Storage and pre-treatment of substrates for biogas production - The Biogas: Science, Production and Applications - page 91

4.3 Electrokinetic disintegration unit (source: ATRES, Munich,

Germany).

Electrokinetic disintegration

Electric fields are used for a variety of processes in modern biotechnology.
Electrokinetic disintegration is mainly used for sewage sludge treatment.
The main inhibiting factor for good anaerobic digestion of sewage sludge is
the presence of flocs and aggregates, which are formed by negatively charged
molecules on microbial extracellular polymeric substances forming ionic
bonds with cations (Tyagi and Lo, 2011; Higgins and Novak, 1997). The
application of an electrical field to sewage sludge disrupts these ionic bonds
and thus breaks apart the flocs (Tyagi and Lo, 2011). It is also likely electric
fields disrupt microbial cells by changing the charge of the cell membranes.
It is not clear what effect, if any, this treatment has on lignocellulosic
material. Some German companies produce electrokinetic disintegration
devices in which the sludge is fed through a section of pipe with an electrode
inside applying a voltage of typically around 30 kV (range 10-100 kV)
(Hugo Vogelsang Maschinenbau GmbH, 2011; Su¨ d chemie AG, 2011).
Figure 4.3 shows such a unit. An increased biogas yield from sewage sludge
of around 20% has been claimed (Su ¨ d chemie AG, 2011). It has also been
claimed that the device can increase biogas production from agricultural
residues (Hugo Vogelsang Maschinenbau GmbH, 2011), but a study by the
Bavarian State Research Center for Agriculture, LfL, showed no significant
increase in biogas production from agricultural residues (Lehner et al.,
2009). Like ultrasonication, electrokinetic disintegration may be better
suited to post-treatment of the liquid effluent from anaerobic digesters or
pre-treatment of substrates similar to sewage sludge.

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