The Nourishing the Planet blog investigates the cost of food waste in the US:
http://blogs.worldwatch.org/nourishingtheplanet/putting-a-dollar-value-on-food-waste-estimates/
Here is a direct link to the study by Buzby and Hyman (2012) that is cited in the blog:
http://www.sciencedirect.com/science/article/pii/S0306919212000693