A Spatial Multi-Criteria Framework for Data-Driven Anaerobic Co-Digestion Substrate Selection in Tropical Regions

The transition towards a circular bioeconomy in developing regions is frequently hindered by operational failures caused by feedstock discontinuity. Whilst biochemical potential is traditionally the primary selection criterion, this study postulates that logistic reliability serves as the governing constraint. To validate this strategic reorientation, a decision-making framework was developed and applied to a representative tropical agro-industrial region. A sensitivity analysis comparing objective, subjective and neutral weighting scenarios identified annual residue production as the dominant factor. Results established cattle manure as the universal baseload substrate essential for mitigating seasonality, outweighing higher-yielding but intermittent agricultural residues. Spatial analysis revealed distinct territorial vocations, identifying a high-availability rice–livestock cluster in the south suitable for centralised industrial plants and dispersed cassava–livestock nodes in the centre favourable for decentralised digestion. Furthermore, the assessment of energy autonomy demonstrated that the prioritised co-digestion scenarios could cover local residential electricity demand between 1.5 times and 81 times. Crucially, residues favoured by expert judgement proved logistically unfeasible despite superior theoretical yields. This data-driven approach demonstrates that successful substrate selection must transcend theoretical yield maximisation to prioritise supply chain reliability, providing a robust roadmap for de-risking bioenergy investments and ensuring regional energy autonomy.