What happens to food waste in landfills? The full environmental impact


Roughly one-third of the food we produce annually is never eaten, food which it takes a combined land mass roughly the size of China to produce. It will, therefore, come as no surprise that the environmental impacts of this are huge. But what actually happens to all that food waste in landfills?

In short, food waste is mostly organic material, composed of carbon, hydrogen, oxygen and nitrogen along with small amounts of some other elements. In a landfill, this organic material is buried and when this happens, microorganisms begin to break it down in a process known as ‘anaerobic digestion’. This is digestion in the absence of oxygen. The microorganisms derive energy from this to support their life cycle however as a by-product of this process, greenhouse gases (methane, carbon dioxide) are produced. If these gases are not captured they are released into the atmosphere.

But why is it that we waste so much food, and what makes this process so bad? In this article, I will explain the full impact of food waste going to landfills and then hopefully offer some solutions too.


How does food waste end up in landfill?


Although many cities now have recycling schemes which encourage people to separate food waste from other garbage which can then be used to potentially create biomass energy (more on that later), large amounts of food waste is still disposed of mixed in with other non-organic waste.

That might be in the home where many people just put all trash into one bin together or it could be in a variety of other places such as public bins.

Despite modern recycling centres, which can sort different materials, it is very difficult to separate out organic waste from other material and so much of it then ends up going to a landfill where it is mixed in with all sorts of other waste.


What happens to that food once in landfill – anaerobic digestion 


This organic food waste material is buried along with all the other waste at a landfill site. By burying it, there is a lack of oxygen and therefore the organic matter is broken down in a process known as ‘anaerobic digestion’, anaerobic meaning ‘without oxygen.’

This process is not carried out by a single microorganism but is carried out by a variety in three stages.

The first group of microorganisms breaks down the organic compounds, the second group converts this into organic acids and then finally methane-producing bacteria convert the acids to methane and carbon dioxide.

On average these gases are produced around 6 months after the waste is first deposited.


What does this mean for the environment?


If the gases end up in the atmosphere


As mentioned already, methane and carbon dioxide are greenhouse gases. This means they are gases that contribute to the ‘greenhouse effect’ by absorbing and reflecting the infrared energy from the sun, trapping in heat and causing warming.

Carbon dioxide is probably the most well known of the greenhouse gases which contributes most significantly to the greenhouse effect currently due to its high concentration. However, methane is calculated to be around 25 to 30 times as good at trapping heat compared to carbon dioxide and so any emissions of this are comparatively much worse.

It is tricky to compare the contribution to climate change of carbon dioxide and methane exactly because although methane is the more potent absorber of heat, that ability to absorb heat drops much quicker over time than carbon dioxide. Either way, they are both not good news and any emissions are not helpful.

According to the Intergovernmental Panel on Climate Change (IPCC) report between 5 and 20% of global human-caused methane emissions are from solid waste in landfills. That is around 1-4% of total annual greenhouse gas emissions.


If the gases are captured


It is now increasingly common, in many developed nations, to try and trap and siphon off these gases before they are released into the atmosphere.

Methane gas has the handy property of being extremely flammable, and for this reason, it can be captured and burned in order to produce electricity, provide heating, or powering vehicles.

This is actually classed by many as a ‘renewable’ energy source. Make of that statement what you will. But it is true that it reduces the direct emissions and is a useful form of energy that can take the place of some fossil fuels.


What is the full environmental impact of food going to landfill


When we talk about the environmental impacts of wasting food we can’t just look at the impact of emissions from landfill. You have to look at the impact of the entire supply chain, i.e from growing/ producing it to when it is finally put in the bin.


Growing the food


The environmental impacts of agriculture are vast and wide-ranging and vary across the globe. I won’t go into detail here but some impacts include:

  • Emissions from farm machinery
  • Emissions of greenhouse gases such as carbon dioxide and nitrous oxides from the soil
  • Land use change (cutting down trees which are an important store of carbon, often burning them and replacing that land with farmland)
  • Degradation of soils (reducing the life within them making them less fertile each year)
  • Pesticides being used incorrectly causing loss of biodiversity
  • Methane emissions from cattle and other livestock
  • High amounts of water use
  • Energy used to heat greenhouses
  • Runoff of soil and pollutants into watercourses
  • Waste from plastic poly-tunnels and mulch films

Virtually all modern food sources are produced with one or more of these environmental ‘side-effects’.


Transportation of food


These days many of us enjoy the luxury of obtaining food on-demand from exotic far off lands. It is now possible to get your hands on fruit from South America, vegetables from Africa and tea from Asia all in the same local supermarket, and at any time of the year. Most people would be confused if they couldn’t get hold of a certain fruit or vegetable in the shop, even if it was the middle of winter!

As great as this is it, of course, it has a cost for the environment. This food has got to be transported from where it is grown to the home of the consumer, and with each mode of transport more carbon emissions.

This starts with the trucks taking the produce to be processed, then the ships or planes that take it overseas, then further land transport to get it to the shops and then most likely the vehicle of the end customer to take it from the shop to their house. Now when you start to think about a banana that ends up in a landfill without even being eaten, it is crazy when you think of the journey it took to get there.

There are even more bizarre stories of food transportation, such as Norwegian cod being shipped to China to be filleted before being sent back to Norway to be sold.

The environmental impact of transportation is still low compared to other impacts from food production but it is rising every year as more people around the world demand food to be ‘in-season’ all year round.




To keep food fresh it has to be kept at a low temperature in a refrigerator or freezer. That includes the various transport vehicles, in the supermarkets and in our homes.

The first impact of all this refrigeration is the power it takes to keep them on. They need to be switched on 24 hours a day to avoid food spoiling and so, therefore, require constant electricity. That is a constant need in most cases for the burning of fossil fuels which all contributes to climate change.

There are other environmental impacts from refrigeration too. Old style fridges are being phased out, but this old equipment used to contain chlorofluorocarbons (CFCs). CFCs were substances that, when released into the atmosphere, caused damage to the ozone layer, an atmospheric layer which prevents harmful radiation from reaching the earth’s surface. But even since this ban, CFCs have been replaced by hydrofluorocarbons (HFCs) which although aren’t damaging to ozone, are still potent greenhouse gases.

Some freezers even contain mercury, which is highly toxic if it gets into soils or water, common when the appliances are not disposed of correctly.


What can we do?


As you may know on this blog I’m about finding solutions as well as highlighting the problems, so what can we do to address these environmental concerns caused by food waste?


1) Waste less


This one may seem a bit obvious, but the best thing we can all do is to start wasting less. Many of us have become numb to the problem of food waste and it can be easy to forget the long journey and thus the cumulative impact a single item of food has had when we see it on a supermarket shelf.

We need to start feeling this pain once more and changing our mindsets to value all food again. This is at an individual level, but also for the suppliers. Other issues such as a demand for perfection with fruit or vegetables lead to large quantities being thrown away before it even reaches the shops due to it not ‘looking perfect’.


2) Use best before and use by dates with caution


In a world where everyone is increasingly paranoid and worried about being sued. Many suppliers of food are deciding not to take any chances and are placing often very over the top instructions of when food items must be consumed by.

This includes best before dates on items such as rock salt! Which has literally been sat in the ground for thousands of years.

We need to apply more common sense. Which we would once have done in the past before we were given printed dates on most items.

‘Use by’ dates are usually to be taken more seriously and are placed on foods that can turn bad quite quickly. Although you should still use common sense, ‘use by’ dates are probably worth paying some attention to.

On the other hand, ‘best before’ dates should be read with suspicion. Most of these items will be fine well after the specified date has come and gone. Use sight and smells and if it looks and smells ok then it will most likely be fine and you can stop all the bad environmental side-effects of sending that product to landfill.


3) Innovative solutions


There are lots of brilliant ideas appearing to help us tackle the vast problem of food waste. I wrote an article recently looking at 6 of these innovative solutions.

These include companies like Olio which is an app to facilitate the sharing of food. This means that if you are going away or no longer have the need for an item of food, you can list it on the app and someone in the local area will come and pick it up from you. Olio have expanded this to cafes and restaurants too, allowing them to donate their unused stock to hungry people rather than simply throwing it in the bin.

I spoke to one of the founders of Olio in the podcast.

Other technological advancements such as renewable energy to prevent many of those greenhouse gases in the supply chain and better refrigeration techniques, will help too. But the key to tackling the problem of food waste doesn’t really rely on getting that food to landfill in a more environmentally friendly way, it means trying to stop it getting to landfill at all!










Rob Wreglesworth

Rob is the head writer at Innovate Eco sharing knowledge and passion cultivated over 10 years working in the Environmental Sector. He is on a mission to build a community of people that are passionate about solving environmental problems.

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