5. Conclusion
Kraft paper mill sludge has great potential as a feedstock for
ABE production. It does not require chemical pretreatment or
detoxification, but only needs to be partially de-ashed to improve
the enzymatic hydrolyzability. Remarkably, the buffering effect of
CaCO3 in paper mill sludge can be effectively used in the SSF process
to produce butanol, because pH control is a critical issue in
butanol fermentation by C. acetobutylicum. The results showed
butanol production from de-ashed paper mill sludge could be carried
out under the solid loading of 6.3–7.4 wt% and enzyme loading
of 10–15 FPU.