Identifying Hotspots in the Carbon Footprint of a Small Scale Organic Vegetable Farm.

Despite its potential to mitigate greenhouse gas (GHG) emissions, organic farming is not immune to contributions to GHG emissions. A full accounting and understanding of the GHG emissions associated with specific activities, materials, and energy used in organic operations is needed. A small-scale organic vegetable farm in Washington State, USA, was used as a case study to determine the carbon footprint (CF) and GHG hotspots to support decision-making for GHG mitigation. A partial life cycle assessment was conducted to identify primary and secondary GHG fluxes associated with activities and materials used in production of potatoes, cauliflower, dry bush beans, winter squash, summer squash, chard, peppers, and onions. Across the farm as a whole, fuel use for both on-farm and upstream off-farm operations, energy use for irrigation, fertilization, and plastic based material use for pest management were identified as the major CF hotspots. Simulation of a switch to the use of biodiesel instead of gasoline and diesel, and the use of solar powered irrigation in place of the current hydroelectric powered irrigation, resulted in a 34% reduction in the total farm CF. The CF associated with each crop ranged from a low of 1.86 t CO₂-eq ha^-1 yr^-1 for dry bush beans to a high of 3.00 t CO₂-eq ha^-1 yr^-1 for peppers. Peppers had the highest CF followed by cauliflower and potatoes. Using a plastic-covered mobile hoop house for pepper production, synthetic row cover for cauliflower production, and peat for greenhouse seedlings were all major contributors to the CF of individual crops. By identifying the CF hotspots of a whole farm and individual crops, particular inputs and activities can be targeted for modification in order to effectively reduce the farm’s CF.