Solid waste management

As population and resource use have grown, so has the production of solid waste. Municipal solid waste results from resource use in homes and businesses. Solid waste is traditionally viewed as a necessary but harmful end product of society’s resource consumption. However, it has been used as a resource in its own right to provide energy and raw materials.

Background

Solid waste management has changed dramatically through time. Until the twentieth century, solid waste was managed primarily for military reasons and the aesthetic pleasure of the wealthy. For example, ancient Athens and medieval Paris created laws to prevent the buildup of trash outside the city walls, because such a buildup could allow enemies to scale those walls. In the twentieth century, large-scale waste management was instituted in many industrialized countries for aesthetic and health reasons, primarily by dumping in landfills. In the last decades of the twentieth century, resource, energy, and environmental considerations led to dramatically increased recycling and energy recovery. These efforts reduced the need to obtain raw natural resources to meet society’s needs. In the twenty-first century, solid waste management strategies necessarily varied by location, and the optimum strategy in one location was not necessarily the same as that of another. However, in almost all cases, the amount of waste generated continues to increase, and so solid waste management becomes an essential part of resource management.

Composition and Generation

The amount of municipal solid waste generated and its composition vary depending on the level of economic productivity and whether the location is urban or rural. This information is important when implementing a cost-effective and efficient solid waste management plan. Solid waste’s composition can dictate the resources that are most easily recycled, the amount of energy that might be expected from energy recovery, the amount that can be composted, and the size requirements for landfills. The quantity of waste that is generated can be used to manage the collection of waste, anticipate recycled goods sales, build an appropriately sized waste-to-energy facility, and predict how long a landfill site will last.

However, detailed information about quantity and composition is often incomplete or not available for a given region or country, so solid waste policy is often made without this important information. Also, because the composition and generation vary depending upon the time of year and location within a country, making generalizations from one set of data is hard. Annual waste quantities vary from less than 0.1 metric ton per person in some developing countries to more than 0.8 metric ton per person in some developed countries. Waste composition in the United States is approximately 33 percent paper, 25 percent yard waste, 12 percent plastic, 8 percent metal, 6 percent wood, and 5 percent glass. In contrast, solid waste composition in developing countries contains less paper, metals, glass, and plastic, and more plant debris, ash, and night soil.

Solid waste can present both health and environmental hazards to society. Dumping waste in open landfills presents acute health risks to scavengers and widespread disease risks to the extended community through increased vermin and disease vector populations, such as mosquitoes. Rainwater trickling through the waste can carry dangerous pollutants to the below, resulting in health hazards and the loss of valuable water resources. Because of the buildup of methane in landfills as bacteria break down the waste, landfills can catch fire, which not only is a risk to the nearby community but also emits dangerous air pollutants over a much larger area. Worldwide, more than 200,000 uncontrolled dumps present environmental and health hazards.

Solid waste significantly contributes to global warming and climate change by generating methane and black carbon emissions. While these emissions do not last as long in the atmosphere as carbon dioxide, they have a greater potential to cause global warming. Waste collection is not as common in developing countries as it is in developed countries. According to the Environmental Protection Agency (EPA), waste collection coverage in developed countries is less than 40 percent of that in developed countries. Because of this, people may resort to burning, which releases black carbon and carbon dioxide emissions into the atmosphere. Dumping solid waste along roadways is also a concern. As it decomposes, it releases methane.

Waste Management Hierarchy

In general, as population and affluence increase, the production of solid waste also increases. Therefore, a preferred waste management hierarchy has been established to help deal with this resource issue. The most important strategy is to prevent waste production in the first place, thereby reducing the amount that is generated. This reduction can be achieved by redesigning packaging, improving products so that they last longer, educating consumers to encourage more sustainable consumption, and developing legislation that holds producers responsible for wastes. Reducing waste will save valuable raw materials and energy that can be used elsewhere for the benefit and prosperity of society. The next strategy is to encourage reuse of materials that still have value in their current form, such as secondhand clothes or grocery bags. While these first two strategies have been recognized for years as being important, little improvement in these areas has been made in any part of the world.

The second most important strategy is recycling and composting waste. This has shown some improvement since the 1960s. For example, in the United States, only 7 percent of the waste was recycled in 1960; however, 25 percent was recycled in 1996, and 33 percent was recycled in 2007. However, by 2023, only 35 percent of waste was recycling, resulting in 65 percent of recyclables were thrown in the trash. In other countries, such as Slovenia and South Korea, more than 50 precent of waste is recycled.

According to the EPA, in 2018, the United States generated 292.4 million tons of solid waste, about 4.5 pounds per person, per day. Of this, the country recycled and composed 94 million metric tons. Of this waste, 32.1 million tons were paper and paperboard; 8.8 million tons were nondurable paper products; 3.3 million tons were newspapers/mechanical paper; 2.9 million tons were lead-acid batteries; 3.1 million tons were major appliances; 3.1 million tons were wood packaging; 3 million tons were glass containers; 2.6 million tons were tires; 1.8 million tons were mixed paper containers and packaging; and 1 million tons were consumer electronics. Recycling and composting 35 percent of solid waste reduced carbon dioxide emissions by around 190 million metric tons. The increase in recycling worldwide is a result of regulatory requirements, improved infrastructure, and growing markets for recycled materials. These recycling efforts conserve valuable raw materials, energy resources, and land resources.

The third most desirable strategy is incineration of waste with energy recovery. Municipal solid waste contains a great deal of energy; 1 metric ton of waste has a heat value of approximately 9 gigajoules, so that the entire world’s energy potential from solid waste is an astounding 8 exajoules per year. Of this entire potential, roughly 130 million metric tons per year are combusted worldwide, producing more than 1 exajoule per year, which is equal to the energy produced by 225 Hoover Dams. Modern incineration facilities control air emissions and can almost eliminate the production of dioxins and furans, which were problems in earlier facilities. However, these modern facilities are extremely expensive. Incineration in Japan is used for almost one-half of the country’s waste, and the practice has grown in Europe as regulations cut back on the use of landfills. In the United States, only 14 percent of the waste is incinerated. In the developing world, almost no waste is incinerated safely; instead, sometimes mass burns are used to reduce the volume of waste, but these emit large amounts of air pollution.

The last and least desirable waste management strategy is landfilling. Modern sanitary landfills reduce the problems posed by open dumps, because the waste is covered every day with dirt to reduce vermin, disease vectors, odors, and windblown trash. Also, the bottom of a sanitary landfill is lined with low-permeability and synthetic sheets to prevent contaminated leachate from leaking down into the groundwater. The leachate is collected and treated. The methane produced by bacteria in a landfill can also be collected and either flared or used to generate heat and electricity. Because solid waste accounts for 5 percent of the world’s greenhouse-gas emissions, and most of this is from landfill methane, collection of landfill methane is also a prudent response to the threat of global warming. Landfills remain the most common end point for solid waste in almost all of the world. However, in the developed world, the percentage of waste going to landfills is decreasing.

Integrated Solid Waste Management

Because the quantity and composition of solid waste vary from country to country, and from location to location within any country, there is no one-size-fits-all approach to solid waste management. Instead, solid waste management plans must be flexible to meet the needs of a given local area. This integrated solid waste management approach takes into consideration the geography of the area, economics, politics, social conditions, and composition and generation of waste. Countries with large populations and relatively small available land area are not as easily served by landfills as are countries with more available land. Therefore, countries such as Singapore and Japan use landfills much less than countries like the United States or Canada.

Another important difference between developing and developed countries concerns issues of recycling. In developing countries, labor is cheap and poverty is high, so there is a larger pool of people who take part in scavenging through bulk waste to find and remove the valuable reusables and recyclables. This approach is effective, but improvement in the scavengers’ working and health conditions is essential. In the developed world, labor is expensive, and so recycling and composting rely heavily on consumers to separate their wastes and on large-scale automation to further separate and handle the recyclables for sale. In urban areas, solid waste typically contains more paper and plastics, while in rural areas a higher percentage of plant materials are present. Thus, given the different constraints posed in different areas, the most efficient and cost-effective solid waste management plan can be different for each area.

Bibliography

"Best Practices for Solid Waste Management: Guide for Decision-Makers in Developing Countries." US Environmental Protection Agency, Resource Conservation and Recovery, July 2023, www.epa.gov/system/files/documents/2023-07/SWM‗Climate-Final.pdf. Accessed 6 Jan. 2025.

Tammemagi, H. Y. The Waste Crisis: Landfills, Incinerators, and the Search for a Sustainable Future. New York: Oxford University Press, 1999.

US Environmental Protection Agency. Municipal Solid Waste in the United States: 2007 Facts and Figures. Washington, DC: US Environmental Protection Agency, Solid Waste and Emergency Response, 2008.

Vesilind, P. Aarne, William A. Worrell, and Debra R. Reinhart. Solid Waste Engineering. Pacific Grove, Calif.: Brooks/Cole, 2002.