Changes in the EU sugar regime have intensified investigations into alternative usages for sugar beet. The production of bioethanol from sugar beet seems to be one of the more attractive options due to dwindling fossil fuel sources. The purpose of this study was to examine the contribution that mathematical modeling with mixed integer non-linear programming can offer to any decision-making about different co-production strategies for sugar and bioethanol, according to changing market situations. An optimization-based conceptual process design that relies on superstructure optimization was used to simultaneously search for an economically and environmentally optimal strategy for co-producing sugar and bioethanol. Two scenarios were considered, the first assuming that a facility for sugar production already exists and serves as a possible candidate pertaining to bioethanol production, whilst the second assumed a non-existing capacity for sugar and bioethanol production. Superstructure optimization for the first scenario revealed that, under current market conditions, the best solution is to keep focusing on sugar production by using a two-stage crystallization scheme and divert raw sugar run-off syrup into ethanol production. The results for the second scenario optimization showed that diverting thick sugar juice directly to bioethanol production gained the best economic results. Sensitivity analysis was applied to both scenarios, in order to identify the effect of changing selected economic parameters to an optimal strategy. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.