HOW we eat is a significant factor in how big our greenhouse emissions are. It's a key part of the story of how we change, globally, locally and in our own kitchens, to avert climate crisis. But it’s often hard to work out where to start, or what are the worst culprits in our shopping baskets. This guide to a few plates of food offers some idea of what has the biggest impact. What's the beef on steak? Is it time we dethroned King Prawn?

We have taken five different dishes, made from ingredients easily available in supermarkets, and crunched the numbers on carbon impact. From these figures it's possible to see how local, eating seasonally, swapping some meat for animal proteins and looking at our portion sizes can have an impact. But we also need to urge our government to push for a change in our supply. This is a challenge for all of us – government, farmers, retailers, consumers. It’s not just what’s on our personal plates that needs to change, but our national larder.

Note: Not all of the greenhouse gas impact of these foods is made by CO2. Other gases are included and their added-together impact is expressed here as what the equivalent in CO2 would be, or as CO2e.

The King Prawn Stir Fry

Farmed King Prawns

75g = 123kg CO2e

Two years ago a study revealed the shock news that king prawns were, by its calculations, worse in terms of emissions than beef. What it said was that around 1603kg of CO2e was produced per kilogram of prawns. That figure was derived by factoring in the fact the aquaculture lagoons in which the prawns were being farmed were created by destroying the mangrove forest. These tropical forests in saltwater are considered a vital storage system of what’s called “blue carbon”. Previously such farmed shrimp were found to result in lower greenhouse gas emissions than wild caught prawns – as North Atlantic prawn fishing involves extensive trips using up huge amounts of fuel.

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Since then the Vietnamese government has said that they are working to improve the way the country farms prawns, and setting new targets for sustainability – though many still continue to farm intensively.

For a lower carbon option, replace with Scottish rope-grown mussels with emissions of only 250g per kilogram.

Red pepper

80g = 470g CO2e

A 2009 World Wildlife Fund report listed that peppers grown in the UK produced around 5.88 kg CO2 emissions. Those grown in warmer parts of Europe release less, at 3.12 kg CO2.


50g = 250g CO2e (air freight) or 20g CO2e (sea)

Mangetout sold in UK stores mostly comes from Africa, arriving predominantly by air, though some does make its way by sea freight. Mike Berners Lee lists mangetout as one of a number of vegetables that are likely “when out of season, to have been air-freighted or (just as bad) grown in an artificially heated greenhouse.”


75g = 260g CO2e

Noodles and pasta are mostly wheat, which causes emissions of around 0.5kg of CO2 per kilogram in the UK.

Cashew nuts

25g = 26g of CO2e

Just round 1.06kg of CO2 released per kilogram of cashews. However labour conditions in the cashew industry are so bad they are sometimes called "blood cashews".

Steak, Tatties and Veg

Sirloin steak

225g = 5 to 10 kg CO2e

The chief reason beef has its huge impact is that cows burp methane, a greenhouse gas 23 times as potent as carbon dioxide. As with most foods, the story around beef isn’t simple. One steak’s emissions aren’t the same as another – and the impact varies widely according to how the beef has been farmed, what the cattle are fed on, what breed they are, and whether they are reared on land cleared by deforestation. It has been calculated that beef raised on deforested land is responsible for 12 times more greenhouse gas emissions than cows on natural pastures. Since Scotland was deforested long ago, this isn’t a factor considered with Scottish beef.

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In Scotland we produce a lot of beef – more than we eat. Are the emissions from a nice grass-fed steak, farmed in Scotland, far better than the global average? And if so by how much? This is a debate that rages. One recent study found that grass-fed beef actually has a higher carbon, as well as land-use footprint. However, research from the Rowett Institute in Aberdeen has also found that a substance found in plants in biodiverse pasture systems added into the diet of lambs reduced emissions of methane by 70%.

The range among farms is huge. But whatever the variation, it remains that case that beef emits 20 times more GHG emissions per gram of edible protein than common plant proteins, such as beans.

Meanwhile, there is still hope for steak lovers. The notion of breeding or bioengineering low emissions cattle has gained a lot of traction recently. Researchers in Scotland have shown that some cattle have a gut flora that produces less methane, and speculated on the possibility that cattle could now be bred for this. There have even been experiments in putting a small amount of seaweed into cows diet – which has resulted in decreased emissions from cow burps.


200g = 80g of CO2

Tatties are low carbon footprint pleasures. According to Mike Berners Lee, author of How Bad Are Bananas 1kg of boiled potatoes, cooked gently with the lid on produces 620g of CO2. Much of this is produced by the boiling of the potatoes and less than 220g can be attributed to the growing.


50g = 110g CO2 equivalent (lower if local grown in season)

Stilton Cheese

25g of Stilton: 350g CO2

Though our UK consumption of meat has been falling, our appetite for cheese,m also produced by methane-burping ruminants, keeps rising. While it’s hard to find a greenhouse gas figure for stilton, calculations do exist for cheddar, of around 14kg CO2 equivalent per kilogram.

Veggie brunch

Scrambled eggs

2 eggs = 733g CO2e

As animal protein sources go, eggs are about as low as it gets. A dozen eggs produce around 2.2kg of CO2e. However, again, numerous factors, around the style of farming, transporting and packaging impact on this. Mike Berners Lee observes that a study from Cranfield University suggests that, in terms of climate change, organic eggs are about 25 per cent worse than those from battery farms. He says, “It’s worth remembering that climate change is not he only issue. If you care about animal welfare as well as climate change, buying fewer eggs but making them organic might be a sensible compromise.”


40g = CO2e

University of Manchester researchers looked at sliced loaves and found footprints ranging from 977 to 1244g CO2 per loaf. They said, “Wholemeal thick-sliced bread packaged in plastic bags has the lowest carbon footprint and white medium-sliced bread in paper bag the highest.”


Half = 211g CO2e

We're now so barmy for the avocado it’s hardly possible to buy a brunch without a splurge of green. This obsession is having its impact. Mexico’s avocado boom has also been blamed for deforestation. A study by Carbon Footprint Ltd found that a small pack of two avocados transported into the UK from Chile had an emissions footprint of 846.36g CO2. Factors included were the energy, water, fertiliser and pesticide required to grow them as well as the resources used for packing and the energy used in processing and transporting.

Cherry tomatoes

50g = 100 to 250g of CO2e

Our beloved cherry tomatoes come with a sting. Those farmed in the UK are mostly grown in greenhouses heated by gas and oil. Overrall Spanish tomatoes rate better. One ten-year-old study found that UK cherry production in stand-alone heated houses created over five times the amount of greenhouse gases as the production and transport of their Spanish equivalent. However, a new generation of high-tech UK greenhouses is becoming more energy efficient. But, without a carbon footprint label on your packet, how can you tell which ones?


50g = 700g of CO2e (estimated from general cheese figure)

The UK is the number one export market for Cypriot halloumi cheese, this sheep's cheese the go-to replacement for bacon in a veggie diet. But cheese, of any type, creates high emissions. The fact that it is sheep’s cheese actually makes it slightly higher, since sheep produce more methane.


100g = 100g of CO2e

Fish and chips

Entire meal = 1.5 kg CO2e

A WWF report estimated that 1.5kg CO2 emissions would be produced by a plate of fish and chips – "the equivalent of 8 miles driving in the average UK car." Of that, 900g was contributed by the cod, just 100g the potatoes. UK chippies are still predominantly using cod and haddock (slightly higher carbon footprint than cod), but it’s possible, in the supermarket to pick up alternative fish, including the Vietnamese pangasius or pollock, which are slightly lower emissions. Bear in mind that most wild fish are in danger of overfishing and that farmed salmon has amongst the highest fish emissions levels.

Fruit salad


50g in season = 40g CO2 equivalent

When Scottish strawberries are in season there's no low emissions treat quite like them. Grown without heating, they come in at 800g per kg. However, outside the season, you have two choices, neither of them good. The first is to buy strawberries grown under glass in the UK, which emit, on average a massive 4kg for every 1kg fruit produced. The other is imported strawberries, most likely flown in, and with air miles related emissions.


Half banana = 120g CO2 equivalent

Mike Berners Lee describes Bananas as “a great food for anyone who cares about their carbon footprint.” This, he observes is because they are grown in natural sunlight, need hardly any packaging, and keep well during transport. “Although,” he writes, “often grown thousands of miles from the end consumer, they are transported by boats (about 1 per cent as bad as flying).”


50g in season = 25g CO2

Blueberries are in season in the UK between July and September, so out of that time you’re going to have to buy them either hot-housed, or imported.

Four tips for going lower carbon

1. Buy local – unless it's hot-housed, out-of-season fruit and vegetables.

2. Buy seasonal.

3. Campaign for the government to change the food supply by setting up the right subsidy programmes for agriculture and regulating retail. The Good Food Nation bill is currently going through parliament and there’s still a chance to be heard.

4. Replace some of your meat and dairy with plant proteins