Regenerative Energie
SUMMARY:
Hydrogen is a clean energy carrier which can be used as a fuel for example in fuel cells. Today, hydrogen is produced mainly by steam reforming of fossil fuels like natural gas or oil. But only hydrogen produced by renewable sources is really a sustainable energy source. One new possibility for hydrogen production is the biological production of hydrogen by the green algae chlamydomonas reinhardtii. In this study, the waste and waste water streams of a photobioreactor system were investigated.
Because of the high water content in the medium (>99,9 %), the solid/fluid-separation of the used green-algae medium was most important for the following steps. Therefore, solid/fluid-separation was tested by laboratory tests with filtration, centrifugation and sedimentation. Each technique was also examined in combination with different flocculants. Additionally, aerobic and anaerobic biodegradation tests of the green-algae medium and the flocculated algae sediment were performed as well as a determination of the heating value and ash-melting point. It turned out, that the sedimentation of green-algae medium already used for biohydrogen production was not efficient if no flocculants were used. Separation efficiencies of 50 % in maximum were achieved. The use of flocculation polymers normally used for sewage sludge dewatering showed the best separation results (>95 %), under both technical and economical aspects. After separation of the algae, different treatment technologies were investigated, biodegradation as well as drying and incineration of the biomass. The biodegradation tests showed different results. Under aerobic conditions, the degree of degradation was at 92 % after two weeks, but the anaerobic batch tests showed a very low degree of degradation. Therefore, also the methane production rate was very low (<120 NL/kg oTS). But, other recycling methods for the gainful use of the separated algae biomass have to be found, because neither anaerobic digestion nor burning of the green-algae seem to be suitable methods for energy recovery. Finally, an assessment of the method was carried out by comparing the process with other hydrogen production methods.
| Copyright: | © European Compost Network ECN e.V. |
| Quelle: | Orbit 2006 (September 2006) |
| Seiten: | 6 |
| Preis: | € 3,00 |
| Autor: | Michaela Krupp Tomaz Petrovic Prof. Dr.-Ing. Renatus Widmann A. Kilzer M. Kretschmann |
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