Effluent sludge from an anaerobic digester was
used as a source of nitrogen, phosphate, sulfur, and other
nutrients in the culture medium of ethanol production by
the yeast
Saccharomyces cerevisiae
. Several pretreatments
(mechanical, chemical, thermal, and thermo-chemical)
were performed on the anaerobic digested sludge (ADS) to
make the nutrients accessible to the yeast cells. Preliminary
experiments revealed that
S. cerevisiae is not able to
assimilate the carbon content of the ADS. However, when
glucose was added to the medium, ethanol production was
observed. The yield of ethanol using untreated ADS was
only 10 % of the theoretical yield, but alkaline pretreatment
improved it up to 43 %. By separating the hydrolysate
of alkaline-treated ADS from the suspended solids,
the ethanol yield from the supernatant was further
improved up to 65 % of theoretical yield. Alkaline-treated
ADS exhibited competitive performance with the mixture
of yeast extract and mineral salts in ethanol fermentation.