⏳ Estimated Reading/Watching Time: 22 - 24 minutes

Describe solid waste disposal methods and their effects.

Types of Solid Waste

The composition of Municipal Solid Waste (MSW) in 2018, totaling 292.4 million tons: Paper and Paperboard at 23.1%, Food at 21.6%, Plastics at 12.2%, Yard Trimmings at 12.1%, and smaller portions for Wood, Metals, Glass, Textiles, Rubber and Leather, and Miscellaneous Organic Wastes. — *The composition of municipal solid waste (MSW) in the United States in 2018*.

Solid waste is any unwanted or discarded material that is not a liquid or a gas. The United States has 4.6% of the world’s population but produces 33% of the world’s solid waste.

Most solid waste in the United States comes from mining, oil and natural gas production and processing, agriculture, and manufacturing. Municipal Solid Waste (MSW) is what ordinary citizens generate every day as waste and pay their local governments or private companies to bring to landfills.

The pie chart to the right shows you the breakdown of municipal solid waste in 2018.

The types and percentages of waste vary from region to region. The chart above is specific to the United States so if you traveled to other countries, you would see differences in their solid waste stream.

Due to a variety of factors including increased awareness, changes in production methods, and recycling, the composition of the types of wastes that make up the solid waste stream continue to evolve and change.

Each year, we produce more waste than the last. This is because the human population is increasing and we are, in general, a “use it and toss it” society. Disposable materials are a huge contributor to this increase in MSW. We use paper plates, plastic cups, disposable diapers, plastic utensils, single use plastic bags, and on and on. This, along with excessive packaging produces the majority of our waste. Making conscious choices in our daily lives can significantly reduce waste. For example, choosing to not use a plastic bag in a store or choosing to not use a plastic straw when purchasing a fountain drink adds up over the course of your lifetime. In our home, we used cloth diapers when our children were small to reduce waste.

Regardless of the composition or the total amount of our waste, paper and paperboard, food waste, and plastics have dominated the waste stream in the United States for many years. As recycling has improved, the percentages of paper and plastics have declined.

The distribution of waste management methods with three sections “Landfills” at 57%, “Recycled,” at 28%, and “Incinerated” waste at 15%, highlighting the reliance on landfills. — *Regardless of its recyclability, most of our waste still goes to landfills*.

Of our MSW, paper, metals, glass, and some of the plastics can be recycled. Yard waste, majority of the food scraps, and wood can be composted. Even though, about 55-60% of our waste goes into landfills, 14-16% is incinerated, and only 28-30% is recycled.

A type of solid waste that has been increasing dramatically over the past several decades is electronic waste also known as “e-waste.” Electronic waste, or e-waste, is composed of discarded electronic devices including computers, tablets, televisions, cell phones, monitors, and computers. According to the EPA, much of the e-waste generated in the United States ends up being shipped to developing countries that have little, if any, restrictions on the import of this potentially harmful waste.

In fact, the EPA issued a statement on this problem:

“We have serious concerns about unsafe handling of used electronics and e-waste, in developing countries, that results in harm to human health and the environment.”

E-waste contains valuable metals that can be removed and sold. However, the removal of the metals includes methods such as burning and acid baths that can endanger the workers using these methods. The EPA encourages the reuse, refurbishment, or recycling of as much e-waste as possible to minimize the chances of this waste becoming deposited in landfills or shipped to developing countries.

Essential Knowledge

Solid waste is any discarded material that is not a liquid or gas. It is generated in domestic, industrial, business, and agricultural sectors.

Electronic waste, or e-waste, is composed of discarded electronic devices including televisions, cell phones, and computers.

Landfills

In general, landfills are places where municipal solid waste (MSW) is put on the ground and covered with earth. Each day, the trash is covered with at least 6 inches of dirt. When full, they are covered with dirt and ignored. Explore the tabs below to learn more about early landfills, problems, and how we've tried to overcome these problems.

Early Landfills
Problems
Modern Landfills

Early Landfills

An expansive landfill under a clear sky. In the foreground, a bulldozer is actively engaged in managing a large mound of mixed waste. — **Early landfills were just holes in the ground filled with trash.**

Early landfills were holes in the ground that had been created by mining or rock quarries. These excavated areas had no environmental considerations other than covering the waste with dirt as it built up.

Solid waste from homes, businesses, and industry contains leachate, liquid residues that can leak out from the bottom of the landfill. The waste also contains liquids that can volatize (VOCs) and evaporate into the atmosphere. Furthermore, the decomposition of waste produces biogas, which is mostly methane, a gas that has been linked to climate change.

As we realized that landfills were polluting air and water, the search began for better landfill designs that would protect both the environment and human health.

Problems

Below are a few of the problems with landfills. Open each problem to learn more about them. Which problem do you think is the worst? Which one can you most help solve?

💧Groundwater Contamination (click to reveal)

An outdoor scene where murky water is being pumped from a white pipe with a blue valve onto a black plastic surface. — ***Leachate can contaminate drinking water.***

Groundwater contamination is the most serious problem with landfills. Leachate is percolated water with chemicals in it.

You know when you take out the trash at your house and it has that yucky trash water in the bottom of the trash bag? That's kind of like leachate.

You don’t want that water seeping into your drinking water. Because of groundwater contamination from leachate, over 145 former landfills in Florida are considered Superfund sites. To fix this problem, we now put special liners on the ground with areas for leachate collection before any trash is added to the landfill.

💨 Methane Production (click to reveal)

An outdoor scene where a pipe is positioned on a large, sloped surface covered with a black protective material. A large bird is sitting on the pipe. The pipe positioned near monitoring equipment. — ***Landfills have pipes to allow methane to escape.***

Methane production is another serious problem with landfills. When trash is decomposed anaerobically (without oxygen), like in landfills, biogas is produced. This gas is 2/3 methane (CH₄) and 1/3 hydrogen gas (H₂) and carbon dioxide (CO₂). Biogas can seep into homes, rocks, and soil and can be also explosive. To remedy this problem, we now install gas wells in landfills that can produce energy from the seeping methane. Additionally, even after landfills are completed and no more waste is entering the landfill, the release of methane from the landfill is still monitored by landfill staff.

⏰ Decomposition Time (click to reveal)

Many things that we throw away take a very long time to decompose, even under ideal conditions.

Common items and their decomposition times: aluminum soda cans and banana peels, taking 2-4 weeks to decompose, foam cups and tin cans, with a decomposition time of 50 years, nylon fabric which take 50-80 years, and glass bottles and fishing lines, which can take up to 1000+ years to decompose. — ***Many things we use every day take a very long time to decompose.***

For example, cigarette butts take 10-12 years to decompose, aluminum cans take 200-500 years, and plastic bags take 200-1000 years to decompose. Plastics, especially, resist decomposition, which is why they make such excellent outdoor furniture or storage devices. Even paper, which usually decomposes fairly quickly under normal conditions, decomposes very slowly in a landfill.

Most substances require water to help decompose, but to avoid leachate generation, landfills tend to be quite dry. Recycling and reusing as much as possible is the best way to combat this problem.

As waste decomposes, it takes up less space and the landfill surface tends to settle. This can cause settling cracks and other problems with the land above and surrounding the landfill.

Modern Landfills

Modern landfills take all the problems from the previous tab into consideration, making them different from traditional landfills.

They are sited on...

✅ high ground

✅ geologically stable areas

❌ away from airports - there tend to be large numbers of birds that congregate around landfills, which could interrupt airplane takeoffs and landings

The floor of modern landfills are contoured so the leachate can drain into a leachate-collection system. They also have plastic liners and 2 feet of compacted soil over the liner before trash is deposited. These landfills are also constructed so that the MSW is built up in the shape of a pyramid, capped with at least 18 inches of dirt, topsoil, and seeded with grass seed. Methane monitoring stations and groundwater monitoring wells are standard technologies in place to ensure that pollutants do not leak out of the landfill.

Each day, the trash is covered with at least 6 inches of dirt. When full, they are covered with dirt and sealed. Monitoring continues even after the landfill is capped and sealed.

The interactive below gives you a better idea of the design of a typical modern landfill. Click "Read Now" to make it full screen. Click on each part of the landfill to watch a short clip about that part.

To combat settling, landfill workers monitor the surface of the landfill and use fill dirt to restore the level of the landfill, if necessary. This settling makes it problematic to use the land above the landfill for heavy buildings but there has been some success in using old landfills for parks or athletic fields.

Essential Knowledge

Solid waste is most often disposed of in landfills. Landfills can contaminate groundwater and release harmful gases.

A sanitary municipal landfill consists of a bottom liner (plastic or clay), a stormwater collection system, a leachate collection system, a cap, and a methane collection system.

Factors in landfill decomposition include the composition of the trash and conditions needed for microbial decomposition of the waste.

Incineration

As an alternative to landfills, we can burn solid waste. Until the 1960s, municipal solid waste (MSW) was burned in open dumps. It created huge clouds of smoke, smelled bad, created air pollution, and was a breeding ground for rats and flies.

Modern incineration facilities do not have most of these problems because it is carefully controlled and monitored incineration of solid waste. The waste is burned at temperatures high enough (900-1000^oC) to consume all combustible material.

Incineration has some advantages over landfills, but it also has some disadvantages that can harm human health and ecosystems if not carefully managed.

Advantages:

✅ Can reduce the weight of trash by 70%

✅ Can reduce the volume of trash by 90%

✅ Frees up landfill space

✅ Smaller weight and volume of incinerated toxic and hazardous waste is easier to handle

✅ Ash can be used to make concrete blocks

✅ Some can also incorporate resource recovery for recycling

✅ Some are able to sell metals to offset operating costs

Disadvantages:

❌ Can produce significant air pollution

❌ Air pollution control strategies (electrostatic precipitators, cyclones, and scrubbers) are expensive

❌ Some areas cannot afford high operation costs

Essential Knowledge

Solid waste can also be disposed of through incineration, where waste is burned at high temperatures. This method significantly reduces the volume of solid waste but releases air pollutants.

Illegal Dumping

As the human population grew and people started staying in one place, disposal of solid waste became a problem. Most often, waste was either burned or dumped in rivers, the ocean, or old quarries and mines that had been abandoned.

A collage of six different scenes, each depicting various forms of waste and pollution in natural environments: discarded tires, a pile of trash in the woods, a heap of metal scrap, barrels left in nature, an overflowing dumpster, and more tires dumped outdoors. — *Illegal dumping is sometimes known as fly tipping or midnight dumping*.

We built factories near waterways so materials could be easily transported to and from the factory, the water could be used for cooling or processing, and wastes could easily be disposed of in the water. This ended up polluting our waterways, sickening humans and animals, and destroying the aesthetics of our waterways.

With rising environmental awareness in the mid-1950s, a need for alternatives to this “open dumping” became apparent. With the passage of both air pollution laws that banned open burning of waste along with laws banning dumping into rivers, streams, and uncovered holes, landfills became the method of choice for waste disposal.

Even still, some items are still often dumped illegally because they are not accepted in landfills. The following items are often dumped illegally:

🛞 Tires
🚽 Refrigerators and other appliances
🛏 Furniture
🗑 Yard Trimmings
🛢 Hazardous Waste

There are few advantages to illegal dumping and MANY disadvantages:

Advantages:

✅ Free

✅ Easy

Disadvantages:

❌ Illegal

❌ Soil, water pollution

❌ Breeding ground for mosquitos and rodents

❌ Increased spread of disease

❌ Fire hazard

❌ Risk of injury

❌ Ugly and smelly

Essential Knowledge

Some items are not accepted in sanitary landfills and may be disposed of illegally, leading to environmental problems. One example is used rubber tires, which when left in piles can become breeding grounds for mosquitos that can spread disease.

Ocean Dumping

The Problem
Impacts
Garbage Patches
Solutions

The Problem

In the past, the solution to pollution was dilution. We built factories near waterways so materials could be easily transported to and from the factory, the water could be used for cooling or processing, and wastes could easily be disposed of in the water. This ended up polluting our waterways, sickening humans and animals, and destroying the aesthetics of our waterways.

During the middle part of the 1900s, laws were enacted making it illegal to dump waste in waters of the United States without a permit.

Wastewater from homes and businesses, which was previously dumped directly into rivers, lakes, or the ocean, now must be channeled through a wastewater treatment plant, which removes a significant amount of the pollution.

While ocean dumping is tightly controlled and regulated in some countries, others may not have ratified international agreements against dumping or may have less robust regional agreements regulating dumping.

Ocean dumping is an excellent example of the tragedy of the commons. Because the vast majority of the oceans are international, and the coastal oceans that belong to each country are artificial borders, if one country does not have laws regulating ocean dumping and allows residents to dump their waste in the ocean, it can affect other countries, even if those countries have laws preventing ocean dumping.

This makes ocean dumping a global problem, but one that is difficult to regulate.

The following items make up the bulk of the waste in the ocean:

A bar graphing showing the quantity of various types of waste items collected. The graph lists Cigarette Butts as the most common item, followed by Beverage Bottles and Food Wrappers at 998,661. Other items include Bottle Caps, Plastic Grocery Bags, Other Plastic Bags, etc. — ***Most of the trash in the ocean is plastic. There are an estimated 5.25 trillion pieces of plastic debris in the ocean.***

Impacts

Below are a few of the problems associated with ocean dumping. Open each impact to learn more about it. Which problem do you think is the worst? Which one can you most help solve?

🥫 Entanglement and Ingestion (click to reveal)

A collage of six images highlighting the impact of plastic pollution on marine life: a seahorse clinging to a plastic straw underwater, a clownfish swimming near coral reefs littered with plastic. a turtle entangled in a plastic bag, a whale shark with plastics floating around, a seal with green netting around its neck, and a crab trapped in plastic. — ***Marine debris can entangle marine life.***

Marine animals are particularly vulnerable to the dangers posed by such actions. Sea turtles, dolphins, and seabirds often mistake plastic debris for food, leading to ingestion of harmful materials that can be fatal. Additionally, creatures like seals and sea lions can get entangled in discarded fishing nets and other debris, impacting their ability to swim and hunt for food.

Ingesting plastics can lead to...

- - - - malnutrition
      - reproductive issues
      - decreased population sizes in affected species

🪸 Habitat Disruption (click to reveal)

A collage of six photos showing environmental pollution: a beach marred by plastic bottles and waste, a beach covered with plastic debris, an underwater scene with garbage floating, an underwater view with plastic bags, a close-up of a sandy beach with tangled green fishing nets and shells, a large pile of discarded black tires among green plants. — ***Marine debris can pollute beaches and ocean waters.***

The accumulation of waste in our oceans has severe ecological repercussions. Plastic pollutants not only harm marine life but also contaminate the water and disrupt underwater ecosystems.

Coral reefs are especially at risk from the damaging effects of ocean waste dumping.

🚢 Navigation Hazards (click to reveal)

Large patches of floating debris can create hazards for ships and smaller vessels. These hazards not only pose risks to marine transportation but also raise concerns about safety and environmental impacts associated with plastic pollution in our oceans.

🛢️ Toxicity (click to reveal)

A square concrete sign with the capitalized text “NO DUMPING DRAINS TO OCEAN.” Above the text, there’s a stylized illustration of a blue dolphin swimming over waves. — ***Chemicals dumped in or near the ocean can affect the health of marine animals and humans that eat those animals.***

As plastics degrade over time, they release harmful chemicals into the water, posing a danger to wildlife. These toxins can not only impact the health of marine animals but also have the potential to enter the food chain, raising concerns about human health risks.

If chemicals are dumped into or near the ocean, they can bioaccumulate in organisms and biomagnify up the food chain, eventually harming humans.

Remember Minamata?

Garbage Patches

A garbage patch is a large area in the ocean where waste material, especially plastic, accumulates due to the movement of ocean currents. There are actually 5 garbage patches worldwide, but the biggest is the Great Pacific Garbage Patch (GPGP).

A world map highlighting the locations of five major oceanic garbage patches within large systems of circulating ocean currents known as gyres: the North Pacific Gyre, the North Atlantic Gyre, the South Pacific Gyre, the South Atlantic Gyre, and the Indian Ocean Gyre — **There are 5 oceanic garbage patches. The North Pacific Gyre patch is the largest and has been dubbed the Great Pacific Garbage Patch (GPGP)**.

How did the garbage patches form?

These patches are formed by gyres, which are large systems of circulating currents that draw debris into their calm center. The short video from NASA below explains how scientists were able to figure this out:

How big are the garbage patches?

The GPGP spans from the West Coast of North America to Japan, comprising two main areas: the Western Garbage Patch near Japan and the Eastern Garbage Patch between Hawaii and California. Estimates suggest that the patch covers an area of about 1.6 million square kilometers (620,000 square miles), making it larger than many countries. with a density of debris that varies.

The other garbage patches are smaller.

What is in the garbage patches?

The waste within these patches ranges from microplastics to large objects like fishing nets and consumer goods. The Great Pacific Garbage Patch includes...

approximately 2.7 million metric tons of trash, 99% of which is plastic
1.8 trillion pieces of plastic
80,000 tons of garbage, 46% of which is discarded fishing gear
92% of its mass consists of larger objects that have not yet broken down into smaller pieces, because plastics take hundreds of years to break down
fishing gear, plastic bottles, bags, lighters, toothbrushes, and other plastic items.

Solutions

The video below explains the problem of marine debris and what we can do to prevent trash in the ocean:

Essential Knowledge

Some countries dispose of their waste by dumping it in the ocean. This practice, along with other sources of plastic, has led to large floating islands of trash in the oceans. Additionally, wildlife can become entangled in the waste, as well as ingest it.

AP Exam Tip

You should know the difference between MSW and other types of waste.

You should know the difference between modern landfills and early landfills.

You should know the types of things that are dumped illegally. Once there was an entire FRQ all about tire dumping!

You should understand the problems with ocean debris and the garbage patches.

[CC BY-NC-SA 4.0] UNLESS OTHERWISE NOTED | IMAGES: LICENSED AND USED ACCORDING TO TERMS OF SUBSCRIPTION - INTENDED ONLY FOR USE WITHIN LESSON.