Food waste is defined by the Food and Agriculture Organisation of the United Nations (FAO) as a decrease in the amount of food available due to the disposal of food that was (at one point) appropriate for human consumption. This could be for various reasons such as negligent food storage (leading to spoilage) or because the consumer buys more food than is needed. The key point that needs to be understood is that food waste is, by definition, avoidable, and yet one-third of food produced globally goes to waste.
As well as being a missed opportunity to improve global food security in a world where 690 million people go hungry every night, food waste also results in the production of greenhouse gases. With a carbon footprint of 3.3 gigatonnes of carbon dioxide equivalent, if food waste were its own country, it would be the third-largest emitter of greenhouse gases after the USA and China.
This is not just a problem at the consumer level-waste can occur along the supply chain long before it ever reaches the consumer, which is known as food loss. Approximately 14% of food spoils before it reaches retailers, which can be attributed to the post-harvest handling, storage and food processing stages of food production. During the transport of food, items need to be properly packaged and refrigerated, so mishandling, or a lack of suitable technology to store food, can lead to losses at this stage. Furthermore, retailers are responsible for wasting a large amount of edible food they deem ‘ugly’; this problem accounts for up to 40% of wasted fruits and vegetables in the UK in 2013 and is hugely avoidable.
Particularly in developed countries, we face the inherent problem of overbuying, purchasing food we will not eat past its ‘best before’. Every year in the UK, retail, households, food manufacturing, hospitality and food service combined produce 10 million tonnes of food waste, of which an incredible 60% could be avoided according to the Waste and Resources Action Programme (WRAP) estimates in 2013 and 2016. In the UK, households dominate the food waste spectrum, resulting in an estimated 6.6 megatonnes of food thrown away in the UK in 2018, or 70% of the total food amount of food disposed of that year.
Figure 1: Food waste distribution from households as of 2020 according to WRAP. Of the 6.6 megatonnes (Mt) thrown away, 4.5Mt is thought to be preventable and could have been eaten.
Other developed countries looking to combat food waste include Japan, which threw out 6.46 million tonnes of food in 2015, (or 136g per person per day), and the USA, which is the global leader in food waste and disposes of 40 million tonnes of food per year. A substantial portion of this food waste can be attributed to consumers misunderstanding food expiration labels, confusing ‘sell by’ and ‘best before’ dates with ‘use by’ dates.
Overall, food waste is a growing problem and something that needs to be tackled at all levels (on the farm, post-harvest, during processing, in stores and at home) on a global scale.
So, what is the problem?
A reasonable question to ask is: what is the actual problem that comes from wasting food? To answer this, we need to consider what is done with the food once it has been disposed of.
In the case of the 97% of UK households without a domestic composter, there are three possible methods of disposal of the contents of a household bin; it can be taken to a landfill site and buried, it can be incinerated, or it can be recycled through anaerobic digestion. The options available can vary by area and their food waste disposal facilities. For instance, the borough of Westminster in London collects food waste separately from general waste, which is then taken to an anaerobic digestion facility.
Currently, 2.3Mt of food waste generated from UK households (approximately 35%) is disposed of via landfill (Figure 1). Over time, the layering of waste leads to the creation of an anaerobic environment, which causes microorganisms present to produce landfill gas as they break down the waste.
The biggest component of this landfill gas is methane, a harmful greenhouse gas with up to twenty-one times more potency than carbon dioxide. Overproduction of methane and other greenhouse gases, such as carbon dioxide, causes them to accumulate in the atmosphere, where they absorb infrared radiation given off by the sun and re-emit the radiation in all directions, causing global warming (Figure 2).
Figure 2: Diagram showing the greenhouse effect. Greenhouse gases such as methane and carbon dioxide accumulate in the atmosphere, trapping infrared radiation in the atmosphere and re-emitting it in all directions, warming the planet.
Thermal treatment (or incineration) is an alternative to landfill which makes up a similarly large proportion of food waste treatment. Astonishingly, incineration of waste in the UK released around 13.3 million tonnes of carbon dioxide emissions in 2019 and can also produce harmful pollutants and toxins which harm the local air quality. Examples of air pollution include ultrafine particulate matter and nitrogen dioxide, which can have an adverse impact on health; long term exposure to air pollutants has been linked to several respiratory diseases.
The third option is to transport the food waste to an anaerobic digestion facility. In these anaerobic digestion facilities, microorganisms break down the food waste in the absence of oxygen; this occurs within a sealed tank or ‘digester’. A methane-rich gas called ‘biogas’ is produced, and instead of dissipating into the atmosphere like landfill gas, this biogas can be used to generate heat and electricity, or converted to biomethane which can then be injected into the gas grid.
Figure 3: Simple diagram outlining the steps of biogas production in an anaerobic digestion facility. Food waste goes into a sealed tank containing microorganisms. In an oxygen-free environment, the microorganisms convert food waste to biogas, which can be used to generate renewable heat and power.
In this way, anaerobic digestion helps to turn waste into a resource, converting the waste via anaerobic digestion into valuable energy. There are over 579 operating anaerobic digestion facilities operating in the UK allowing for food waste to be recycled on a mass scale.
However, since the mass transportation of food waste to anaerobic digestion facilities produces a substantial amount of greenhouse gases in itself, this means that although anaerobic digestion is a preferable solution to both landfill and thermal treatment, it still is not completely environmentally friendly.
Figure 4: Summary diagram of some of the benefits (shown by the green arrows) and drawbacks (shown by the red arrows) of various food waste disposal methods: landfill, incineration, compost and anaerobic digestion. Although recycling reduces the emission of greenhouse gases (abbreviated to GHG in the diagram), mass recycling is still just as reliant on mass transport of food waste as other methods of waste disposal, so some greenhouse gas emissions still occur.
The problem with mass consumerism
Aside from the distinct impact that food waste has on our climate, our mass consumerism in itself is not sustainable. By 2050, it has been predicted that we will need to increase our food production by 50% to feed an ever-growing population. However, we have a limited supply of some resources such as fresh water and farmable land – therefore, new technologies to make for more efficient farming are being developed with increased urgency.
Fertilisers are one possible solution to aid in more efficient farming and are frequently applied to soils to increase crop yield. However, fertilisers can also pose environmental risks. For example, if fertilisers run off into surrounding bodies of water, this can lead to eutrophication, which can influence surrounding wildlife.
The algal blooms that grow as a result of the accumulation of fertiliser nutrients in the water consume the oxygen of a water body, resulting in the death of other plants and animals inhabiting that area. As we increase the demand on the farmers by continuing to buy food we are not using, we put pressure on the system itself to produce more and better food, potentially damaging the surrounding wildlife.
The discrepancy in consumer habits across different parts of the world should not be ignored either; in some areas, a much greater proportion of food waste can be attributed to the consumer than in others. For example, in North America and Europe, consumers are responsible for 61% and 46% of food waste respectively, while in Sub-Saharan Africa consumers only account for 5% of food waste. This highlights that developed regions of the world must address their food waste problems at the consumer level if they are to make a significant reduction in the proportion of food wasted.
Solutions: don’t throw your toast-compost!
There are several solutions to the food waste problem which can be implemented on both an individual level and a national level. One way to reduce food waste is to use large-scale composting facilities, but one issue with these is that damaging greenhouse gases are still produced in the mass transport of food. Home composting is a popular alternative and is accessible to virtually anyone with a garden, allowing individual households to easily recycle food.
On depositing food in a compost heap, the organic matter is gradually converted to compost over several months of digestion by microorganisms. As long as the compost is prepared properly, with frequent aeration, unpleasant smells can be avoided. However, a common complaint is that it is a time-consuming process and takes up space.
Alternatives to home composts include wormeries and bokashi bins (anaerobic fermenters) to expand the accessibility to those in flats and smaller accommodations. These allow the disposal of food waste in a smell-free, convenient manner. Bokashi employs specialist bacteria to ferment food waste into usable soils in a shorter amount of time (around ten days) in comparison to other composting methods.
People can also take responsibility for their food by taking advantage of evolving technologies. Mobile applications such as Too Good to Go help to minimise food waste from restaurants and cafes by allowing them to sell food they would otherwise dispose of at lower costs to customers. This is a more sustainable alternative to other takeout methods as it helps to minimise the carbon footprint of the company and the consumer. Other apps, such as Olio, have been developed to connect communities, allowing people with surplus food to anyone who might be in want of whatever is going spare. This allows the redistribution of food and a reduction in the amount of food going to waste.
Overall, there are many steps that individuals can take to minimise their food waste and help to lower their carbon footprint. These methods bypass the typical routes food will go through to landfill or incineration and allow the food to be recycled into soil or eaten by someone who needs it. However, where food waste is unavoidable, governments need to take an active role in redirecting food waste to composting and anaerobic digestion facilities and placing tighter restrictions on businesses.
The impact of food waste on global food security and the environment is beginning to be recognised globally by most governments-countries such as France, the Netherlands and Japan are just a few examples of countries that are currently taking big steps to overcome this issue.
The UK government first came forward in 2018 with a plan to eradicate food waste, which was particularly focused on motivating businesses to reduce their food waste, but also included strategies to improve consumer food storage and educate consumers about how best to store their food. The UK Environmental Secretary, Michael Gove, stated: “Nobody wants to see food go to waste. It harms our environment, it’s bad for business - and it’s morally indefensible.”
Why should we care about food waste?
Food waste is unethical and preventable. As humans, we are massively draining the world’s resources, cutting down forests for farmland, poisoning rivers, and eradicating entire species of plants and animals in the process of catching up with the increasing demand for food. However, as the statistics have shown us, we do not need, or even use all of the food we buy. Most of it ends up in landfills or incinerators, and only occasionally is the energy from food waste recycled in some way.
These landfill sites and incinerators produce the greenhouse gases that are contributing to climate change, the consequences of which are already observable in the form of increased forest fires and flooding across the world. They also produce air pollutants and particulate matter which harm the air quality in areas surrounding the incinerators and landfill sites and put everyone at risk.
This lack of recycling is not only damaging our quality of life but also risks the future of humanity and our world as a whole. Food waste will continue to be a problem in many countries until our perspectives on mass consumerism change and we begin to become more considerate in our purchases and storage of our food. We will all need to make progress towards a change in attitude towards food, one meal at a time.
BSc Biological Sciences
Imperial College London