Is local food more sustainable?

One argument against suburban sprawl is that it sterilises agricultural land. A particular variation on this contention is that land should be preserved for agriculture so that carbon emissions in transporting food from farm gate to plate – “food kilometres” – can be minimised.

A frequently cited estimate is that food in the US travels on average 2,400 km from where it is produced to where it sold to consumers. We should therefore seek to grow as wide a range of food as possible as close to Melbourne as possible.

From Weber and Mathews, Food Miles and the Relative Climate Impacts of Food Choices in the US

All things being equal that makes sense. But of course it’s never that simple. Here are some pertinent issues to consider.

First, transport is not a major component of the total carbon emissions from agriculture. These researchers estimate that on-farm production accounts for 83% of the average US household’s carbon emissions from food whereas delivery from producer to retail outlets accounts for just 4%.

Second, most food can’t be grown locally without resorting to potentially environmentally damaging practices like excessive application of fertiliser, irrigation or artificial heating of greenhouses. This article cites a British study which found that because British tomatoes are grown in heated greenhouses, they emit 2.4 metric tons of carbon dioxide per ton grown whereas Spanish tomatoes emit 0.6 tons. Further:

Another study found that cold storage of British apples produced more carbon dioxide than shipping New Zealand apples by sea to London. In addition, U.K. dairy farmers use twice as much energy to produce a metric ton of milk solids than do New Zealand farmers. Read the rest of this entry »