Co-digestion of animal manures and Sudan grass in agricultural biogas plants: optimisation of fermentation substrate and biogas yield
Abstract
Co-digestion of energy crops and animal manures in agricultural biogas plants offers considerable potentials for production of renewable energy and for improving economic efficiency of agricultural biogas production. Anaerobic digestion of Sudan grass (Sorghum sudanense) has so far not been investigated. Sudan grass yields much biomass and is thus a promising option for biogas production from energy crops. The research project aimed at investigating biogas and methane yield from anaerobic digestion of Sudan grass and at developing recommendations on choice of variety, optimum harvesting time and conservation. Methane yield of co-digestion of Sudan grass and cattle farmyard manure was to be determined. Experiments were carried out at lab scale with the eudiometer technology according to the German DIN standard No. 38414. Parameters of the anaerobic digestion process such as temperature or hydraulic residence time can exactly be controlled with this technology and were kept constant throughout all experiments. CO2 and CH4 concentrations in the biogas were analysed by gaschromatography. Substrate composition (Nt, NH4, Ct, cellulose, hemicellulose, crude fibre, protein, fat, dry matter, ash) was analysed before and after the digestion process. Substrate pH was monitored throughout the digestion process. Effectiveness of biogas production was assessed by the following criteria: biogas yield, methane yield, biogas quality, and decomposition of organic substance. Experiments comprised the following trials: fresh Sudan grass varieties Susu and Piper at three different harvesting times (early, medium, late), Sudan grass silage (Piper; early and late harvesting) and mixtures of Sudan grass (Piper; early and late harvesting) and cattle farmyard manure at 30:70, and 60:40 % VS. Co-digestion with cattle farmyard manure resulted in lower energy transfer rates from biomass to methane. However, animal manures stabilise methane fermentation. The fermentation substrate stays more homogeneous than without co-digestion of sudan grass and animal manures. After fructification, a growing lignification of sudan grass can be observed. This reduces methane yield. Thus, sudan grass should be harvested before fructification to achieve high methane yields per hectare. Anaerobic digestion lasted for 67 days (fresh plants) and 55 days (Sudan grass silage). Biogas yield varied between 331 and 385 Nl biogas (kg VS)-1 (fresh plants) and 201 and 368 Nl biogas (kg VS)-1 (silage). Biogas contained 62 to 64 % methane. This results in methane yields between 143 and 239 Nl CH4 (kg VS)-1. Methane yield per hectare ranged from 2740 to 6248 Nm3 CH4. Neither variety nor time of harvesting influenced the methane yield. This is due to the fact that there was no significant difference in composition of Sudan grass from different varieties and harvesting times. However, variety Susu yielded more biomass per hectare than variety Piper and thus had a higher methane yield per hectare, which is important for economic efficiency. Biogas and methane yields decreased when Sudan grass was co-digested with cattle farmyard manure. During anaerobic digestion of Sudan grass alone, 55 to 66 % of gross energy were broken down. 31 to 47 % of gross energy were transferred to methane energy. Co-digestion with cattle farmyard manure resulted in lower energy transfer rates from biomass to methane.
keywords biogas energy grass greenhouse gas emissions
Publikationen
Endbericht "Cofermentation von Wirtschaftsdüngern mit Energiegräsern in landwirtschaftlichen Biogasanlagen."
Autoren: Amon, Th., Hackl, E., Jeremic, D., Amon, B. Jahr: 2002
Forschungsbericht (extern. Auftraggeber)
Das Grünland und den Acker für die Biogasproduktion nutzen
Autoren: Amon, Th., Forschungsinitiative Biogas Jahr: 2003
Newspaper / Magazine article
Nutzung der Grünlandbiomasse sowie anderer Feldkulturen für die Biogasproduktion
Autoren: Amon, Th., Amon, B., Kryvoruchko, V., Hopfner-Sixt K., Buga, S., Pötsch, E., Zollitsch, W., Plank, J., Mayer, K. Jahr: 2003
Conference & Workshop proceedings, paper, abstract
Potentiale für kostendeckende Brennstoffpreise aus landwirtschaftlichen Biogasanlagen
Autoren: Amon, Th., Amon, B., Hopfner-Sixt, K., Hackl, E., Jeremic, D., Boxberger J. Jahr: 2001
Conference & Workshop proceedings, paper, abstract
Neue Entwicklungen der landwirtschaftlichen Biogaserzeugung in Österreich
Autoren: Amon, Th., Hackl, E., Hopfner-Sixt. K., Amon, B., Jeremic, D., Boxberger J. Jahr: 2001
Conference & Workshop proceedings, paper, abstract
Biogas production from animal wastes, energy plants and organic wastes
Autoren: Amon Th., Hackl, E., Jeremic, D., Amon, B., Boxberger, J. Jahr: 2001
Conference & Workshop proceedings, paper, abstract
Österreich: Ökostromgesetz könnte Bauboom auslösen
Autoren: Amon, Th. Jahr: 2002
Chapter in collected volumes
Biogas production from energy crops - A new system (MEVS) to calculate the methane energy value from biomass
Autoren: Amon, Th., Kryvoruchko, V., Amon, B. Jahr: 2002
Conference & Workshop proceedings, paper, abstract
Entwicklung eines "Methanenergiewertsystem (MEWS)" zur Bewertung des Methanbildungsvermögens von Biomasse
Autoren: Amon, T., Kryvoruchko, V., Amon, B., Pötsch, E., Zollitsch, W. Jahr: 2003
Conference & Workshop proceedings, paper, abstract
Biogaserträge aus landwirtschaftlichen Gärgütern.
Autoren: Amon, T., Kryvoruchko, V., Amon, B., Buga, S., Amid, A., Zollitsch, W., Mayer, K., Pötsch, E. Jahr: 2004
Conference & Workshop proceedings, paper, abstract
Biogas Forum Austria-Network of research, extension service, and commercial farms.
Autoren: Amon, T., Amon B., Kryvoruchko V., Hopfner-Sixt K., Moser, A., Zollitsch, W. Jahr: 2006
Conference & Workshop proceedings, paper, abstract
Monitoring of energy crop digestion in Austria.
Autoren: Hopfner-Sixt, K., Amon, T., Milovanovic, D., Amon, B. Jahr: 2006
Conference & Workshop proceedings, paper, abstract
Project staff
Barbara Amon
Priv.-Doz. Dr. Barbara Amon
barbara.amon@boku.ac.at
Project Staff
08.01.2001 - 31.07.2002
Gerhard Moitzi
Dipl.-Ing. Dr.nat.techn. Gerhard Moitzi
gerhard.moitzi@boku.ac.at
Project Staff
08.01.2001 - 31.07.2002
Helmut Wagentristl
Ass.Prof. Dipl.-Ing. Dr.nat.techn. Helmut Wagentristl
helmut.wagentristl@boku.ac.at
Tel: +43 1 47654-95501, 95511
Project Staff
08.01.2001 - 31.07.2002