Resource-oriented Sanitation of Cattle Urine: Nitrogen Recovery as Solid Calcium Ammonium Phosphate Fertilizer alongwith Neutralization/ Deodorization of Liquid Urine Fertilizer

IJEP 45(12): 1063-1073 : Vol. 45 Issue. 12 (December 2025)

Full Text

Rituparna Saikia, Tushmita Das, Shamiran Baroi, Saranga Baishya and Robin Kumar Dutta

Tezpur University, Department of Chemical Sciences, Napaam, Tezpur – 784 028, Assam, India

Abstract

Cow, buffalo, or pig urine, which is rich in nitrogen, potassium and other micronutrients, is usually considered waste. Ammonia formed by the urease decomposition of urea in urine raises the pH above 9.0, which is harmful to plant growth and seed germination. Evaporation of malodorous ammonia from cattle urine also causes nitrogen loss, reducing its potential as fertilizer and pollutes the environment, creating problems in handling and storing the urine as a liquid fertilizer. Here, we show that neutralizing cattle urine with phosphoric acid (H3PO4, PA), KH2PO4 and K2HPO4 in the presence of Ca(NO3)2 precipitates Ca(NH4)HP2O7·H2O, a solid fertilizer enriched with P and Ca, instead of precipitating struvite (Mg(NH4)PO4·6H2O), which occurs in the absence of the Ca-salt. The nitrogen recovery as solid Ca(NH4)HP2O7·H2O was found to increase with the neutralizing agents in the order: PA < KH2PO4 <<K2HPO4. Interestingly, K2HPO4, a stronger base than ammonia, can neutralize urine by removing ammonia as a precipitate. The formation of this solid fertilizer also helps in removing the urine’s malodour, resulting in a pH-neutral and easier-to-handle liquid fertilizer.

Keywords

Removal of urine malodour, Cattle urine as liquid fertilizer, Nitrogen recovery as solid fertilizer, Urease, Ammonia neutralization by precipitation

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