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Context

The anaerobic digestion is a widely spread technology that consists in the degradation of organic matter by a highly coordinated chain of reactions, which eventually gives CH₄ and CO₂ as principal products, in approximately 50/50 ratio. CH₄ can be used as an energy carrier. However, in order to use it, CO₂ has to be depleted from the mixture, this process is called biogas upgrading. Nowadays, the biogas upgrading methods are not environmentally friendly however, there are biological ways to use the CO₂ and upgrade the biogas. CO₂ can be reduced to CH₄ or to acetate by microorganisms using H₂ as energy source. H₂ can be provided by other environmentally friendly technologies as windmills or solar panels. These technologies are weather-dependent; in consequence, their energy production is fluctuant. However, by the Power-to-Gas concept the electric energy surplus can be transformed into H₂ by water electrolysis, then the produced H₂ can be injected into a digester and fixed into CH₄ or acetate by hydrogenotrophic methanogens or homoacetogens, respectively. Both of these products can be easily stored. However, the biological biogas upgrading processes have some limitations: on one hand, H₂ has a low dissolution rate which could lead to a low CH₄ or acetate yields, as it cannot be used by the microorganisms and in the other hand, the high H₂ partial pressure can lead to anaerobic digestion process imbalance and eventual process failure. In order to optimize this type of process is necessary to overcome these limitations. 

Description

The objective of this 6-months internship will consist in the optimization of a biological biogas upgrading process using an organic substrate and H₂/CO₂ gas mixture.

The student will be assigned the design and implementation of an experimental plan on several key biogas upgrading parameters. The experiments will involve the monitoring of the reactors, by the analysis of the biogas production and composition (using gas chromatography). The composition and concentration of the microbial metabolites will be also evaluated by different analytical methods (gas chromatography and HPLC). Using these data, the performances of the reactors will be evaluated (COD mass balance, productivity and yields calculations) along the internship in order to better understand the influence of the studied parameters and to optimize the conditions for the biogas upgrading process. Afterwards, the microbial community will be analyzed by sequencing and qPCR. The obtained results will help to understand the observed performances of the reactors.

Candidate

This internship is intended for students at the Engineering or Master's level who have been trained in Microbiology, Environment or Process Engineering.

In addition, the candidate must have, during his or her studies, demonstrated an aptitude for experimental research and must demonstrate autonomy, curiosity, and rigor.

Please send your application to:

• Supervisors: Renaud ESCUDIE (renaud.escudie (arobase) inra.fr), Jean-Philippe DELGENES (jean-philippe.delgenes (arobase) inra.fr), Eric TRABLY (eric.trably (arobase) inra.fr)
• Co-supervisor: Lucia BRAGA NAN (lucia.braganan (arobase) inra.fr)