Food-Energy-Water Nexus: Quantifying the Energy and GHG Emissions of Water Embodied in Food Flows within the U.S

Global climate change, resource depletion, and population growth place imminent pressure on food, energy, and water (FEW) systems. Significantly heightened demand for food, energy, and water is expected within the next forty years as the world’s census will surpass 9 billion people (Finley & Seiber, 2014). FEW systems are deeply interwoven, interdependent, and interconnected. Quantifying and understanding the interdependencies and linkages between the FEW systems is critical for understanding their environmental sustainability and vulnerability of the FEW nexus to disruptive events. There is an urgent need for a systems approach incorporating life cycle thinking to understand the complex nature of the FEW nexus.

A critical piece of the FEW trilemma is the energy and greenhouse gas (GHG) emission burden of water consumed in food production. 30-40% of the U.S. water withdrawals are for irrigating crops; this statistic nearly doubles when referring to the global water withdrawals. Acquiring, pumping, and transporting water for crop production is energy and GHG intensive. Previous research has investigated the virtual water content (VWC) associated with international food trade and food flows in the United States (Dang, 2014) & (Bazilian et al., 2011). However, the embodied energy (EE) and GHG emissions associated with the virtual water content of food production is not well understood. A systems approach with life cycle thinking for understanding the embodied energy and GHG cost of virtual water can aid in understanding the vulnerability and threshold to disturbances of food production systems to scarcity in water and energy resources. We combine detailed information on food flows within the U.S. with water footprint data. Synthesis of the datasets provided by the Commodity Flow Survey and National Agricultural Statistics Service assisted with the determination  of the virtual water trade flows. These flows used in conjunction with the Farm and Ranch Irrigation Survey and US Energy Information Administration, as well as several life cycle inventory databases allowed for the modeling of EE and life cycle GHG emissions. Preliminary findings reveal that over 476 billion m³ of virtual water was traded, 332 trillion MJ of primary energy was expended, and 190 billion kg CO₂ equivalents was associated with domestic food transfers. The information regarding the virtual water and life-cycle energy costs of water is essential to understand impending issues that can arise in highly interdependent FEW systems.