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Volatile methyl siloxanes (VMS) are persistent contaminants extensively used in industrial applications. Their presence in biogas constitutes a major hindrance for its energetic valorization or its use as renewable natural gas. Current commercial siloxanes abatement technologies are based on physical-chemical methods, whose good performance is impaired by their high investment costs, and a hefty environmental impact. Research evidences that VMS are indeed biodegradable, which opens the possibility of implementing bio-based technologies as a cost-effective and sustainable alternative for the removal of these compounds. This review uncovers the most plausible organisms and microbial pathways involved in biological VMS degradation, a relatively unexplored area. Additionally, the most commonly applied configurations and the main operating challenges are thoroughly revised and discussed, evidencing that a feasible implementation relies on the optimization and scale-up of enhanced mass transfer bioreactors. Finally, the techno-economic and environmental analysis demonstrate that, although in a very early stage, emerging biological technologies for siloxanes removal will play an important key role on the future abatement of VMS from waste gas streams such as raw biogas. [ABSTRACT FROM AUTHOR]

Graphene – a carbon nanomaterial has gained huge research interest due to its intriguing and extraordinary properties such as large surface area, excellent electrical conductivity, ultra-thinness, high electron mobility, and superior mechanical strength. The combination of graphene with other inorganic nanoparticles can significantly boost its physiochemical properties and hence, opens up new frontiers of its utilization. Grapheneis significantly exploited for the energy storage systems due to its great potential for electrochemical energy storage. However, the experimental electrochemical performance of graphene is still far away from the theoretical facts. This study critically evaluated the existing synthesis routes for the production of graphene, graphene-based composites and their utilization in the energy storage applications. Furthermore, the techno-economic analysis of the synthesis methods was undertaken to determine the best routes in terms of sustainability for commercial graphene production. Lastly, the fundamental understanding of graphene growth mechanisms and the overall intricacies of the synthesis processes were highlighted and the possible way forward is proposed. Therefore, in the quest for the development of effective alternative yet sustainable energy storage devices; it is hoped that this research will give useful insights to researchers and key players in the electronics industry. [ABSTRACT FROM AUTHOR]