| Abstract |
The process of biological methanation (BM), which involves the reaction between carbon dioxide (CO 2 ) and hydrogen (H 2 ) producing methane (CH 4 ), is a circular economy strategy that can alleviate the problem of energy storage and also reduce CO 2 emissions. By harnessing a renewable energy source to facilitate H 2 production through water electrolysis and by capturing CO 2 , e.g. from industrial flue gases or biogas, this Power -to -Gas (PtG) technology produces CH 4 , the predominant compound of synthetic natural gas (following appropriate purification/enhancement towards biomethane). During the last decade, BM process has been examined fundamentally by various research groups both in lab-scale, as well as in pilot-scale experiments/applications. Nevertheless, a significant portion of these studies lack presentation of technical details and implementation strategies, regarding the operation of existing BM units in real-world applications. The current work aims to offer a thorough review of biological methanation, focusing on its practical implementation, particularly examining the most notable full-scale (industrial) applications utilizing this technology. To the best of the authors ' knowledge, the specific review provides the first comprehensive insight on the application of biological methanation and potentially consists a 'technology catalogue ' that includes both the latest lab-/pilot-scale research advancements and the most significant demonstration-/full-scale plants currently installed in Europe. After the presentation of BM process fundamentals and the respective basic reactor types, the study presents the current research, and also substantial information, regarding the operation of certain (largest) full-scale BM plants, installed in Germany, Switzerland and Denmark. Biomethanation integrates two solutions to pressing environmental challenges, likely related to waste and carbon emissions reduction and aligns with the principles of the circular economy, that aims to minimize waste and make the most of resources by reusing and recycling. Additionally fits into the emerging field of Carbon Capture and Utilization (CCU) aimed at mitigating Greenhouse Gas (GHG) emissions. However, although the scale-up of BM process has evolved, further operating information and economic data on demo- and full-scale plants should be appropriately investigated to ensure the economic feasibility and, therefore, the widespread application of this PtG technology. |