Periodic Reporting for period 1 - ATMESPHERE (Advanced Technology for Microbial Electro-Synthesis of Platform cHemicals and Efficient in-situ Recovery via Electrodialysis)
Reporting period: 2022-02-01 to 2024-01-31
The intensive use of fossil fuels caused the raise of atmospheric CO2 levels. High (>400 ppm) CO2 concentrations in the atmosphere are resulting in environmental problems including global warming, and in an increased frequency and severity of extreme weather event. To counteract these issues, EU committed to cut by 40% its greenhouse gas emissions by 2030. The achievement of such ambitious target is linked to a switch from fossil fuels to renewable sources of energy and chemicals. This is driving carbon-intensive industries such as paper, food, energy, cement, and oil refining industries, towards the circular economy concept, in which side- and waste-streams, including CO2 streams, are a feedstock for fuel and/or chemical production. Indeed, CO2 is a building block for synthesising a wide array of chemical and energy-rich products through (bio)technological routes. Biological processes, in which enzymes or microorganisms are employed to convert CO2 into products, are inherently circular, enable carbon-neutral or even carbon-negative balance, and demand less energy than chemical processes. Among these biological processes, microbial electrosynthesis (MES), in which specific bacteria convert CO2 and renewable electricity to green chemicals and fuels, is a promising technology to contribute reducing industrial CO2 emissions, and at the same time enable circular economy. However, to date, the adoption of MES in industry is hindered by sub-optimal production rates, yields and product purity. The ATMESPHERE project aimed to develop a novel, multi-step process for the production, extraction and purification of caproic acid, a platform chemical that finds application in the food and chemical industry, from CO2.
Overall, the ATMESPHERE project reached the planned objective by developing (i) a bioelectrochemical platform for CO2 capture and utilization, (ii) a fermentation platform for further upgrading MES products such as ethanol and acetic acid to caproic acid, and (iii) a downstream processing method to concentrate and purify the final products. Technologies such as those developed in ATMESPHERE will contribute to the paradigm shift towards resource recovery and circular economy, leading the way towards a “green” industrial revolution. This will drastically reduce waste generation and pollution in comparison with the traditional, linear economic model, with clear benefits for the well-being of the whole society.
Overall, the ATMESPHERE project reached the planned objective by developing (i) a bioelectrochemical platform for CO2 capture and utilization, (ii) a fermentation platform for further upgrading MES products such as ethanol and acetic acid to caproic acid, and (iii) a downstream processing method to concentrate and purify the final products. Technologies such as those developed in ATMESPHERE will contribute to the paradigm shift towards resource recovery and circular economy, leading the way towards a “green” industrial revolution. This will drastically reduce waste generation and pollution in comparison with the traditional, linear economic model, with clear benefits for the well-being of the whole society.
The bioelectrochemical platform developed consisted in compact, electrically efficient electrochemical cells inoculated with microorganisms capable of capturing CO2 and converting it to valuable product including carboxylic acids (acetic and butyric acids) and alcohols (ethanol and butanol). In this study, we focused on tailoring the operation conditions (pH, hydrogen partial pressure, CO2 concentration) to selectively produce butyric acid, while minimizing the electric energy input necessary for the conversion. We achieved butyric acid production with up to 78% selectivity, consuming an average of 34.6 kWh/kg. The results of this study are publicly available (https://doi.org/10.1016/j.ese.2023.100303(opens in new window)) and have been disseminated by oral presentation at the last EU-ISMET conference in Wageningen.
The fermentation platform consisted in a novel, membrane-based reactor configuration that allowed to isolate the caproic acid producing microbial community from both microbiological and chemical contamination in the feed stream. The membrane used indeed allowed the diffusion of the substrates necessary for caproic acid production (ethanol and acetic acid) while retaining microorganisms and the majority of chemical pollutants. Furthermore, it allowed to control the diffusion ratio between ethanol and acetic acid, which is a crucial factor for optimizing caproic acid production, by simply modifying the pH of the feed solution and the membrane wall thickness. This resulted in selective (99%) production of caproic acid at a highest rate of 3.1 g/L/d. The technology was then validated both using synthetic solutions and a real ethanol containing stream (wine lees). The technology is currently under evaluation for patenting and therefore, the results have not yet been disclosed.
For the downstream project, we evaluated and compared two different technologies (electrodialysis and forward osmosis) for the concentration of carboxylic acids from solutions simulating the MES cell and fermenter effluents. This allowed to concentrate the caproic acid to up to 45 g/L. Then, by simple acidification and phase separation, we obtained an 84% pure product (784 g/L caproic acid) that could be commercialized. These results will be made soon available by open access publication.
The fermentation platform consisted in a novel, membrane-based reactor configuration that allowed to isolate the caproic acid producing microbial community from both microbiological and chemical contamination in the feed stream. The membrane used indeed allowed the diffusion of the substrates necessary for caproic acid production (ethanol and acetic acid) while retaining microorganisms and the majority of chemical pollutants. Furthermore, it allowed to control the diffusion ratio between ethanol and acetic acid, which is a crucial factor for optimizing caproic acid production, by simply modifying the pH of the feed solution and the membrane wall thickness. This resulted in selective (99%) production of caproic acid at a highest rate of 3.1 g/L/d. The technology was then validated both using synthetic solutions and a real ethanol containing stream (wine lees). The technology is currently under evaluation for patenting and therefore, the results have not yet been disclosed.
For the downstream project, we evaluated and compared two different technologies (electrodialysis and forward osmosis) for the concentration of carboxylic acids from solutions simulating the MES cell and fermenter effluents. This allowed to concentrate the caproic acid to up to 45 g/L. Then, by simple acidification and phase separation, we obtained an 84% pure product (784 g/L caproic acid) that could be commercialized. These results will be made soon available by open access publication.
The ATMESPHERE project advanced the state-of-art by revealing the optimal operating conditions to achieve selective butyric acid production from CO2 in MES cells, and suggested a strategy to upgrade it to butanol, a higher alcohol that can be used as drop-in fuel replacing the fossil-based alternatives. Furthermore, a novel process (including downstream) to selectively produce highly concentrated caproic acid from ethanol containing feeds was developed. The caproic acid production can find application in agriculture as green pesticide, or can be further upgraded to a surrogate of jet fuel or diesel fuel, contributing to decarbonize the transportation sector. Replacing fossil-based fuels with green alternatives is in full agreement with the European Green Deal objectives and will positively impact the environment and the by reducing greenhouse gas and particulate emissions, avoiding exhaustible resource depletion, and mitigating the dependence on unstable foreign suppliers.