This came up in class: contribution of transportation to GHG emissions

During tonight’s class, someone asked about the relative contribution of transportation to a product’s total GHG emission, and how the GHG emissions of vegetables/grains compare with meat.  After a bit of digging, I found the following peer-reviewed research paper published last year – here’s the abstract (and here’s the paper):

Despite significant recent public concern and media attention to the environmental impacts of food, few studies in the United States have systematically compared the life-cycle greenhouse gas (GHG) emissions associated with food production against long-distance distribution, aka “food-miles.” We find that although food is transported long distances in general (1640 km delivery and 6760 km life-cycle supply chain on average) the GHG emissions associated with food are dominated by the production phase, contributing 83% of the average U.S. household’s 8.1 t CO2e/yr footprint for food consumption. Transportation as a whole represents only 11% of life-cycle GHG emissions, and final delivery from producer to retail contributes only 4%. Different food groups exhibit a large range in GHG-intensity; on average,red meat is around 150% more GHG intensive than chicken or fish. Thus, we suggest that dietary shift can be a more effective means of lowering an average household’s food-related climate footprint than “buying local.” Shifting less than one day per week’s worth of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable-based diet achieves more GHG reduction than buying all locally sourced food.

If there are any experts out there reading this, please weigh in the comments – was this study performed properly?  How valid are their assumptions?

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Dave Semeniuk spends hours locked up in his office, thinking about the role the oceans play in controlling global climate, and unique ways of studying it. He'd also like to shamelessly plug his art practice:

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