Conservation Strategies for Arizona's Food-Energy-Water Nexus

As concerns for food security grow, increasing attention is being focused on the ability of certain regains to maintain or increase agricultural production. However, the increasing of agricultural output is constrained not... [ view full abstract ]

As concerns for food security grow, increasing attention is being focused on the ability of certain regains to maintain or increase agricultural production. However, the increasing of agricultural output is constrained not just by water availability but also by access to energy. While there have been many studies that have quantified the relationships between energy and water systems, there remains limited knowledge of the requirements and dynamics of the food-energy-water (FEW) system. Understanding the FEW nexus is critical as constraints on resources shift, and this is particularly true in the US state of Arizona, where access to water and climate change threaten agricultural enterprises. We estimate the water and energy inputs into agriculture in Arizona by identifying the inter-connectivity between the systems.

The energy and water inputs for agriculture are estimated using the LCA framework accounting for production, transportation and storage. The direct and embedded energy and water invested in the various stages of an agricultural product’s life are estimated. In the production phase, water consumption is modeled using the Pennman-Montieth method, capturing requirements during plant growth stages specific to Arizona’s climate. Energy consumption is estimated using surveys from the Cooperative Extension of Arizona. Transportation energy is estimated using data from the Freight Analysis Framework (FAF) which provides data on food trade between US states. The energy invested in storage is estimated using the specific heats of the various crops. The energy-water nexus relationship in Arizona is used to determine the embedded energy in water as well as the embedded water in energy. The results from the various phases are aggregated and amount to 26 PJ of energy and 2.6 billion cubic meters of water for the year 2014, or 1.7% and 28% of Arizona’s energy and water use. The efficiency of crops on a per kg and per acre basis was also estimated. Several crops consume large fractions of total agriculture energy but not water, or water but not energy, raising questions about effectively deploying conservation measures. Several conservation strategies were considered – No Tillage, Low Energy Precision Application (LEPA), Low Energy Spray Application (LESA), Subsurface Drip Irrigation (SDI), Replacing fertilizer with manure, off-grid renewable energy, truck fuel efficiency improvements, and storage technology improvements. When compared to the baseline case, LEPA systems are 20% more water efficient as they reduce evaporation while fuel efficiency standards can reduce the energy consumption of trucks by up to 40%. Thus LEPA (36% water savings) and EPA standard truck (8% energy savings) strategies are the best conservation strategies.

The results highlight the distributed nature of energy across the nexus while water is concentrated in the production phase. The results identify the crops and processes where conservation strategies should be focused. Given that energy is more distributed across the nexus than water, broad efficiency policies will be needed.