Many green substitutes for petroleum based chemicals are being produced by the fermentation of sugars obtained from biomass. The products must be extracted from the aqueous broth in which they were created. Pass-through Distillation offers lower energy consumption than conventional distillation plus other significant benefits. PTD equipment is immune from thermally induced fouling, which can be a costly operational problem with conventional distillation. PTD requires no preheating step prior to distillation; it can operate at the same temperature as the fermentor. These advantages apply to all cases whether the product is volatile, like alcohol, or non-volatile like succinic acid.
Where the product is volatile, there is a more important benefit: concurrent removal of product during the fermentation process (CARAF). This technique keeps the concentration of the product in the fermentation broth low enough to prevent it from inhibiting the performance of the biocatalyst, resulting in rapid and complete sugar conversion. Equipment size is reduced along with its capital cost. A shorter fermentation time reduces risk of infections.