A mathematical model for the vacuum evaporation process was developed and validated to remove ammonia from anaerobically digested sludge under different pH and temperature conditions. Six combined process scenarios were tested using Anaerobic Digestion Model 1. The most effective options were vacuum evaporation as a post-treatment at pH 9 and as an intensification step at pH 9, both recovering over 76% of the influent nitrogen without reducing methane production. Economic analysis showed that the pH-9 intensification scenario was cost-neutral, performing significantly better than the control scenario, which had a net present value of –22 million dollars.
Vacuum-evaporation-coupled-with-anaerobic-digestion-for-process-intensification-and-ammonia.pdfThe growing volume of anaerobic digestate makes its sustainable reuse increasingly important and challenging. This study examines both established and emerging technologies that treat digestate as a secondary resource for nutrient recovery. A review of digestate composition showed large variations in nutrient content, with nitrogen ranging from 1.6–21% and phosphorus from 0.1–3.5% (dry basis). These levels highlight its potential as a feedstock for producing higher-value bio-based fertilizers within circular, zero-waste systems. The collected knowledge was then used to design two integrated biorefinery scenarios capable of converting digestate into bio-based products for new supply chains.
Exploring-technological-alternatives-of-nutrient-recovery-from-digestate-as-a-secondary-reso-2.pdf