Demonstration of Power Generation from Fertilizer Solutions via Pressure-Retarded Osmosis

Highlights Mechanical work can be generated from fertilizer via pressure-retarded osmosis. Laboratory tests show up to 5 Wh of energy recovered per kg of fertilizer. Tradeoffs between energy recovery and power generation are demonstrated. Maintaining power above 5 W m -2 is reasonable given current membrane technology. Abstract . Large amounts of energy are released when concentrated fertilizers are diluted in water. In this study, we demonstrate the use of fertilizer to generate useful mechanical work via pressure-retarded osmosis (PRO). A number of common single solutes and fertilizer blends were analyzed using both experimental and numerical methods. Laboratory test trials showed energy recovery of up to 5 Wh kg-1 of fertilizer and power of up 6 W m-2 of membrane area given commercial cellulose triacetate membranes. A drop in power was demonstrated throughout the fertilizer PRO batch process, and the resulting tradeoffs between energy recovery and power density are discussed. Simulation results suggest that high-performance membranes can be used to maintain elevated power above 5 W m-2 throughout the batch process, while recovering approximately 5 Wh kg-1. The loss of valuable fertilizer via leakage to the feed stream was found to be less than 1% of the initial fertilizer mass, suggesting that this non-ideal dynamic can be reasonably minimized. Implications at the food-energy-water nexus are discussed. Keywords: Fertilizer osmosis, Forward osmosis, Fertilizer energy, Food-energy-water nexus.