Enhancement of biogas production using nanostructured magnetite (Fe ₃ O ₄ ) 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 (<i>Cavia porcellus</i>) manure (PGPM). The nanoparticles were synthesized <i>via</i> 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.