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Evaluating the effects of electroporation pre-treatment on the biogas yield from ley crop silage.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. (MERO)ORCID iD: 0000-0002-8268-1967
Division of Waste Science and Technology, Luleå University of Technology, Luleå, Sweden.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. (MERO)
AnoxKaldnes AB, Lund, Sweden.
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2014 (English)In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, Vol. 174, no 7, p. 2616-2625Article in journal (Refereed) Published
Abstract [en]

Exploiting the full biogas potential of some types of biomass is challenging. The complex structures of lignocellulosic biomass are difficult to break down and thus require longer retention times for the nutrients to become biologically available. It is possible to increase the digestibility of the substrate by pre-treating the material before digestion. This paper explores a pre-treatment of ley crop silage that uses electrical fields, known as electroporation (EP). Different settings of the EP equipment were tested, and the results were analyzed using a batch digestion setup. The results show that it is possible to increase the biogas yield with 16 % by subjecting the substrates to 65 pulses at a field strength of 96 kV/cm corresponding to a total energy input of 259 Wh/kg volatile solid (VS). However, at 100 pulses, a lower field strength of 48 kV/cm and the same total energy input, no effects of the treatment were observed. The energy balance of the EP treatment suggests that the yield, in the form of methane, can be up to double the electrical energy input of the process.

Place, publisher, year, edition, pages
2014. Vol. 174, no 7, p. 2616-2625
Keywords [en]
Electroporation, Pre-treatment, Ley crop silage, Anaerobic digestion, Pulsed electric field, Lignocellulose
National Category
Bioenergy
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-26080DOI: 10.1007/s12010-014-1213-7ISI: 000345331100023Scopus ID: 2-s2.0-84916623709OAI: oai:DiVA.org:mdh-26080DiVA, id: diva2:753953
Available from: 2014-10-09 Created: 2014-10-09 Last updated: 2018-01-03Bibliographically 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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Lindmark, JohanThorin, EvaDahlquist, Erik

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