title: Optimisation of digester performance with increasing organic loading rate for mono- and co-digestion of grass silage and dairy slurry.
abstract: This study investigated the feasibility of mono-digesting grass silage, dairy slurry and the co-digestion of the two substrates at a range of concentrations with a specific focus on digester performance while increasing organic loading rate (OLR). The results show that the higher the proportion of grass silage in the substrate mix the higher the specific methane yield (SMY) achieved. Optimum conditions were assessed for 100% grass silage at an OLR of 3.5 kg VS m(-3) d(-1) generating a SMY of 398 L CH4 kg(-1) VS equating to a biomethane efficiency of 1.0. For co-digestion of grass silage with 20% dairy slurry the optimum condition was noted at an OLR of 4.0 kg VS m(-3) d(-1) generating a SMY of 349L CH4 kg(-1) VS and a biomethane efficiency of 1.01. Hydraulic retention times of less than 20 days proved to be a limiting factor in the operation of farm digesters.
authors.affiliation: Bioenergy and Biofuels Research Group, Environmental Research Institute, University College Cork, Cork, Ireland; School of Engineering, University College Cork, Cork, Ireland; Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co. Meath, Ireland.
authors.forename: David M
authors.initials: DM
authors.lastname: Wall
authors.affiliation: Bioenergy and Biofuels Research Group, Environmental Research Institute, University College Cork, Cork, Ireland; School of Engineering, University College Cork, Cork, Ireland.
authors.forename: Eoin
authors.initials: E
authors.lastname: Allen
authors.affiliation: Department of Agricultural, Food and Environmental Science, Perugia University, Perugia, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Straccialini
authors.affiliation: Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co. Meath, Ireland.
authors.forename: Padraig
authors.initials: P
authors.lastname: O'Kiely
authors.affiliation: Bioenergy and Biofuels Research Group, Environmental Research Institute, University College Cork, Cork, Ireland; School of Engineering, University College Cork, Cork, Ireland. Electronic address: jerry.murphy@ucc.ie.
authors.forename: Jerry D
authors.initials: JD
authors.lastname: Murphy
mesh_terms: D056804:Biofuels; D019149:Bioreactors; D008697:Methane / Q000096:biosynthesis; D006109:Poaceae / Q000737:chemistry / Q000378:metabolism*; D059205:Renewable Energy
chemical_list: D056804:Biofuels; D008697:Methane
keywords: Biomethane; Dairy slurry; Grass silage