So with all this talk about food miles and buying local to save the enviroment and so forth, I was wondering if there was actually any objective data on just how much it benifits the environment to buy local.
Is there anywhere that has sources on rough estimates on the amount of oil it takes to ship a kilogram of something one kilometer via the various transportation modes. ie: shipping, rail, truck, car, air etc.
It seems to me that if shipping and rail is drastically more oil efficient that the other methods, then the conventional notion of food miles is invalid.
This train of thought was sparked by a recent talk I heard on the global shipping industry where the speaker quoted a cost of around $700 to ship one TEU worth of goods from China to the Port of Tacoma. One TEU is approximately 36m^3 so it costs about $20/m^3. If you assume a m^3 weighs a ton, then it’s about 2 cents a kilogram which is mindbogglingly cheap.
a) I don’t care about cost, I care about oil usage.
b) It’s obvious that water will be the most efficient. What I want to know is by how much.
In other words, if I’m faced with a choice between buying oranges shipped in from Chile and oranges trucked in from Calinfornia, which is better for the environment and by how much?
I found this graph which shows the ton miles per gallon for different transport modes although it doesn’t show ships. Assuming you buy 20 pounds worth of groceries (0.01 short tons) and it’s a 5 mile round trip to the grocery store and your car gets 25 miles per gallon, then you’ve used 0.2 gallons of fuel to transport 0.01 tons. Assuming that container ships have the same efficiency as inland barges, a container ship could transport the same amount of goods 10,000 miles around the world for 0.2 gallons! Thats almost exactly halfway around the world.
To me, that seems like the entire idea of “food miles” is bullshit. In fact, farmers markets which transport all of their goods in by small trucks and which people drive many miles to get to probably emit more carbon that giant supermarkets selling lamb from New Zealand and cherries from Chile.
I don’t have much time on my hands today to really look into this, but the vessel I have figures for on my desk in front of me is a little handysize container/general purpose vessel with a deadweight (cargo capacity) of 22401 metric tonnes. That’s 24700 short tons.
It consumes 25 tonnes of IFO and 1 tonne of MDO a day @13 knots. So that’s 27,340 litres or 7229 gallons per 360 statute miles. Which is 0.0798 miles to the gallon. But multiply that by the load in tons and you get 1230 ton-miles per gallon, which kicks the ass of even of inland barges.
This little vessel in turn wouldn’t have anywhere near the economy of a large container vessel.
OK, Page 15 of this article(pdf) cites $13,000,000 annual fuel costs for a 12,000 TEU, 6000 hour operation container ship. That works out to be 0.18 dollars per TEU per hour. From url=Container ship - Wikipedia]Wikipedia, we get a top speed of 25 knots, lets call it 20 knots average speed to get 0.00784 dollars per TEU per mile. Assume fuel costs $80 a barrel which is 42 gallons and you get 242 TEU-miles per gallon. From here, we get the average weight of a TEU is 7 tons so 1700 ton-miles per gallon or about 3 times as efficient as inland barges and about 30 times more efficient that trucks.
IFO is Intermediate Fuel Oil (aka “bunkers”) and MDO is Marine Diesel Oil. The former is what the ship basically runs on, the latter is used to run generators and so on, and in some ships also at manoeuvring speed (when the engines aren’t running hot enough to reduce the viscosity of IFO enough).
IFO prices depend on where and what grade but US$330/metric tonne delivered might be in the ballpark at the moment, which is nearer $50/barrel.
A 12,000 TEU vessel is seldom going to be carrying 12,000 so you’d have to apply a fudge factor there, too.
Pardon the bump, but what about the getting the food on and off the ship? I’m rather clueless as to the possibilities of local food (what can be grown where, how close to shops can farms be expected to be, etc), but I suppose that at least for places far away from ports, there’d be a huge advantage to it.