Trends in optimized biogas production: synthesis, characterization and use of magnetic iron nanoparticles to enhance the anaerobic digestion process

Abstract

Magnetic iron oxide nanoparticles were investigated for their potential to enhance biogas production through the anaerobic digestion of fruit and vegetable waste. The nanoparticles were synthesized via co-precipitation and characterized using Atomic Force Microscopy (AFM), UV-visible spectroscopy, and Magnetic Force Microscopy (MFM). MFM analysis revealed a magnetic force of -20 nN at a distance of 42 nm from the nanoparticles, with a magnetic gradient extending up to 100 nm in nanoparticle clusters. Anaerobic digestion experiments, conducted in Erlenmeyer flasks, employed a factorial design to optimize conditions such as moisture content, temperature, and inoculum percentage. Results demonstrated that the addition of iron oxide nanoparticles, at 34°C with 7% inoculum and 42% moisture content, led to a 55.53% reduction in substrate residual compared to control tests without nanoparticles. The presence of lactic acid confirmed the occurrence of acidogenesis, while higher concentrations of acetic acid in nanoparticle-enhanced tests suggested an influence on the acetogenesis phase. Additionally, the nanoparticles showed potential as adsorbents. These findings highlight the potential of magnetic iron oxide nanoparticles as an effective and sustainable method for improving biogas production from organic waste, with implications for urban areas and fueling centers seeking alternative, renewable energy solutions.