Comparative TEA–LCA of CHP, Biomethane, and Hybrid Biogas Utilization Pathways for Poultry Manure with Fruit and Vegetable Waste Co-Digestion Systems

Anaerobic digestion of organic waste offers renewable energy and waste-management benefits, relevant to multiple SDGs. This study evaluates a proposed 50 t/d farm-based biogas plant co-digesting poultry manure (PM) and fruit/vegetable waste (FVW) in South Africa. Five substrate blends (100% PM, 100% FVW, and three PM–FVW mixtures) and three biogas utilization routes (100% electricity via a combined heat and power (CHP) system, 50/50 CHP–biomethane, and 100% biomethane) were modelled in a combined techno-economic analysis (TEA) and life-cycle assessment (LCA) framework. Key metrics included GWP100 per ton of feedstock and the project’s internal rate of return (IRR), debt service coverage ratio (DSCR), and net present value (NPV) over a 20-year project lifespan. Under base-case assumptions, electricity-led pathways yield the highest returns; in the best case, 80% FVW + 20% PM with 100% CHP achieves a project IRR of 10% with a minimum DSCR of 2.4. The LCA shows total GWP100 ranging 118–168 kgCO2-eq/t, minimum for pure FVW, maximum for pure PM, and clearly identifies digestate handling as the dominant emission source. Overall, the CHP-only configuration emerges as the most financeable option at this scale, and emphasis on closed digestate management is recommended to minimize emissions.