Environmental Analysis of Food-Energy-Water Systems: Focus on High-value Crops and Logistics in the United States
Agriculture is one of the most influential ways that humans interact with the environment. Our food system demands approximately 30% of global energy consumption, 70% of freshwater withdrawals, and 90% of consumptive water use. Roughly half of the Earth’s habitable land area is already being used in the service of agriculture. One quarter of global greenhouse gas emissions can be attributed to food production, primarily as a consequence of land use change, livestock farming, and fertilizer use. This is to say nothing of the multitude of other impacts such as conventional air and water pollution, habitat destruction, and species extinction. Several prominent trends including population growth, the expansion of the global middle class, and urbanization threaten to further strain our already deteriorating natural systems. Estimates suggest that food production must increase 70% by 2050 in order to meet demand. Attaining this target in a sustainable manner requires the acceptance of a holistic integrated engineering approach to food, energy, and water systems. It is only through such an approach that we can arrive at optimal solutions that minimize waste streams and natural resource depletion while maximizing food output. At the core of this dissertation are three interrelated research projects addressing the production and supply of fresh produce in the United States. First, we perform an environmental assessment of four high-value crops in Ventura County, California: strawberries, lemons, celery, and avocados. We calculate life-cycle energy and greenhouse gas emissions footprints and assess the impact of switching from conventional irrigation to recycled or desalinated water. Next, we expand upon the Ventura County model to include the post-harvest processing, packaging, and transportation stages. Using oranges as a case study, we estimate the carbon footprint per kilogram of fruit delivered to wholesale market in New York City, Los Angeles, Chicago, and Atlanta, and assess the relative importance of transportation mode, transportation distance, and seasonality. Finally, we apply this cradle-to-market model at a national level to assess the environmental impact of fresh tomatoes delivered to ten of the largest cities in the United States. Using linear optimization, we compute the optimal tomato distribution scheme that minimizes greenhouse gas emissions while satisfying tomato demand. This dissertation contributes to the current body of knowledge by presenting life-cycle footprints for six high-value agricultural commodities using uniquely specific regional and temporal data. We develop a holistic cradle-to-market life cycle model that integrates growing practices, water use, and embedded energy. We then apply this model in combination with linear optimization in order to mitigate the environmental impact of a popular agricultural commodity at the national level. This research underscores the importance of crop-specific and regionally-specific data collection and carbon footprinting. The adoption of a universal framework for agricultural data reporting would greatly expand the applications and accuracy of agricultural environmental assessments. Such a framework would lay the groundwork for optimal decision-making at the nexus of food, energy, and water. It would also allow for efficiency benchmarking in agricultural production and supply, and perhaps the incorporation of a performance-based ecolabel for resource-efficient crops.