Techno-economic analysis of nutrient recovery from urine: Centralized treatment of hydrolyzed urine vs. decentralized treatment of fresh urine.

The centralized process integrating "Thermal NH stripping → Na-chabazite adsorption → Struvite precipitation" has been proposed for nutrient recovery from hydrolyzed urine. Meanwhile, a decentralized approach involving Na-chabazite and biochar adsorption has been suggested for fresh urine, followed by urea hydrolysis and the subsequent centralized integration of struvite precipitation and thermal stripping. However, a systematic comparison of nutrient recovery processes for fresh and hydrolyzed urine, evaluating both technical viability and financial feasibility, is lacking. This study addresses the gap by thoroughly examining both scenarios over a 30-year project, using Université Laval as a case study. It provides a comprehensive roadmap for techno-economic assessment, offering guidance for evaluating nutrient recovery processes prior to scaling up. The decentralized process achieved higher recovery efficiencies for nitrogen and phosphorus, at 89.4 % and 98.7 %, respectively. Financially, the decentralized scenario demonstrated its advantage in the lower initial investment requirement, thereby generating higher gross profits compared to the centralized scenario. As a result, it is projected to reach the break-even point in the 21st year, demonstrating its potential economic feasibility. Sensitivity analysis indicated that a 20 % increase in urine inflow rate and the price of urea-enriched biochar could further enhance the economic viability of both processes. Beyond financial considerations, both scenarios have the potential to reducing the contaminant loading rate in the downstream wastewater treatment plants and promote nutrient recovery and recycling.