Gas bioconversion An opportunity for the ecological transition

Gas bioconversion refers to the set of bioprocesses through which specialized microorganisms (e.g., microalgae, methanotrophs, acetogenic bacteria, hydrogenotrophic archaea, hydrogen-oxidizing bacteria – hydrogen-oxidizing bacteria – or purple bacteria) convert gaseous substrates (CH ₄ , CO ₂ , CO, H ₂ ) into high-value-added products such as biofuels, platform molecules, polyhydroxyalkanoates, or microbial proteins. Unlike conventional physicochemical processes (e.g., Fischer-Tropsch, steam reforming), these biological pathways operate under mild conditions (temperature, pH, pressure, etc.), with intrinsic catalytic selectivity (i.e., they are capable of directing the carbon flow toward a target product) and low energy consumption.

Industrial societies are based on a linear model: extraction–, processing–, consumption–, and disposal—the effects of which have now been quantified: four of the nine planetary boundaries (biosphere integrity, biogeochemical flows, climate change, and land-use change) have now been exceeded . In light of this reality, the paradigm of resource recovery is essential: it is no longer a matter of disposing of waste, but of rethinking it as valuable inputs—a prerequisite for the sustainability of the circular economy.

In this context, the concept of a biorefinery integrates biological and chemical processes to transform biomass into a diverse range of products. Gases play a central role in this process: anaerobic digestion (AD), widely used in organic waste management, produces biogas (a mixture of CH ₄ and CO ₂ ); fermentation produces...