a Biogas upgrading is an expanding field dealing with the increase in methane content of the biogas to produce biomethane. Biomethane has a high calorific content and can be used as a vehicle fuel or directly injected into the gas grid. Bioelectrochemical systems (BES) could become an alternative for biogas upgrading, by which the yield of the process in terms of carbon utilisation could be increased.The simulated effluent from a water scrubbing-like unit was used to feed a BES. The BES was operated with the biocathode poised at À800 mV vs. SHE to drive the reduction of the CO 2 fraction of the biogas into methane. The BES was operated in batch mode to characterise methane production and under continuous flow to demonstrate its long-term viability. The maximum methane production rate obtained during batch tests was 5.12 AE 0.16 mmol m À2 per day with a coulombic efficiency (CE) of 75.3 AE 5.2%.The production rate increased to 15.35 mmol m À2 per day (CE of 68.9 AE 0.8%) during the continuous operation. Microbial community analyses and cyclic voltammograms showed that the main mechanism for methane production in the biocathode was hydrogenotrophic methanogenesis by Methanobacterium sp., and that electromethanogenesis occurred to a minor extent. The presence of other microorganisms in the biocathode, such as Methylocystis sp. revealed the presence of side reactions, such as oxygen diffusion from the anode compartment, which decreased the efficiency of the BES. The results of the present work offer the first experimental report on the application of BES in the field of biogas upgrading processes.
The
stricter regulation regarding the use of fluorinated gases
(F-gases), as a consequence of their high Global Warming Potential
(GWP), represents a challenge for the refrigeration industry. The
design of alternatives requires the recycling of the low to moderate
GWP compounds from current refrigerant blends. However, there is not
a developed and standardized technology available to recover them,
and once the life cycle of the refrigeration equipment has ended,
most gases are incinerated. Fluorinated ionic liquids (FILs) can effectively
perform as absorbents to the complex separation of F-gas mixtures.
In this work, a methodology based on the COSMO-RS thermodynamic package
integrated into an Aspen Plus process simulator was used to evaluate
the performance of an FIL to recover difluoromethane (R-32) from the
commercial blend R-407F. The environmental sustainability of the recovery
process (circular economy scenario) was analyzed with a life cycle
assessment (LCA) approach, comparing the obtained results with the
conventional R-32 production (benchmark scenario). The results reveal
a 30% recovery of 98 wt % R-32 suitable for further reuse with environmental
load reduction in the 86–99% range compared to the R-32 production.
This study can guide the development of new F-gas recovery technologies
to improve the environmental impacts of these compounds from a circular
economy perspective.
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