Exergy and Thermo-Economic Evaluation of an Integrated Waste-to-Hydrogen and Carbon Capture-Utilization System Using Waste-Derived CaO

The increasing global demand for clean energy carriers, coupled with the urgent need to mitigate greenhouse gas emissions and manage municipal solid waste (MSW) sustainably, has intensified interest in integrated waste-to-energy and carbon capture technologies. Hydrogen-rich syngas is widely recognized as a versatile intermediate for power generation, synthetic fuels, and chemical production, while carbon capture and utilization (CCU) offers a pathway to transform CO₂ from a liability into value-added products. Gasification of MSW provides an attractive solution by simultaneously addressing waste disposal challenges and enabling renewable hydrogen production. However, conventional gasification processes are often constrained by CO₂ emissions, energy inefficiencies, and limited economic competitiveness. This study presents an integrated modelling and simulation of waste gasification, calcium looping, and carbon capture utilization (CCU) for sustainable hydrogen-rich syngas and value-added calcium carbonate production. A gasification system processing 1000 kg/h of municipal solid waste was simulated in Aspen Plus, producing syngas with 54–58 vol% H₂, 23–26 vol% CO, 10–12 vol% CO₂, and 6-7 vol% CH₄, corresponding to a hydrogen output of approximately 520 kg/h and a cold gas efficiency of 78%. In parallel, 500 kg/h of waste cow bone was calcined to generate 320 kg/h CaO with >95% conversion, achieving 88% CO₂ capture efficiency and yielding 560 kg/h of CaCO₃ via carbonation. Exergy analysis revealed an overall exergy efficiency of 62%, with the gasifier accounting for the largest irreversibility share (35%). Thermo-economic assessment showed a total capital investment of USD 6.8 million, an annual net profit of USD 1.2 million, a net present value (NPV) of USD 4.5 million, and a payback period of 4.1 years. Sensitivity analysis identified gasification temperature and CaO regeneration efficiency as dominant factors affecting hydrogen yield and system profitability. The strong coupling between gasification operating conditions and calcium looping performance highlights the importance of integrated process design rather than isolated unit optimization. Overall, the proposed framework demonstrates a scalable and environmentally robust pathway for carbon-efficient hydrogen production, simultaneous waste valorization, and circular carbon utilization through CaCO₃ synthesis. By converting municipal solid waste and animal-derived residues into clean energy and marketable materials, the system aligns with circular economy principles and offers practical support for the transition toward low-carbon, resource-efficient, and sustainable energy systems.