Production de spiruline à la ferme : produire de la spiruline à la ferme grâce au digestat et à la chaleur excédentaire d’une installation de biogaz

Abstract

The development of projects coupling an agricultural anaerobic digestion installation with the production of spirulina is an attractive concept, since the waste streams from the methanisation and from biogas valorization can be used to produce a high value product. This principle allows a better energetic valorization of surplus heat and of exhaust gases coming from the cogeneration unit. The limits of this configuration have been evaluated for Switzerland to study if the implementation of such coupling increases the competitiveness of agricultural anaerobic digestion. The thermal autonomy of the plant has been established as the main criterion to design the spirulina production units. For different working conditions (light radiation, nutrients source, size of methanisation units), the potential production of spirulina has been evaluated. The process energy yield, the environmental impact and the process economy show that 50% of surplus heat can be valorized, being 85-90% of heat contained in the exhaust gases; that the decrease in carbon dioxide emissions is not relevant and that, for the conditions tested, the operating costs are currently too high to allow the economic feasibility of the project