Life Cycle Analysis and Operating Cost Assessment of a Carbon Negative Catalytic Pyrolysis Technique Using a Spent Aluminum Hydroxide Nanoparticle Adsorbent-Derived Catalyst: Insights into Coproduct Utilization and Sustainability

Abstract

The current research is intended toward the life cycle analysis (LCA) and operating cost assessment of catalytic and noncatalytic pyrolysis. The study assessed the impact of waste material-based catalysts (spent aluminum hydroxide nanoparticle (AHNP) adsorbent-derived catalysts) on the process’ overall environmental load and operating cost. Incorporating the utilization of process coproducts through recycling both noncondensable gases (NCGs) and biochar in the pyrolysis process, as well as exporting biochar as a coal substitute, reduced the values of the environmental impact and operating cost. Results revealed that biochar market export as coal replacement (for earning coal credits) is comparatively more beneficial than its back-recycling in the pyrolysis process (for offsetting natural gas requirements) from the environmental perspective. However, the reverse is true from the economic viewpoint in terms of operating cost. Among different considered processes, nickel-doped AHNP (Ni/Al)-catalyzed pyrolysis with scenario 2 (wherein all the produced biochar was coal-credited and all the NCGs were back-recycled) portrayed the highest environmental benefits owing to the maximum negative emissions (∼0.031 kg CO2 equivalent GHG emission saving). Low standard deviations (<10%), as obtained through Monte Carlo uncertainty analysis, indicated toward the reliability and robustness of the obtained LCA impacts. The present study exemplified the renewability and environmental friendliness of the AHNP-catalyzed pyrolytic biofuel over conventional petroleum-derived diesel and gasoline fuels.