Biochar as a Carrier of Struvite Precipitation for Nitrogen and Phosphorus Recovery from Urine

Abstract

Struvite precipitation is a promising approach to recover nitrogen (N) and phosphorus (P). However, poor solid−liquid separation of struvite precipitation crystallization can significantly decrease resource recovery efficiency. This study systematically investigates the recovery of N and P from urine through a combination of biochar with struvite precipitation. The N and P recovery efficiencies reach 4%–5% and 99%, respectively, and are stable with four different types of biochar at an optimized pH of 9.. A second-order kinetics model is demonstrated to describe the N and P recovery processes, which supports the further development of the promising resource recovery process. N and P recovery are enhanced via biochar adsorption and struvite precipitation, respectively. These results indicate that biochar, as a carrier of struvite precipitation to recover N and P from urine and as a slow-release fertilizer in agriculture, is feasible and practical.