title: Retooling the ethanol industry: thermophilic anaerobic digestion of thin stillage for methane production and pollution prevention.
abstract: Anaerobic digestion of corn ethanol thin stillage was tested at thermophilic temperature (55 degrees C) with two completely stirred tank reactors. The thin stillage wastestream was organically concentrated with 100 g/L total chemical oxygen demand and 60 g/L volatiles solids and a low pH of approximately 4.0. Steady-state was achieved at 30-, 20-, and 15-day hydraulic retention times (HRTs) and digester failure at a 12-day HRT. Significant reduction of volatile solids was achieved, with a maximum reduction (89.8%) at the 20-day HRT. Methane yield ranged from 0.6 to 0.7 L methane/g volatile solids removed during steady-state operation. Effluent volatile fatty acids below 200 mg/L as acetic acid were achieved at 20- and 30-day HRTs. Ultrasonic pretreatment was used for one digester, although no significant improvement was observed. Ethanol plant natural gas consumption could be reduced 43 to 59% with the methane produced, while saving an estimated $7 to $17 million ($10 million likely) for a facility producing 360 million L ethanol/y.
authors.affiliation: Malcolm Pirnie Inc., Tucson, Arizona, USA.
authors.forename: Scott H
authors.initials: SH
authors.lastname: Schaefer
authors.forename: Shihwu
authors.initials: S
authors.lastname: Sung
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D019149:Bioreactors; D004063:Digestion; D004787:Environmental Pollution / Q000517:prevention & control*; D000431:Ethanol / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D014465:Ultrasonics; D003313:Zea mays
chemical_list: D005232:Fatty Acids, Volatile; D000431:Ethanol; D008697:Methane