Dry Anaerobic Digestion as a Waste-to-Energy Pathway: A Systematic Review of Performance, Scalability, and Deployment Evidence from 2010 to 2025

Abstract

Dry anaerobic digestion (DAD) is increasingly recognized as a promising waste-to-energy pathway for treating high-solids organic wastes. However, the extent to which the contemporary peer-reviewed literature addresses conditions relevant to scalable implementation remains unclear. This systematic review synthesizes evidence from 148 studies on technological performance, process stability, scalability readiness, and deployment conditions. The evidence base was geographically and methodologically concentrated, with a predominance of laboratory-scale, batch-operated, and mesophilic systems. Co-digestion, pretreatment, operating-condition optimization, and recirculation were frequently investigated strategies. Methane performance varied substantially, reflecting differences in feedstock characteristics, solids content, reactor configurations, and operating conditions. Process stability remained a central concern, with pH, volatile fatty acids, and ammonia-related parameters the most frequently reported indicators, consistent with challenges associated with acidification, ammonia inhibition, and mass-transfer limitations. The scalability assessment showed that most studies provided limited evidence on advanced deployment maturity and enabling conditions, while commercial-scale implementation, financing, stakeholder engagement, and policy support were infrequently represented in the reviewed literature. The 2010–2025 peer-reviewed evidence base remains more strongly oriented toward technological and experimental optimization than integrated deployment-oriented assessment. Greater integration of long-term operational validation with techno-economic, institutional, and implementation-related evidence is needed to understand conditions for reliable and scalable DAD deployment.