Production de microalgues à partir de carbone résiduel pour une implantation dans la bioraffinerie de 2e génération

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The cellulosic ethanol production process requires not only fermentable sugars but also complementary micro- and macro-nutrients which will aid the uptake of these carbohydrates and their conversion to ethanol by the involved yeast. However, the lignocellulosic biomass generally lacs these compounds and thus requires the addition of nutrient mixtures such as yeast extract or complementary nitrogen and mineral sources for the efficient fermentation of the cellulosic carbohydrates. Furthermore, the lignocellulosic sugar streams will generate a new type of residue which will become a challenge for the valorization chain of the current first generation ethanol industry (grains and solubles). A complementary nutrient addition through microalgal biomass for instance could bring value to the process, making thus the second generation ethanol more competitive with respect to the first generation. Besides these realities, the first generation ethanol production process generates significant anthropogenic CO2, especially in Canada where heating requirements are important. These CO2 emissions significantly impact thus the carbon balance of the first and eventually second generation ethanol production processes. In the same time however, this CO2 represents a valuable carbon source which could potentially be converted, especially by autotrophic microalgae, to biomass. The alcoholic fermentation process generates a protein-rich sidestream with low added value, the backset, which could be used as cultivation media for these microalgae. Thus, the present project aims to transform two of the most important constraints faced by the ethanol industry into an opportunity by utilizing the effluents generated by the first generation ethanol production process to support the implementation of second generation ethanol technologies while simultaneously reducing their CO2 footprint.