Fancy a curry? Curry is one of the nation's favourites but the price we pay for a ready-made plateful isn't just the one on the carton
Adisa Azapagic unpacks the carbon footprint of her evening meal and asks if we should be worried about it...
You know the feeling - the end of a hard day at work, no time (and, in my case, no inclination) to cook. So you do what 30 per cent of Brits normally do: stop at a supermarket on your way home and buy a ready meal. What is it going to be? Tonight I fancy lamb curry. Mmm - looking forward to it.
But because of my research on environmental impacts of food, I know my lamb curry has the carbon footprint of around 6kg of carbon dioxide equivalent (CO2 eq.) per person*. So it may be tasty and convenient, but by choosing and eating this curry I will have contributed to climate change, through the greenhouse gases emitted on its journey to my plate.
But so what? Should I worry about it? Probably not, if I was the only person in the country favouring convenience. But I'm not, and the lamb curry ready meals eaten in the UK every year - just lamb curry, not the many others - have an annual carbon footprint equivalent to 140 million car miles - that's 5500 car trips around the world.
We've estimated this based on the figure of 30 per cent of adults in Britain eating ready meals at least once a week. Curry, as one of the nation's favourites, accounts for up to 10 per cent of ready-meal sales, which have soared during the recession.
Every stage of the meal's life cycle emits greenhouse gases. Rice paddies and sheep give off methane, a greenhouse gas 25 times stronger than CO2. Sheep (and cows) also emit methane because of their digestive systems. Fertilisers used on land emit nitrous oxide, which is 300 times more potent than CO2. The vehicles that transport the ingredients to the manufacturers and take their products to the retailer, burn fossil fuels, which in turn produce CO2. And that's before you've even driven to and from the shop and cooked your meal.
The main contributors to the carbon footprint are the meal's ingredients, which emit around 70 per cent, with the lamb alone contributing more than half of the total. Meal manufacture adds a further 10 per cent and packaging 5 per cent.
Despite popular belief, the contribution of transport is relatively small, adding less than 2 per cent to the total. In contrast, refrigeration of ingredients and the meal contribute around 10 per cent, largely due to leaking refrigerants which are powerful greenhouse gases. You get a similar picture for most meat-based foods.
So, what could we do to reduce the carbon footprint of the food we eat? Our research shows there are at least two things: eat less meat - particularly red meat - and cook more at home.
For example, if we were to eat the same ready-made curry made with chicken instead of lamb, the total carbon footprint would go down from 6 to around 3kg CO2 eq. per person - simply because sheep and cows emit methane, while chickens and turkeys don't.
The same lamb curry prepared at home would have a carbon footprint up to 15 per cent lower, mainly because you cut out meal refrigeration at the retailer, but also because you'll typically waste less food.
We have found that even more elaborate meals made at home, such as a traditional Christmas dinner, have a lower carbon footprint than ready-made lamb curry, coming in at only 2.5kg CO2 eq. per person.
We are currently researching how we can reduce the environmental impacts of our food and diet across the whole of its life cycle, from agriculture to food processing to the way we prepare food at home. We have developed a free tool, CCaLC, to help the food industry and consumers find out the carbon footprint of hundreds of different food items.
You can use the tool to look up different meal ingredients, or to prepare your own meal virtually by adding the ingredients of your choice, 'transporting' and 'cooking' them. You can compare the carbon footprint of different meal options to help you choose the lowest carbon alternative. We have also developed a simplified version, CCaLC Lite, for android tablets and mobile phones, which is fun to play with (we think!). It includes the carbon footprint of lamb curry.
Which reminds me - I can hear the microwave beeping so I'd better go back to my dinner. Tomorrow, I may cook at home - just food for thought...
PS. Even the French are at it. Apparently, the largest M&S store in Paris sells more chicken tikka masala than any UK branch. Bon appétit!
* This measure includes all greenhouse gases, such as carbon dioxide, methane and nitrous oxide, emitted in the life cycle of this meal, from farm to plate. Some of these are stronger greenhouse gases than others, so they are scaled to give an equivalent measure in CO2.
Adisa Azapagic is Professor of Sustainable Chemical Engineering at the University of Manchester, where she leads the Sustainable Industrial Systems group.
Article appears in: Planet Earth Online feature.