Are you wasting food?

Monday, November 27, 2017

Food waste

When we think about food waste we become emotionally involved- we make the link between hungry, poor people, and the food we throw away, often untouched and edible. It seems immoral, doesn't it? And this emotional connection forces us to reason about how we can change things.

In this article, we try to trace where food waste comes from, measure how much there is, think about the impacts and talk about how we can prevent throwing food away and when we have to, how to make sure it goes to the right treatment. We try to help you understand how your own behaviour can be modified to make a positive impact for the global environment. 

What is food waste?

Well, let's get one matter out of the way immediately.  We have to distinguish between what is avoidable food waste, and what is not. I would argue that banana skin, fish bones, meat fat, bones and gristle, fruit and vegetable peelings, are not food waste. We can feed some of these to animals if we possess them but unless we own pigs or a goat, that is, if we live in a city, we are unlikely to be able to do so. Country folk have that option, using their animals as a treatment system for food waste, and where possible, this is a great solution. City slickers can’t do that.

I would argue that an orange gone mouldy is avoidable food waste because if we were not going to eat it, we should not have bought it. Once it is black and inedible it becomes waste but waste we could have avoided making. And this applies to dairy products gone mouldy, fruit and vegetables allowed to go rotten, fish allowed to become smelly, bread that goes stale - yes, these have become waste but by planning our purchases and meals better, we could have avoided much of this waste.

Life is not perfect and we should not be too hard on ourselves- an impromptu night out means the planned meal sits in the fridge and could become unpalatable the day after.  We may just not feel like eating the fruit we bought a few days ago; the cake your favourite aunty brings round just may not be to your liking. You can give it away, but sometimes that is hard too. So, let's stop feeling guilty about sometimes not being able to eat it all and work positively to improve on our current habits without beating ourselves up.

WRAP estimate that in the UK of the 7,3 million tons of food waste thrown away by households some 60% (4.4 million tons) could have been eaten; roughly therefore 40% is unavoidable. Click here for more info. 

That can depend upon seasons, location, local events like a fete or concert occurring, or simply something like a product batch having to be rejected by a shop or producer.  Food waste varies throughout the year, from city to countryside, from country to country. Someone living and working or retired at home, or in a rural context, is more likely to cook for themselves and produce more food waste than a city office worker, whose food is bought processed and pre-packed. Here he/she will produce more packaging.  Someone working in a factory with a staff canteen will individually produce no food waste during their time there- but the canteen will. 

You can do the measurement yourself at home.  Supply yourself with two food waste caddies, with their compostable bin liners to improve the aeration and avoid odours. Over the course of one week put in one all that food which you throw away uneaten. The rotten tomato, the sour yoghurt, the mouldy cheese, stale bread, and so on. In the other put the leftovers of eaten food like bones from fish and meat, peelings from fruit and vegetables, cheese rinds, meat trimmings etc. 

At the end of the week, look at which contains or weighs more.  Do this once a week for a few months and see how the characteristic of your food waste changes with the seasons- for example, more salad trimmings, water melon skins and pineapple cores in the summer; more waste from potatoes, vegetables, roast meals, stews and soups, during the colder months. This will help you understand what can be avoided and you may decide to purchase less of that when you next go shopping. 

Sources of food waste

But that is only part of the story, the part we see as householders and consumers. In the UK, this amount of household food waste is estimated to be somewhere in the region of 7,3 million tons, around 110 kilos per person per annum or two kilos a week each.

Then we have to add to that amount the waste produced through the production, transport and retail chain. Best estimates for the UK come from WRAP and the total is estimated to be around 1,9 million tons annually. Click here for more info.

Surprisingly, contrary to most of our perceptions, food waste produced at the retail stage (supermarkets, shops and markets) is a small proportion of the total, around 200,000 tons.  When you think about it, that makes sense. Why would a retailer selling food want to waste it? That would mean throwing away not only resources but money as that food is paid for, even if not sold to a final consumer. So naturally, the retail industry works hard to reduce its food waste and thus reduce the money it throws away.  More could be done. In France and Italy laws exist to oblige shops to give away to charity those foodstuffs remaining unsold whose sell-by date has arrived. Charities then distribute these foods to foodbanks for low income or homeless consumers to take for free. 

In the UK many shops, stores and supermarkets operate voluntary schemes which have the same finality. Examples are Fareshare (, Foodcycle ( and the Felix Project ( and many others. Above all retailers are working hard on reducing the waste before having to give it away; Sainsbury's and Tesco are examples whilst just this month (November 2017), all major UK supermarkets agreed to measure and publish their food waste data.

Restaurants and catering industries are another large source both of avoidable and unavoidable food waste. Awareness of how to avoid wasting food is growing through these sectors but given their nature, is harder to penetrate.  A cook will discard products which he thinks are not suitable or good enough for his kitchen; buffet lunches and dinners will tend to cater for more mouths than they will eventually feed; preparing food for large gatherings creates more waste as it is difficult to judge how much each person will eat- some may eat nothing. 

The really large amounts of food waste however, are those we don't see- in the farming and transformation industries.  We especially do not see the waste produced in other countries that export their food to us.  A Kenyan bean farmer that has to cut the bean tips and tops to fit the supermarket packaging requirements, keeps that waste there. We don't see it nor do we count it among our own waste, but our market criteria create it. And as we import a lot of food which is in some way prepared or trimmed, that food waste constitutes a significant volume.

Fruit and vegetables discarded in huge volumes, either because they are blemished "wonky veg" or go unsold due to market conditions, represent volumes we cannot imagine. The UN Food and Agricultural Organisation estimate globally 1.3 billion tons of food waste is produced annually, and this is increasing.  

Most of that is the waste derived from growing and producing food. An area equivalent to the land area of China is planted and produces food which we then throw away each year. 

In warm developing countries, the lack of transport infrastructure and refrigerated storage facilities lead to food rotting quickly, adding to losses from production and transformation.

So, farming, storage, transformation, retailing, catering and domestic are all sources of food waste.

Depressing? Let's not be depressed. The world has made a wonderful job of affordably feeding a growing population. Food prices have risen more or less only in line with inflation as measured since 1970 until today, but global population has doubled in that same time.  In OECD countries food represents a declining amount of our total income. On average an American will spend just 8% of income on food, whilst a poor city dweller in India will spend 30%.  Food has become relatively cheaper as our quality of life has improved, and this is one of the reasons we think we can afford to waste it.

The impacts of food waste

Why is the food waste issue so important? 

As we will read further below in the paragraph on collections, untreated food waste has negative impacts on the environment.  Fermenting, it produces gas which is a mixture of methane and CO2.  Whilst a single rotting fruit won't ruin the climate, 1.3 billion tons of rotting food waste are contributing to climate change. The World Resources Institute estimates that were emissions from food waste to be quantified as a nation, it would be the third emitter of greenhouse gases after China and the USA. These emissions are happening from untreated food production residues in farms, and food waste which ends up in landfills or open dumps.  

In those situations, the problems caused by food waste multiply.  Rotting waste attracts rodents, animals which feed off it, birds and in tropical climes, mosquitoes.

The local health impact of food waste in open dumps damages the health of around 60 million people globally, according to the International Solid Waste Association. These includes malaria, dengue fever, respiratory problems, sanitation impacts from polluted water tables.  Large open dumps represent the most polluted sites on Earth. Click here for more info.

Beyond the impacts of improperly disposed food waste, a situation common across at least 70% of the Planet, the wider issue revolves around the resources used to produce food which is not consumed. The massive use of water for irrigation, the energy, human labour, addition of fertilisers and pesticides to crops, the resulting soil quality depletion and loss of fertility, are all factors which are caused by intensive agriculture.  Add to these the emissions from dairy and beef production (methane emissions from cattle) and the emissions from organic carbon depletion in soils, the transport of food, we can see that the impact of food production represents one of the largest causes of anthropic greenhouse gas emissions.  Of these, “livestock production is the largest, accounting for an estimated 14.5 percent of global GHG emissions from human activities. Meat from ruminant animals, such as cattle and goats, is particularly emissions-intensive.” Click here for more info.

Soil is cultivated to produce 95% of the world’s food, yet we disregard soil fertility and allow soil quality to degrade across the world. Desertification is an increasing threat to soil quality and erosion, pollution and building on soils, also reduces the amount we have available for cultivation.  So, whatever we can do (like use compost to improve soil fertility) to reduce loss of fertile soils is necessary to ensure long-term production of food. We may think this is not a British phenomenon but it is-  just look at the two graphics below.

SOil degradation in the UKDesertification across the globe

Whilst we can reasonably explain the need to feed ourselves and in some way justify emissions from meat production (vegetarians would justifiably disagree); or some loss of soil fertility, it makes no sense that we put humanity at risk from climate change and soil erosion to produce food we are not going to consume. Indeed, it is madness. 

Thus, our need to reduce the food we waste- it is not just about recycling, it is actually a question of enormous importance central to the whole debate about the survival of humanity as a species, reducing the risks from climate change and building agricultural resilience. 

But how to prevent wasting food?

Rather than writing about prevention I suggest you see this very nice short insight in to the Cloud Sustainability eLearning module, that gives you several easy steps to prevent your food waste depending upon where you are producing it.

Have a look through our eLearning module on how to prevent food waste here.


What do we do with the food waste we have and could not prevent?

If you live in the countryside and keep some farm animals you have a ready-made, free, constant treatment source: pigs, goats, chickens, dogs and cats. Since the origins of Man and animal husbandry, we have been feeding our inedible food to animals and we can still do that.  Legally, we are bound by the EU Regulation on Animal By-Products, 142/2011 (and amendments) to prevent animals eating animal waste.  This is an excellent piece of legislation which applies above all to the meat processing and fertilizer industries. Consequently, I suggest that when feeding food left-overs to your animals, you exclude any that contain uncooked meat- meat, bones, fat, fish. Those parts can go to your compost pile or into external food waste collections.

If you live in an urban area, as most of us do, many councils in England, and almost all those in Scotland, Wales and Northern Ireland, offer a dedicated food waste collection service to millions of householders. Given the different schemes implemented from council to council, there is not one single standard collection scheme to describe. However, there are many common features. See further guidance here.

Food waste can be collected in the kitchen in a small 10 litre plastic caddy which is usually lined with a compostable plastic or paper liner bag. The advantage of compostable materials is that they slow down the decomposition of food in the caddy and the bags can then biodegrade naturally with the food content in in-vessel compost plants.  In UK, anaerobic digestion plants which use food waste to produce biogas with a process that is different to composting, food can also be delivered in non-compostable bags as they are stripped out and sent to landfill leaving the food waste content for biogas production.  However, this causes more odours in the kitchen as fermentation is accelerated in plastic bags. In Europe, the stripped-out material is then composted and there, compostable bags are preferred.

In any case, the householder is called upon to separate out the food waste and give it to weekly or fortnightly collections organised by local councils or their service operators. 

What is really important for householders is to ensure food waste is clean- not contaminated with plastics, aluminium foil, glass etc.  The processes for treating food waste all rely upon natural bacterial degradation, and contaminants block these processes. 

Food waste collection has a series of huge advantages on leaving it with other mixed waste. Firstly, being wet, food waste contaminates the dry waste which can be recycled, like paper, cardboard, plastics, textiles, metals.  So, by collecting food waste separately, all the dry fractions are easier to recycle.

Moreover, food waste collection and treatment has another major role to play in the global battle against climate change- when food waste biodegrades, it produces methane gas as we saw above.  If we do not capture this gas, that is when the food waste ends up in a landfill, the methane flows into the atmosphere and helps cause climate change. Methane is reputedly equivalent per ton to 25+ tons of CO2 according to the EPA.

But if we capture that methane through separate collection and treatment in a plant that controls the biodegradation within a closed space, we can use the methane as a fuel. Burning it, we can drive turbines to make electricity; pumping it into the national gas grid, we can use it as a cooking or heating gas at home; refining it, we can use it as a fuel for cars, HGVs and buses; perhaps in the future, for airplanes. Those of us old enough to have seen Back to the Future, will remember Doc’s car fuelled by waste – today, reality has caught up with fiction. 

So, the simple act of separately collecting food waste sparks off a whole chain reaction of virtuous opportunities- more dry material recycling, less waste to landfill, production of compost as a soil fertiliser, reduction of the use of synthetic fertilisers, production of biogas to produce renewable energy and meeting our climate change goals. The extra effort from all of us really pays dividends for the global environment.

Treatment methods for food waste.

Essentially two types of facility exist- aerobic composting (including at home) and anaerobic digestion.

Aerobic means in the presence of oxygen, anaerobic means in absence of oxygen. 

An aerobic process allows microbes to work their way through the food waste and break it down into mulch or humus.  This natural biodegradation process happens in nature every time a leaf falls to the ground; it rots, breaking down into pieces as microbes eat away leaving some mulch, some water and some CO2.  In an industrial plant, exactly the same happens except it is usually in a closed environment to avoid smells permeating into the neighbourhood and infestations of rodents and birds.

Aerobic composting of food waste can take anywhere from 30 to 180 days, depending upon climate, technology used, density of the mass and other elements. As food waste is very wet, it will generally be mixed with garden waste to ensure air can filter through the mass and allow the bacteria to breathe.  Eating away, they gradually turn the waste into a homogeneous material similar to soil called compost. Once this has reached the right stability, and the bacteria have finished their job, compost can then be taken out of the plant and sieved, to eliminate residual contaminants like pieces of plastic. Then it is sold.  The compost produced can be used as a base for gardening media, soil improvers in farming, and even as a remediation cover for degraded soils and sites. Mixed with other materials, compost is the base for many natural fertilisers, substituting fertilisers made from fossil fuels.

 Composting description

If you are lucky enough to have a garden you may also want to undertake home composting of your food and garden waste. Home composting requires some time and effort to get right but can be really rewarding because using your own compost on your garden shows that in- house recycling works, reduces the waste sent from your home, and provides a natural product for your garden. Your worms will approve! You can find a guide here.

An anaerobic process, also known as anaerobic digestion, occurs where food waste is put into a closed vessel and allowed to ferment. In the absence of oxygen which is gradually consumed by the bacteria causing the fermentation, methane gas and CO2 are produced. The retention time of food waste in this vessel, or digestor, can be around 20 to 40 days.  During this time, the methane is emitted and captured in storage tanks. The sludge material which remains in the digestor after the methane is drawn off is known as digestate.

Digestate from the anaerobic digestion process also serves as a soil improver, and like compost contains nitrogen, potassium, humic acids and organic carbon that are all needed to maintain soil quality and help plants grow.

Here is a schematic plan of anaerobic digestion which as we can see shows the many products that can come from our humble food waste collection.

Anaerobic Digestion schematic


When we realise the global impact food waste has upon the Planet, we understand how the daily act of separating it and sending food waste away for treatment can improve the environment.  Not only are we taking preventative measures in terms of reducing emissions of greenhouse gases, or stopping food waste going to open dumps and landfills, we are actually making a positive contribution- producing compost or digestate for agriculture, and energy to power our homes and transport systems.  That humble banana skin suddenly has a value.

Technology is making rapid developments. Pilot scale experiments are already underway to use food waste as a feedstock from which to capture the sugars and starches that can be transformed into bio-based chemicals. One such project ( financed by the European Commission, will use this feedstock to produce biodegradable plastics.  These are materials which biodegrade back to soil when discarded and collected with food waste giving back to the soil part of the nutrients used to produce food in the first place. If this becomes an industrial scale solution, we would have a perfect circularity- food produced from soil, collected with bio-plastics and food waste sent to composting to produce compost that returns to soil. 

This piece is written by our Advisor on the Circular Economy, David Newman.

Related news

Are you wasting food? | Cloud Sustainability

Recruitment: Learning Developer

Monday, February 19, 2018

Read More

April Spring 2016 Newsletter

Wednesday, April 13, 2016

Read More

Leap Year Day

Tuesday, March 1, 2016

Read More