Carbon-neutral polygeneration utilizing biogas-reforming and biomass-combustion; life cycle assessment and machine learning assisted optimization

Growing global energy demand, and relying heavily on fossil fuels to meet these energy needs led to serious environmental and economic concerns. Within the gate-to-gate operational boundary, this work introduces a revolutionary polygeneration carbon neutral process that can concurrently produce valuable products (electricity/heating/cooling/syngas) with negligible CO2 emissions. This configuration combines a biomass combustor, with biogas bi-reforming unit, Rankine cycle with orthoxylene organic working-fluid, and absorption chiller, which are simulated using Aspen-HYSYS software. The study applies the evaluation process integrated with life cycle assessment and profitability analysis, while the optimal operating is determined using comparative machine learning-assisted multi-objective optimization approach. With a net electricity of 356 kW, heating and cooling capacities of 282 kW and 325 kW, and a syngas production of 0.7754 kg/s, the system shows exceptional efficiencies of 96.92% and 71.63% for energy and exergy. Furthermore, the system maintains a nearly zero CO2 footprint (0.000858 kg/kWh) along with negative global warming potential (−0.0038 kgCO2-eq/kWh), which highlight its novelty contribution toward low-carbon system. Moreover, the system demonstrated indicates that the energy production and product generation processes operate at a competitive cost level, with the cost of energy of 0.19 $/kWh and the total unit cost of product (TUCP) of 4.21 $/GJ, which results net present value of 8.26 million $, and a payback-period of 6.21 years. The Firefly optimization algorithm find the optimal configuration with efficiency of 73.60% for exergy and TUCP of 4.03 $/GJ. The Monte-Carlo sensitivity evaluation indicates that the mass flow of biogas as the most influential variables affecting system performance.