The 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.
Biogas production generates anaerobic digestate, a nutrient-rich byproduct that, if unmanaged, can pose environmental and safety risks such as greenhouse gas emissions and soil contamination. This review proposes globally applicable guidelines for sustainable digestate management, emphasizing nutrient conservation, micropollutant control, and alignment with carbon neutrality and the Sustainable Development Goals. It evaluates biological, chemical, thermal, and mechanical valorization methods to improve digestate quality before soil application, enhancing fertilization benefits while reducing environmental impacts. The review provides practical insights and research directions to support circular and sustainable management of anaerobic digestate.
