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Hygiene aspects of the biogas process with emphasis on spore-forming bacteria

Bagge, Elisabeth (2009). Hygiene aspects of the biogas process with emphasis on spore-forming bacteria. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2009:28
ISBN 978-91-86195-75-5
[Doctoral thesis]

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Biogas is a renewable source of energy which can be obtained from processing of biowaste. The digested residues can be used as fertiliser. Biowaste intended for biogas production contains pathogenic micro-organisms. A pre-pasteurisation step at 70°C for 60 min before anaerobic digestion reduces non spore-forming bacteria such as Salmonella spp. To maintain the standard of the digested residues it must be handled in a strictly hygienic manner to avoid recontamination and re-growth of bacteria. The risk of contamination is particularly high when digested residues are transported in the same vehicles as the raw material. However, heat treatment at 70°C for 60 min will not reduce spore-forming bacteria such as Bacillus spp. and Clostridium spp. Spore-forming bacteria, including those that cause serious diseases, can be present in substrate intended for biogas production. The number of species and the quantity of Bacillus spp. and Clostridium spp. in manure, slaughterhouse waste and in samples from different stages during the biogas process were investigated. The number of species of clostridia seemed to decrease following digestion, likewise the quantity. However, Bacillus spp. seemed to pass unaffected through the biogas process. In laboratory-scale experiments the effects on clostridia during pasteurisation and digestion were investigated. Pathogenic clostridia were inoculated in substrates from homogenisation tanks and digester tanks. The inoculated clostridia remained after pasteurisation, but the impacts of digestion differ between different species. Culture followed by identification of C. chauvoei by PCR in samples from cattle died from blackleg, is faster and safer than culture followed by biochemical identification of C. chauvoei. However, for environmental samples the PCR method is not practically applicable for detection of C. chauvoei. To avoid spreading of diseases via biogas plants when digested residues are spread on arable land, a pasteurisation stage at 70°C for 60 min before anaerobic digestion gives adequate reduction of most non spore-forming bacteria, such as salmonella. However, caution should be exercised before digested residues are spread in areas without endemic problems of pathogenic spore-forming bacteria. In Sweden, official recommendation is that digested residues from biogas plants only should be applied on arable land, and not on grasslands for animal pasture.

Authors/Creators:Bagge, Elisabeth
Title:Hygiene aspects of the biogas process with emphasis on spore-forming bacteria
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2009
Number of Pages:89
ALLI Bagge E, Sahlström L, Albihn A. (2006). The effect of hygienic treatment on the microbial flora of biowaste in biogas plants. Water Research 39, 4879-4886. II Sahlström L, Bagge E, Emmoth E, Holmqvist A, Danielsson-Tham M-L, Albihn A. (2008). A laboratory study of survival of selected microorganisms after heat treatment of biowaste used in biogas plants. Bioresource Technology 99, 7859-7865. III Bagge E, Persson M, Johansson K-E. Diversity of spore forming bacteria in cattle manure, slaughterhouse waste and biogas plants. In manuscript. IV Bagge E, Albihn A, Båverud V, Johansson K-E. Survival of pathogenic spore-forming bacteria after pasteurisation and during digestion in biogas plants - a laboratory study. In manuscript. V Bagge E., Sternberg-Lewerin S., Johansson K.-E. (2009). Detection and identification of Clostridium chauvoei in clinical cases bovine faeces, and substrates from a biogas plant isolates by PCR. Acta Veterinaria Scandinavica 51:8.
Place of Publication:Uppsala
ISBN for printed version:978-91-86195-75-5
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:bacillus, clostridium, biogas, agricultural wastes, PCR, hygiene, safety, disease control, sweden
Keywords:Bacillus spp., biogas plants, Clostridium spp., digested residues, Sweden, environment, hygiene safety, PCR, 16S rRNA sequencing
Permanent URL:
ID Code:1980
Department:(VH) > Dept. of Biomedical Sciences and Veterinary Public Health
Deposited By: Elisabeth Bagge
Deposited On:14 Apr 2009 00:00
Metadata Last Modified:02 Dec 2014 10:15

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