A Simple Resource-oriented Sanitation of Cattle Urine as a Value-added Liquid Fertilizer

Abstract

Evaporation of malodourous ammonia formed due to urease-decomposition of urea of cattle urine causes loss of nitrogen and creates difficulty in handling the urine for application as a liquid fertilizer. Here we show that phosphoric acid (PA), along with neutralization of urine, can inhibit urease-decomposition of cattle urine while converting urine into pH-neutral, odourless, nitrogen-intact, and phosphorous-enriched liquid fertilizer with an additional advantage of utilization of the urine-water in water scarce regions or seasons. Pre-dosing of cattle urine with the optimized doses of PA has been shown to restrict the pH of the liquid fertilizer within 8.0 for at least seven weeks retaining undecomposed urea in cow, buffalo, and pig urine as 4.25gL^-1, 5.74gL^-1 and 4.78gL^-1, respectively. A small precipitate of struvite, magnesium ammonium phosphate hexahydrate, obtained during PA-treatment of the cattle urines may be used as a solid N-P fertilizer. The addition of optimum doses of PA increases the P-content of the urine of lactating cattle from 25mgL^-1, 46mgL^-1and 48mgL^-1to 1.47gL^-1, 1.87gL^-1, and 1.33gL^-1, respectively. Application of PA is a potential green way to resource-oriented sanitation of cattle urine converting the urine into a convenient value-added liquid fertilizer at almost no cost due to its atom efficiency.