Biogas is one of the most attractive renewable resources due to its ability to convert waste into energy. Biogas is produced during an anaerobic digestion process from different organic waste resources with a combination of mainly CH4 (~50 mol/mol), CO2 (~15 mol/mol), and some trace gasses. The percentage of these trace gases is related to operating conditions and feedstocks. Due to the impurities of the trace gases, raw biogas has to be cleaned before use for many applications. Therefore, the cleaning, upgrading, and utilization of biogas has become an important topic that has been widely studied in recent years. In this review, raw biogas components are investigated in relation to feedstock resources. Then, using recent developments, it describes the cleaning methods that have been used to eliminate unwanted components in biogas. Additionally, the upgrading processes are systematically reviewed according to their technology, recovery range, and state of the art methods in this area, regarding obtaining biomethane from biogas. Furthermore, these upgrading methods have been comprehensively reviewed and compared with each other in terms of electricity consumption and methane losses. This comparison revealed that amine scrubbing is one the most promising methods in terms of methane losses and the energy demand of the system. In the section on biogas utilization, raw biogas and biomethane have been assessed with recently available data from the literature according to their usage areas and methods. It seems that biogas can be used as a biofuel to produce energy via CHP and fuel cells with high efficiency. Moreover, it is able to be utilized in an internal combustion engine which reduces exhaust emissions by using biofuels. Lastly, chemical production such as biomethanol, bioethanol, and higher alcohols are in the development stage for utilization of biogas and are discussed in depth. This review reveals that most biogas utilization approaches are in their early stages. The gaps that require further investigations in the field have been identified and highlighted for future research.

Currently, a novel green material, defatted spent coffee ground (DSCG), is employed as a support to prepare DSCG supported Ru (DSCG‐Ru) material. DSCG and DSCG‐Ru materials are characterized by advanced surface analytical techniques such as N2 adsorption‐desorption, X‐ray diffraction, X‐ray photoelectron spectroscopy, and H2‐temperature‐programmed reduction. Characterization results revealed that DSCG‐Ru was prepared successfully. First, DSCG‐Ru is prepared at varying Ru contents on deoiled coffee waste and hydrogen production experiments are performed by the methanolysis of sodium borohydride on the DSCG‐Ru catalysts. It is observed that optimum conditions for the catalyst preparation are examined on the 10% Ru containing DSCG‐Ru catalysts and found as 10% Ru, 300°C, and 60 minutes. DSCG catalyst containing 10% Ru completed the methanolysis reaction in 1.5 minutes. Capacitive measurements to investigate the supercapacitor property of DSCG‐Ru catalysts prepared at optimum conditions 10% Ru, 300°C, and 60 minutes is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge‐discharge measurements. Results revealed that gravimetric capacitance of the electrode at a current density is found as of 0.5 A/g and 43 F/g, greater than the literature values. DSCG‐Ru, green novel supported Ru catalyst, has a dual promising performance in hydrogen production and supercapacitor measurements.

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