Microfluidic Approaches mimicking BIoGeological conditions to investigate subsurface CO2 recycling

Periodic Reporting for period 3 - Big Mac (Microfluidic Approaches mimicking BIoGeological conditions to investigate subsurface CO2 recycling)

Okres sprawozdawczy: 2020-11-01 do 2022-04-30

The management of anthropogenic CO2 will be one of the main challenges of this century given the dramatic impact of greenhouse gases on our living environment. It is a fragile equilibrium between the will to reduce the human impact over the environment and the political and economic context. It is now critical to provide solutions to capture and use/store industrial CO2 emissions. In addition to enhance oil recovery through CO2 injection, two strategies with different timescale are envisioned to proceed with (i) the immediate use and transformation of small amount of CO2 to beneficial products and (ii) the CO2 Geological Storage (CGS) within deep saline aquifers. Nevertheless, this “storage” option is costly insofar that no profit can be realized, the CO2 being an expensive waste.
Little is known about the interest of CO2 as a raw material and about the effect of CO2 sequestration on subsurface microbial communities, which have been proved to have a strong activity to transform matter in such geological formations. Therefore, a fascinating strategy to restore the advantages of stored CO2 as a raw material, would be to consider a slow biological upgrading process of CO2 in deep geological formations to restore energy resources. This should allow the valorization of a part of the large quantities of disposed CO2, before their natural geological transformation to carbonates. Although chemotrophic methanogenesis is slow, appreciable amount of methane could probably form in parallel to CO2 injection. Being able to promote and speed up the biological conversion of CO2 to methane in geological formations could constitute a very advantageous long-term strategy that is worthy of scientific investigation.
The BIC MAC project aims at studying for the first time the mechanisms involved in the biogeological conversion process of CO2 to methane in conditions typical of geological reservoirs. This will be realized using a multiscale approach taking advantage of (i) the fast screening capability of microfluidics approaches to investigate the mechanisms occurring at pore scale and (ii) by performing the process at the liter scale to demonstrate process scaling.
The project has four scientific objectives :
- Developing and using new microfluidics-based experimental means (BioGLoCs) for investigating the microbial survival and growth conditions and the CH4 production rates.
- The evaluation and quantification of H2 production from iron oxidation in multiphasic CO2 / brine environments.
- The full CO2 to methane transformation process investigation (H2 generation and methane production).
- The demonstration of process scalability.

Objective 1: Methanogenesis investigations using BioGLoCs
The new sapphire microfluidics reactors mimicking porous media were developed, leading to a patent. Microfluidics methodologies were developed to screen parameters for determining favorable conditions for the microorganisms’ growth. In particular, a novel fast screening methodology was develop to perform fast temperature phenotyping of piezophile strains in a wide range of temperature and pressure. Millifluidic bioreactors in sapphire were also developed. The methodologies were tested with two model strains and two fermentative strains. Then, the full methane production kinetics for one thermophilic methanogen strain (65°C) at 100 bar. The kinetics determination with another strain working at higher temperature (85°C) are currently performed. Since kinetics are strain-dependent, it is critical to identify the best candidates for the methane production. Experiments are being run using BioGLoCs to integrate the geometrical parameter effect on the determination of methane production rates.
Objective 2: Evaluation of in situ hydrogen production
The generation of hydrogen in situ in geological media was identified as one of the major risk of the BIG MAC project but we were able to demonstrate the full potential of this strategy. The reaction kinetics of hydrogen production through iron oxidation in CO2 / water media under pressure and temperature conditions have been determined. The kinetics are fast and a full conversion can be reached in short times. Other materials were tested for hydrogen production such as Olivine (Fe,Mg)2SiO4), which is a representative mineral from deep underground environments. Experiments in flows using realistic porous medium configuration have shown that the main parameters that need to be mastered concern the transport and reactivity of iron nanoparticles in a porous medium. Besides, experiments were performed on hydrogen generation from iron particles carbonation.
Objective 3: Full process investigations in 2D and 3D reactive BioGLoCs
3D reactive BioGloCs have been fabricated by integrating reactive particles into microchannels. Preliminary tests of X-Rays imaging have been performed at ERSF, demonstrating the successful implementation of this technique. Current work concern the injection of olivine (Fe,Mg)2SiO4) into the reactor to recreate minerals reactivity in porous medium. Several tests have been conducted in millifluidics reactors, demonstrating: (i) the viability of the methanogens strains in the presence of iron, (ii) the production of methane in short time range (few hours). Some limitations have also been identified such as the too high concentration of CO2, which can clearly reduce the development of strains and the methane production. This reaction is now implemented in 3D reactive BioGLoCs and tests will be conducted in millifluidics reactor to account for the presence of geominerals (CaCO3, Olivine).
Objective 4: Process-scaling demonstration
The development of a 150mL biocompatible sapphire reactor was realized. It implemented with in situ probe (p, T) and can be coupled to ex situ Raman and UV-Vis probes. When running in continuous mode, ex situ GC-MS characterization of the liquid and the gas phases with auto-sampling will achieve real-time monitoring of methane production rates and biomass evaluation. The methanogenesis reaction was investigated using the 150mL biocompatible sapphire reactor. Tests have proven that similar reaction kinetics were obtained as in smaller reactors, demonstrating the scalability of the process.

The ERC BIG MAC project has contributed so far to four major progresses:
The development of a new microfluidic technology with the fabrication of the first all sapphire microreactors allowing accessing extended harsh conditions (pressure, temperature and chemical compatibility), which were never reported in the literature.
The development of fast screening approaches (using both micro- and millifluidics methodologies) which were applied to high-pressure microbiology. Our approach, based on biochemical engineering has led to the development and the implementation of new tools for investigating the deep biosphere, which is still scarcely studied and understood so far due to technological limitations of the current reactors.
The demonstration of hydrogen generation in situ under high pressure and moderate temperature conditions from the recycling of two wastes, i.e. CO2 and iron. The measured kinetics are rather fast (few hours), which is a key step towards the valorization of wastes with energy production.
The demonstration of the main objective of the BIG MAC project, i.e. recycling CO2 to methane in deep environmental conditions thanks to methanogens archaea microorganisms has been demonstrated.

Scheme and pictures of methanogenesis reaction in BioGLoCs

Sapphire microchips and compression fittings

BioGloCs design for temperature fast screening

Comparison of 2 temperatures growth of microorganisms with fluorescence microscopy

Millifluidcs sapphire tubes used for accessing quantitative methanogensis kinetics

Sapphire bioGLoCs set-up under the microscope

Sapphire microreactor

Detailed view of a random porous medium in a sapphire BioGLoC

Close view of methanogens microbes growing inside a BioGLoC

Periodic Reporting for period 3 - Big Mac (Microfluidic Approaches mimicking BIoGeological conditions to investigate subsurface CO2 recycling)

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