Supermarkets are huge sources of carbon emissions, single-use plastic and food waste, so how do they compare?

Plastic bottles


Supermarkets are on the frontline in the fight against climate change. Their sheer size and dominance mean they are major contributors of greenhouse gas emissions, plastics and food waste.

What’s more, their future existence depends on getting these issues under control – having resilient, dependable supply chains will be key to their survival as staples in the UK’s economy.  Supermarkets face sustainability issues on multiple fronts.

Firstly, their operations – powering their shops, refrigerators, delivery vans and depots, packaging their products and handling their waste. And secondly, the products they sell have big environmental impacts, whether it’s carbon emissions from shipping them across the world, or issues such as deforestation and water use in their production.

They also play a key role when it comes to influencing both consumers and suppliers – what they stock, as well as how it’s labelled and priced, can all make a difference. How their businesses compare when it comes to key environmental sustainability issues is crucial but hard to find out.

That’s why we’ve dug deep into their annual reports, crunching the data and asking the difficult questions to find out which are the greenest grocers of them all – and what more needs to be done.

Lidl and Waitrose jointly top our overall table as the greenest supermarkets. Lidl might be best known for its prices but it seems its ultra-efficient business model that keeps these low also helps make it the greenest of the big UK supermarkets.

Its carbon emissions are lower than almost all the others and it has a very ambitious target to reach net zero. It produces smaller amounts of plastic for the volume of items it sells than most rivals and has one of the highest proportions of own-brand plastic that’s recyclable in household collections.

However, it’s near the bottom of the table for its food waste.  Waitrose did very well on plastic use, as well as achieving relatively high scores on greenhouse gas emissions and food waste.

Together, they are both clear leaders of the supermarket pack.  Iceland sits at the bottom in our analysis, performing worst on greenhouse gas emissions by a fair way. This might be due to its focus on frozen food, which requires energy-hungry cold storage. It also uses the most plastic relative to the number of items sold. One positive, however, is that it does relatively well on food waste.

How we compare supermarket sustainability

Our groundbreaking research is the first to compare shops on a range of sustainability criteria, including their first full year of mandatory greenhouse gas emissions reports.

Most supermarkets publish these figures in their annual reports, but in order to compare them fairly we also worked with the supermarkets to acquire the most accurate and directly comparable data available.

To make it as fair as possible, we used intensity measures for some key data – measuring greenhouse gas emissions per million pounds sterling of revenue, and plastic use per 100,000 grocery packs sold. And similarly, we looked at food waste not as an absolute total, but as a proportion of the food on sale.  We compared greenhouse gas emissions from the supermarkets’ entire operations – including stores, deliveries, warehouses and other services – which they directly control.

Wider supply chain emissions can be more than 90% of the total, so are crucially important, but none of the supermarkets report comprehensively on these yet, so we couldn’t include them.  It’s worth noting that these retailers have different business models, which inevitably affect these comparisons – whether it’s online-only Ocado with more delivery-related emissions or Iceland using more energy for its freezers.

We compared operational emissions, which are referred to in the industry as ‘Scope 1 and 2’. These are the ones that companies can reduce most easily, by using energy more efficiently and switching to low-carbon and renewable fuels.

Aldi, Co-op, Iceland, Lidl, M&S and Tesco all told us they use 100% renewable energy in stores. While commendable in terms of supporting a greener energy market, our green energy research shows some renewable tariffs are greener than others. Therefore, we’ve compared carbon dioxide emissions using the average emissions factor for the national grid, as reported by supermarkets themselves, per million pounds of revenue.

All the supermarkets we surveyed have a net zero target date, meaning that they are aiming for a point at which they will remove the same quantity of greenhouse gases from the atmosphere as they emit.

Iceland’s emissions intensity is almost four times that of the lowest emitters (Aldi and Lidl). That means every pound spent in Iceland results in four times the emissions of a pound spent in the other discounters.

Although supermarkets don’t comprehensively report supply chain emissions (referred to as Scope 3), they do plan to reduce them.

Supply chain emissions are harder to control, requiring the co-operation of a global network of producers, manufacturers and distributors.

The supermarkets all plan to make their plastic packaging 100% reusable, recyclable or compostable by 2025 at the latest. By weight, 94% of Co-op own-brand plastic is already recyclable at home, with the remainder recyclable in-store. Ocado has further to go: less than 40% of its own-brand plastic is recyclable at kerbside.

M&S told us it aimed to make all food packaging recyclable by the end of this year.

Using less plastic is better for the environment than recycling, so we compared how many tonnes of plastic each supermarket puts onto the market annually, per 100,000 items sold. We found that Iceland’s plastic intensity was the worst, while Waitrose does the best. We found buying a basket of 20 items at Iceland could result in 73% more plastic packaging than buying 20 typical items at Waitrose.

We’re pleased to see that no UK supermarket sends food waste to landfill, and they’ve all pledged to cut food waste by 50% by 2030. Tesco and Ocado redistribute the majority of their surplus food for human consumption (eg. to food banks), while the rest send the majority for anaerobic digestion (AD) to be turned into biogas and compost. M&S also told us it has donated 34 million meals to charity since 2015.

We asked supermarkets to report the amount of food waste going to AD as a percentage of their total weight of food sales.

Ocado does best, at just 0.04%. Aldi, Co-op, and Lidl’s food waste is considerably higher at around 1% of total food sales. For every kilo of food bought at these stores, around 10g of food is wasted; at Ocado, it’s just 0.4g.

How you can make a difference

Many of these issues can seem beyond the power of ordinary consumers, but there are important ways we can act.  Your individual circumstances – where you shop, what you buy, how you get there, and what you do with the food once home – all make an impact. Only you will know where you can make the best, and most practical, changes for your household.  There are key choices you can make in the supermarket aisles – here are some of our top tips:

Follow the seasons: Fruit and veg that’s naturally in season is more likely to be produced locally without using a heated greenhouse. Look for UK-grown produce, and get them when they’re at their best. They are usually better value then, too, so buy in bulk and preserve or freeze them to enjoy all year round. Out-of-season food can be grown sustainably in warmer climates, but avoid any that’s air-freighted, as flying adds a big carbon footprint.

Waste not, want not: Plan meals and write a shopping list so you’re less likely to buy more than you need. Don’t be tempted by two-for-one offers, especially on perishable items, unless you know you can use or freeze them. Buying in bulk can reduce packaging, but if you can’t eat it all immediately, freeze portions for later. Remember the ‘sniff test’: food can still be eaten beyond ‘best before’ and ‘display until’ dates – just use your judgment.

Shop ‘naked’: Avoid plastic packaging by buying loose, unpackaged groceries. Take your own reusable produce bags for fruit and veg, and jars or lidded containers if your supermarket has refill stations for dry goods such as pasta or cereals. Some shops also allow you to fill your own container with deli products. Look out for easily recyclable paper and cardboard packaging, and choose refillable products, which are generally better for the environment.

Be flexible: A ‘flexitarian’ diet includes more plant-based foods, while still allowing for some animal products. Beef, lamb and dairy have the biggest carbon footprints in our diet, so try replacing some of your red meat intake with vegetables and pulses, which are often cheaper and healthier as well as better for the planet.

There’s a wide range of dairy alternatives too, with oat milk and pea milk considered to be among the most sustainable choices. Find out more about milk alternatives and how to buy the most sustainable seafood.

Choose an eco slot: Online deliveries can be a lower-carbon option, with some supermarkets offering ‘eco’ or ‘green’ delivery slots, where their drivers are already delivering in your area.

And although you might realistically need to rely on your car for the weekly shop, if you happen to have a short shopping list, walking, cycling or using public transport will all help to cut your petrol bills as well as your carbon footprint.

What supermarkets should do

We’ve looked at three of the biggest environmental sustainability issues to create our greenest grocer league tables. But it’s only the start of the story – other issues to consider include water use, deforestation, organic production, sustainable fish, and biodegradable cleaning products, for example.

These are mostly further down the supply chain, beyond the scope of the supermarkets’ direct operations, and comparable data can be hard to find. We want every supermarket to set ambitious greenhouse gas reduction targets, for their own operations as well as the wider supply chain, with clear steps to reach them.

They should also eliminate unnecessary plastic and make their own-brand plastic as widely recyclable as possible – and labelled as such. Plus, we’d like to see a focus on food waste: it’s simply not good enough that Aldi, Co-op and Lidl have 24 times as much food waste proportional to their size as Ocado, for example.

Big brand packaging investigated

We have investigated the packaging of popular groceries over the past few years. Our latest grocery packaging investigation, conducted in September 2020, looked at 89 best-selling brands like Cadbury and Coca-Cola. Our analysis found only just over a third had packaging that was fully recyclable in household collections.

And almost four in 10 had no labelling to show if it could be recycled. And there were big differences in packaging for very similar products.  Some brands use easily recyclable packaging, while others offer almost-identical products with packaging that’s very hard to recycle.


What is the UK Plastics Pact?

Almost all of the UK’s major supermarket chains have signed up to the UK Plastics Pact, which launched in April 2018. The pact, led by sustainability experts at WRAP (Waste and Resources Action Programme), aims to tackle plastic waste by bringing together businesses from across the entire plastics value chain, UK governments and NGOs.

More than 120 organisations, including major food and drink brands, manufacturers, retailers and plastic reprocessors, have signed up to hit a series of targets by 2025.

These include: Eliminate problematic or unnecessary single-use plastic packaging through redesign, innovation or alternative (re-use) delivery models. 100% of plastic packaging to be reusable, recyclable or compostable. 70% of plastic packaging effectively recycled or composted. 30% average recycled content across all plastic packaging.

What is government doing about plastic?

A UK government ban on single-use plastic straws, stirrers and cotton buds came into force in October 2020. And the Government plans to introduce a tax on plastic packaging with less than 30% recycled plastic in April 2022.  But Which? still believes more needs to be done.  Clear recycling labelling would make a big difference. We know 67% of Which? members often or always look for recycling info on grocery packaging before deciding how to dispose of it.