Anaerobic digestion for biogas production is one of the most used technology for bioenergy. However, the
adoption of nanoparticles still needs further studies. Therefore, this study was designed to examine the effect of
metal oxide nanoparticles (MONPs) at four different concentrations in two different combinations, 20 (R1) and
100 (R2) mg/L for Fe2O3, 100 (R3) and 500 (R4) mg/L for TiO2, and a mixture of Fe2O3 and TiO2 at rates of 20,
500 (R5) and 100, and 500 (R6), on hydrogen sulfide (H2S) mitigation, biogas, and methane (CH4) yield during
the anaerobic digestion of cattle manure (CM) using an anaerobic batch system. The results showed that H2S
production was 2.13, 2.38, 2.37, 2.51, 2.64, and 2.17 times lower than that of the control (R0), respectively,
when the CM was treated by the aforementioned MONPs. Additionally, biogas and CH4 production were 1.09
and 1.105, 1.15 and 1.191, 1.07 and 1.097, 1.17 and 1.213, 1.10 and 1.133, and 1.13 and 1.15 times higher than
those of R0 when R1, R2, R3, R4, R5, and R6 were supplemented with MONPs, respectively. The highest specific
production of biogas and CH4 was 336.25 and 192.31 mL/gVS, respectively, which was achieved by R4 supplemented
with 500 mg/L TiO2 NPs, while the corresponding values in the case of R0 were 286.38 and 158.55
mL/gVS