Iron-based nanoparticles have emerged as promising additives for enhancing biogas production and improving process stability in anaerobic digestion systems. This study evaluates three key iron nanoparticle types: zero-valent iron (NZVI), iron oxide (Fe₂O₃), and magnetite (Fe₃O₄), examining their performance across different particle sizes, concentrations, and waste treatment applications.

Results demonstrate that smaller particles (7-25 nm) consistently outperform larger variants due to their greater surface area. NZVI shows the highest reactivity, achieving methane production increases up to 120% at concentrations of 10-1000 mg/L, though it requires careful dosing to avoid negative effects. Fe₃O₄ provides the best balance of performance and sustainability, increasing biogas production by up to 154% at 100 mg/L while offering magnetic recovery capabilities for reuse. Fe₂O₃ delivers stable biogas improvements (up to 117%) with excellent methane quality (85.7%) and the lowest cost among the three options.

All iron nanoparticles effectively reduce hydrogen sulfide—a problematic gas that causes corrosion and odors—with NZVI achieving 70-90% removal. When combined with pretreatment methods, Fe₃O₄ can enhance methane production by 161-201%. Economic analysis shows potential annual savings of $272,400 and carbon dioxide emission reductions of 1,660 tons per year compared to conventional anaerobic digestion systems.These findings demonstrate significant potential for iron-based nanoparticles to advance waste-to-energy technology, with Fe₃O₄ offering the optimal combination of high performance, sustainability, and economic viability for commercial implementation.