Discovery: A strain of algae may accelerate the industrial transition from the use of polluting gray hydrogen to environmentally friendly green hydrogen

A new discovery by Tel Aviv University may greatly accelerate the industrial transition from the use of polluting gray hydrogen to environmentally friendly green hydrogen. In the study, the researchers identified a mutant of a known strain of microscopic algae that allows, for the first time, the production of green hydrogen gas via photosynthesis on a scale suited to industrial requirements.

The study was led by doctoral student Tamar Elman, under the supervision of Prof. Iftach Yacoby from the Renewable Energy Laboratory of the George S. Wise Faculty of Life Sciences at Tel Aviv University. The study was recently published in the prestigious journal Cell Reports Physical Science.

The researchers explain that hydrogen gas is a non-polluting fuel that can be used to power various types of electric vehicles. Hydrogen-powered bicycles and cars have been in serial production for several years and, in these vehicles, the polluting lithium battery is replaced by a fuel cell that converts hydrogen to electricity.

However, most of the hydrogen in the world today is still produced in a highly polluting process from natural gas and is therefore called gray hydrogen. Alternatively, hydrogen gas produced only through renewable energy is called green hydrogen, due to the fact that its production does not emit either pollution or carbon dioxide into the atmosphere. Therefore, humanity's transition to the use of green hydrogen will be the ultimate solution to the problem of global warming.

The researchers add that the production of green hydrogen is possible through solar panels wired to devices that perform water breakdown into hydrogen and oxygen (electrolysers), but this process is expensive due to the fact that it requires precious metals and distilled water.  Alternatively, or in addition, biological processes can be used to produce hydrogen. In nature, hydrogen is produced as a by-product of photosynthesis for periods of minutes by micro-algae, unicellular algae found in every water reservoir and even in the soil. But for this process to become a sustainable source of energy, humanity must engineer micro-algae strains that produce hydrogen for days and weeks.

Prof. Yacoby explains that as part of the laboratory tests, the researchers identified a new mutant in microscopic algae that prevents oxygen from accumulating at any lighting intensity, and therefore hypothesized that continuous hydrogen production could be achieved from it.

Subsequently, with the help of bioreactor measurements in liter volumes, they were indeed able to prove that hydrogen can be produced continuously for more than 12 days. Prof. Yacoby stated: "The new mutant overcomes two major barriers that have so far prevented continuous production of hydrogen. The first barrier is the accumulation of oxygen in the process of photosynthesis. As a rule, oxygen poisons the enzyme that produces hydrogen in algae, but in the mutation, increased respiration eliminates the oxygen and allows favorable conditions for continuous hydrogen production. The second barrier is the loss of energy to competing processes, including carbon dioxide fixation into sugar. It, too, has been solved in the mutant and most of the energy is being channeled for continuous hydrogen production."

To industrialize these results, the research team led by Prof. Yacoby is working on a pilot program of larger volumes and the development of methods that will allow the time of hydrogen harvest to be extended, in order to reduce its cost to competitive levels. "The rate of hydrogen production from the new mutant reaches one-tenth of the possible theoretical rate, and with the help of further research it is possible to improve it even further," concludes Prof. Yacoby.

Link to the article:

https://doi.org/10.1016/j.xcrp.2022.100828