Farming and marketing system affects carbon and water footprint – a case study using Hokaido pumpkin

The objective of the study was to determine the carbon footprint for four farming and marketing systems, using primary data obtained on the farms for autumn pumpkin as an example and model crop. Area for the crop cultivation and weight, i.e. kilogram of saleable product, for the marketing phase were employed as the two functional units with system boundaries from seed acquisition to pumpkin disposal; offset was not used. In the farm carbon footprint (FCF), pumpkins from the organic farm with 240kg CO₂eq/ha scored best due to the lowest (50kg N/ha) (organic) nitrogen application compared with twice that value (448kg CO₂eq/ha) for the IP farm. This was due to nitrous oxide emissions, as a consequence of N fertiliser, with 75–99% of FCF in the cultivation phase; it contributed ca. 10% and plant protection (methiocarb in the ‘integrated production’; IP) <1% to the product carbon footprint (PCF). Neither the form (organic or inorganic) nor the amount of applied nitrogen (a 2.5 fold difference) largely influenced the final product carbon footprint. The large specialised farm showed the best product carbon footprint with 139g CO₂eq/kg pumpkin due to use of potassium fertiliser and 3-fold larger yields (18t/ha versus 5.8t/ha in the organic [716g CO₂eq/kg]) and, to a lesser extent, the scale of the farm business. On the other two farms, cultivation is more extensive with the main income not from pumpkin; any increase in farm size or their pumpkin acreage would not improve their efficacy and product carbon footprint. The imported organic Argentinean pumpkin scored second best with 243g CO₂eq/kg despite the long-distance transport due the lower energy consumption of bulk sea freight. The private consumer shopping distance in both cases (retail versus farm shop) amounted to as much as ca. 89% of the product carbon footprint. For a cleaner production, carbon reduction potential appears in improving the potassium fertilisation in all farming systems, except for the large farm, and consumer behaviour regarding the means of transport for shopping. A simple water footprint assessment, based on irrigation and produce washing, resulted in 0.4 (IP), 0.9L (organic) to 9L (large scale) blue water/kg pumpkin.