Hydrogen production from fishing net waste for sustainable clean fuel: Techno-economic analysis and life cycle assessment

Fishing net waste (FNW) represents more than half of marine debris, posing a substantial challenge to marine ecosystems. Conventional disposal methods, such as landfills and incineration, contribute to environmental pollution and overlook valuable material recovery. To address this issue, an innovative process that converts FNWs into high-purity hydrogen (H₂) through pyrolysis under CO₂ conditions, integrated with a natural gas (NG) reforming process, was proposed. The resulting gas undergoes a water–gas shift (WGS) reaction with NG-reforming syngas, amplifying H₂ production yield. High-purity H₂ is achieved through pressure swing adsorption (PSA). The high-temperature flue gas from pyrolysis oil combustion is utilized to generate electricity via the steam Rankine cycle (SRC) process. Furthermore, CO₂ in the flue gas is liquefied and stored through a carbon capture and storage (CCS) process. Techno-economic evaluation and life-cycle assessment (LCA) were performed to scrutinize the efficiency and feasibility of the proposed process. This study first demonstrated that the CO₂-based waste fishing net pyrolysis integrated H₂ production process yielded 10.66 kmol h⁻¹ of H₂, providing a significant step toward sustainable H₂ production. Second, 87.13 % of wasted energy was recovered through the thermal integrated energy optimization of the waste fishing net and NG reforming process, and an additional 539.1 kW of electricity was generated through the SRC process, demonstrating high energy efficiency. Finally, although the levelized cost of hydrogen (LCOH) was slightly greater than that of the steam methane reforming (SMR) process, LCA revealed a significantly low greenhouse gas (GHG) index. Therefore, the proposed process serves as an eco-friendly approach to increase hydrogen production yield, which is a clean raw material with no carbon emissions, concurrently addressing the recycling of FNWs.