How Do Landfills Work?

How Do Landfills Work?

Humans have been dealing with trash for thousands of years, and modern-day landfills are essential for managing waste responsibly. We all know our trash goes to landfills, but what exactly is a landfill and how do they work?

What Exactly Are Landfills?

Simply put, a landfill is a site for disposing of trash. Today, modern landfills are highly engineered and well-managed facilities that handle the solid waste we as humans generate. They are intentionally located, designed, monitored, and operated to comply with regulations from the EPA. Their design and daily operations help protect the environment from the hazardous byproducts of decomposing garbage.

Before we begin, here are some landfill definitions to know:

Leachate: A liquid that forms from waste decomposition and contains harmful contaminants.

Cell: A section of a landfill designated for waste disposal, separated from adjacent cells by a liner system.

Groundwater: Water located beneath the earth's surface that can become contaminated by pollutants.

Anaerobic decomposition: The breakdown of organic matter in landfills by microorganisms without oxygen, producing landfill gas.

Greenhouse gases: Gases that trap heat in the Earth's atmosphere, including those produced by landfill decomposition.

Flaring: Burning of landfill gas emissions to convert methane into less harmful carbon dioxide and water vapor.

EPA: The Environmental Protection Agency, a federal agency in the United States that sets waste management standards and regulates landfills.

Difference Between A Landfill and A Dump

When people think of landfills, they often mix them up with dumps. Unlike outdated dumps, landfills are highly regulated by the government and have a liner at the bottom to catch liquid produced by the decomposing trash. This helps to protect the groundwater and reduces environmental impact. 

How Landfills Used to Work

The oldest known landfill was discovered in Crete, and it dates back to about 3,000 BCE. In the United States before the mid-1900s, communities used dumps for all of their waste. These locations were usually placed on the outskirts of towns and in rural areas.

Before the modern landfill liner system, the soil surrounding dumps was often contaminated with toxins and hazardous liquids. This caused issues with the surrounding water supplies and caused harm to the health of nearby communities.

The History of Landfill Regulations

The Second Industrial Revolution was followed by an increase in consumerism and dumps no longer could contain the trash generated by the economy. In 1965, Congress passed the first legislation to address growing concerns about waste management. The Solid Waste Disposal Act gave authority to the Environmental Protection Agency (EPA) to set standards and regulate waste disposal.

In the 1970s, Congress took further action to regulate waste disposal and set higher standards to protect the environment. The passage of the Resource Conservation and Recovery Act (RCRA) in 1976 defined how landfills were to be built, operated, monitored, and closed.

How Modern Landfills Are Made

Landfills aren’t all made the same way, but they use the same basic landfill design principles for environmental protection. The parts of a landfill are generally the same including:

1. A bottom liner to protect surrounding soil and groundwater from leachate leaks located at the bottom of the landfill.

2. Landfill cells, which are individual sections of a landfill where trash is deposited. Landfills usually only have one cell open at a time.

3. A leachate collection system designed to capture and contain any liquid generated from the waste in the landfill. 

4. A stormwater drainage system to control and manage stormwater runoff from the landfill. These systems are separate from the layering system and keep water out of the landfill.

3. A groundwater monitoring system to collect groundwater data like water contamination levels and leachate presence in the water.

4. A landfill gas collection system to collect gas generated from the decomposition of waste. Since landfill gases contribute about 14% of the total global methane emissions, the gas collection system plays a critical role in protecting the environment.

5. A landfill capping system to protect the environment from any potential contamination. Materials such as soil or asphalt are used to cover the landfill. 

Other factors like the placement of the landfill and its capacity are based on an environmental risk assessment study, as recommended by UNEP in 2002.

 What are the 4 layers of a landfill?

The structure of a landfill is a 4-layer system designed to keep waste byproducts from entering the environment. They make use of these layers to keep leachate, gases, and other toxins from polluting the surrounding climate. 

Generally, the four layers of a landfill are: 

Layer 1: Protective Liners

The first layer of a landfill is a protective liner composed of a thick layer of clay, followed by a layer of 60-mil plastic. It is meant to keep out water and prevent leachate.

Layer 2: Drainage 

The drainage layer sits on top of the protective liners and collects leachate, which is then transported to a treatment facility before being returned to the environment.  A layer of sand is placed on top of the drainage system to protect it.

Layer 3: Gas Collection 

The gas collection layer is a collection of pipes placed throughout the landfill to collect gases emitted during anaerobic decomposition. The gas collection system directs gases to a single location, where they are collected for energy or flared. 

Layer 4: Trash 

Trash is deposited in cells, and compacted using heavy equipment. Higher compaction rates make better use of landfill space. Each day, the cell is covered with dirt to prevent odors and deter wildlife.

Strict federal regulations require landfill designs to meet criteria to protect human health and the environment. The parts of a modern landfill work together to preserve groundwater quality and prevent air pollution. Landfill monitoring systems such as groundwater monitoring systems and LFG monitoring systems are essential to the landfill's health. 

What happens to garbage in a landfill? 

Most people don’t think much about trash after it gets picked up by the garbage truck. However, solid waste management is a complex science that involves heavily regulated daily operations. The daily operation of modern-day landfills is complex and involves many processes to protect the environment and public health. 

Tipping

The dumping process is known as tipping. Each day, garbage trucks come from all over the region to one central location, hauling trash collected from dumpsters and residential trash bins. The waste is then tipped into the open cell of the landfill, called the working face. Waste management companies pay landfill tipping fees to dump their waste.

Compacting

Once the trash is tipped into the working cells of landfills, it is compacted or crushed to save space. 

Daily Cover

A layer of soil known as the daily cover is used to cover the garbage in order to prevent odors, scavenging, and the spread of disease. Daily covering is required by the EPA standards outlined in the RCRA.

Daily Landfill Monitoring

Landfills are closely monitored and daily housekeeping tasks are performed by landfill operators to ensure that dumping facilities are performing in accordance with federal regulations.

Landfill Classifications

States categorize landfills into classes or types. These categories are not designated by the EPA, and they can vary in meaning from state to state. For example, Class 1 landfills in California are designated for accepting oil field waste, while Class 1 landfills in Tennessee are for household waste.

Even though classification varies at the state level, all states are regulated by the EPA under the umbrella of the RCRA. Here is the most common categorization of non-hazardous waste landfills:

Class 1- Household Waste

Class 2- Industrial and Commercial Waste

Class 3- Organic Waste

Class 4- Construction and Demolition Waste

Hazardous waste landfills are not included in this classification. However, they are strictly regulated under the RCRA.

Different Types of Landfills

Under the RCRA, all waste is categorized as either municipal solid waste, industrial waste, or hazardous waste. 

Municipal Solid Waste Landfills

Solid household waste is disposed of in Municipal Solid Waste Landfills (MSWLFs) that are governed by local and state municipalities. These are designed to handle non-hazardous household waste. 

Bioreactor landfills

A subcategory of MSWLFs designed for handling organic waste that degrades quickly. About 20% of all waste that goes into landfills is organic, including all plant or animal-based materials. Unless organic waste ends up in a bioreactor landfill, it doesn’t decompose properly.

Industrial Waste Landfills

American industries produce billions of tons of waste each year, but it’s hard to track and measure. Some industrial waste is recycled, and it’s even sold as a commodity to other countries, like China. Industrial food waste is often composted or made into biodiesel fuels. 

There are two types of Industrial Waste Landfills with exclusive designations:

Construction and Demolition (C&D) Debris Landfills- designed to accept waste from all types of construction and demolition projects

Coal Combustion Residual (CCR) Landfills- designed to dispose of coal ash

Hazardous Waste Landfills

Waste that is toxic to humans and the environment is considered hazardous, and it requires special handling. Hazardous waste can be liquids, solids, or contained gases, and must be disposed of carefully.

Do Landfills Ever Get Full?

Landfills have a capacity for how much trash they can take in. Once a landfill gets full, there is a capping process that prevents air and water pollution from occurring. A final layer of heavy plastic is used to cover the landfill and prevent water from seeping into it. Soil is then placed on top of the cover, and vegetation is planted to stabilize the ground and prevent runoff. 

Once a landfill is closed, it may be repurposed into building sites or used as solar and wind farms. In some cases, cities are built on top of capped landfills, like parts of Manhattan, New York.

What is Landfill Mining?

Landfill mining is becoming more popular as a way to free up landfill space and improve waste management sustainability practices. Landfill mining involves excavating old or closed landfills in order to recover and recycle materials, such as metals, plastics, glass, and soil, while also removing hazardous material. 

US Landfill and Garbage Statistics

The average American produces 4.6 pounds of waste each day, for a total of about 290 million tons of garbage each year in the U.S. The lifespan of a landfill is about 30 to 50 years, and waste management experts predict that landfill space could be used up by 2050. 

Many states are quickly running out of landfill space. New York City, which pays $1 million per day to other states to handle its waste, ran out of landfill space years ago.

It makes sense that we are running out of landfill space given the rate we produce trash and the size of the average landfill, which is 600 acres. The biggest landfill in the United States is the Apex Regional Landfill, located near Las Vegas, Nevada. With a capacity of over 1 billion tons of waste, it has twice the capacity of the next largest landfill, located in Utah. Even with large landfills like these, the United States faces serious waste management problems.

Can Landfills Be Sustainable?

There are a lot of problems with landfills, and their sustainability is questionable. It takes about 450 to 600 years for a landfill to decompose, during which time it continues to produce toxins, gases, and leachate. Plastic comprises almost 20% of municipal solid waste and never decomposes. Even though it has only been produced abundantly since the 1950s, plastics are quickly filling up landfills.

Another sustainability issue is landfill gases, which are the third largest contributor to greenhouse gases in the United States. Gases like methane, carbon dioxide, and hydrogen sulfide, also known as sewer gas, contribute to climate change and have an impact on public health. 

Landfill Alternatives

As space for our trash runs out, alternatives to landfills become more critical. When city governments focus on alternatives like prevention, recycling, and recovery, they can reduce solid waste disposal.

Waste incineration is an option for some municipalities and many states operate waste-to-energy plants. However, waste incineration delivers toxins into the air and requires strict regulations.

Organic landfills are not required by EPA regulations, but they are becoming more popular as communities look for eco-forward solutions like composting. Green landfills provide a place for people to take organic waste and save valuable space in MSWLFs, which prevent food and organic waste from decomposing because of the layering system.

Additionally, many communities are focusing on zero waste management practices that change the way resources are used. By allowing for more recycling and recovery of materials through practices like composting and using biodegradable packaging, municipalities can reduce the need for landfills.