How do landfills work? A look at what happens to your trash
Ever wonder what happens to the stuff you toss in the trash? Discover how landfills work and learn about the risks they pose to human health and the environment.
Americans produce about five pounds of waste per person per day. Although we make up only 4% of the global population, we generate 12% of the world’s trash. More than a quarter of this waste is packaging that is used just briefly before we throw it away.
All this stuff has to go somewhere. Some is recycled or composted, but about 146 million tons of material ends up in landfills each year. Today, the United States has about 3,000 active landfills and 10,000 closed sites.
In the current waste management landscape, landfills play a necessary role. But they also threaten human health, wildlife, and the environment. That’s why it’s important that we work together to reduce our reliance on landfills. Here’s how landfills work — and how we can make them our last resort.
What is a landfill?
Let’s start by talking about what a landfill is not. A landfill is not a dump. These terms are sometimes used interchangeably, but there is a significant difference between the two. Dumps are openings in the ground to bury trash. Often built in low-lying areas or wetlands, they have little oversight, planning, or regulation. A federal law ended the practice of open dumping in the United States in 1983. In developing countries, however, open dumping continues to be a common practice for managing waste.
Landfills, on the other hand, are engineered facilities for disposing of solid waste. They must adhere to certain regulations about where they are located and how they are designed, operated, and monitored. That’s not to say they are safe — the pollution emitted by landfills is a major contributor to climate change, and people who live near landfills may face negative health impacts. (More on that soon.)
There are several different types of landfills, including industrial landfills, construction and demolition landfills, bioreactor landfills, and hazardous waste landfills. Most landfills, and the ones we focus on, are municipal solid waste landfills. These facilities receive the waste that your garbage collection company picks up from your home. These landfills may also receive solid waste generated by businesses and industry. There are nearly 2,000 municipal solid waste landfills in the United States, all managed by the states where they are located.
What happens to trash in a landfill?
Let’s say you eat an apple, then throw the core in the trash. The next day, a garbage truck takes your trash to a landfill. What will your apple look like a year from now? Or many years from now? It may surprise you that organic materials may look much the same, even after a long time buried in a landfill.
Landfills are designed to store trash — not break it down. There is little oxygen or moisture inside a landfill, so items like your apple decompose very slowly, or hardly at all. That’s why decades-old newspapers have been found in old landfills, the newsprint still easily readable. The city of Calgary, in Canada, has pictures on its websites showing grass clippings from the 1970s that were placed in a landfill — they look practically the same.
What happens to plastics in a landfill?
Most of the plastic we use ends up in landfills. There, it can take up to 1,000 years to degrade, potentially leaching toxic substances into the environment. More attention is being paid to the danger and ubiquity of microplastics.
The environmental and health risks of landfills
The amount of waste generated by Americans has increased by 231% since 1960. Although some is recycled or composted, most of it ends up in landfills, releasing pollution that poses serious risks to climate change and human health.
Air pollution
When waste first enters a landfill, it decomposes through an aerobic process, involving oxygen. But typically within a year, the decomposition process becomes anaerobic, due to the absence of oxygen. That’s when the waste starts to release a gas that is part carbon dioxide and part methane, a potent contributor to climate change. Landfills are the third-largest source of human-caused methane emissions, according to the EPA, emitting methane in amounts equivalent to the greenhouse gas emissions of more than 24 million cars driven for one year.
But it gets worse. The Environmental Defense Fund says satellite measurements suggest actual landfill emissions could exceed 6 million metric tons, a significantly higher amount — and far more dangerous.
Landfills also emit other gases, like sulfur dioxide and nitrogen dioxide, as well as unpleasant odors. For the two million Americans who live within one mile of a landfill, air pollutants from the landfill can cause respiratory problems like asthma, disproportionately impacting our society’s most vulnerable, who live near landfills at higher rates than the population at large.
Water and soil contamination
Although landfills are designed to stay as dry as possible, some water does enter the facility. As it drips through the trash and soil, this water picks up contaminants, including the biological waste products of decomposition. The fluid produced by a landfill is called leachate. Typically, it is acidic. If leachate escapes the landfill and enters the surrounding groundwater, it can have negative consequences for soil quality, aquatic life, and human health.
Human health risks
People who live close to landfills have experienced serious health issues, including lung cancer, asthma, and birth defects. Children are especially at risk. An infamous case is the Love Canal landfill, the final destination for a large amount of toxic materials in New York during the 1930s and 1940s. By the mid-1970s, researchers discovered that chemicals had leaked into nearby streams and sewers, with tragic outcomes for many people who lived there.
How a landfill is designed
Landfills must adhere to regulations set by the federal government and by the state where they are located. They must be set apart from features like geological faults, wetlands, and floodplains.
Landfills include these parts:
A liner system: A liner system helps prevent waste from exiting the landfill. The liner system starts with a protective layer comprising two feet of sand. Underneath is a leachate collection system that removes the rainwater that enters the landfill and the liquids produced by slowly decomposing waste. This is followed by a composite layer of two feet of clay with a plastic liner, another drainage layer, and finally a second composite layer made of compacted clay and a plastic liner.
Cells: These are distinct sections in the landfill where waste is placed before it is compacted or crushed. Once a cell is filled, it is covered by multiple layers, including a clay barrier and soil layer. Waste is then placed in a new cell.
Stormwater drainage: This system collects rainwater that falls on the closed and temporarily covered parts of the landfill to minimize how much water comes into contact with garbage.
Leachate collection: This system collects the contaminated liquids that are released by decomposing waste. The leachate is then removed and treated.
Gas collection: A series of pipes collects landfill gas. The gas is either vented to the atmosphere or burnt through a flare to produce energy.
Cap: Once a landfill is completely full, a final cover is placed to seal the site and prevent water and pests from reaching the garbage. The cap includes a clay and plastic layer, two feet of soil, and six inches or more of topsoil where grass or other vegetation can be planted.
Landfills also include multiple systems to monitor the landfill’s impact on groundwater and the air.
Waste-to-energy facilities
The United States has about 75 waste-to-energy facilities for handling municipal solid waste. At these facilities, garbage is burned in a combustion chamber. The heat that is released converts water to steam, which is then sent to a turbine generator to produce electricity.
A typical day at a landfill
Your trash gets picked up and taken away in a garbage truck. Now what happens?
Depending on their size, garbage trucks may carry 12 to 14 tons of waste from more than 800 homes. Once the truck is full, it heads to the landfill, joining potentially a couple hundred other trucks also making drop-offs.
At the landfill, the truck is directed to a designated area to dump its load into a cell. Most landfills have just one cell open at a time. After waste is added to the cell, the garbage is compacted or crushed to save space. The compactor vehicle can compact about 1,400 pounds of garbage into one cubic yard of space.
Each day, the active cell is covered with a layer of soil or other type of material to minimize odor and ward off pests, this is called the “daily cover.” And the next day, more trucks come, adding more and more trash until eventually the cell is full. It’s covered in multiple layers, then closed, and the trucks move on to the next cell.
What happens when a landfill is full?
The average life expectancy of a municipal solid waste landfill is about 30 to 50 years. Once it’s full, the landfill is closed with a final cover and a top layer of soil. No more trash will be added — but the work of monitoring the landfill continues for decades. Landfill operators pump out leachate, inspect the covering, and test groundwater, checking that the landfill is not leaking toxic chemicals.
In some cases, there is life after landfill. In the late 1960s and 1970s, city officials in Virginia transformed a 640-ton mound of trash into America’s first landfill park. This green space, called Mount Trashmore, is now a popular destination for Virginia Beach residents and tourists, who fly kites off the park’s hills, run up and down its steep stairs, and take their children to its playgrounds.
Banned from the landfill
Landfills store quite a lot of materials, but not everything. Most states ban certain items from the landfill, either because they have the potential to cause environmental damage or endanger human health, or in some cases due to their value as a recyclable material.
Examples of items banned from landfills include car batteries, motor oil, hazardous chemicals, mercury-containing products like CFL bulbs, used tires, yard waste, computers and other electronics, rechargeable batteries, large appliances and aluminum cans.
Communities often have local guidelines with alternate ways to get rid of these items.
Reducing our reliance on landfills
At the moment, landfills are a necessary part of our waste management system. But it’s clear that we need to dramatically reduce how much we rely on them. Only then can we limit the dangerous pollution they emit and protect the environment and human health.
The EPA’s Waste Management Hierarchy provides a helpful model to follow. An inverted pyramid, it recommends an approach to managing waste that focuses primarily on reducing, reusing, recycling, and composting, with the overall goal of reducing greenhouse gas emissions.
Unfortunately, the amount of waste created continues to grow — and it’s a global problem. The United Nations predicts that annual solid waste generation will grow to 3.8 billion tons by 2050, up from 2.1 billion tons in 2023.
Our waste problem is daunting, but we see reasons to be hopeful.
More communities, like Chicago, are launching food scrap collection programs, making it easier for their residents to dispose of food waste by composting. This is critical, because more food ends up in landfills than any other material.
Communities are also adopting increasingly ambitious zero waste goals. For example, in 2020, the city of Gainesville banned single-use plastic straws and stirrers in restaurants and retailers. It was a small step, but now they’ve taken several others. The Florida city has banned foam containers and made single-use plastic food accessories permissible by request only. Recycling is mandatory in multi-family residential properties and restaurants must take steps to divert excess food from landfills. Just a few years after starting with straws and stirrers, Gainesville has set a big goal: achieving zero waste by 2040.
And what about packaging, those easy-come, easy-go materials that have exploded in use? Some places are beginning to address this growing challenge with extended producer responsibility policies that put the responsibility for managing the recycling of packaging on the manufacturers, producers, or brands. As more places adopt an EPR system, we can improve our circular economy and recycle more of the material that ends up in landfills today.
So what can you do to limit how much you rely on landfills? Reduce how much you buy. Reuse items. Donate things you no longer need. Recycle what you can. Start composting. The less you put in your trash can, the more you’ll help us break away from our overreliance on landfills.
