title: Reducing the risk of foaming and decreasing viscosity by two-stage anaerobic digestion of sugar beet pressed pulp.
abstract: Anaerobic digestion (AD) of sugar beet pressed pulp (SBPP) is a promising treatment concept. It produces biogas as a renewable energy source making sugar production more energy efficient and it turns SBPP from a residue into a valuable resource. In this study one- and two-stage mono fermentation at mesophilic conditions in a continuous stirred tank reactor were compared. Also the optimal incubation temperature for the pre-acidification stage was studied. The fastest pre-acidification, with a hydraulic retention time (HRT) of 4 days, occurred at a temperature of 55 °C. In the methanogenic reactor of the two-stage system stable fermentation at loading rate of 7 kg VS/m³ d was demonstrated. No artificial pH adjustment was necessary to maintain optimum levels in both the pre-acidification and the methanogenic reactor. The total HRT of the two-stage AD was 36 days which is considerably lower compared to the one-stage AD (50 days). The frequently observed problem of foaming at high loading rates was less severe in the two-stage reactor. Moreover the viscosity of digestate in the methanogenic stage of the two-stage fermentation was in average tenfold lower than in the one-stage fermentation. This decreases the energy input for the reactor stirring about 80 %. The observed advantages make the two-stage process economically attractive, despite higher investments for a two reactor system.
authors: Bioenergy 2020+ GmbH, Inffeldgasse 21b, 8010, Graz, Austria, elitza.stoyanova@boku.ac.at.
authors: Elitza
authors: E
authors: Stoyanova
authors: Boris
authors: B
authors: Forsthuber
authors: Stefan
authors: S
authors: Pohn
authors: Christian
authors: C
authors: Schwarz
authors: Werner
authors: W
authors: Fuchs
authors: Günther
authors: G
authors: Bochmann
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000378:metabolism*; D027461:Beta vulgaris / Q000737:chemistry / Q000378:metabolism* / Q000382:microbiology; D001673:Biodegradation, Environmental; D056804:Biofuels / Q000032:analysis*; D019149:Bioreactors / Q000382:microbiology*; D004063:Digestion; D005285:Fermentation; D007218:Industrial Microbiology / Q000295:instrumentation*; D014783:Viscosity; D014866:Waste Products / Q000032:analysis*
chemical_list: D056804:Biofuels; D014866:Waste Products