Advancing food waste anaerobic digestion: linking life cycle assessment and techno-economic analysis for sustainable energy

Zainab I. Elkahlout, Muhammad Aamir Shahzad, Zukhruf Asim, Farah Sangor, Arjumand Shah Bano, Abdullah M. AlSalal, Fares AlMomani, Kashif Rasool

Food waste valorization through Anaerobic Digestion (AD) represents a sustainable and circular approach to managing organic residues by converting them into valuable bioenergy and biobased products. Despite a growing body of literature on food waste AD, a critical methodological gap persists in which existing reviews largely treat reactor-level performance, life cycle assessment (LCA), and techno-economic analysis (TEA) as discrete fields, leaving the spreading of high-rate reactor uncertainties into integrated LCA/TEA scaling decisions largely unresolved. This review directly bridges that gap by systematically linking process-level performance metrics to sustainability and economic outcomes within a cohesive analytical framework. The biochemical composition of food waste is examined first, emphasizing carbohydrate, protein, and lipid content influence digestion efficiency and methane yields. Recent technological advancements in high-rate digestion systems are critically analyzed, including Upflow Anaerobic Sludge Blanket (UASB), Expanded Granular Sludge Bed (EGSB), and Internal Circulation (IC) reactors with particular attention to operational bottlenecks such as granule stability, inhibitory compound accumulation, and scale-up constraints that limit real-world performance relative to laboratory benchmarks. Two-stage AD (TSAD) configurations and membrane bioreactor (MBR) innovations are assessed for their capacity to enhance CH₄ yields and improve biomass retention, though at the cost of increased capital expenditure and process complexity. Substrate pretreatment strategies are assessed for their effectiveness in enhancing biodegradability and biogas production by 25–80%, combined with the energy penalties and reagent costs that frequently offset these gains on a commercial scale. These process-level trade-offs are carried forward into a structured synthesis of co-digestion approaches are examined for synergistic benefits. Whereas LCA studies confirm that AD reduces environmental impacts across multiple impact categories relative to landfilling and incineration. Critically, TEA findings reveal that economic viability remains sensitive to feedstock heterogeneity. The integration of AD within sustainable food systems supports nutrient recovery, decentralized waste management, and renewable energy generation. However, realizing these co-benefits at scale requires resolving constant uncertainties in digestate quality standards, gate fee structures, and carbon accounting methodologies from most TEA framework. Thus, these findings advance the transition toward a circular bioeconomy by providing a coherent, critically grounded framework that connects high-rate reactor design to real-world sustainability performance.