title: Anaerobic digestion of sulfate-acidified cattle slurry: One-stage vs. two-stage.
abstract: Two strategies to include acidified cattle manure (AcCM) in co-digestion with normal cattle manure (CM) are presented in this work. The strategies are a single thermophilic (50 °C) continuous stirred tank reactor (CSTR) anaerobic digestion and a two-step (65 °C + 50 °C) CSTR process. In both strategies, two different inclusion levels of H2SO4-acidified CM (10% and 20%) in co-digestion with normal CM were tested and compared with a control CSTR fed only CM. Important enhancement of methane (CH4) yield and solid reductions were observed in the thermophilic one-step CSTR working with 10% AcCM. However, a higher inclusion level of AcCM (20%) caused volatile fatty acid accumulation in the reactor and a more than 30% reduction in CH4 production. In terms of CH4 production, when 10% of AcCM was co-digested with 90% of CM, the two-step anaerobic co-digestion yielded less than the single step. During the first step of the two-step CSTR process, acidogenesis and a partial sulfate reduction were achieved. However, sulfide stripping between the first and the second step must be promoted in order to advance this technology.
authors.affiliation: Aarhus University, Department of Engineering, Blichers Allé 20, DK 8830, Foulum Tjele, Denmark. Electronic address: VeronicaM.Hernandez@eng.au.dk.
authors.forename: Veronica
authors.initials: V
authors.lastname: Moset
authors.affiliation: Aarhus University, Department of Engineering, Blichers Allé 20, DK 8830, Foulum Tjele, Denmark.
authors.forename: Lars Ditlev Mørck
authors.initials: LD
authors.lastname: Ottosen
authors.affiliation: Aarhus University, Department of Engineering, Blichers Allé 20, DK 8830, Foulum Tjele, Denmark; Animal Science, Federal University of Mato Grosso do Sul, Avenue Senador Filinto Müller, 2443, Zip Code 79070-900, Campo Grande, Brazil.
authors.forename: Cristiane de Almeida Neves
authors.initials: Cde A
authors.lastname: Xavier
authors.affiliation: Aarhus University, Department of Engineering, Blichers Allé 20, DK 8830, Foulum Tjele, Denmark.
authors.forename: Henrik Bjarne
authors.initials: HB
authors.lastname: Møller
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D019149:Bioreactors; D002417:Cattle; D005232:Fatty Acids, Volatile / Q000032:analysis; D006358:Hot Temperature; D008372:Manure; D008697:Methane / Q000032:analysis; D013431:Sulfates / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D005232:Fatty Acids, Volatile; D008372:Manure; D013431:Sulfates; D008697:Methane
keywords: Anaerobic digestion; Sulfate-acidified slurry; Two-step continuous stirred tank reactors