What happens to waste when it ends up in a landfill

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

About the life cycle of a landfill and how even ordinary waste becomes toxic.

Not far from your home - maybe a couple of tens of kilometers, and maybe much closer - there is a large-scale chemical reactor, where every day new portions of ingredients are loaded, the composition of which no one knows for sure, and the result of the reactor itself is not quite predictable. This reactor is called a landfill, or, translated into bureaucratic language, a landfill for solid household waste. Everything that is thrown away by city dwellers ends up here. N + 1 and Lifehacker decided to find out what happens to the garbage when it ends up in a landfill.

In 2015 in Russia, according to the analytical company Frost & Sullivan, 57 million tons of municipal solid waste were produced, which is only slightly less than the volume of steel production (71 million tons). Household waste in Moscow and the region What is waste? (about 11 million tons per year) is mainly composed of food waste (22 percent), paper and cardboard (17 percent), glass (16 percent) and plastic (13 percent), fabric, metal and wood each account for 3 percent. another 20 percent for everything else.

In Russia, landfills receive up to 94 percent of garbage, only 4 percent is recycled, 2 percent is incinerated.

For comparison: in the EU, 45 percent of waste is recycled, 28 percent ends up in landfills, and 27 percent is incinerated.

Russian landfills annually emit 1.5 million tons of methane and 21.5 million tons of CO into the atmosphere₂… In total in Russia in 2015 there were 13, 9 thousand operating landfills, of which in the Moscow region - 14. Only one Moscow landfill in the Chekhovsky district (the Kulakovo landfill) issued MSW landfills in the MOSCOW REGION during the year: CURRENT ENVIRONMENTAL SITUATION

AND PROSPECTS FOR RECLATING 2.4 thousand tons of methane, 39.4 tons of carbon dioxide, 1.8 tons of ammonia and 0, 028 tons of hydrogen sulfide into the atmosphere.

A properly organized landfill is a complex high-tech structure. Before it is ready to receive garbage, it is necessary to prepare the bottom: lay it out with a layer of clay about a meter thick, lay on top a waterproof geomembrane, a layer of geotextile, a 30-centimeter layer of rubble, in which you need to lay a pipe system to collect the filtrate - the liquid that will be collected from debris, and on top there will also be a protective permeable membrane. The bottom of the landfill should be at least half a meter above groundwater.

Next to the landfill, a pumping and treatment station will be required to pump out and neutralize the filtrate, which is saturated with organic acids and other organic matter, heavy metal compounds. In addition, in the layer of garbage, when it begins to accumulate, it will be necessary to install a system of pipes for collecting and utilizing landfill gas, a station for its cleaning and incineration.

When the landfill is full (usually the landfill takes 20-30 years of garbage), you need to close the landfill from above with another protective layer, preserving the landfill gas collection system - it will have to work for decades.

Landfill life

The chemical life of garbage in a landfill can be roughly divided into four main phases by Landfill Gas Basics. During first phase aerobic bacteria - bacteria that can live and grow in the presence of oxygen - break down all the long molecular chains of carbohydrates, proteins, lipids that make up organic waste, that is, mainly food waste.

The main product of this process is carbon dioxide, as well as nitrogen (the amount of which gradually decreases over the life of the landfill). The first phase continues as long as there is enough oxygen in the debris, and it can take months or even days for the debris to be relatively fresh. The oxygen content varies greatly depending on the degree of compaction of the debris and how deeply it is buried.

Second phase starts when all the oxygen in the garbage has already been used up. Now the main role is played by anaerobic bacteria, which convert substances created by their aerobic counterparts into acetic, formic and lactic acid, as well as into alcohols - ethyl and methyl.

The landfill environment becomes very acidic. As acids mix with moisture, it releases nutrients, making nitrogen and phosphorus available to a diverse community of bacteria, which in turn intensively produce carbon dioxide and hydrogen. If the landfill is disturbed or oxygen somehow penetrates into the mass of the garbage, everything returns to the first phase.

Third phase in landfill life begins with the fact that certain types of anaerobic bacteria begin to process organic acids and form acetates. This process makes the environment more neutral, which creates conditions for bacteria that produce methane. Bacteria methanogens and bacteria that produce acids form a mutually beneficial relationship: "acid" bacteria produce substances that consume methanogens - carbon dioxide and acetates, which in large quantities are harmful to the acid-producing bacteria themselves.

Fourth phase - the longest - begins when the composition and level of gas production at the landfill becomes relatively stable. At this stage, landfill gas contains 45 to 60 percent methane (by volume), 40 to 60 percent carbon dioxide, and 2 to 9 percent other gases, in particular sulfur compounds. This phase can last for about 20 years, but even 50 years after the garbage has stopped being brought to the landfill, it continues to emit gas.

Methane and carbon dioxide are the main decomposition products of waste, but far from the only ones. The landfill "repertoire" includes hundreds of different volatile organic compounds. Scientists who surveyed seven landfills in Britain found Trace Organic Compounds in Landfill Gas at Seven U. K. Waste Disposal Sites contain about 140 different substances in landfill gas, including alkanes, aromatic hydrocarbons, cycloalkanes, terpenes, alcohols and ketones, chlorine compounds, including organochlorines such as chloroethylene.

What could go wrong

Marianna Kharlamova, the head of the RUDN University Environmental Monitoring and Forecasting Department, explains that the exact composition of landfill gas depends on many factors: on the time of the year, on adherence to technologies in the construction and operation of the landfill, on the age of the landfill, on the composition of the waste, on the climatic zone, on the air temperature and humidity. …

“If this is an operating landfill, if the supply of organic matter continues, then the composition of the gas can be very different. For example, there can be a process of methane digestion, that is, mainly methane gets into the atmosphere, then carbon dioxide, ammonia, hydrogen sulfide, there can be mercaptans, sulfur-containing organic compounds,”says Kharlamova.

The most toxic of the main components of emissions are hydrogen sulphide and methane - they can cause poisoning in high concentrations.

However, Kharlamova notes, a person is able to feel hydrogen sulfide in very small concentrations, which are still very far from dangerous, therefore, if a person smells hydrogen sulfide, this does not mean that he is immediately threatened with poisoning. In addition, when garbage is burned, dioxins can be released - much more toxic substances, which, however, do not have an immediate effect.

Landfill operation technology assumes that landfill gas is collected using a degassing system, then it is cleaned of impurities and burned in flares or used as fuel. Kharlamova notes that the burning of untreated landfill gas, as was done Degassing in "Kuchino". How landfill gas is removed at the Balashikha landfill, for example, at the Kuchino landfill, can create many new problems with toxic combustion products.

In this case, for example, sulfur dioxide (during the combustion of hydrogen sulfide) and other toxic sulfur compounds are formed. In normal gas utilization, it is necessary to first clean it from sulfur compounds.

Marianna Kharlamova

Another threat arises when a strong heating begins in the mass of debris, a fire without access to air, similar to peat. In this case, the landfill dramatically changes its repertoire, aldehydes, polyaromatic hydrocarbons, chlorinated polyaromatics appear in emissions in large quantities. “This creates a characteristic smell. A common landfill smell is putrefaction from hydrogen sulfide and mercaptans. In the event of a fire, it starts to smell like fried potatoes - this is the smell of hydrogen fluoride, which is formed during combustion,”explains Kharlamova.

According to her, sometimes they try to stop the release of landfill gas into the atmosphere by covering the landfill from above with a film and then with a layer of earth. But this creates additional problems: "When decaying, voids are formed and there are dips in the soil, in addition, the film does not allow water to pass through, which means that swamps will arise from above," she says.

The main source of problems with landfills, Kharlamova notes, is food and organic waste. It is they who basically create the conditions for the "production" of methane and hydrogen sulfide. Without food waste, garbage can be sorted and recycled much better. “If we managed to organize a waste collection system so that organic matter does not get to the landfills of solid waste, this would solve most of the problems with landfills that arise today,” the scientist believes.