Greenhouse gas emissions analysis of lettuce grown in an urban farm in Ohio

More than 70% of the total lettuce produced in the United States is produced in California, which requires longer transportation (with refrigeration) distances to reach to consumers in Ohio. In recent years, with increasing number of vacant lots in many U.S. metropolitan areas, urban farming has been gaining more interest as food can be grown locally with minimal input. Thus, the objective of this study was to evaluate the greenhouse gases emissions (GHGe) of the urban lettuce farming in Ohio, and compare with the conventional lettuce production in California for consumption in Ohio. This study considered two scenarios for irrigation (city and rainwater) and fertilization (chemical fertilizers and compost) for urban farming. The data used for the analysis were obtained from field visit, literature, and database. GHGe associated with lettuce production in the urban farm in high tunnel was lower by 69-83% compared to the conventional farming. For conventional lettuce farming, transportation contributed the most to the GHGe (0.39 kg CO2e/kg lettuce), followed by chemical fertilizer use and irrigation (0.07 and 0.06 kg CO2e/kg lettuce, respectively). Net GHGe for urban farming was in the range of 0.09-0.17 kg CO2e/kg lettuce. Lettuce farming in only 30% of the available vacant lots in Ohio can produce around 126550 metric ton of lettuce, which is enough for Ohio, and will also generate $461 million in revenue. Lettuce production at this scale can reduce the GHGe by ~64,400 metric ton CO2e, equivalent to emissions from 257 million km driven by an average passenger vehicle.