Biogas production from energy crops produced in sustainable crop rotations in Styria and economic efficiency
Abstract
The aim of the project was to determine optimal mixtures of fermentation raw material from energy crops from typical habitat and production terms and conditions of Styria for biogas production. For this purpose five different energy crop species were used: (1) sugar beets, (2) maize (maize for silage and maize of corn), (3) sun flowers, (4) field forage (clover) and (5) cereal (green rye). All energy crop species were grown and harvested in species experi-ments of the Syria chamber of agriculture and forestry. The biomass yield was determined and for the subsequent laboratory investigations all energy crops were preserved as silage. An exception was the maize for corn which was used as CCM (Corn-Cob-Mix). Beside the energy crops pig manure and crude glycerin (byproduct from the bioethanol production) were used as additional fermentation raw material. All fermentation raw materials were investigated alone and in mixtures. The used mixtures differed in their protein-energy-proportion. There were three blocks: block 1 = energy-rich mixtures (mixture 1 to 5), block 2 = protein-rich mixtures (mixture 6 to 9) and block 3 = variants with a balanced protein-energy-proportion (mixture 10 to 13). Mixture 1 (a mixture of maize silage, CCM and pig manure) was supplemented with 4% crude glycerin, as a performanceenhancing additive. For the used energy crops nutrient analyses were done to have an exact characterisation of the fermentation substrates. Based on DIN 38414 and VDI 4630 (2006) the alteration of matter and energy in the fermentation raw material (mono-fermentation) and the mixtures (co-fermentation) were measured in fermentation experiments of at least 40 days at 38°C. In the fermenters the composition of the volatile fatty acids were determined, the pH-value was measured as well as the content of methane, hydrogen sulfide and ammonia in the biogas. Analyses of the ingredients also were completed for all fermentation residues to be able to determine the fertilisation value. The degradation of TS and VS as well as the energy efficiency of the methane formation was calculated. The hydraulic residence time was derived from the development of the generated biogas over time. The specific biogas and methane yield of the fermen-tation raw material and mixtures were determined. With monofermentation of the fermentation raw material, CCM showed the highest specific methane yields with 344 lN/kg VS. With co-fermentation this value was even exceeded. With four mixtures a specific methane yield above 380 lN/kg VS was achieved (mixture 13: 427 lN/kg VS, mixture with the highest proportion of maize silage; mixture 8 and 9: 395 and 386 lN/kg VS, respectively, mixtures with high proportions of clover and green rye silage; mixture 1: 383 lN/kg VS, mixture with the additive crude glycerin). For these four mixtures a cofermentation effect could be determined of +39 to +49%. With the exception of mixture 12 all mixtures had a posi-tive co-fermentation effect. This means, that through the fermentation of fermentation raw material in mixtures almost always more methane will be produced as compared to monofermentation. Based on the specific methane yield and the biomass yield, the methane yields per hectare of the used energy crops and energy crop mixtures were calculated. For the energy crop mixtures regression equations estimating the specific methane yield were developed (Methane Energy Value Model). Recommendations for optimal mixtures of fermentation raw material and a guidelines for ecologically balanced and sustainable crop rotations for the biogas production of typical habitat and production terms and conditions of Styria as well as economic efficiency calculation were derived from the experimental results. Possibilities of whole crop sugar beet silage as fermentation substrate for biogas production were discussed. A biorefinery concept was favoured.
www.landwirtschaftsverlag.comProject staff
Michael Eder
Assistenzprofessor Dipl.-Ing.Dr.nat.techn. Michael Eder
michael.eder@boku.ac.at
Tel: +43 1 47654-73313
Project Staff
01.10.2005 - 10.05.2007
Jürgen Kurt Friedel
ao.Univ.Prof. Dipl.-Ing.Dr. Jürgen Kurt Friedel
Tel: +43 1 47654-93317
Project Staff
01.10.2005 - 10.05.2007
Marion Ramusch
Marion Ramusch
marion.ramusch@boku.ac.at
Tel: +43 1 47654-31302
Project Staff
01.10.2005 - 10.05.2007
Helmut Wagentristl
Assistenzprofessor Dipl.-Ing.Dr.nat.techn. Helmut Wagentristl
helmut.wagentristl@boku.ac.at
Tel: +43 1 47654-95501, 95511
Project Staff
01.10.2005 - 10.05.2007
Werner Zollitsch
Univ.Prof. Dipl.-Ing.Dr. Werner Zollitsch
werner.zollitsch@boku.ac.at
Tel: +43 1 47654-93211, 99101, 99111
Project Staff
01.10.2005 - 10.05.2007
Barbara Amon
Priv.Doz.Dr. Barbara Amon
barbara.amon@boku.ac.at
Sub Projectleader
01.10.2005 - 10.05.2007
BOKU partners
External partners
Chamber of Agriculture, Styria
Dr. Karl Mayer
partner
SEEG
ÖKR. Karl Totter
partner
Funder
Land Steiermark, Ressort für Land- und Forstwirtschaft