What is it?
Microorganisms such as green algae and blue-green algae (cyanobacteria) split water into hydrogen and oxygen via direct or indirect bio-photolysis. In direct biophotolysis, hydrogenase in green algae drives hydrogen evolution. In indirect biophotolysis, nitrogenase in blue-green algae drives nitrogen fixation.
Why is it important?
Biophotolysis could be used for producing hydrogen from wastewater with sunlight as an energy source.
- Inputs: Direct: Water, sunlight. Indirect: Carbon monoxide, water, sunlight
- By-products: Direct: oxygen. Indirect: carbon dioxide
- Operating temperature: Ambient
- Low-to-net zero carbon
- Could be used in wastewater or water which cannot be used for drinking or agriculture
- Biocatalysts are inexpensive and biodegradable
- In the case of direct biophotolysis: Oxygen produced inhibits the hydrogen production reaction. Oxygen that is evolved destroys the hydrogen enzyme. Separate streams of high purity H2 and O2 are not obtainable
- Indirect biophotolysis: hydrogenase enzyme provides low hydrogen yield, and produces carbon dioxide
- Requires large surface area
- Need to cope with the intermittent nature of solar irradiation supply for the process
- Improve production rates and conversion efficiency, both of which are currently low
- Reduce cost of photobioreactors
- Develop oxygen resistant hydrogenase
- Continue materials development, including characteristics such as increased durability
- Investigate immobilisation of microorganism cultures to achieve improvement
- Technology development while sustaining high rate of biohydrogen production
Known active organisations
- The University of Adelaide
- The University of Queensland