The application of fuel cells is gaining an increasing interest in the world of energy production. The advantages of fuel cells are clear: energy conversion is more efficient when compared to traditional energy conversion systems and they produce zero emissions. However the feedstock for the fuel cell, hydrogen, is derived from fossil fuels and its use contributes to the increase in carbon dioxide. Gasification of biomass is currently studied as a method to produce hydrogen from renewable resources, but is still hampered by high investment and operational costs. This project is aimed at the biological production of hydrogen from biomass employing (hyper)thermophilic micro-organisms in combination with photoheterotrophic micro-organisms. This alternative approach offers several advantages: it can be operated with fairly low technology, it can handle 'wet biomass', the produced hydrogen is free from contaminants and, above all, the theoretical production of hydrogen cellulose is higher than that produced by gasification.
The main objective of this proposal is the development of a system for the production of hydrogen from renewable resources that meets the specifications for application in fuel cells. By this method, the advantages of fuel cells, i.e. higher energy conversion and zero emission, will become exploitable without the traditional carbon dioxide emission associated with the utilisation of fossil fuels. This goal will be achieved through integrating the work on processing the biomass from energy crops and waste streams, the development of a microbial hydrogen-producing 'factory', and the recovery and application of the product. The pan-European involvement of scientists and industrialists will support the objective of spreading the knowledge and potential introduction of biological hydrogen production across Europe.
Progress to Date
Progress in the project has proceeded as envisaged. Hydrogen was produced successfully from the two feedstocks studied (sweet sorghum and paper sludge hydrolysate). The production rates and efficiencies were both high, showing great promise for making an industrial process. Optional H2 recovery methods have been evaluated, aimed at the development of low energy intensive and safe H2 handling procedures. Finally, the elucidation of the maturation process of the hydrogenase is an important step towards further optimisation of the hydrogen production process.
Biomass production from two different sweet sorghum varieties in Greece was studied. For every 32 tonnes of dry matter of sweet sorghum 'Keller', per ha 14.5 tonne of sugar was produced for hydrogen fermentation. Byproducts could be used for biofuel as an additive in low density polyethylene composites or as a substrate for fermentation after pre-treatment and hydrolysis. The theoretical production in the bioprocess under consideration from the 14.5 tonne sugars/ha could amount to 1 452kg hydrogen/ha.
The pre-treatment of sweet sorghum bagasse for increasing fermentability was further optimised. In view of the application of simultaneous saccharification and fermentation (SSF) of paper sludge, Thermoascus auranticus, a thermophilic cellulolytic fungus, was grown on Sloka Floc cellulose powder. So far, the explorations of the opportunities for SSF are rather disappointing and will not be pursued.
Hydrogen production from numerous samples of sweet sorghum juice showed that it is an excellent substrate. Similarly, the potential of paper sludge was tested using C. saccharolyticus. Sweet sorghum juice and paper sludge hydrolysate enable thermophilic hydrogen production with good yields and rates.
The work on photobiological hydrogen production was continued using a pure culture of Rhodopseudomonas sp. in a chemostat culture. Another culture, R. CJR, was used to produce hydrogen from the effluent of a thermophilic culture, provided by ATO. Using a model for the simulation of the performance of chemostats, two designs for a photobioreactor could be envisaged. Under low-light intensities and substrate, a tubular photobioreactor is the best choice although the drawback here is the low volumetric hydrogen productivity. The second option is operating under high-light intensities, which requires a turbulently mixed high-density culture as can be obtained in a flat-panel photobioreactor. However, in this case the simulations showed that retention of biomass is required to prevent wasting of light energy.
For heterologous expression of hydrogenase it was found that the transfer of hydrogenase acitivity depends on several phenomena. A modular broad-host range expression plasmid was constructed, which enabled expression of foreign genes in two different hosts. Homologous expression was studied aimed at increasing the expression of hydrogenase by increasing the gene dosage.
Scientist responsible for the project
Ms PIETERNEL CLAASSEN
Bornsesteeg 59 Box 17
6708 PD Wageningen
Netherlands (The) - NL
Phone: +31 317 475 325
Fax: +31 317 475 347
||Agrotechnological Research Institute
||01 February 2000
||2 308 700 €
|Total EC contribution
||1 495 669 €