ABSTRACT
The United States has more than 330 million acres (134 million ha) of agricultural croplands, which produce an abundant supply of food, feed, fiber, fuels, and other products. In 2011, 13 million tons of nitrogen and 4 million tons of phosphate fertilizers were applied to agricultural land for crop production (USDA 2012a). From these, 1.3 million tons of nitrogen and 0.7 million tons of phosphates were converted into waste at animal feed operations (Lory et al. 2006). Anually, aquaculture in the United States generates wastewater containing about 40,000 tons of nitrogen fertilizer. Globally, 5 million tons per year of nitrogen is discharged into the environment as wastewater from aquaculture processes.
