a plastic membrane, a clay layer, and another layer of protective fabric. This cap keeps rainwater from infiltrating the waste and prevents gas from escaping uncontrolled.
After sealing, the site enters a mandatory post-closure monitoring period that lasts at least 30 years. During this time, operators must maintain the integrity of the cap (repairing erosion, settling, or subsidence), continue operating the leachate collection system, and monitor groundwater through a network of testing wells. If groundwater monitoring detects contamination at the end of the 30-year period, the monitoring obligation extends until the problem is resolved.
Closed landfills are sometimes repurposed as parks, golf courses, or solar farms, but the land can never be used for buildings or agriculture. The waste remains underground, slowly producing diminishing amounts of gas and leachate for decades.
How the U.S. Compares Globally
The United States landfills 50 percent of its municipal solid waste, down from 94 percent in 1960. Another 32 percent gets recycled or composted, and about 12 percent is burned in waste-to-energy facilities. That trajectory shows real progress, but the country still relies on landfills more heavily than many peer nations.
High-income countries as a group landfill about 39 percent of their waste, diverting 36 percent to recycling and composting and 22 percent to incineration. Countries with limited land, like Japan and several in Northern Europe, lean heavily on incineration with energy recovery. Upper-middle-income countries actually landfill the most, at 54 percent, often because they’ve built collection infrastructure but haven’t yet invested in alternatives. Americans generate about 4.9 pounds of trash per person per day, and while recycling rates climbed from 6 percent in 1960 to around 35 percent by 2017, that figure actually dipped slightly to 32 percent in 2018.