(photo by Leslie Duss)
One of the most talked about aspects of eating local food is how it can reduce food miles–the distance that food travels between the farm and your kitchen. The farther your food travels means an increase in the amount of fuel burned, and therefore an increase in greenhouse gas (GHG) emissions, which many scientists agree contribute to global warming. Therefore, the theory goes, shipping tomatoes 2,000 miles from Mexico or lamb 8,000 miles from New Zealand will always create more CO2 emissions than if you plumped for the local option.
Once I started digging into these claims, however, it became surprisingly apparent that straight food miles don’t always tell the whole story.
Scientists at Lincoln University in New Zealand calculated that lamb shipped from New Zealand actually produced far fewer CO2 emissions than lamb raised locally in the UK. New Zealand lamb produced 688kg/ton of carbon dioxide emissions while British lamb produced 2,849 kg/ton. How on earth can this be possible? Well, New Zealand producers had higher-quality pasture land and more sunshine, which meant that they didn’t have to give their animals supplementary feed, as producers in the UK were forced to—feed which required a lot of extra fertiliser, water, and energy to produce.
A report from the UK’s Department for Environment Food and Rural Affairs (Defra) also found that tomatoes grown in Spain or Israel and shipped to northern Europe produced far fewer GHG emissions than tomatoes grown locally in hothouses. How come? The greenhouses in northern climates needed to be heated in cold weather, which required far more fuel energy than was expended in growing tomatoes in an open field and then shipping them north.
And although air shipment produces the most CO2, the method of production still usually counts way more than the flight alone. Kenyan green beans, produced with entirely manual labour and then flown to the UK, still have a smaller carbon footprint overall than beans produced year-round in heated British greenhouses or even in fields treated with chemical fertilizers and farmed with diesel-burning tractors. The same principle applies closer to home. Sean Cash at the University of Alberta’s Department of Rural Economy estimates that, in the case of produce being shipped to Edmonton supermarkets, transport makes up only 1/3 of food’s CO2 emissions—the rest is taken up with production (figure not cited in this article but is in the actual report, available from the researchers).
So what about those exhaust-belching heavy trucks that transport the vast majority of our food? They do get terrible fuel mileage—10mpg or less—and food trucked in from thousands of miles away has to be refrigerated the whole time, which consumes more energy. In contrast, most farmers bringing produce to the farmers’ market don’t need special refrigerated transport; they simply have to have a truck that’s cool from sitting indoors first thing in the morning. The average half-ton or van travelling to the market once a week could get close to 30mpg on the highway.
But the sad fact is that CO2 savings from buying local produce can be quickly eaten up by the emissions created by customers driving their vehicles to the market (or supermarket). In the UK, cars driving to and from the supermarket create 20% of the total CO2 emissions involved in mass food transport. That percentage would be much higher in the case of locally produced food—if you drive across the city to the market and back, your personal responsibility for those local carrots’ total CO2 emissions will jump to 90% or even higher.
This brings us to the impact of the ‘local loop’, where consumers individually drive to a farm to obtain a locally produced product. Although the individual distance travelled may be relatively short, it quickly adds up to a surprisingly huge number. Say 100 people each make a 30 mile round trip to buy a small quantity of food direct from the farm gate. They have just collectively racked up 3,000 miles on the odometer, when all of their food could have been transported all at once in a larger vehicle in a mere 30-mile round trip! A 6mpg heavy diesel truck is still far more energy-efficient in terms of work accomplished than tens of thousands of people dashing all over town and into the surrounding countryside alone in their gas-guzzling cars, half-tons, and SUVs.
So as you can see, reducing your food miles isn’t as easy as just totting up the mileage. There are a host of highly complicated factors to consider when you pick up that apple or green pepper, including the method of production, the way it was transported, whether you bought it out of season, and even how long it was kept in cold storage (and we’re just talking about produce here–trying to work out the emissions for processed food will really make your head spin). The whole life cycle has to be taken into account–not just how far it has travelled from home.
There are still a lot of very important reasons to buy locally produced food, as I’ll be talking about in future posts. But the quickest way for the average person to make a big reduction in their food’s CO2 emissions? Don’t climb into a car to go and buy it.
I confess that I do struggle against 
