[api_or_ipa]

Not all fuel consumption is the same. Gasoline is way under-priced in the US when traffic, pollution and road construction costs are factored in. On the other hand, high quality, sustainably farmed produce is overpriced, most significantly from sustained subsidies for corn and the associated increase in the cost of arable land.

[fovc]

CO2 emissions alone add ~$0.50/gal or ~25% if you had to capture all that carbon.

[1] Can't find a great all-encompassing source, but e.g.: http://www.c2es.org/publications/cost-us-forest-based-carbon... says $30-90 per ton

[2] Burning as is about 9kg CO2 per gal. http://www.eia.gov/tools/faqs/faq.cfm?id=307&t=11

[barrkel]

There is also the cost of getting the food to you. Often the most efficiently produced food will be produced some distance from you and a surprisingly large fraction of the cost will be shipping.

[incongruity]

It would definitely be interesting to see the carbon footprint per mile of all of these options...