Carbon and fossil resource depletion footprints of milk production from Canterbury dairy farms

Among the different sustainability metrics, the carbon footprint is the most commonly reported, but the depletion of non-renewable resources such as fossil fuels, is also important. This study aimed to calculate the “cradle to farm-gate” carbon and fossil resource depletion footprint of milk production in Canterbury, New Zealand, comparing two different farm systems: one pasture-based with a relatively small amount of brought-in feed (Lincoln University Dairy Farm, LUDF) and an average Canterbury farm. The estimate of the carbon footprint of milk production was 0.68 and 0.80 kg CO2-eq/kg of fat and protein-corrected milk (FPCM) for the LUDF and Canterbury average, respectively. The main contributor to the carbon footprint for both farms was enteric fermentation, but differences were found mainly in the emissions from the supplementary feed. Conversely, the Canterbury average farm showed lower fossil resource depletion footprint (1.05 MJ/kg FPCM) when compared with the LUDF farm (1.13 MJ/kg FPCM). The differences were mainly related to fertiliser use. However, this difference is small if compared with farms overseas. The study shows that it is important to look at more than one environmental metric when proposing mitigation practices.