Closing the phosphorus loop: circular economy approaches for phosphorus recovery from agricultural wastes in India

Abstract

Abstract

Phosphorus (P) is an important macronutrient vital for plant development, energy transfer, and food production, making its steady availability essential for agricultural yields and food security. Nonetheless, its availability mainly hinges on limited phosphate rock deposits and fertilizer systems that heavily depend on imports. In India, issues like reliance on fertilizers, varying levels of fertility across many regions, and the rise in agricultural waste production highlight the necessity for implementing more circular P management methods. Existing farming methods, such as residue burning and poor nutrient cycling, worsen P depletion and harm the environment. This review examines major waste streams in India that have potential for P recovery, including crop residues, livestock waste, fish processing waste and food processing waste. It also highlights key recovery methods like struvite crystallization, adsorption, thermochemical processing, chemical extraction, biological treatment and hybrid approaches. These waste streams hold significant quantities of P, which if properly harnessed, can lessen dependence on limited phosphate rock supplies and minimize nutrient leakage into the environment. Research shows that recovery efficiency differs significantly depending on the feedstock type, processing conditions and operational scale, indicating a requirement for customized extraction methods to enhance P recovery. Recovered P can aid in replacing P fertilizers, thus minimizing environmental losses and improving nutrient use efficiency. Nevertheless, widespread adoption in India encounters obstacles including gaps in collection and segregation, contamination risks, elevated capital and operational costs, and insufficient integration into value chain, alongside societal pushback against altering practices such as residue burning. Enhancing policy backing, performing localized techno-economic evaluations, establishing incentive structures, and crafting market routes for recovered P products will be vital for broadening circular P systems and boosting long-term nutrient security, while easing environmental and economic stresses.