Distillieries - Environmental Clearance

DistilleriesThe information furnished here is based on the exhaustive literature survey, informationcollected during the survey and also the consultants view regarding the above.3.10.1 Fermenter sludgeThe volume of fermenter sludge generated from distilleries is about 0.3 kL/kL of RSproduced. For distilleries having capacities of 5000 kL/annum and 10000 kL/annum ofRS the volume of fermenter sludge would be about 4.5 kL/day and 9 kL/day,respectively. The fermenter sludge has solid content of about 30% by weight whichcomprises of mostly the spent yeast and mineral matter. The spent yeast is highlybiodegradable so that the fermenter sludge stream has a biochemical oxygen demand ofthe order of 1,25,000 mg/L. Hence the fermenter sludge stream, although low in volume,when discharged as composite stream from fermentation house results in BOD adding tothe tune of 560 kg/day and 1,120 kg/day for distilleries of 5,000 kL/annum and 10,000kL/annum capacities respectively.It may be possible to treat the fermenter sludge in one of three ways, either to provide asecondary yeast source or to provide cattle feed adjunct or use as fertilizer.a) Processing for secondary yeastFrom an examination of the composition of fermenter sludge, the solid content of theslurry and the requirement and propagation of yeast, it is clear that the solid matter of thefermenter sludge is mostly spent yeast, the aqueous part having about the samecomposition as that of the inflow stream to the analyzer column.This spent yeast can be separated from the fermenter sludge stream by dewatering on ascreen followed by filtration in a filter press. The filtrate will have a composition similarto that of spent wash, with a little higher percentage of alcohol and allied chemicals whichin this case have not been stripped. The BOD of the filtrate will therefore be only slightlyhigher than that of the spent wash and can be easily treated along with the latter.The pressed yeast can be used as secondary yeast either for growing primary yeastcultures or as bakers’ yeast. Such use of this yeast had been popular abroad until the1950's, but the practice fell more or less into obsolescence as the demand for yeastbecome too high to be met from such sources and quality control requirements becamemore stringent. However, it is felt that scope for such use may still be there in India andwould be worth exploring.b) Processing for cattle feed adjunctAn alternative solution, which can reduce the pollution from this stream to zero, would beto concentrate the fermenter sludge by evaporation and finally dry the concentratedmatter. It has sufficient nutrient value to form excellent cattle feed. However the highmineral matter content and the nature thereof are likely to have a laxative effect on thecattle and therefore may not be fed as such. It can be used along with other feed materialwhich would act as a diluent of the laxative effect and will none-the-less utilize thenutritional value. It is relevant to note in this context that some distilleries have maltingor brewery along with a distillery and can therefore use this in conjunction with the spentgrain from malting or the brewers grain from breweries or spent slops from cereal-baseddistilleries, the recovery of which has been suggested in the relevant sections.TGM for Distillery Industry 3-37 August 2010