First up, biologists at the Ruhr-Universität Bochum (RUB) have uncovered a mechanism for the production of hydrogen that has not been examined in depth before. The team has found how green algae accomplish the unusual process of producing hydrogen in the dark.
Professor Dr. Thomas Happe, head of the working group Photobiotechnology explains, “Hydrogen could help us out of the energy crisis, If you want to make green algae produce more hydrogen, it is important to understand all the production pathways. However, Chlamydomonas and other close relative species only form hydrogen under stress. The disposal of the energy-rich gas serves as a kind of overflow valve so that excess light energy does not damage the sensitive photosynthetic apparatus.”
But Chlamydomonas can also produce hydrogen in the dark, a fact that has been known for decades, H2 synthesis in the absence of light has barely been studied because much less of the gas is produced in the dark than in the light. Moreover, it is complicated to isolate large quantities of the key enzyme of the dark-reaction, the so-called pyruvate:ferredoxin oxidoreductase. Nevertheless the RUB researchers tackled the project.
A little genetic engineering came into play to reconstruct the core of the dark hydrogen production in vitro and demonstrate the underlying mechanism. First they introduced the corresponding genes of the green algae into the gut of the bacterium Escherichia coli, particularly the gene for the pyruvate:ferredoxin oxidoreductase. The E. coli then produced the proteins according to this blueprint. Happe’s team isolated the proteins from the bacterial cells and examined them like a construction kit. In the test tube, the biologists analyzed how different combinations of proteins interacted with each other under specific environmental conditions.
That’s how they found that under stress in the dark, the algae switch to a metabolic pathway, which is normally only found in bacteria or single-celled parasites.
Jens Noth also from the working group Photobiotechnology takes over the explanation, “Chlamydmonas has an evolutionarily ancient enzyme. With the help of vitamin B1 and iron atoms, it gains energy from the breakdown of sugars.” This energy is then used by other green algal enzymes, the hydrogenases, to form the hydrogen.
The unicellular microalgae switch on this metabolic pathway when they suddenly encounter oxygen-free conditions in the dark. Because, like humans, the green algae need oxygen to breathe if they cannot draw their energy from sunlight. The formation of hydrogen in the dark the oxygen that helps the cells to survive these stress conditions.
“With this knowledge, we have now found another piece of the puzzle to get an accurate picture of H2 production in Chlamydomonas”, said Professor Happe. “In future, this could also help to increase the biotechnologically relevant light-dependent H2 formation rate.”
Second is the PhD thesis of Aingeru Remiro-Eguskiza, a chemical engineer of the University of the Basque Country (UPV/EHU), that deals with the quest for a process to produce hydrogen from bio-oil that has a lower impact on the environment than the current processes.
Remiro-Eguskiza goal in the thesis was to contribute towards the laboratory scale development of a process for producing hydrogen from bio-oil by means of catalytic reforming using water vapor.
Currently, hydrogen is obtained through various methods that require separating the hydrogen from other chemical molecule sets like carbon in fossil fuels and the oxygen from water. The methods used for this purpose are not practical from an environmental or economic perspective as far as commercial large-scale production of hydrogen is concerned.
Remiro-Eguskiza used bio-oil from a heterogeneous mixture of wood-based oxygenated products, the catalytic transformation of which routinely entails problems of operability and deactivation of the catalyst. That’s because when bio-oil is being heated, a fraction of the compounds that make up the bio-oil form a solid residue (the so-called pyrolytic lignin) that collects on the inlet pipes of the reactor and in the reactor itself. The bio-oil used for the research in the thesis was developed at an IK4-Ikerlan plant.
Remiro-Eguskiza solved the problems caused by the use of bio-oil with in-house designed reaction unit comprised of two stages: the thermal and the catalytic stages. In the thermal stage (in which the bio-oil is heated) the controlled deposition of the pyrolytic lignin takes place and this minimizes the operational problems and the deactivation of the catalyst. That way the compounds obtained in the thermal stage are more susceptible to being transformed.
Then Remiro-Eguskiza added a third stage incorporated into the process. Here the CO2 capture is intended to intensify the production of H2 to increase its purity and cut the associated contaminating emissions. The process involves using an adsorber in the reaction bed and which is designed to capture the CO2. “When the CO2 is eliminated from the reaction bed, we are encouraging the displacement of the reaction equilibriums and, as a result, a greater yield and a greater output of hydrogen are obtained,” explains Remiro-Eguskiza.
In this context, he stresses that improvement in the CO2 capture in the reaction bed was verified when extremely pure hydrogen, close to 100%, was obtained and at a lower operating temperature with respect to the process minus the CO2 capture.
The RUB work might have a highly useful adaptation to the algae work underway by enriching the output and showing a way for the algae to cope with stress.
Remiro-Eguskiza is offering a whole new way to exploit the bio-mass to fuel pathway for renewable fuel.
Both are worthy additions to the basic understanding of sourcing free hydrogen. Eventually the storage issues and fuel cell problems will get worked out. It looks more and more like providing the hydrogen won’t be so difficult and expensive as everyone has been thinking.