Process Route 1 (batch fermentation with steam stripping distillation),
used previously for the commercial production of biobutanol,
could not compete with the petrochemical pathway in terms
of butanol production costs. Therefore advanced fermentation and
novel downstream processing techniques are needed to render a
process economically viable.
The most effective method to increase the volumetric productivity
of a process was to employ fed-batch fermentation with
in situ gas stripping instead of batch fermentation. Large sterilisable
pressure vessels for fermentation are very expensive and account
for roughly 60–70% of the equipment cost [23]. In this
study it was found that process designs with low overall process
productivity (specifically those using batch fermentation) have
much higher TPCC due to the fact that the equipment is larger
and more expensive.