Enhancing carbon capture efficiency in biogas upgrading: A comprehensive review on adsorbents and adsorption isotherms
Authors: Selim Mahmoud M. , Tounsi Abdelouahed , Gomaa Hassanien , Shenashen Mohamed 
Published: April 2024

Biogas results from the anaerobic digestion of organic materials, a reliable and sustainable process that simultaneously manages organic waste and generates renewable energy. However, the presence of secondary impurities, such as carbon dioxide (CO2) and other gases, in raw biogas diminishes its efficacy, significantly lowering its energy content and restricting its utility across industry sectors. Moreover, these impurities contribute to various health and environmental concerns, including their role in exacerbating climate change and global warming. Consequently, efficient separation of CO2 is essential for upgrading biogas. The interest in utilizing biogas as a transportation fuel or as a substitute for natural gas has spurred the advancement of biogas upgrading technologies. While various methods exist for biogas upgrading, those relying on carbon dioxide absorption stand out as particularly significant. Carbon capture efficiency in biogas upgrading pertains to the ability of a method to effectively capture and separate CO2 from biogas, typically composed of methane (CH4) and other gases. This process is crucial for producing high-quality biogas with minimal carbon emissions, thus promoting environmental sustainability. Enhancing the carbon capture efficiency of the biogas upgrading process is essential for reducing greenhouse gas emissions and promoting cleaner energy production. The efficacy of CO2 separation relies on adsorbents and adsorption isotherms, which are integral components of this process. Improving these elements is vital for enhancing biogas purity, ensuring its suitability for various applications, and mitigating its environmental footprint. Traditional methods enhance the carbon capture efficiency by employing adsorbents, such as zeolites and activated carbon, as well as by optimizing adsorption isotherms. Surface modifications and adjustments to process parameters have also led to improved CO2 selectivity over other gases. Traditional methods still have drawbacks, such poor selectivity, difficulties with regeneration, and scalability. These limitations draw attention to the necessity of ongoing optimization, investigating substitute materials, and gaining a thorough grasp of how capacities, kinetics, and selectivity interact. Adsorbents and adsorption isotherms are the main topics of this study’s thorough analysis, which examines the state of the art in increasing carbon capture efficiency in biogas upgrading. It discusses conventional methods, their drawbacks, and suggests alternate materials, customized adjustments, and optimization techniques as a means of achieving ongoing progress. It is suggested that customized changes, ongoing optimization, and investigation of substitute materials be used to increase the effectiveness of carbon capture. To guarantee consistency, the study suggested specific rules for the procurement, preparation, and calcining of materials such as eggshells. In addition, to balancing CO2 and CH4 adsorption, improving adsorbent composition and addressing scalability, long-term stability, and practical implementation challenges are critical. The results of this study direct future studies toward a more sustainable and efficient energy landscape by adding to our understanding of carbon capture in biogas upgrading.