Integration of a biogas plant into a bioethanol plant using thin stillage

A biogas plant treating thin stillage is integrated into a bioethanol plant. The focus lies on an economic and sustainable optimised process. The aim is on the one hand to establish a constant and stable anaerobic process including a nitrogen sink (aerobic treatment or ammonia stripping). On the other hand the produced digestate is treated via evaporation, membranes or aerobically. The purified process water is reused in the yeast fermentation of the bio-ethanol plant. The nitrogen in the proteins is made available by anaerobic digestion as an assimilable nitrogen source to the yeasts, apart from that the water and other nutrients are recycled into the bioethanol plant to achieve a nutrient cycle. In addition, other points have to be investigated: degradation of metabolites from yeast fermentation, influence on animal feed quality, effect of recirculated process water on yeasts, economic significance of process.