Base Assumptions:
I based my calculations on our past consumption of chicken noodle soup. As a family of four we consume at a minimum one can per person per week.
  - This equates to about 200 cans in a year.
  - Each can weighs 1.4 pounds.
  - The highway distance from Vineland, New Jersey to San Jose, California is 2,947 miles.

Carbon Emissions Data:
Our CO2 emissions data was derived from a June 2001 report: Food, Fuel, and Freeways:  An Iowa perspective on how far food travels, fuel usage, and greenhouse gas emissions.  It was published by the Leopold Center for Sustainable Agriculture, at Iowa State University.  The report referenced a study in Table 7 on page 31 from: Atmosphere Emissions from the Use of Transport in the United Kingdom Volume 2. 1989. It shows the emissions pollution generated by shipping via different modes of transportation.  Even though the study is nearly two decades old, the numbers are still very relevant. They identified four modes of transport, air, road, rail and water.

We converted the metric system based data regarding CO2 emissions, (grams of CO2 emissions per metric ton-kilometer shipped) into the English based system (lbs of CO2 emissions per lb-mile shipped). 

Emissions for different modes of freight transport

  A lb-mile is defined as shipping something that weighs one lb a distance of one mile.  5 lbs shipped 200 miles is 1000 lb-miles.

A lb-mile is defined as shipping something that weighs one lb a distance of one mile.  5 lbs shipped 200 miles is 1000 lb-miles.

According to this study, shipping via water is the least polluting mode of transportation in terms of CO2 emissions per lb–mile. Looking at the other modes; rail was about one third more polluting BUT road transportation was about 7 times more polluting and air transportation was 42 times more polluting.  Unfortunately, most of our food is shipped via road and some fresh items are now shipped via air. 

Calculations:
CO2 Emissions for Shipping by Road from New Jersey to California
Road transport emissions = 0.0003331 lbs of CO2 emissions/lb-mile
Weight shipped= 1.4 lbs (per can of soup)
Distance shipped= 2947 miles
(0.0003331 lbs of CO2  emissions/lb-mile X 1.4 lbs X 2947 miles) =
1.374 lbs of CO2 emissions (per can of soup)

Shipping 200 cans of soup
1.374 lbs of CO2  emissions/item X 200 items =
274.80 lbs of CO2 emissions