There is no single agreed method for calculating a product’s embedded carbon, and the differing assumptions used in terms of the scope and boundary of the life cycle assessment can yield dramatically different results for the same goods. Furthermore, data availability, reliability and compatibility are critical problems; gathering reliable data at producer level for agricultural products is particularly difficult. As a result, the variety of PCF labelling schemes used by different private retailers are a concern. These were food labels that calculated embodied carbon in only a limited portion of the life cycle: transport to market. The result was to penalise foreign producers on the basis of distance to market, and in particular to penalise airfreighted out-of-season food imports. The schemes were poorly conceived.