Free-Methane: Waste carbon dioxide methanation with and without solid catalyst

Nowadays, one of the critical environmental problems on a global scale is the production of energy using technological methodologies reducing greenhouse gas emission and employing renewable resources. Recently, our research group was involved in a research project named “Free-Methane” aimed at developing and characterizing the optimal operating working conditions of the methanation reactor ProGeo having a 20kW output power [1]. The main goal of the “Free-Methane” project is to use either low cost or renewable energy to reuse waste CO2, generated by various industrial activities, as for example the ones produced in the ratio of 1.9 kg per liter from grapes fermentation of Marsala wine from Sicily (Italy), and those from fermentation of vegetable exhausted material supplied by the pharmaceutical drugs and herbal industry “VIS MEDICATRIX NATURAE S.r.l.” (Marradi, Florence, Italy), to generate methane in a circular economy scheme. To this end we have also undertaken the investigation of a new methanation pathway aimed at avoiding or minimizing the use of the solid catalyst, by exploring mechanisms involving a plasma generation by electrical discharges or by vacuum ultraviolet (VUV) photons on CO2 + H2 gas mixtures [2,3]. The experimental determinations performed using a microwave discharge beam source developed in our laboratory, gave useful indications on how to proceed to develop alternative solutions to the present Ni catalysed ProGeo apparatus by resorting to a gas-phase-only process for the reduction of CO2 to CH4. Such results highlighted the role played by the presence of CO+ and O+ ions having a very high kinetic energy on enhancing the chemical reactivity of plasmas containing CO2.