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Abstract
The demand for carbon footprint (CF) studies of agricultural products is increasing, but the calculation methods differ. At the example of manure, we compare two methodological options: the 'cut-off approach' outlined in the International Dairy Federation's (IDF) LCA guidelines, whereby all emissions of manure application are excluded from the animal and assigned to the plant system; and the approach outlined in the FAO-LEAP guidelines, whereby the share of manure which is applied in excess of plant nutrient requirements (“over-fertilisation”) is attributed to the animal system. We find that the choice of methodological approach has a significant impact on the carbon footprint (CF) of winter wheat and cow milk, with the FAO-LEAP method resulting in an increase of nearly 3% of cow milk CF. We then analyse how the consideration of manure in CF studies is linked to scientific and normative principles, which are intertwined with interests and incentives. We argue that in order to facilitate harmonization and reach widespread acceptance, a normative concept for decision making would need to be developed that considers stakeholder views.