Why buying local isn’t an easy answer

Local agriculture promises to reduce greenhouse gas emission associated with transporting food, but the truth is more complicated

One of the great enthusiasms for local agriculture is its promise to reduce the greenhouse gas emissions that are associated with transporting food long distances from farm to plate. It’s a notion that Vancouver authors Alisa Smith and J.B. MacKinnon popularized in 2007 with their best-selling book, The 100-Mile Diet.

Certainly “food miles” are an issue. A 2008 study by Christopher Weber and Scott Matthews from Carnegie Mellon University in Pittsburgh reported that the average foodstuff rides 1,640 kilometres from its point of production to your plate. Throw in the additional transportation costs of transporting inputs to the farm in the first place and that number jumps to 6,760 kilometres. It’s a big part of the reason that 20 per cent of the average North American’s total personal greenhouse gas output is attributable directly to the food they eat.

But planner and author Mark Holland, who was the City of Vancouver’s first manager of sustainability, says, “The actual carbon footprint is so unique to each product.” A California green pepper, grown in the sun and then efficiently picked, packed and shipped to Vancouver in a new fuel-efficient truck, might actually arrive on the shelf with a lower carbon budget than one that has been grown in a natural gas-heated hot-house in Delta. The Cali-pepper might even outperform a perfect summer competitor that was part of a small load driven from the Fraser Valley to a local farmers market in a badly tuned, 15-year-old half-ton pick-up truck.

Weber and Matthews also documented a raft of complications. For example, a strawberry trucked from Mexico could have a much higher carbon content than one shipped a much greater distance (but in a more carbon-friendly manner) on a freighter from Argentina. They recommended that rather than obsess about local food, the carbon-conscious shopper should just walk by the meat aisle—especially avoiding beef. In addition to the extremely high input costs for industrial-scale beef production, the American Society of Animal Science reports that cows—which suffer no social constraints about burping and farting—generate up to 500 litres daily of methane, a greenhouse gas 20 times more powerful than carbon dioxide. It is, in every way, a burden on the atmosphere.