Stairway to Hydrogen: Objectives, State of the art and Innovation

Objectives
The objective of  'Stairway to Hydrogen' is to make a blue-print for a sustainable hydrogen industry targeted at de-centralised hydrogen economies where 5-10% of the electricity demand is covered by hydrogen from locally produced biomass.

Scientific objectives
The main scientific objective of this project is to develop and optimise a process train of fermentative and thermochemical processes which leads to the cost-effective production of pure hydrogen from multiple biomass feedstocks. Several other objectives contributing to the main scientific objective are:

1. Assessment of biomass feedstocks, security of supply and market opportunities spread over Europe
2. Identification of biomass pretreatment technologies for optimal utilisation in fermentative and thermochemical conversions
3. Comparative assessment, development and optimisation of fermentation systems for hydrogen production from fermentable biomass
4. Comparative assessment, development and optimisation of (small-scale) thermochemical technologies for hydrogen production from non-fermentable biomass
5. Optimisation of hydrogen separation, purification, handling and safety devices
6. Energy analyses and benchmarking of the studied hydrogen production routes

Technological objectives
The technological objective is the building of a prototype plant in which the whole chain for converting biomass to hydrogen at fuel cell specifications is represented.
The sub-objectives to be achieved are developments of:

1. Bioreactors for fermentative hydrogen production
2. Reactors for (small-scale) thermochemical hydrogen production
3. Devices for monitoring and control of the hydrogen production process

Socio-economic objectives
Besides scientific and technological objectives, this project also provides for socio-economic objectives based on socio-economic research and activities aimed at increasing public awareness and societal acceptance necessary for the successful implementation of a future hydrogen-based energy system. Wide-spread training in innovation will be provided to allow commercial exploitation, particularly by the SME's involved in the project. Future stakeholders will be identified and legal consequences inherent to the introduction of a hydrogen industry will be addressed.

Finally, all objectives taken together are aimed at strengthening the European Research Area in sustainable energy systems, especially there where the focus is on the production of hydrogen from renewable sources.
 
State of the art
Because of the general insight that more hydrogen will be required in the future as e.g. described in reports like ‘Future Needs and Challenges for Non-Nuclear Energy Research in the European Union’ (2002) also renewable sources like biomass will be exploited for hydrogen production. Distinct advanced strategies for the production of hydrogen from biomass are currently being studied: the biological conversions using the so-called dark hydrogen fermentation and the photo-fermentation, and thermochemical technologies such as supercritical water gasification.

State of the art 'Biological hydrogen production'
The potential of biological hydrogen production is recognized worldwide. At the recent international conference Biohydrogen 2002, with 150 participating researchers from around the world, the status and progress in fundamental microbiological /biochemical/technological research in dark and photo-fermentative hydrogen production have been reviewed (Special issue Int J Hydrogen Energy (2002) 27: 1123-1506).
Biohydrogen 2002 showed that the international attention and R&D efforts in fermentative hydrogen production from biomass are rapidly increasing.
The Netherlands is leading in research on application of thermophilic bacteria for hydrogen production from biomass after having completed nationally and European funded projects, followed by Hungary.
In the USA the activities for the transition to a hydrogen economy are combined in the ‘Hydrogen, Fuel Cells & Infrastructure Technologies Program’ supported by the DOE. In November 2002 the ‘National Hydrogen Energy Roadmap’ was presented in which biological hydrogen production is seen as one of the options for renewable hydrogen production on the longer term.
The international recognition of the potential of fermentative hydrogen production has stimulated an increasing focus of expert groups of various disciplines throughout Europe, Canada, Asia and the USA. This focus is supported by the rapid progress in research on hydrogenase (i.e. enzyme responsible for hydrogen production) and by new insights in basic physiological parameters. This may form the basis for continuation and expanding the hydrogen-from-biomass development in Europe following the approach in The Netherlands which is based on fundamental insight and combination of various disciplines and differs distinctly from the usual pragmatic (black box) approach carried out in e.g. Asia.

State of the art 'Thermochemical hydrogen production'
A number of thermochemical processes are, worldwide, under development  to produce hydrogen from a variety of biomass feedstocks. So far, none of these processes can be considered as commercial. Examples of specific technologies are: gasification, bio-oil reforming, indirect processes - redox processes  and gasification in supercritical water.
In the previous years the gasification of biomass in supercritical water (SCW) received increasing interest in the international scientific community. Currently, significant effort is put into this development in Europe, USA and Japan.
A Dutch-led consortium started to work on the SCW process in 1997-98 in a CRAFT project that included a techno-economic analysis. Following the promising outcome of this study, the consortium secured other funding as e.g. from the International Joint Research Grant Program of NEDO of Japan, and the European Commission.


Innovation
This Integrated Project is aimed at the innovative combination of biological with thermochemical hydrogen production processes.
Generally, biological processes are considered less energy-intensive and more environmentally friendly than thermochemical processes. Furthermore, the fermentative hydrogen production  delivers the cleanest hydrogen with an elegant and simple technology and is suitable even for small-scale application.
The proof of principle of producing hydrogen from biomass by dark fermentation and subsequent photofermentation has been delivered in a previous FP5 project 'BioHydrogen', coordinated by The Netherlands. The same is true for the alternative route where the effluent from the dark fermentation is fermented to methane (as an intermediate to hydrogen) production. Besides these advantages, biological hydrogen production is limited to the fermentable fraction of biomass, i.e. sugars derived from starch and (hemi)cellulose and proteins. Even though the fermentable fraction in general amounts to 50-70% of the biomass, the residual part must be utilised also to make an economically viable hydrogen-from-biomass industry. Generally, by using the 'wet' part of biomass for fermentative hydrogen production and the 'dry' residue for thermochemical hydrogen production, the potentials of both technologies are fully exploited. However, the suitability of technologies depends on the intrinsic properties of the biomass. For instance: the energy crop Sweet Sorghum can be divided in a wet part (juice) and a dry part (cake). The juice is an excellent substrate for fermentation, the cake is as dry that combustion could be considered. On the other hand, the energy crop Miscanthus is, for pure hydrogen production, pretreated to give a hydrolysate suited for fermentation and a black liquor suited for SCW treatment.
The tailor-made combination of biological conversion with thermochemical conversion technologies will contribute to augmenting the current state of the art and provide the basis to make a breakthrough with respect to hydrogen production from multiple biomass feedstocks, ensuring a secure supply for an industry producing renewable hydrogen for fuel cells at 10 Euro/GJ.