In many cases, transport is a tiny proportion of total greenhouse gas emissions per unit of food – for example, it’s less than 1% of the carbon footprint of one lb of beef. However, food miles are often cited as an environmental proxy to differentiate between food choices, the assumption being that an egg which travels 2,000 miles across the country is less environmentally-friendly than one produced in the next county. Indeed, one farm website proclaims that “We do not ship anything anywhere. We encourage folks to find their local producers and patronise them”, while on the same page, a customer testimonial proudly proclaims: “I drive to <Farm X> 150 miles one-way in order to buy clean meat for my family”.

Given the dichotomy between these two statements, let’s compare buying eggs from a grocery store with a local farm (full analysis here). Food miles are far greater for eggs that have traveled from Texas to Virginia to be sold in the grocery store (2,405 miles round-trip), compared to driving to the local farm (300 miles round-trip); and the fuel efficiency is far worse for a truck (5.4 mpg) than a car (22.6 mpg); yet a modern truck can carry 23,400 dozen eggs.

Unless your car is packed to the roof with eggs, traveling to the farm to buy them emits 55X more greenhouse gas emissions than driving to the store to buy them. Bottom line? Unless the local farm is closer than the store, or you’re able to walk/cycle there*, it’s more environmentally-friendly to buy eggs from the store, because the greenhouse gas emissions attributable to one dozen eggs out of 23,400 dozen is a tiny fraction of the total.

One report claims that greenhouse gas emissions from one large container ship is equivalent to 50 million cars – however, in this instance it’s the result of sulphur dioxide emissions from poor quality shipping fuel rather than inefficiency. Mass transport may not have a feel-good factor associated with driving out to a farm, but it allows us to enjoy a wide variety of affordable foods with a low carbon footprint – essential factors for a sustainable food future.