title: Impact of nickel and cobalt on biogas production and process stability during semi-continuous anaerobic fermentation of a model substrate for maize silage.
abstract: The importance of nickel and cobalt on anaerobic degradation of a defined model substrate for maize was demonstrated. Five semi-continuous reactors were operated for 250 days at 35 °C and a well-defined trace metal solution was added to all reactors. Two reactors each were limited regarding the concentration of Ni(2+) and Co(2+), respectively, for certain time intervals. The required nickel concentration was depending on the organic loading rates (OLR) while, for example, above 2.6 g ODM L(-1) d(-1) nickel concentrations below 0.06 mg kg(-1) FM in the process significantly decreased biogas production by up to 25% compared to a control reactor containing 0.8 mg Ni(2+) kg(-1) FM. Similarly, limitation of cobalt to 0.02 mg kg(-1) FM decreased biogas production by about 10%. Limitations of nickel as well as cobalt lead to process instability. However, after gradual addition of nickel till 0.6 mg and cobalt till 0.05 mg kg(-1) FM the OLR was again increased to 4.3 g ODM L(-1) d(-1) while process stability was recovered and a fast metabolisation of acetic and propionic acid was detected. An increase of nickel to 0.88 mg kg(-1) FM did not enhance biogas performance. Furthermore, the increase of cobalt from 0.05 mg kg(-1) FM up to 0.07 mg kg(-1) FM did not exhibit a change in anaerobic fermentation and biogas production.
authors.affiliation: Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria.
authors.forename: Herbert
authors.initials: H
authors.lastname: Pobeheim
authors.forename: Bernhard
authors.initials: B
authors.lastname: Munk
authors.forename: Harald
authors.initials: H
authors.lastname: Lindorfer
authors.forename: Georg M
authors.initials: GM
authors.lastname: Guebitz
mesh_terms: D000693:Anaerobiosis; D056804:Biofuels; D019149:Bioreactors; D003035:Cobalt / Q000008:administration & dosage / Q000494:pharmacology*; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000008:administration & dosage / Q000494:pharmacology*; D012820:Silage; D003313:Zea mays / Q000378:metabolism*
chemical_list: D056804:Biofuels; D005232:Fatty Acids, Volatile; D003035:Cobalt; D009532:Nickel