Modular Biorefineries for Municipal Organic Waste in South America—Part I: National-Scale Screening of Technical Potential and Conditional Economic Thresholds

Previous Biorefinery Unit Block (BUB) work assessed the circular-economy concept at city scale. This Part I reformulates it as a physically consistent, replicable BUB (four digesters, 21,600 m3 effective volume, 6480 t of municipal organic matter per month) and scales it to ten South American countries under a uniform recoverable municipal-organic-matter coefficient and national pooling assumption, with the combined heat and power engine assigned by grid frequency. Economics combine an energy-only ledger with conditional screening of liquid-digestate (biol) valorization. For 435.734 million inhabitants, the model requires 729.07 equivalent and 734 physical BUBs (99.33% utilization), giving technical potentials of 56.69 Mt/yr of organic matter, 4.535 × 109 Nm3/yr of biogas, 9.489 TWh/yr of net electricity and 221.3 Mm3/yr of biol, with screening process-plant capital expenditure of USD 3.844 billion. The energy-only break-even is 75.29–78.48 USD/MWh at national utilization; 11 of the 13 country–price scenarios lie below it. Under a common Peru-reference marker, the required product of biol-use and value-capture fractions falls below 0.9 in several tested combinations when application and haul costs are low, and potassium credit is high. These are conditional thresholds, not evidence of viability: fractions are not empirically assigned, and country-specific costs are excluded.