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.
