Techno-Economic assessment of Energy-Optimised grass biomethane and biofertilizer production simulated with Aspen plus and pinch technology.

This study presents a techno-economic and energy assessment of anaerobic digestion (AD) fed by grass, with water scrubbing and ammonia stripping. Three plant capacities (25,000, 40,000, and 60,000 tonne/year) and three energy supply configurations were evaluated: A (conventional), B (Heat Exchanger Network (HEN)), and C (HEN and Heat Pump (HP)). The optimized HEN achieved full internal heat recovery, while HP supplied up to 63% of heating and 36% of cooling demands. Energy integration reduced utility consumption by 30-35% for Configuration B and by 55-60% for Configuration C. Economic analysis found that breakeven biomethane sale prices ranged from 103 €/MWh (122 $US/MWh) at an ammonia sale price of 200 €/tonne (236 $US/tonne) to 96 €/MWh (114 $US/MWh) at 1000 €/tonne (1183 $US/tonne) for large scale plant and configurations B and C. Overall, thermal recovery enhanced energy efficiency and economic profitability of AD plants. These results point to AD plant configurations that support climate-neutral and circular bioeconomy developments.