Integrated digestate management: Contaminant control, valorisation and circular pathways

Digestate management is essential to both environmental protection and sustainable agriculture. However, its safe and effective agricultural use is increasingly challenged by strong variability in composition and the presence of persistent contaminants, including heavy metals, pharmaceuticals, microplastics and per- and polyfluoroalkyl substances. While numerous treatment and recovery technologies have been developed, existing research remains fragmented, often addressing individual contaminants or processes without a unified framework linking environmental risk, technological performance and system-level decision-making. This review systematically synthesizes current knowledge on digestate characteristics, contaminant profiles and treatment technologies, with particular emphasis on nutrient recovery, contaminant control and circular valorisation pathways. Conventional, advanced and emerging technologies are critically compared across Technology Readiness Levels, highlighting trade-offs between recovery efficiency, contaminant fate, energy demand and the generation of secondary waste streams. The analysis reveals that many widely applied technologies primarily redistribute contaminants into concentrated side streams, underscoring the need for integrated treatment trains that combine separation, recovery and destructive steps. Building on this synthesis, the review proposes a structured decision framework that links digestate composition and management objectives with appropriate technology combinations, explicitly integrating techno-economic feasibility, environmental performance and technology maturity. This framework provides a practical tool for selecting and designing digestate valorisation strategies tailored to feedstock characteristics and regulatory constraints. Finally, critical research gaps and policy needs are identified to support the transition toward environmentally safe, economically viable and circular digestate management systems.