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Valorisation of used cooking oil sludge by codigestion with swine manure.

Authors
  • Fierro, J1
  • Martínez, E J1
  • Morán, A1
  • Gómez, X2
  • 1 Chemical and Environmental Bioprocess Engineering Department, Natural Resources Institute (IRENA), University of León, Av. de Portugal 41, 24071 León, Spain. , (Spain)
  • 2 Chemical and Environmental Bioprocess Engineering Department, Natural Resources Institute (IRENA), University of León, Av. de Portugal 41, 24071 León, Spain. Electronic address: [email protected] , (Spain)
Type
Published Article
Journal
Waste management (New York, N.Y.)
Publication Date
Aug 01, 2014
Volume
34
Issue
8
Pages
1537–1545
Identifiers
DOI: 10.1016/j.wasman.2014.02.006
PMID: 24594254
Source
Medline
Keywords
License
Unknown

Abstract

The addition of lipid wastes to the digestion of swine manure was studied as a means of increasing biogas production. Lipid waste was obtained from a biodiesel plant where used cooking oil is the feedstock. Digestion of this co-substrate was proposed as a way of valorising residual streams from the process of biodiesel production and to integrate the digestion process into the biorefinery concept. Batch digestion tests were performed at different co-digesting proportions obtaining as a result an increase in biogas production with the increase in the amount of co-substrate added to the mixture. Semi-continuous digestion was studied at a 7% (w/w) mass fraction of total solids. Co-digestion was successful at a hydraulic retention time (HRT) of 50 d but a decrease to 30 d resulted in a decrease in specific gas production and accumulation of volatile and long chain fatty acids. The CH4 yield obtained was 326 ± 46 l/kg VSfeed at an HRT of 50 d, while this value was reduced to 274 ± 43 l/kg VSfeed when evaluated at an HRT of 30 d. However these values were higher than the one obtained under batch conditions (266 ± 40 l/kg VSfeed), thus indicating the need of acclimation to the co-substrate. Despite of operating at low organic loading rate (OLR), measurements from respirometry assays of digestate samples (at an HRT of 50 d) suggested that the effluent could not be directly applied to the soil as fertiliser and might have a negative effect over soil or crops.

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