Microbial conversion of oily wastes to methane: effect of ferric nanomaterials

Abstract

Petroleum-based oily wastes are generated by the oil industry and can be treated/valorized by anaerobic microbial conversion to methane. However, this process is generally slow. Conductive nanomaterials were reported to accelerate the interspecieselectron transfer in anaerobic communities and therefore their addition to anaerobic processes treating hydrocarbons may also be advantageous. In this work, two ferric nanomaterials (magnetite and carbon nanotubes impregnated with 2% iron) were tested in microcosms amended with hexadecane and 1-hexadecene. Assays were also made with palmitate, acetate and H2/CO2, which are intermediates of hydrocarbons biodegradation.With the exception of hexadecane, methane was produced at close-to-stoichiometric amounts for each of the substrates tested. Methane production rates were similar with and without the nanomaterials, possibly due to the inability of the microorganisms to receive/transfer electrons to the materials in this microbial community, suggesting that electron transfer occurred indirectly via soluble electron shuttles (e.g. hydrogen or formate).