Enhancement of biogas production using nanostructured magnetite (Fe3O4) in a biodigester fed with Peruvian guinea pig manure†

Magnetite nanoparticles were used to increase biogas production in a biodigester fed with Peruvian guinea pig (Cavia porcellus) manure (PGPM). The nanoparticles were synthesized via two different methods—coprecipitation and polyol—and thus showed different sizes of 410.7 nm and 34.03 nm, respectively. Likewise, various configurations were tested using three distinct Fe₃O₄ proportions, with each configuration tested in triplicate biodigesters. The coprecipitation trial with Fe₃O₄ was tested with an initial substrate of 5.57 g of chemical oxygen demand (COD) and 0.96 g of volatile solids (VSs) as inoculum. This ferrous additive led to a methane production increase of up to 9.61%, with a biodegradability of 57.91%. At the same time, the polyol trial with Fe₃O₄ was tested with an initial substrate of 34.47 g of COD and 0.80 g VS as inoculum, increasing methane production by up to 64.5% with a biodegradability of up to 8.56%. Moreover, the inhibitory effect of the synthesized Fe₃O₄, which was inconsequential for bacterial growth, was analyzed. Therefore, these nanoparticles have been shown to support methanogenic bacteria in enhancing methane production.