Background guide #1
Food Miles
Thanks in part to concerns about climate change, more people are stopping to consider the impact that everyday goods - including food - have on the environment. So, what are the hidden costs of a weekly shop?
Food miles measure the distance products and their ingredients travel from their source before reaching consumers' tables.
Quick Jump
The rise of food transport
Long-distance food transport is nothing new - from saffron to coffee, food and drink have been traded between nations for centuries. But today we don't just import a few delicacies to supplement local produce.
We truck huge volumes of food around the road networks of the UK and beyond. And we import air-freighted, out-of-season produce from other continents that is expensive to grow at home.
All of this fossil-fuel-powered transport contributes to climate change. A DEFRA report from 2005 estimates that transporting food within, to and around the UK produced 19 million tonnes of CO2 - equivalent to around 5.5 million typical cars.
Air, road and sea
Much of the debate around food miles has focused on air-freight, due to the heavy climate impact of planes. Air-freighting food typically creates around ten times more carbon emissions, per kilo per mile, than road transport and around 50 times more than shipping.
Though air-freight is only widely used for high value perishable products such as out-of-season berries and mange tout, these products account for around 11 per cent of the UK's food-transport emissions .
Still, the vast majority of emissions from food transport - roughly three-quarters - are the result of delivery trucks and consumers' cars on UK roads.
More than miles
The problem with the food miles concept is that the distance travelled by a product is an insufficient means of judging its overall carbon footprint.
Take beef, for example. Even if it's produced very locally, it's likely to have a very large footprint due to the large quantities of methane that cattle emit.
Also, transportation doesn't necessarily make a product's carbon footprint bigger. For example, spring-grown tomatoes produced in heated greenhouses in the UK may have a higher carbon footprint than those grown and imported from hotter countries, even including the transport.
Similarly, according to one highly publicised study from Lincoln University (NZ) lamb reared in New Zealand and shipped to the UK may be more energy-efficient than lamb farmed in Britain on lower-quality pastures.
Consumer choices
What can you do? One response is to walk to local shops when possible, choose British produce in its season and avoid air-freighted foods.
But food transport is only part of the picture. Another effective way to achieve a low carbon diet is to cut down on meat and dairy, and to minimise waste through buying and cooking the right amount of food.
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