Identifying hotspots in the carbon footprint of a small scale organic vegetable farm

Despite its potential to mitigate many environmental impacts of agriculture, organic farming does contribute to greenhouse gas (GHG) emissions. A full accounting and understanding of the GHG emissions associated with specific activities, materials, and energy used in organic operations are needed to support decision-making for GHG mitigation. 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. 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 grown in a crop rotation. The CF associated with each crop ranged from a low of 1.68 t CO2-eq ha− 1 yr− 1 for chard to a high of 2.67 t CO2-eq ha− 1 yr− 1 for cauliflower. Cauliflower had the highest CF per ha followed by potatoes and pepper. Across the farm as a whole, the major CF hotspots were fuel use for both on-farm and off-farm operations (38%), fertilization (18%), soil emission (12%), and irrigation (11%). Simulation of a switch to biodiesel instead of petroleum gasoline and diesel resulted in a 32% reduction in the total farm CF. 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.