Continuous biogas production from fodder beet silage as sole substrate

Since April 2000 a two-step anaerobic plant with two subsequent 500 m3 reactors has been producing biogas from fodder beet silage (pH 3.4-4.1) as the sole substrate. The plant is located at Kirchlengern near Bielefeld, Germany. Initially the reactors were inoculated with swine manure at 37 degrees C...

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Bibliographic Details
Published in:	Water Science & Technology Vol. 48; no. 4; pp. 229 - 233
Main Authors:	SCHERER, P. A, DOBLER, S, ROHARDT, S, LOOCK, R, BÜTTNER, B, NÖLDEKE, P, BRETTSCHUH, A
Format:	Conference Proceeding Journal Article
Language:	English
Published:	London IWA 01-01-2003 IWA Publishing
Subjects:	Agriculture Agriculture, rearing and food industries wastes Agronomy. Soil science and plant productions Anaerobic Digestion Applied sciences Bacteria, Anaerobic Beta vulgaris Bioelectric Energy Sources Biogas Biological and medical sciences Biological treatment of sewage sludges and wastes Biomass Bioreactors Biotechnology Carbon Dioxide - analysis Environment and pollution Exact sciences and technology Fatty acids Feeding Fodder Forage Fundamental and applied biological sciences. Psychology Gas production General agronomy. Plant production Germany, Kirchlengern Hydraulic retention time Hydrogen-Ion Concentration Industrial applications and implications. Economical aspects Inoculation Load distribution Loading rate Methane Methane - analysis Oil and gas production Organic loading pH effects Pig manure Pollution Propionic acid Reactors Recovery Refuse Disposal - methods Retention time Silage Swine Temperature Use of agricultural and forest wastes. Biomass use, bioconversion Volatile fatty acids Volatile solids Wastes Germany
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Summary:	Since April 2000 a two-step anaerobic plant with two subsequent 500 m3 reactors has been producing biogas from fodder beet silage (pH 3.4-4.1) as the sole substrate. The plant is located at Kirchlengern near Bielefeld, Germany. Initially the reactors were inoculated with swine manure at 37 degrees C. After a start-up phase the process was sustained at pH 7.5-8.0 by feeding the silage as sole substrate with an HRT of about 55 d twice a day. Parallel to the biogas plant at Kirchlengern four one-step laboratory reactors were continuously driven at temperatures of 37 degrees C, 45 degrees C, 60 degrees C and 65 degrees C. They were fed with the same silage, but only once per day (one impulse). The organic loading rate (OLR) was adjusted to 3.9 g volatile solids (VS)/(ld) with a concomitant hydraulic retention time (HRT) of 27 d. There was no problem with starting the reactors, but after 86 days the volumetric gas production of the 65 degrees C reactor ceased and a high amount of approximately 65 mM propionate could be determined. By decreasing the temperature down to 60 degrees C a stable reactor performance was recovered for a period of at least 600 further days. Interestingly microscopic analyses revealed that the morphology of methanogenic bacteria in the 60 degrees C was quite different from the 37 and 45 degrees C reactor exhibiting only rodlike methanogens whereas at 37 degrees C coccoid morphotypes besides rodlike methanogens were dominant. In a 55 degrees C reactor (separate experiment) a mixture of coccoid and rodlike methanogens established. During impulse feeding with 3.9 g (VS)/(ld) it was observed that the quickest recovery of gas production, the pH, CH4 and CO2 content as well as the redox value could be observed at 37 degrees C or at 45 degrees C. Recovery of 75% gas volume (related to the value before or after impulse feeding) was obtained after 5.5 and 7.5 h of feeding time point whereas the 60 degrees C reactor needed 16 h. Slight significant differences were seen in the spectrum of volatile fatty acids (VFA) reaching at 37 degrees or 45 degrees C its maximum with 10-30 mM total VFA at 2-3 h after feeding. After this the VFA level declined to nearly zero (except for the 60 degrees C reactor). Therefore the 37 degrees C reactor was favoured. A double experiment with a second 37 degrees C reactor was started by a somewhat different inoculation procedure from the remaining 3 reactors, but revealed similar results. An impulse feeding experiment with a very high OLR of 16.5 g (VS)/(ld) lasting 1 week offered a stable reactor performance with a peak GPR of up to 24 l/(l reactor d) and an HRT of 5.45d. Therefore a long term operation with an HRT of only 7.5 days and an OLR of 12 g (VS)/(l*d) should be possible. By increasing the temperature no significantly different specific gas production rates and methane yields could be observed, e.g. it gave 600-7001 biogas from 1 kg VS. The corresponding methane content ranged between 62-64%. With a methane content of 63 +/- 1% a yield of 40.1 +/- 2 m3 methane/ton fresh fodder beet silage was obtained.
Bibliography:	SourceType-Books-1 ObjectType-Book-1 content type line 25 ObjectType-Conference-2 SourceType-Conference Papers & Proceedings-2 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISBN:	9781843394495 1843394499
ISSN:	0273-1223 1996-9732
DOI:	10.2166/wst.2003.0260