Life cycle assessment of eight urban farms and community gardens in France and California

Urban agriculture (UA) is often positioned as an environmentally sustainable food supply for cities. However, life cycle assessments (LCA) measuring environmental impacts of UA show mixed results, because of inconsistent application of LCA and reliance on hypothetical case studies. To address these shortcomings, we performed an LCA of eight urban farms and community gardens in Paris, France and San Francisco, California, USA. We collected primary data from sites representing diverse growing systems (low-intensity open-field to open-air hydroponics) and motivations (education, civic engagement, and commercial production). We found that medium-tech farms, with minimum social engagement had the lowest impacts using a kilogram-based functional unit, but socially-oriented farms had the lowest impacts with an area-based functional unit. Most impacts came from infrastructure (irrigation pipes, hydroponics structures), irrigation, compost, and peat for seedlings. Our findings can help LCA practitioners perform UA LCAs more completely/consistently, and help urban farmers/ gardeners target high-environmental-impact practices to optimize.

Automated summary

Urban agriculture is often seen as a sustainable food supply for cities, but life cycle assessments of its environmental impacts have shown mixed results due to inconsistent application and reliance on hypothetical case studies. To address this, we conducted a life cycle assessment of eight urban farms and community gardens in Paris, France and San Francisco, California, USA. We found that medium-tech farms with minimum social engagement had the lowest impacts using a kilogram-based functional unit, while socially-oriented farms had the lowest impacts with an area-based functional unit. Our findings can help improve the consistency and completeness of life cycle assessments for urban agriculture and guide farmers and gardeners in optimizing their practices.