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Effects of mechanical pre-treatment on the biogas yield from ley crop silage
Mälardalen University, School of Sustainable Development of Society and Technology. (MERO)ORCID iD: 0000-0002-8268-1967
Växtkraft.
SLU.
Mälardalen University, School of Sustainable Development of Society and Technology.ORCID iD: 0000-0002-3485-5440
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 97, 498-502 p.Article in journal (Refereed) Published
Abstract [en]

Previous studies on substrates for biogas production have shown that different types of pre-treatments make the material more accessible for microbial degradation by breaking down the complex structure of the organic material, thereby increasing their potential for gas production. In this paper, two different mechanical pre-treatment apparatus, i.e. a Grubben deflaker (Gd) and a Krima disperser (Kd), were tested in a full scale setup to evaluate their effects on ley crop silage. The treatments were investigated with regard to their effects on particle size, methane potential, capacity and energy balance. The results after 115 days of incubation in a batch assay show that methane production increased by 59% and 43% respectively after grinding with Gd and Kd. In both treatments, 90% of the ley crop was ground to particles of less than 2 mm and more than 50% of the sample was reduced to particles smaller than 0.125 mm. The energy balance was positive for Gd and around the break-even point for Kd. Analysis of the setup showed that Kd had almost twice the capacity of the Gd. If installed in the co-digestion biogas plant Vaxtkraft in Vasteras, Sweden, the Gd and Kd could increase annual biogas yields by 790 MW h and 585 MW h respectively. (c) 2012 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
2012. Vol. 97, 498-502 p.
Keyword [en]
Mechanical pre-treatment, Biochemical methane potential, Biogas, Ley crop silage, Particle size
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-17725DOI: 10.1016/j.apenergy.2011.12.066ISI: 000307196000057Scopus ID: 2-s2.0-84862307407OAI: oai:DiVA.org:mdh-17725DiVA: diva2:588254
Conference
3rd International Conference on Applied Energy (ICAE), MAY 16-18, 2011, Perugia, ITALY
Projects
BioGasOpt
Available from: 2013-01-15 Created: 2013-01-15 Last updated: 2014-10-10Bibliographically approved
In thesis
1. Developing the anaerobic digestion process through technology integration
Open this publication in new window or tab >>Developing the anaerobic digestion process through technology integration
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Process optimization is needed for the development and expansion of the biogas industry and to meet the ever growing demand for methane. This thesis explores process technologies for the development of the anaerobic digestion process and includes pre-treatments, studies on the effects of different mixing modes and evaluation of a water treatment technology.

Two pre-treatments were evaluated, mechanical and electroporation, for treatment of ley crop silage. Mechanical treatment included two milling machines designed for recycling of paper, Grubben deflaker and Krima disperser, and showed an increased biogas production of 59 % and 43 % respectively as well as a positive energy balance and economic results.. Electroporation increased the biogas production with 16 %, however, development is needed to increase its energy efficiency.

Digester mixing has an effect on the digestion result. The performed review and experiments show that the mixing demand increases with organic loading. Excessive mixing during process start up, instabilities and shock loads leads to increased volatile fatty acid concentrations and process inhibition. Reduction of mixing reduces the effects of process instabilities and periodical mixing with mixing breaks has been shown to be beneficial for biogas production.

A high temperature membrane filtration unit was evaluated at 70 °C, 90 °C and 110 °C to determine separation efficiencies, permeation speed when treating process water at a biogas plant.  Improved separation can increase the capacity of the substrate pre-processing and reduce process related problems. The results show a total solids separation of 60 %, and an increasing filtration speed with temperature with fluxes of between 113 and 464 L/ h m2. The substrate pre-processing could theoretically handle up to 29 % more substrate as a result.

Integration of these technologies in a biogas plant show that the pre-treatments studied exhibits a good performance when integrated and that mixing reduction has the potential to lower the process electricity demand by 23 % in the performed case study. However, even though the membrane filtration unit shows promising results it would demand a relatively high energy consumption and lead to limited benefits to a process already at it maximum organic loading.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2014
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 165
National Category
Bioenergy
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-26081 (URN)978-91-7485-166-3 (ISBN)
Public defence
2014-11-19, rum R2-025, Mälardalens högskola, Västerås, 09:00 (English)
Opponent
Supervisors
Available from: 2014-10-10 Created: 2014-10-09 Last updated: 2014-11-03Bibliographically approved

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Citation style
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