Technology and economics of ethanol production from fodder beets via solid-phase fermentation

Abstract

Operating conditions for our semi-continuous, solid-phase fermentation system were optimized for conversion of fodder beets to fuel ethanol and distiller's wet feed (DWF). This information was then used to estimate operating parameters achievable in a commercial plant, and likely baseline production costs of such a plant. Initial acidification of pulp to pH 2.9–3.2 was effective in controlling bacterial contamination. The maximum operating capacity of the fermentor was approximately 92%, with 75% used for commercial application. A fermentation time of 24 h was sufficient to completely ferment the beet pulp to 8–9% (v/v) ethanol. Based on these parameters, a fodder beet cost of $19.25/metric ton ($17.50/ton), other operating and capital costs, and a PF credit of $0.14/L ($0.53/gal), ethanol production costs were estimated to be $0.49/L ($1.87/gal).