Breathe inside the box: optimizing conditions for bioelectrochemical methane production to indoor carbon dioxide valorization and enhance air quality

Abstract

Carbon capture and utilization technologies play an essential role in improving indoor air quality by reducing elevated levels of carbon dioxide (CO2) in enclosed spaces, which have a wide range of effects on human health. Coupling microbial electro-methanogenesis (EM) with direct air capture (DAC) technologies might open a new window of possibilities for decentralized, modular, smaller-scale, real-world applications. This study evaluated, for the first time, the operation of a novel hybrid platform integrating a DAC unit for indoor CO2 capture and concentration with a bioeletrochemical system for methane production (EM-BES). The DAC unit produces two key outcomes: a concentrated CO₂ stream and clean indoor air. The indoor captured CO2 stream (purity 7–17 %) was used by the EM-BES unit, achieving a methane production rate of 13.3 ± 5.1 L m−2 d−1 and nearly complete carbon conversion to grid-standard quality methane (>96 % methane content, higher heating value 39.8 MJ Nm−3). This experimental work provides a baseline for validating the technology in a real indoor environment. Finally, an assessment of its possible exploitation strategy and inclusion in the green urban infrastructures of the future is presented

This research was funded by the Spanish Ministry of Science (AEI) through the grant Proyectos de Transición Ecológica y Digital (TED2021-129452B-I00) in the framework of the De-Cent project. S.B. was a “Juan de la Cierva Formación” fellow (JdC F 2021, ref. FJC2021-047260-I) at the time of the experimentation and acknowledges the funding from the Spanish Ministry of Science and Innovation. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101018274 (L.R. López). S.P. is a Serra Hunter Fellow (UdG-AG-575) and gratefully acknowledges the funding from the AGAUR–ICREA Academia Programme, supported by the Department of Research and Universities of the Government of Catalonia. LEQUIA and EcoAqua have been recognized as “consolidated research groups” (Ref. 2021 SGR01352 and 2021 SGR01142) by the Catalan Government. Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier.

7

9