ELECTROPORATION AS AN OPTIMIZING STEP IN THE DRYING OF GREEN BIOMASS *

Martin Sack, Christian Eing, Lothar Buth, Thomas Berghöfer, Wolfgang Frey, Hansjoachim Bluhm

Forschungszentrum Karlsruhe GmbH,

Institute for Pulsed Power and Microwave Technology

P.O. Box 3640, 76021 Karlsruhe, Germany

The replacement of exhaustive energy resources by renewable energy resources nowadays becomes an important field of work for our future energy supply. There are already some examples for the use of plants as a source of renewable energy, e.g. ethanol made from sugar cane and sugar beets to power spark ignited engines or rape seed oil for Diesel engines. Moreover, new processes like the BIOLIQ-process /1/ enable the adaptation of fuel to the needs of the engines or to synthesize raw substances for the production of polymers. For the BIOLIQ-process dry biomass is required. Hence, the amount of raw material can be increased by drying of green biomass, e.g. whole maize plants (Zea mais).

During the last few years the electroporation of plant cells became an interesting new method for an energy efficient denaturisation of plant cells. During the electroporation process high-voltage pulses are applied to the plant cells. The electric field set up across the cell membranes causes the formation of pores. Examples are the electric treatment of apples to increase the yield of juice, or the electroporation of cossettes of sugar beets in order to save energy compared to the conventional thermal process /2/. For the mentioned applications of electroporation the plant material is immersed in water in order to guarantee a good contact to the electrodes. But for a drying process it is essential to omit the use of additional water. Hence, it has been tested in laboratory scale experiments, to use the water inside the plants only: slices of plant material are pressed before the electroporation, until the space between the plant material and the electrodes is filled with juice. After a second pressing step, the plant material is dried in an oven.

The energy required for the electroporation and the drying process has been evaluated and compared to the energy required for the drying process without electroporation. A clear advantage in energy saving for the drying process with electroporation has been observed. Diagrams showing the required energies of the different steps are presented for Zea mais.

1. Dinjus, E.; Henrich, E.; Dahmen, N.: “Synthetic fuels from biomass - barriers and solutions", Bio-Logical Futures III, Saskatoon, CDN, October 16-17, 2006

2. S. Frenzel, T. Michelberger, M. Sack, H. Bluhm, M. Kern: “Entwicklung und Bau einer Elektroimpuls-Pilotanlage", Abschlussbericht, Förderkennzeichen 0330434, TIB-Hannover, 2005.

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* Work supported by Bundesministerium für Ernährung, Landwirtschaft und Verbraucherschutz (Federal Ministry of Food, Agriculture, and Consumer Protection of the Federal Republic of Germany) in the frame of the BioLog - project (FKZ 22031ff).