Selective hydrogenation of eggshell/clamshell to methane with the assistance of the alkaline earth and transition metals at room temperature.

[Display omitted] • Mechanochemical hydrogenation of shell wastes was studied at room temperature. • Alkaline metals can selectively assist the hydrogenation of shell wastes to CH 4. • The calcium metal has a better effect and the methane yield can reach 45.04%. • By doping Ru the methane yield of shell wastes can be improved to 54.76%. • This study provides a method to eliminate shell wastes and produce CH 4 fuel. Producing clean fuel using shell wastes (eggshell and clamshell) can eliminate food waste and alleviate the energy shortage. Mechanochemical hydrogenation of eggshell/clamshell was investigated at room temperature. The results show that the alkaline earth metals can effectively assist the hydrogenation of shell wastes to CH 4. The calcium metal has a better effect, and the methane yield for the calcium-assisted hydrogenation of clamshell and eggshell reaches 45.04% and 33.30% with 100% CH 4 selectivity. At the same time, the calcium-assisted methanation of shell wastes in the presence of transition metals (Fe, Co, Ni, Ru) was investigated. By doping Ru, the methane yield of clamshell and eggshell was improved to 52.62% and 54.76%, respectively. The milling time, rotating speed, hydrogen pressure, and the species of the doped transition metals influence the calcium-assisted methanation of shell wastes. This study provides an alternative method to eliminate shell wastes and produce clean CH 4 fuel at room temperature. [ABSTRACT FROM AUTHOR]