Humans produce a lot of waste, but when we throw something away, how much do we know about where it goes and how it is handled? This is the second in a five-part series investigating what could happen.
Approximately half of the trash generated in the United States ends up in a landfill, and these days a significant portion of recycling also goes there.
It may be depressing to think about all that waste going to the dump, but it’s not at all the environmental nightmare that many environmentalists think of. Here, we will explain the background of modern sanitary landfills and how they work.
dump
Humans have been throwing away trash for as long as trash has been generated.
prehistoric tomb It is an important source of information for archaeologists and anthropologists. In ancient Rome, municipal waste collection was carried out. However, the first municipal sanitary landfill built in fresno Late 1930s.
dump multiplied in the US until the mid-2020sth century. Some of them, like the one in Fresno, were true sanitary landfills. This meant layering trash and soil in the trench, compacting both, and then covering the filled area daily to minimize rodent and debris problems. Some people line the holes and trenches with clay before filling them to minimize leaching. However, many of them were just holes in the ground that were only covered with earth after being filled, and they were real garbage dumps.
sanitary landfill
In 1965, the federal government established an office to manage trash. Waste disposal law. This law has since undergone many amendments and still regulates waste disposal in the United States.
By the mid-1970s, states were required to establish waste management regulations. today, Resource Conservation and Recycling Act (RCRA) creates a framework for the proper management of all types of solid waste. subtitle D RCRA establishes strict design, operation, and closure requirements for sanitary landfills. Subtitle D does not permit the construction of new landfills in environmentally sensitive areas.
Modern sanitary landfills are complex structure Isolate the waste from the surrounding environment until it becomes inert. The landfill consists of a bottom liner made of clay and a durable synthetic plastic. Leachate collection system to remove liquid. A stormwater management system that prevents surface water from flowing into garbage. and a methane collection system that removes landfill gas as it is produced.
Leachate, rainwater and gas collection systems are constantly monitored. Landfills must be budgeted for monitoring and maintenance for decades after they close to ensure they don’t leak harmful chemicals.
How does a landfill work?
Landfills are divided into sections called cells, which are filled and closed in stages. Cells can be located anywhere from 2,500 square feet up to 20 acres or more, depending on the size of the landfill. The current trend is to require larger cells and landfill sites.
Once the new cell is constructed, the hole is lined with 2 feet of compacted clay, a durable plastic liner, and a non-porous geotextile membrane. The outliner’s lining is covered with a layer of granular material that helps collect liquid into the leachate collection system. Layer up to 2 feet of soil on top of the litter before adding it. Often the first layer of litter consists of a special material, such as an old mattress, to further protect the lining.
Once the cells are constructed, municipal solid waste is dumped inside and run over by compaction tractors. At the end of each day, trash should be completely covered to minimize odors, deter pests, limit rainwater runoff, prevent waste fires, and impede cleanup. daily cover Most consist of 6 inches of soil. This can cause the cells to fill up more quickly, so alternative covers such as geotextile cloth or certain types of waste such as ash or tires are sometimes used to maximize efficiency. well and ditch Collect landfill gas They will be placed at regular intervals as the landfill fills.
This diagram is advanced disposal shows the elements of a modern sanitary landfill.
Once the cell is completely filled, the final cover or cap is installed, as is the bottom liner. The cap will be further covered with topsoil and planted with vegetation during a multi-decade monitoring period following closure.
landfill gas
The biggest environmental impact of landfilling is landfill gas (LFG).
Landfills are designed to minimize decomposition, but organic materials will eventually decompose in the landfill. At that time, LFG is produced as a byproduct. LFG is approximately half methane and half carbon dioxide, and is a potent greenhouse gas. All landfills must collect LFG. At most landfills, the collected gas is burned off at flare stations, making landfills the third largest source of anthropogenic methane emissions in the United States.
Nevertheless, LFG can be used to make landfills more environmentally friendly. Some landfills convert the collected LFG into usable energy rather than burning it. The collected gas may be used to power boilers and furnaces, or it may be refined into renewable natural gas. Most often used for power generation.
Whatever the end use, LFG to Energy Project Between 60% and 90% of the LFG produced in landfills can be recovered and the same amount of energy replaced from non-renewable sources.
Limits of landfill
Older landfills were either unlined or simply lined with clay, which could crack, and there was no funding for post-closure monitoring. As a result, many keep leaching Chemicals enter nearby soil and groundwater. Current landfills are much better at containing and monitoring their contents. However, the risk of future failure is always present and there is some evidence. all landfills leak.
Modern landfills are huge and their ability to compact waste is constantly improving, but eventually even the largest and most efficient landfills will become full. When existing landfills run out of space, it may be impossible to find space for new ones.
landfill must be installed Areas with safe hydrogeological features, i.e. areas away from faults, wetlands, floodplains, and other hazardous areas. Large rural sites are required, and few communities enthusiastically embrace a waste disposal site of any kind.
When it comes to waste disposal, nothing beats modern sanitary landfills. However, it still has an impact on the environment. No matter how cleanly you dispose of things, all disposal results in waste, so there is no perfect disposal method.
Garbage dumps may not be as filthy places as we imagine, but it’s still impossible to truly throw anything away.
Read Part 3 of this 5-part series: How Commercial Composting Works.
Editor’s note: This article was originally published on October 22, 2019 and updated in December 2024.
