Exploring the effects of static magnetic fields for the enhanced valorization of sewage sludge by anaerobic digestion

Anaerobic digestion (AD) is an interesting and sustainable option to handle sewage sludge (SS), as it generates a methane-rich biogas and a digestate with potential fertilizing properties. Several strategies have been proposed to enhance AD performances and the valorization of SS. Among these, the application of a static magnetic field (SMF) has been poorly evaluated and recently gained attention. This work investigated the effect of low-intensity SMF (20-50 mT) on methane production from AD of SS, comparing it to the effect deriving from the application of a high-intensity SMF (1.5 T). Magnetic pretreatment at 20 mT was particularly effective, as it increased biomethane production up to 12.9% compared to the control test. On the contrary, 1.5 T was detrimental in terms of cumulative methane production, as it resulted in a 20.9% decrease. These outcomes suggest that SMF intensity is inversely related to biomethane generation and that further investigations are worthy to understand the mechanisms underlying AD enhancement by SMF application.