Thermophilic Biogas Upgrading via ex Situ Addition of H and CO Using Codigested Feedstocks of Cow Manure and the Organic Fraction of Solid Municipal Waste.

Bioconversion of renewable H and waste CO using methanogenic archaea is a promising technology for obtaining high-purity CH, which can serve as an alternative for natural gas. This process is known as ex situ biogas upgrading. This work highlights the pathway toward the bioconversion of renewable H and CO into high-purity biomethane by exploiting highly accessible agro-municipal residues: cow manure (CM) and the organic fraction of solid municipal waste (OFSMW), which used to be called "waste materials". More specifically, an ex situ thermophilic (55 °C) biogas upgrading process was conducted by CM and OFSMW codigestion at different mass proportions: 100:0, 80:20, 70:30, 60:40, and 50:50. Maximum CH concentrations of 92-97 vol % and biogas volumetric production rates of 4954-6605 NmL/L.d were obtained from a batch reactor of 3 L working volume. Feedstock characterization, pH monitoring, and the carbon-to-nitrogen ratio were critical parameters to evaluate during biogas upgrading experiments. In this work, the usefulness of agro-municipal substrates is highlighted by producing high-purity biomethane-an energetic chemical to facilitate renewable energy conversion, which supports various end-use applications. This process therefore provides a solution to renewable energy storage challenges and future sustainable and green energy supply.