Integrated valorization of algae residue and oily sludge into hydrogen and liquid biofuels: detailed process simulation and preliminary operational assessment

The use of biomass for fuel production can considerably reduce the environmental footprint of the energy sector. In this context, microalgae residue and industrial oily sludge emerge as promising feedstocks for the production of sustainable fuels. This work evaluates the technical feasibility and provides a sensitivity analysis of an integrated waste-to-fuel pathway for the co-production of hydrogen and liquid biofuels from waste-derived feedstocks. The pathway combines microwave pyrolysis, reforming and water gas shift of the gaseous fraction, hydrogen-free hydrodeoxygenation of the liquid fraction, and valorization of the solid residue as activated carbon. The same framework is applied to algae residue and oily sludge to assess its robustness toward feedstock variability. Mass and energy balances of the process are derived through Aspen Plus and Aspen HYSYS simulations, allowing the evaluation of key performance indicators. The results show overall energy efficiencies between 41% and 48%, with oily sludge yielding higher liquid fuel production and superior energetic performance. A sensitivity analysis further identifies the hydrocarbon-rich liquid yield and microwave conversion efficiency as the most critical parameters. The results indicate that the proposed process layout represents a promising process configuration for the valorization of waste-derived feedstocks, while co-pyrolysis configurations are left for future investigation.