Landfills 101: Everything You Need to Know

Quick Key Facts

• There are 2,600 landfills for municipal solid waste (MSW) in the U.S.
• The average person generates 4.9 pounds of MSW each day, and by 2050 global waste generation is expected to increase by 73% from 2020 levels. 
• Modern sanitary landfills are not merely open repositories for waste, but have many complex components, including a composite liner, collection systems for methane and leachate, and environmental monitoring systems. 
• In the absence of light, oxygen and the necessary bacteria, it can take decades for food to break down completely in a landfill, producing methane as it slowly decomposes.
• Landfills are the third largest source of methane — a greenhouse gas that’s 25% more potent than CO2 — emissions in the U.S. 
• In 2018, 600 million tons of construction and demolition debris were generated, which is more than twice the amount of MSW.
• The documented adverse health outcomes correlated with living near landfills include higher risk of cancer and birth defects in infants.
• A 1983 study conducted by Congress’s Government Accountability Office found that in eight southeastern states, 75% of hazardous waste landfill sites were located in communities that were primarily Black, Latine and low-income.

What Is a Landfill? 

Most of us barely have to think about our trash. We throw it in a bin, take the bag to the curb, then the garbage truck comes and takes it away. Pretty quickly, our waste becomes invisible to us, but it has to end up somewhere. 

Waste comes from many different streams — households, industrial settings, workplaces, medical facilities, etc. — and our current system for trash and garbage disposal primarily entails burying it underground. In the U.S., waste generated by homes and businesses is most commonly sent to landfills: huge repositories in the earth to be filled with trash and covered over. The first modern sanitary landfill was created in California in 1937, but the practice became more widely adapted in the 1960s and 70s as waste production rose, and municipalities sought ways to limit unsanitary waste disposal. In 1976, the Resource Conservation and Recovery Act was passed and created requirements for landfills to protect surrounding environments. Now, there are more than 2,600 landfills for municipal solid waste (MSW) in the U.S., a waste category that encompasses things like wood, paper, textiles, furniture, glass, plastic, some electronics and more. 

Why Do We Have Landfills? 

We generate huge amounts of waste and we’re only creating more. Single-use plastics and highly wasteful industries like fast fashion have become ubiquitous in practically every area of our lives. Trash generation has more than tripled since the 1960s, resulting in a current average of 4.9 pounds of MSW generated per person per day. With 11.2 billion tons of MSW produced every year, we need somewhere to put it, and landfills provide that solution. 

Our increased waste is also tied to population growth and urbanization. The more the population grows, the greater our demand for manufactured products and materials, and the more we depend on landfills. According to the World Bank, global waste generation is expected to increase by 73% from 2020 levels by 2050. 

The U.S. in particular generates a great deal of waste. Despite making up only 4% of the global population, the U.S. is responsible for 12% of the planet’s trash. It has historically exported its waste to other countries to handle, but in recent years, China, Malaysia, Thailand and Vietnam have put bans in place on imported waste, further increasing the need for domestic repositories for trash, such as landfills. 

While some waste can get recovered or recycled — and some of it is burned — the majority is sent to landfills. In 2018, 69 million tons of MWS was recycled and 25 million tons was composted, which amounts to about 32.1% of all MWS. About 3 million tons was combusted, leaving 146 million tons — half of the total — to be sent to landfills. In the absence of large-scale municipal recycling and composting programs, waste is thrown away when it could have been diverted to other streams. Our recycling system, however, isn’t perfect either — ultimately, only 9% of plastics gets recycled. With bans on our junk being imported to other countries to deal with — leaving about 19,000 shipping containers worth of plastic recycling with nowhere to go every month — much of this waste is being sent to domestic landfills instead.

Are There Different Types of Landfills? 

^{U.S. Environmental Protection Agency}

Different types of landfills exist for different types of waste, as categorized by the EPA. All are supposed to meet nationwide criteria established under the Resource Conservation and Recovery Act (RCRA), which sets forth requirements for landfills in the absence of state programs including location restrictions, requirements for liners and toxin collection/removal systems, and required operating practices.

Solid Waste Landfills 

Municipal Solid Waste Landfills (MSWLFs) are primarily for the waste that’s generated in our homes, schools, hospitals and businesses, as well as some nonhazardous materials from industry and construction. There are about 2,600 MSWLFs in the U.S., managed by the individual states they reside in. MSW is usually brought to transfer stations in municipalities, then transported on large, long-distance trucks to MSWLs. 

Bioreactor landfills also fall under this category, and are used for degrading organic waste quickly. In these landfills, liquids are added to help bacteria break the waste down using either aerobic or anaerobic techniques. 

^{The Yolo County Landfill Bioreactor in California was built to accelerate the decomposition of waste and produce renewable energy in 5 to 10 years. Yolo County}

Industrial Waste Landfills are used for commercial and institutional waste. For example, Construction and Demolition Debris Landfills are repositories for heavy and bulky materials like wood, concrete, drywall, salvaged components of buildings like plumbing and windows, metal and glass generated during construction and demolition of roads, bridges and buildings. This accounts for a large amount of waste in the U.S. — in 2018, 600 million tons of C&D debris were generated, which is more than twice the amount of MSW. Demolition itself accounts for 90% of all C&D waste. 

Coal Combustion Residual Landfills fall under the Industrial Waste category too, housing the nearly 130 million tons of coal ash generated every year from the burning of coal in power plants. After a large coal ash spill in Tennessee in 2008 flooded 300 acres of land and got into two rivers, the EPA established that these materials must be disposed of in such landfills. 

Hazardous Waste Landfills

Hazardous Waste landfills are exactly what they sound like: repositories for only hazardous waste that is flammable, toxic or chemically reactive, including things like household cleaners, chemical waste, paint and aerosols. These types of landfills are the most regulated by the EPA, and are monitored even after their closure for toxic leachate.

Open Dump Landfills 

When we talk about landfills, we’re typically referring to “sanitary landfills” — that is, municipal landfills that are regulated and controlled. However, open dump landfills are common in many areas of the Global South, and are used by about 70% of countries for disposing MSW. Without municipal waste disposal programs, these dumps are where trash often ends up. 

Because these landfills typically aren’t regulated or controlled, they’re more likely to cause fires, attract pests and pollute the surrounding area. The toxic gases they produce are also not contained, so methane is released into the nearby environment. Water contamination is a primary problem around open dump landfills. Without groundwater monitoring systems in place, toxins make their way into groundwater and nearby drinking water, which has the potential to transmit infection and disease.

Basic Components and Operations of a Landfill 

Open dumping is illegal in the U.S., and landfills must follow certain design and operation guidelines as established under the Resource Conservation and Recovery Act (RCRA), although they’re created and managed state-by-state. 

The major components of sanitary landfills include the following:

• Leachate collection system. Leachate is the liquid that percolates through the landfill, picking up toxins as it moves. Once it reaches the bottom of the landfill, it’s collected by perforated tubes and pumped out into a collection area, and then a holding pond where it’s treated to remove the harmful toxins. 
• Plastic liner system (or “composite liner”). The liner — created from a layer of compacted clay and specific types of plastic — is meant to keep the landfill completely sealed so groundwater and soil aren’t contaminated by leachate.

• Cells are the areas where trash is dumped and compacted, allowing landfills to be filled in a segmented manner. Every day, waste is tipped into the active cell, which gets mechanically compacted. Layers of soil are laid down to cover the trash at intervals, and help to prevent odor. When the cell becomes full, another one is started.
• Stormwater drainage systems collect the rainwater that lands on the landfill, move it to drainage ditches, and then to collection ponds. 
• Methane collection systems are needed to collect the methane — a potent greenhouse gas — that forms during the decomposition of organic waste. Landfills are among the largest sources of methane in the U.S., and collection systems prevent it from being released into the air. Wells, pipes and pumps collect the methane, where it’s then piped to a facility that processes it and removes impurities. From there, the refined methane can be distributed for such uses as vehicle fuel and electricity. About 500 MSW landfills collect methane for energy in this way.

The Pioneer Crossing Landfill in Berks County, Pennsylvania uses methane gas, a byproduct of the decomposition of waste, to produce electricity for the local utility company. J.P. Mascaro & Sons

• Environmental monitoring systems monitor the groundwater, storm water, and gas around landfills. Pipes go down into the groundwater to find whether they’ve become warmer or more acidic, which could mean that leachate is escaping and getting into the landfill’s surrounding environment.
• The Cap seals the top of the landfill. Usually, a layer of compacted soil or clay is put down, then layers of fabric and plastic before a 2-foot layer of soil (sometimes followed by more inches of topsoil) is put down so vegetation can grow on top of it.

How Does Waste Act Inside a Landfill?

Waste acts much differently inside a landfill than it would in your trash can, or when merely left out in the open. Different types of waste also act differently, posing unique problems depending on their makeup. 

Organic Waste 

What’s so bad about putting food in a landfill? It’ll just break down eventually, right? Not exactly.

Food is the largest category of landfilled material, according to the EPA, accounting for about 24%. The dark, anaerobic — that is, oxygen-free — environment of a landfill means that the insects and microorganisms needed to properly break down these materials aren’t present. Decomposition thus happens much, much slower, and releases a lot of methane as a byproduct. In a landfill, it can take decades for food to break down completely. By some estimates, a head of lettuce won’t completely decompose for 25 years. In other cases, food may not decompose at all. 

Plastics

In landfills, most polymers and plastics remain “unchanged,” according to a 2022 study. Abundant evidence shows that plastic never really degrades, but rather breaks down into smaller and smaller pieces, eventually creating microplastics. The forces and environmental conditions of landfills — like gas, the pH of leachate, high salinity, temperature fluctuation, high pressure, etc. — can cause plastics to fragment into microplastics that can then be transported out of landfills in leachate and pollute nearby areas. Microplastic abundance in landfill refuse is between 20,000 and 91,000 items/kg — higher than the concentration in sewage sludge and agricultural soil. Therefore, when you throw a piece of plastic in a bag of landfill-bound trash, that doesn’t guarantee it’ll remain sealed off from the environment forever. 

Energy Recovery in Landfills 

Sometimes after a landfill is capped, the gases that form within it over time are vented out for energy recovery efforts. These gases can be used to generate electricity or as medium-Btu fuel, and have uses for vehicle fuel, pipeline gas, industrial and institutional buildings, and creating electricity for the grid. They’re recovered using a series of wells and vacuum systems that direct it to a collection area, after which it’s processed and can then be used. About 68% of all landfill gas (LFG) projects is for generating electricity, and 16% is used to offset another fuel, like fracked gas and coal. Another 16% is used to make renewable natural gas (RNG), a high-Btu gas that can be used instead of fossil natural gas. 

Why Are Landfills a Problem? 

On the surface, landfills seem like a logical solution to our waste — if we have nowhere else to put it, why not bury it? Landfills do, however, present serious and potentially life-threatening risks to nearby communities and the environment.

Location 

Federal and state regulations mandate where landfills can be built, placing restrictions on building near wetlands or flood zones without certain performance standards in place. In some states, they can’t be put near bodies of water at all. But many landfills are poorly managed, leaving them susceptible to environmental conditions and leading to pollution. Landfills are also associated with poorer quality of life when placed near residential communities, discussed further in the next section. 

Soil Pollution 

Like water moving through coffee grounds, rainwater moving through landfills becomes saturated with the toxins inside the trash, eventually reaching the bottom as leachate. Some of this liquid does get collected by the leachate collection system, but if there are any holes in the lining, it can easily escape into the surrounding environment. Nearby soil is destroyed by the toxic chemicals, impacting the ability of plants to grow there and threatening the biodiversity of the area. 

Air Pollution 

Air quality also suffers around landfills. Particulates, dust and other air pollutants can escape from landfills. Vinyl chloride, ethyl benzene and toluene, are just some of the hazardous air pollutants emitted from MSW landfills. Respiratory problems — among other adverse health conditions — have been linked to landfill-related air pollution. 

Water Pollution 

When landfill leakages occur and leachate gets into groundwater, it becomes contaminated with toxins in industry and household waste, as well as electronics, which contain mercury, cadmium and lead. Ammonia is often in leachate, and produces nitrate. High concentrations of nitrate in ecosystems causes eutrophication, a process by which a high nutrient concentration in water leads to an explosion of plant life and algal growth, creating “dead zones” devoid of oxygen. Besides ammonia, leachate can also transport bacteria and heavy metals into groundwater, potentially contaminating drinking water. 

Landfill Gas and Greenhouse Gases 

Landfill gas (LFG), formed from the breakdown of organic waste inside the landfill, is mostly methane and CO2 (90-98%), but also contains nitrogen, oxygen, ammonia, hydrogen, and sulfides, among others. Its makeup depends on the specific conditions and age of the landfill, as well as temperature and water content, but some landfills can produce gas for up to 50 years. 

Methane is a primary cause for concern in LFG, formed from the slow decomposition of organic matter in the airtight, anaerobic conditions of the landfill. Landfills are the third largest source of methane emissions in the U.S., and for a greenhouse gas that’s 25% more potent than CO2, this has major implications for global climate change. Methane is also highly flammable. In March 2022, a massive fire started at a landfill site outside of Delhi, India, releasing toxins into the air. The fire, unfortunately, came right on the heels of an analysis stating that New Delhi was already the most polluted capital in the world. 

Besides its climate-warming components, landfill gases can also get into structures near the landfill. They come up through the soil in a process called “soil vapor intrusion,” collecting in poorly-ventilated areas and polluting the indoor air of nearby buildings.  

Human Health 

These gases, pollutants and toxins impact the health of people who live near landfills. Open or poorly-managed landfills can lead to drinking water contamination, thereby transmitting diseases and causing infection. Documented adverse health outcomes include higher risk of cancer and birth defects in infants. Trichloroethylene (TCE) is just one carcinogen associated with leachate, entering the soil and groundwater near landfills. Ammonia and hydrogen sulfide are also harmful to humans and can cause coughing, difficulty breathing, and trigger asthma, headaches, nausea, and irritation in the eyes, nose and throat. For those who live near waste lagoons of landfills, adverse health outcomes are an especially serious problem. 

Why Are Landfills an Environmental Justice Issue?

It has long been the case that landfills are constructed more often near communities of color and low-income neighborhoods. A 1983 study conducted by Congress’s Government Accountability Office found that in eight southeastern states, 75% of hazardous waste landfill sites were located in communities that were primarily Black, Latine and low-income. This puts marginalized communities at greater health risk. The proximity of landfills to housing also keeps property values low, which can make it hard for residents to sell their property and escape the health hazards. 

What Can We Do? 

Minimize Waste

In the simplest terms, to reduce our dependence on landfills, we need to reduce our waste. Diverting our waste through recycling and composting can keep waste out of landfills, as can just using less stuff altogether. 

The recycling system in the U.S. is far from perfect. Due to a combination of many factors — including the un-recyclability of many materials, poor waste systems and lack of recycling systems in some areas — only about 9% of plastic actually gets recycled. However, when done properly, taking part in recycling programs keeps these materials out of landfills. Composting at home or through municipal programs is another important step, and is possible no matter where you live. An estimated 8-10% of yearly GHG emissions are associated with unconsumed food, and 30-40% of our national food supply is wasted every year. Composting keeps that organic waste from entering landfills in the first place, where it’ll decompose and produce methane. 

Because construction and demolition are huge sources of landfill waste, it’s also crucial that we reduce their waste materials by preserving existing buildings rather than constructing new ones, or by reusing and repurposing existing materials. 

Legislative Action

Many of these solutions might seem like they’re out of our hands. How are we as individual people supposed to create a better global recycling system? How are we supposed to redistribute construction materials so they aren’t wasted? We can stop using single-use plastics on our own, but how can we make that change on a larger scale? How can we as individuals create a more just and sustainable MSW system?

Voting isn’t a silver bullet for all of our problems, but it’s an important tool we have in bringing about change. Vote for local and federal legislators who have platforms based on environmental action and justice, including the implementation of sustainable integrated waste management on a larger scale. Better-managed and engineered facilities for waste that meet environmental requirements and aren’t placed in sensitive areas is an important step. New York City — where residential composting is now mandatory – is one success story, and shows how large-scale composting solutions can be implemented by people in power. There are models for other ways of handling our waste. In Sweden, for example, 0% of MSW ends up in landfills, due in part to good recycling infrastructure and biological treatment of waste.

Coming up with other uses for the land that landfills occupy has been another topic of conversation. Many landfills in the U.S. have been identified as promising locations for solar farms, and many have already been built, using that land to create clean, renewable energy. 

Takeaway

Landfills aren’t merely dumping grounds for our trash, but rather are complex, regulated structures with many components. Soil, air, and water pollution is just one set of issues associated with landfills, along with greenhouse gas emissions, injustices on nearby communities, and steep costs to human health. Creating a more just and sustainable system of waste management that minimizes our reliance on landfills — and makes the landfills we do have better-engineered, better-managed, and better-monitored – will be an effort that incorporates both personal action and large-scale legislation, and changes in how we view and handle waste in our culture.