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Leachate: the ugly truth about food waste in landfills

Leachate. It's the kind of thing you rarely think about. The kind of thing you might not have even heard about until just now.

Well, unfortunately, we're going to have to burst your bubble a bit.

This article is going to go over exactly what leachate is, what it does to the surrounding environment, how it's related to food waste and why municipalities are struggling to control it.

What Is Leachate Anyways?

Leachate is the liquid which leaches from landfills, either through rain run-off, or the organic components of landfill heaps themselves creating leakage.

Landfill sites are supposed to have leachate collection systems, which are often lagoons or closed tanks filled with the grossest possible stink-water you could ever imagine, and an underground system of pipes to collect any liquid generated over the lifetime of the landfill.

However, these collection systems do not always do what they're supposed to. According to the US Geological Survey (USGS): "Landfills are often not the final repository for leachate which can be discharged to surface waters following onsite or offsite wastewater treatment."

You know that wonderful Jeff Goldblum quote, from Jurassic Park?

Well, this is especially true of human-made systems, such as landfills and leachate collection systems. Leaks happen: the direction of how groundwater naturally flows, as well as the permeability of the nearby soil structure may not always be accounted for, or properly mitigated by leachate collection systems.

Leachate spills and spreading is compounded by irregular weather patterns:

"Long drought years and occasional heavy wet spells lead to accelerated dispersion of leachate in the surrounding areas causing surface and subsurface contamination."

- Richard Espinoza

As weather patterns continue to become more and more unpredictable with the complex climate change matrix, these leaks may very well increase in both severity and regularity. Time alone will tell.

Research has shown that 0.1% - 0.4% of all groundwater is polluted by landfills and industrial reservoirs. The United States Environmental Protection Agency (USEPA) provide statistics which prove that most landfills leak. (Scientific Reports, 2019)

Why Is Leachate A Problem?

Leachate, as the name might imply, can leach - or leak - into the surrounding environment. Of particular concern, leachate can enter local water tables and bodies of water.

Among all [environmental dangers caused by landfills], leakage of leachate affects the surrounding environment the most, especially the surface and ground water bodies as the leachate consists of high concentrations of heavy metals, organic compounds and toxic contents.

- B. P. Naveen, J. Sumalatha & R. K. Malik

Is this serious?

You might be wondering "what the big deal is". Well, here are some considerations:

  • Leachate contains ammonia:

Organic waste which decomposes anaerobically - without aeration/dehydration - generates ammonia, a chemical cousin of nitrogen. When organic materials decompose with proper aeration, such as in composting systems, nitrogen is produced and, in reasonable quantities, can be highly beneficial to your micro-environment.

However, this is not the case with anaerobic environments, where high concentrations or organic waste and lack of air produce toxic levels of ammonia. 3 X the "safe" level of ammonia have been found in nearby groundwater and waterways as a result of leachate.

While most water is treated with chlorine in bustling urban and suburban settings, making it technically safe to drink, chlorine can actually react with some of the compounds found in leachate - ammonia among them.

Ammonia is toxic to humans and animals, causing pulmonary irritation and damage to the sinus system and eyes. If ingested in high enough concentrations, ammonia can be lethal.

  • Leachate contains fecal matter:

That's right. Poop. Leachate contains poop, which in turn can contain E.Coli.

Ever wonder what happens when you throw out your little baggies of dog or cat excrement? It goes to the dump. And whenever the organic waste content of the landfill begins to "sweat" during anaerobic decomposition, or rain falls on the landfill, this leakage can then end up in local water sources.

While bacterial contamination can be handled through boiling or other disinfection (chlorination) by municipal water treatment plants, this is an added stress to local infrastructure, not to mention an added cost consideration.

  • Leachate can contain lead and arsenic:

Lead-based paints and arsenic in lead alloys (such as car batteries) often leach into groundwater once these materials have been dumped in landfills. Lead in groundwater is extremely troubling, as traditional municipal disinfection or chlorination do not effect or screen heavy metals.

Ingestion of lead can cause a host of health risks, the least of which are anemia, physical weakness, kidney and brain damage. Lead also puts pregnant women and their unborn children at severe risk by crossing the placental barrier and affection a fetus' developing nervous system.

Arsenic - a primary component of rat poison - is extremely toxic and can lead to stomach pain, vomiting and nerve damage, as well as skin and tissue irritation if ingested for short to medium term, and an increased risk of a host of different cancers if ingested in the long term.

  • Leachate contains nitrate:

Nitrate is formed naturally whenever nitrogen combines with oxygen. As you may know, organic waste produces nitrogen during the natural decomposition process when aerobic (or anaerobic) bacteria break down organics. Whenever this material is exposed to air, nitrate is formed and can then leach into groundwater.

Nitrate is ubiquitous in municipal solid waste landfills, and - through leachate - has been linked to blue baby disorder, miscarriage and increased risk of non-Hodgkin's lymphoma.

Leachate affects our food supply:

Any compounds which affect the water supply are assured to affect nearby fauna and flora, and the ecosystem as a whole.

For example, high nitrogen levels in the soil can cause a "nitrogen glut" in plants, leading to lower overall yields. As we've seen, landfills produce large amounts of nitrogen and ammonia which leach out to nearby waterways and inevitably in local soil as well.

What Does Food Waste In Landfills Have To Do With Leachate?


As we've seen, leachate is generated from two sources:

1) Rainfall pulling toxins and organic compounds from landfill sites into the surrounding environment

2) Organic materials within the landfill waste heaps themselves generating moisture through the natural decomposition process

Food waste in traditional landfills (without organics collection systems in place) accounts for up to 40% of all landfilled waste. Food waste has a moisture content of 73%. Further:

Almost 80% of the mass remaining in the landfill following food waste biodegradation is water. [...] most of the weight of biodegraded food waste in landfills is due to moisture, while most of the weight of biodegraded mixed waste is undecomposed waste.

- MSW Management

This means that, the weight of landfill waste is majority based on the moisture content of food waste. This also means that, as food waste decomposes, the remaining moisture (80% of total remaining mass) will inevitably leak down into - and, in most cases - out of leachate collection systems.

In arid regions with little rainfall, "landfill[...] leachate was mainly originated from the moisture content of the dumped wastes." (Polish Journal of Environmental Studies)

While organics decomposition may not be the greatest source of leachate in areas with a rainier climatology, it is still a major player in the generation of leachate, particularly as rainfall generally affects the outer layer of landfill heaps, whereas organic waste affects the entirety (wherever there are organics present) of landfill volume.

Are Municipalities Dealing with Leachate Effectively?

This is a tough question to answer, as every municipality is different, and uses different tactics to mitigate the risks and effects of leachate.

However, in the broad sense, we can comfortably say that most municipalities are overwhelmed by the requirements of a growing waste stream, and are probably missing some opportunities to improve their landfill system.

There are multiple methods for dealing with leachate after the fact, one it has already become a hazard in municipal landfills. The primary methods include:

  • Aerobic Biological Treatment such as aerated lagoons and activated sludge.
  • Anaerobic Biological Treatment such as anaerobic lagoons, reactors
  • Physiochemical treatment such as air stripping, pH adjustment, chemical precipitation, oxidation, and reduction.
  • Coagulation using lime, alum, ferric chloride, and land treatment.
  • Advanced techniques such as carbon adsorption, ion exchange.

(HBRC Journal)

While these methods have varying degrees of success in neutralizing the dangers of leachate, they don't actually have any effect on the production of leachate.

So, instead of handling the cause of the problem, municipalities have been throwing a lot of money at landfills: a stop-gap measure rather than a solution. And these methods cost a lot of money to install and run.

For example, the anticipated leachate treatment costs per year average $3.6 million in the US. As waste levels continue to rise, and landfills continue to grow in both size and number, this cost is not going to stabilize any time soon.

On top of the financial burden, the environmental costs of such systems too cannot be ignored. Aerobic leachate lagoons produce methane, while anaerobic systems and chemical systems are subject to spills and/or malfunctions.

"A lot of sites are able to take landfill liquids like leachate and condensate and dispose of them at local treatment plants, but that outlet for disposal is currently being threatened by stricter standards from those treatment plants."

Waste 360

So, if traditional forms of leachate reduction and removal are on their way out, what are municipalities and other waste regulation bodies to do?

What Could Municipalities Be Doing Instead?

Rather than spending money every year on a broken system, municipalities should be turning their attentions to innovative and sustainable solutions to the problem of leachate.

This problem has never been so important to tackle, as it has been proven that "landfills can continue to produce leachate for several hundred years after they have ceased to operate, making the sustainable management of leachate a long-term problem for landfill operators and regulators." (Science for Environment Policy)

Who'll Stop the Rain?

One method to limit the production of leachate would be to ensure that landfills have sufficient covering from rainfall and the negative effects of drought, by using a geomembrane or tarp to protect areas of the landfill which are not going to be serviced any time soon.

However, all methods for tarping landfill are temporary and dependent on the landfill being unused. Further, this method does not stop the internal organics from generating leachate, nor does it stop existing landfill waste leachate from draining into the nearby soil or waterways.

No Food Waste!

As we've seen, much of the volume of traditional landfills is actually composed of liquids and organic waste, which are also primarily responsible for the existence of leachate in the first place.

If municipalities and waste regulators were to reduce or even completely eliminate the influx of organic waste from landfills through either anaerobic digesters, community compost facilities or through a form of in-home subsidized waste reduction system, the production of leachate would drastically be reduced.

To Summarize

- Leachate is terrible for the environment and for people

- Leachate is produced through water run-off from landfill sites

- Food waste is one of the main causes of leachate

- By limiting organic waste in landfills, municipalities could save millions on leachate collection systems, and eliminate much of leachate production from local landfills


A Note on Terminology

The FoodCycler™ is a countertop electric food waste recycler that breaks down food scraps through a mechanical process into a dry, lightweight by-product that can be used in gardening applications as a fertilizer. The FoodCycler™ and other electric food waste recyclers are not composters, nor do they produce compost or soil as they do not require additional microbes to break down food waste with bacteria. However, the term "electric composter" has been used to describe the FoodCycler™.