How Landfills Work
Humans generate a lot of waste. From getting take-out to buying something new – trash is an inevitable byproduct of modern civilization. But have you ever wondered about what happens to trash once it leaves your home?
Most of the time, trash ends up in the landfill. But what are landfills exactly? A feat of engineering, landfills are designed to take in all of the waste that we generate in a way that minimizes environmental impact. Your trash, as well as waste from businesses, hospitals, and restaurants, journeys to the landfill where it is then compacted and buried.
While landfills are supposed to minimize the damage caused by waste, they’re problematic in their own right. For example, landfills release considerable amounts of greenhouse gasses as well as a chemical soup called leachate. But even so, landfills are essential. In this article, we’ll take a closer look at how landfills work and why we need them.
Photo by Sam LaRussa
What is a landfill?
While you might imagine a landfill as a giant pile of trash, that couldn’t be further from the truth. Broadly speaking, a landfill is an engineered facility designed to hold waste. Here’s the EPA’s slightly more technical definition:
“Modern landfills are well-engineered and managed facilities for the disposal of solid waste. Landfills are located, designed, operated and monitored to ensure compliance with federal regulations. They are also designed to protect the environment from contaminants, which may be present in the waste stream.”
Landfills are literally an embodiment of the huge amounts of waste that we humans produce on a daily basis. Despite increased rates of recycling and composting, the majority of trash (otherwise known as municipal solid waste, or MSW) still ends up in the landfill. The EPA’s latest data (2018) is telling. Here are just a few key statistics:
The average person in the US generates 4.9 pounds of trash per day
50% of MSW is landfilled
21.6% of MSW, or 63.1 million tons, is food waste
12.1% of MSW, or 35.4 million tons, is yard trimmings
The total MSW composted in 2018 was only 25 million tons
The 3 main types of landfills
Can you imagine what the world would look like if we didn’t have landfills? Piles of trash would line the streets, rivers would experience massive blockages, and there would be a lot more burning of waste.
In fact, you don’t have to go far to see examples of this; even with landfills, litter is a common sight in the environment. Even the most remote places in the world – including unpopulated islands and fresh arctic snow – are impacted by our trash.
Landfilling is the most common method for waste management, because it’s often the cheapest and most convenient option. For example, building and maintaining recycling and composting facilities is an expensive undertaking. However, in order to minimize environmental impact, landfills have to be carefully designed and engineered.
In the US, there are currently three main types of landfills:
Municipal Solid Waste Landfills
Municipal Solid Waste Landfills, or MSWLFs, are the main type of landfill in the US, and the one where most of your trash ends up. This type of landfill is designed to collect and manage all household waste and other nonhazardous waste.
MSWLFs are divided into many “cells,” with just one or two open at a time. These get filled with waste, which gets crushed, compacted, and covered with soil on a daily basis. Once a cell is full, incoming trash gets redirected to a new cell. When the entire landfill has reached capacity, it’s closed up. Sometimes, closed landfills are repurposed or reclaimed, for example into parks or soccer fields.
As mandated by the EPA, closed landfills are monitored for 30 years to control and prevent the leakage of contaminants.
A subtype of MSWLFs are bioreactor landfills, which process and transform organic waste.
Industrial Waste Landfills
Industrial waste landfills collect commercial and institutional waste such as construction debris. While also being strictly regulated, industrial landfills come with fewer environmental concerns than MSWLFs.
There are two types of Industrial Waste Landfills: Construction and Demolition (C&D) Debris Landfills and Coal Combustion Residual (CCR) Landfills. C&D Debris Landfills collect construction, renovation, and demolition debris such as rock, concrete, wood, and glass. CCR landfills manage coal ash and other coal combustion residuals.
Sometimes, C&D Debris includes materials that are actually considered “clean fill.” Clean fill includes broken rock, asphalt, soil, etc. that is uncontaminated by chemicals or other types of waste. Processed clean fill can be repurposed in construction to support foundations or fill areas where more soil is needed, thereby reducing the pressure on local landfills.
Hazardous Waste Landfills
A portion of the waste we produce as a society is considered hazardous to human health and the environment. As a result, it’s considered hazardous waste and treated separately from all other kinds of waste. Hazardous waste includes materials such as:
Paints and stains
Solvents
Fuels
Aerosols
Pesticides, herbicides, and fertilizers
Rechargeable batteries
Fluorescent bulbs
Medical waste
Hazardous Waste Landfills are designed to be able to hold these kinds of materials without leakage. Some hazardous waste is incinerated or treated to change its chemical composition.
Where are landfills typically located?
One of the biggest challenges faced by landfilling is the lack of available space. Landfills require a lot of land in order to operate, and as our society continues to grow and expand, swaths of land are not easy to come by. Plus, pressure on landfills continues to increase as we produce more and more trash, and there are concerns that landfill space in the US could run out within a matter of decades unless we are able to recycle and compost significantly more.
Additionally, local residents often fight against proposed landfill sites, citing concerns over wildlife, water pollution, environmental degradation, and more. While many of these concerns are extremely valid, our society isn’t in a place where it can do without landfills. The truth is, we all benefit from the convenience of landfills, but we don’t want to be reminded of it on a daily basis.
Even without public pushback, however, finding a place to put a landfill is not an easy task. Landfills have to be built on geologically safe ground, i.e. away from faults, wetlands, and floodplains. Moreover, landfills can’t be built in protected or environmentally-sensitive areas, making it even more difficult to find an appropriate location.
Still, due to transportation and logistical challenges, landfills can’t just be built in the middle of nowhere. Most of the time, landfills are located on the outskirts of towns or cities, and depending on the size they might service a whole county, or more. For a list of landfills in each state, check out this resource.
What goes in landfills?
All waste that doesn’t get reused, recycled, or composted has to be managed somehow. While some of our trash gets incinerated, most of it ends up in the landfill. For most of us, this means our household waste, including things such as:
Plastic bags
Tubs, jugs, bottles, etc.
Food waste
Paper and cardboard
Old furniture, mattresses, and appliances
Unfortunately, a lot of what ends up in landfills could have been reused, donated, recycled, or composted. While landfills serve an important purpose, we have limited space for building new ones. Plus, they can pose serious health and environmental risks, especially if they are poorly managed.
The biggest thing that we can do as consumers is to reduce the amount of waste we produce, increase recycling, and start composting.
Why is food waste bad in landfills?
While rates of composting are increasing, a lot of biodegradable materials still end up being landfilled, including food waste and yard trimmings. Not only do these materials take up valuable space, but they also release greenhouse gasses as they break down.
Because landfills need to maximize space and soil stability, everything gets crushed and compacted on a daily basis. This means that there’s no room for air, resulting in an anaerobic environment where biodegradable materials are broken down anaerobically rather than aerobically.
In a composting system, air pockets supply oxygen to aerobic bacteria that break down food scraps and other biodegradable materials, turning it into black gold. While both aerobic and anaerobic decomposition are key processes, anaerobic decomposition releases methane, a greenhouse gas 28 times more potent than carbon dioxide.
In fact, it’s estimated that roughly 6-8% of our global emissions come from food waste. Diverting food waste from landfills, therefore, is key to reducing greenhouse gas emissions and extending the life of landfills.
What is leachate?
No matter how well-designed a landfill is, there’s usually some amount of leachate. Simply put, leachate is any liquid (usually rainwater) that has percolated through landfill waste and collected chemicals and suspended solids along the way. The resulting “chemical soup” poses serious pollution risks, particularly to groundwater, so landfills are required to have leachate collection systems in place.
Despite leachate collection efforts, leachate is a serious source of groundwater and environmental pollution. While there are some treatment options, the best course of action is to reduce the amount of landfill waste and safely dispose of hazardous wastes in the first place.
How familiar are you with landfills? Let us know if you have any other questions below!
