title: Assessing anaerobic co-digestion of pig manure with agroindustrial wastes: the link between environmental impacts and operational parameters.
abstract: Anaerobic co-digestion (AcoD) is established as a techno-economic profitable process by incrementing biogas yield (increased cost-efficiency) and improving the nutrient balance (better quality digestate) in comparison to mono-digestion of livestock wastes. However, few data are available on the environmental consequences of AcoD and most of them are mainly related to the use of energy crops as co-substrates. This work analysed the environmental impact of the AcoD of pig manure (PM) with several agroindustrial wastes (molasses, fish, biodiesel and vinasses residues) using life cycle assessment (LCA) methodology. For comparative purposes, mono digestion of PM has also been evaluated. Four out of six selected categories (acidification, eutrophication, global warming and photochemical oxidation potentials) showed environmental impacts in all the scenarios assessed, whereas the other two (abiotic depletion and ozone layer depletion potentials) showed environmental credits, remarking the benefit of replacing fossil fuels by biogas. This was also confirmed by the sensitivity analysis applied to the PM quality (i.e. organic matter content) and the avoided energy source demonstrating the importance of the energy recovery step. The influence of the type of co-substrate could not be discerned; however, a link between the environmental performance and the hydraulic retention time, the organic loading rate and the nutrient content in the digestate could be established. Therefore, LCA results were successfully correlated to process variables involved in AcoD, going a step further in the combination of techno-economic and environmental feasibilities.
authors.affiliation: Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain. Electronic address: ivan.rodriguez@usc.es.
authors.forename: Ivan
authors.initials: I
authors.lastname: Rodriguez-Verde
authors.affiliation: Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors.forename: Leticia
authors.initials: L
authors.lastname: Regueiro
authors.affiliation: Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Carballa
authors.affiliation: Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors.forename: Almudena
authors.initials: A
authors.lastname: Hospido
authors.affiliation: Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Lema
mesh_terms: D000383:Agriculture; D000693:Anaerobiosis; D000818:Animals; D001673:Biodegradation, Environmental; D056804:Biofuels; D008372:Manure / Q000382:microbiology*; D012037:Refuse Disposal / Q000379:methods*; D013552:Swine
chemical_list: D056804:Biofuels; D008372:Manure
keywords: Biogas; Co-substrates; Digestate; Environmental impact; LCA; Statistical correlations