less fermentation by-products and higher volumetric productivities during fermentation,
together with less energy intensive separation and purification techniques. These new technology
developments have the potential to provide a production process for butanol from sugarcane molasses
that is economically viable in comparison to the petrochemical pathway for butanol production. This
objective was investigated by developing process models to compare three different possible process
designs for biobutanol production from sugarcane molasses. The first two process routes incorporate well
established industrial technologies: Process Route 1 consisted of batch fermentation and steam stripping
distillation, while in Process Route 2, some of the distillation columns were replaced with a liquid–liquid
extraction column. Some of the best production strains in these process routes, which include Clostridium
Acetobutylicum PCSIR-10 and Clostridium Beijerinckii BA101, can produce total solvent concentrations up
to 24 g/L. Process Route 3 incorporated fed-batch fermentation and gas-stripping with CO2, an unproven
technology on industrial scale. Process modeling in ASPEN PLUS and economic analyses in ASPEN Icarus
were performed to determine the economic feasibility of these biobutanol production process designs.
Process Route 3 proved to be the only profitable design in current economic conditions in South Africa.
Improved fermentation strains currently available are not sufficient to attain a profitable process design
without implementation of advanced processing techniques. Gas stripping is shown to be the single most
effective process step of those evaluated in this study, which can be employed on an industrial scale to
improve process economics of biobutanol production.