Approaching circular economy through waste-to-blue hydrogen: Systems modeling and multi-objective optimization

Hydrogen is gaining increasing recognition as a clean and versatile energy carrier. The conversion of waste materials into energy or chemical products plays a crucial role in the circular economy paradigm. This study provides a comprehensive analysis of the waste-to-blue hydrogen process. The process entails co-gasification of a mixture of waste materials such as plastics and biomass. The system incorporates a rigorous modeling of the carbon capture process using a blended MDEA/PZ solvent to produce blue hydrogen. A multi-objective optimization framework is introduced to simultaneously minimize the levelized cost of hydrogen and the cradle-to-gate lifecycle endpoint value. The minimum levelized cost of hydrogen determined through this analysis is $3.02/kg, which substantiates the economic feasibility of the system under consideration. The minimum life cycle endpoint value is 247.23 mPt per kilogram of H₂, 49.38 % lower than the conventional steam methane reforming technique. The observations indicate that increasing the mass fraction of biomass in the feedstock, raising the gasifying temperature, and lowering the oxygen-to-feed ratio have a positive influence on both the final levelized cost of hydrogen and the life cycle endpoint value. The Pareto curve provides decision-makers with valuable insights into the trade-off between the two objectives.