title: Synergism and effect of high initial volatile fatty acid concentrations during food waste and pig manure anaerobic co-digestion.
abstract: Anaerobic co-digestion of food waste (FW) and pig manure (PM) was undertaken in batch mode at 37°C in order to identify and quantify the synergistic effects of co-digestion on the specific methane yield (SMY) and reaction kinetics. The effects of the high initial volatile fatty acid (VFA) concentrations in PM on synergy observed during co-digestion, and on kinetic modelling were investigated. PM to FW mixing ratios of 1/0, 4/1, 3/2, 2/3, 1/4 and 0/1 (VS basis) were examined. No VFA or ammonia inhibition was observed. The highest SMY of 521±29ml CH4/gVS was achieved at a PM/FW mixing ratio of 1/4. Synergy in terms of both reaction kinetics and SMY occurred at PM/FW mixing ratios of 3/2, 2/3 and 1/4. Initial VFA concentrations did not explain the synergy observed. Throughout the study the conversion of butyric acid was inhibited. Due to the high initial VFA content of PM, conventional first order and Gompertz models were inappropriate for determining reaction kinetics. A dual pooled first order model was found to provide the best fit for the data generated in this study. The optimal mixing ratio in terms of both reaction kinetics and SMY was found at a PM/FW mixing ratio of 1/4.
authors.affiliation: Civil Engineering, College of Engineering & Informatics, National University of Ireland, Galway, Ireland.
authors.forename: Conor
authors.initials: C
authors.lastname: Dennehy
authors.affiliation: Teagasc, Pig Development Department, Animal and Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland.
authors.forename: Peadar G
authors.initials: PG
authors.lastname: Lawlor
authors.affiliation: Agro Paris Tech, 16 Rue Claude Bernard, 75005 Paris, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Croize
authors.affiliation: Civil Engineering, College of Engineering & Informatics, National University of Ireland, Galway, Ireland.
authors.forename: Yan
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Earth and Ocean Sciences, School of Natural Sciences, National University of Ireland, Galway, Ireland.
authors.forename: Liam
authors.initials: L
authors.lastname: Morrison
authors.affiliation: Department of Science, Waterford Institute of Technology, Waterford, Ireland.
authors.forename: Gillian E
authors.initials: GE
authors.lastname: Gardiner
authors.affiliation: Civil Engineering, College of Engineering & Informatics, National University of Ireland, Galway, Ireland. Electronic address: xinmin.zhan@nuigalway.ie.
authors.forename: Xinmin
authors.initials: X
authors.lastname: Zhan
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D005232:Fatty Acids, Volatile / Q000032:analysis*; D005735:Garbage; D008372:Manure / Q000032:analysis*; D008962:Models, Theoretical; D034421:Sus scrofa; D018505:Waste Management
chemical_list: D005232:Fatty Acids, Volatile; D008372:Manure
keywords: Anaerobic digestion; Co-digestion; Kinetics; Synergism; Volatile fatty acids