I came across a nifty study of the carbon footprint of bread, just published in the International Journal of Life Cycle Assessment. The study looked at bread produced and consumed in the U.K. The bottom line: the carbon footprint of bread ranges from 977 to 1,244 g CO2 equivalent per 800 g loaf. On their own those numbers aren’t that interesting,though the fact that carbon footprint exceeds the weight of the product itself, while not all that unusual, does makes one think.
The study was interesting for what it revealed about the major sources of carbon emissions (the so called hot spots) in the life cycle of a loaf of bread . The study is also interesting because it compared the footprint as calculated using primary data from a specific U.K. bread supply chain against calculations using generic data from life cycle inventory databases. Using primary data tends to be costlier and more time consuming. So if generic data can suffice to acheive the goals of a life cycle assessment, it is a more economical choice.
According to the study, wheat cultivation contributes 35 percent of the carbon footprint, and consumption (including refrigerated storage and toasting) contributes another 25 percent. Assumptions about the amount of food consumers waste suggest that another 5-10 percent is contributed by waste bread being discarded by consumers. Packaging and transportation were relatively small contributors to the carbon footprint.
The hot spots were the same for primary-data analysis and the secondary-data analysis, supporting the idea that the goal of a study should determine its data-gathering strategy. Carbon-labeling–providing data to consumers supposedly to enable them to make purchase decisions based on product carbon footprints–requires data from specific product supply chains. But other uses, including identifying the hot spots so a manufacturer could focus on those for improvement, could well be supported by secondary data.
My favorite finding from the study is that whole wheat bread has a lower carbon footprint than white bread. Milling the flour for white bread uses about 23 more energy per loaf, because it uses the grain less efficiently. So eat healthier and reduce your carbon footprint.