COLIN BARRAS
With vegan lifestyles becoming more popular, and food manufacturers printing carbon footprints on their packaging, we wonder what it really takes to eat a diet that doesn’t damage our planet
Colin is a freelance science writer. In this issue, he finds out the best ways to reduce the carbon footprint of your diet.
Look at a packet of Quorn mince and you’ll discover that a 75g serving contains 10.9g of protein, 3.4g of carbohydrates and 0.4g of saturated fat. Later this year, a glance at the packet will tell you something else: that producing the 75g serving released the equivalent of 0.16kg of carbon dioxide into the atmosphere.
Since 2011, Quorn Foods has been working with researchers at Sheffield Hallam University and Innovate UK, a nondepartmental public body, to calculate the carbon footprint of its meatless products. Now it has had the information certified by the Carbon Trust, and plans to add it to product packets later this year. Doing so should, says Quorn Foods, “better [inform] people who want to understand the environmental impact of the foods they buy”. But will the move really help Britons understand and lower their dietary carbon footprint – and how close can we get to a zero-carbon diet? Judging by the volume of media coverage on the subject, consumers are increasingly interested in cutting their carbon footprints. Focusing on food is a good place to start. According to a 2012 study, food-related processes release about one-fifth of the UK’s total annual greenhouse gas emissions, or 167 million tonnes of CO2e. (Greenhouse gas emissions are often measured in CO2e – carbon dioxide equivalent – for simplicity. This is a single measure that includes the warming potential from all greenhouse gases emitted by a given industry, including carbon dioxide, methane, nitrous oxides and so on.)
NO MEAN FEAT
There’s another reason why Brits wanting to lower their carbon footprint should begin with their diet: it’s one aspect of our lives over which we have a relatively high degree of control. “Many people are in rental accommodation so there’s little they can do to make their home more energy efficient, and they don’t necessarily have much choice about transportation to and from work,” says Prof Peter Scarborough at the University of Oxford, who researches population, nutrition and sustainability. “But diet is absolutely something they can choose to change.”
This doesn’t necessarily mean that footprint labelling on food will help UK consumers lower the carbon cost of their diet. For
several years now, nutritional ‘traffic light labels’ have been added to some foods. Scarborough has conducted research into the way UK consumers respond to such traffic light labelling, but has found that it is difficult for people to use the information to make decisions.
If, for instance, one product has two ‘green lights’ and two ‘red lights’, a consumer might legitimately wonder whether it is healthier than a rival product with one ‘green’, one ‘red’ and two ‘ambers’. Likewise, a consumer standing in the food aisle might find it difficult to quickly work out whether the carbon footprint of a pre-prepared Bolognese sauce is higher or lower than the carbon footprints associated with a tray of minced beef, an onion, some fresh basil and a bag of fresh tomatoes.
Speaking of tomatoes, they highlight another problem with carbon footprint labels: apparently identical food items can differ drastically in their carbon costs. Last year, Prof Adisa Azapagic and her colleagues at the University of Manchester published a study on the environmental impact of vegetable consumption in the UK, including the carbon footprints that different vegetables carry. Azapagic’s team concluded that putting one kilo of UK-grown fresh tomatoes on the British dining table produces 12.5kg CO2e. Perhaps surprisingly, putting one kilo of foreign-grown tomatoes on the table produces just 1.3kg CO2e. The explanation for this, says Azapagic, is that the climate in the UK means tomatoes must be grown in greenhouses that are heated mainly with electricity. Spanish tomatoes don’t carry this carbon cost because tomato plants thrive in warm Mediterranean fields.
This neatly punctures another popular misconception: that imported products must have a higher carbon cost than local food because of transportation. A lot of food is transported by boats and lorries rather than planes, and in environmental terms the cost of transportation is usually tiny compared with the cost of actually growing the food. “Even when you account for transportation, the Spanish tomato still has a much lower carbon footprint than the British,” says Azapagic.
VEGETATIVE STATE
So, if eating local won’t make a difference, what will? The answer, says Scarborough, is to eat less meat. In 2014, he and his colleagues calculated the carbon footprints of various British diets. A meat-eater diet released between 4.7 and 7.2kg CO2e each day depending on how much meat it contained – the vegan diet released just 2.9kg CO2e. Vegetarians and people who eat fish but not meat came out in-between: their daily diets released 3.8kg and 3.9kg CO2e respectively.
One reason meat has such a high carbon footprint is that livestock is typically fed grain that could instead be given directly to humans. Animals then use the energy in that grain for all manner of processes including maintaining body temperature and keeping their internal systems functioning. A relatively small
“EVEN WHEN YOU ACCOUNT FOR TRANSPORTATION, THE SPANISH TOMATO HAS A LOWER CARBON FOOTPRINT THAN THE BRITISH TOMATO”