I’ve posted this before in various venues but I thought it was worth a revisit:
So there’s been a lot of talk in the last few years of “food miles”, eating locally and 100 mile diets. Some of the supposed benifits of eating locally is that you become more in tune with the seasons, you support your local community, you eat fresher food and just general all round feel goodness. Now all of these are valid claims and I am not disputing any of them. But the chief claim that the “food mile” movement is making is that eating locally helps the environment through lowering the use of oil. On the face of it, this sounds fairly intuitive but I wasn’t convinced so I decided to dig a bit further and try and answer the question does the choice to eat locally decrease the amount of carbon emitted and it seems like the answer is no.
This graph shows the Ton-Miles per Gallon for Truck, Rail and Barge shipping. Ocean shipping is roughly twice as efficient as inland barges so lets call it 1000 Ton-Miles per Gallon.
Now assume that the typical surburban family drives a 25 Miles Per Gallon vehicle, lives 2.5 miles from their nearest supermarket and buys 20 pounds of groceries in the average shopping trip. So on one round trip, they will travel 5 miles and use 0.2 gallons of petrol to transport 0.01 tons of groceries. A container ship could move that 0.01 tons of groceries 20,000 miles for the same amount of fuel. You could move that 20 pounds of groceries all the way around the world by ship for the same amount of fuel as it takes for you to go to the store and back. If you buy 40 pounds of groceries rather than 20, then it’s a half way around the world. If you live 5 miles instead of 2.5 miles, then it’s twice around the world. If you drive a SUV which gets 12.5MPG and you live 5 miles away, then it’s four time around the world. You can fiddle around with the numbers all you like but the conclusion seems inescapable, where your food comes from is less significant than how you choose to get it.
The math is even more disturbing when you look at exactly what eating locally actually means. For most people, that means buying as much of your food as possible from farmers markets. However, you can’t get everything from farmers markets so it’s likely that you need to still make the same amount of trips to the supermarket to get all of the other stuff you need. Your trips to the farmers markets then become an added fuel expenditure on top of your existing supermarket trips. In addition, farmers markets are usually further away that supermarkets, just by virtue of there are less of them so thats an even bigger fuel cost.
How the goods get from the farm to the market is also an important consideration. Your typical farmers market has many small farmers from within a 100 mile or so radius individually shipping in small amounts of good via cars and small trucks. Again, far less efficient than massive containerized shipping and trucking.
Now, does this on the face of it means that eating locally is crap? Of course not, all of the previous reasons to do with freshness, seasonality and supporting local farmers are still valid. But what is total crap is the idea that somehow eating locally is good for the environment through the decrease in carbon emissions from shipping. While the idea has immediate intuitive appeal, if you peer at the actual numbers, the reality is that modern containerized shipping and distribution has become so efficient that it’s only really the last few miles that are important.