28.07.20 “As green as hydrogen can get” Hans-Joachim Ziegler • 6 min.

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Hydrogen is touted as a key energy source for a sustainable future. But it’s only as climate-friendly as its source. So far that source has been either very carbon-intensive or relatively expensive. Thanks to new scientific discoveries, however, making hydrogen could be simpler and greener than ever. A research team at Kiel University in northern Germany is the first in the world to fuse a special protein onto living bacteria so that their photosynthesis produces mainly hydrogen. Although the research is still in its infancy, the potential is enormous.

Hydrogen is an important input. Large quantities of it are used to refine petroleum and to produce fertilizer and other chemicals. Hydrogen can also be used as a medium to store renewable energy, thereby helping to ensure supply security and grid stability. Its role for Europe’s climate strategy can hardly be overestimated.

Hydrogen’s carbon footprint depends on its source. Nearly all of today’s hydrogen is grey. It’s produced from natural gas in a process that’s both energy- and carbon-intensive. Green hydrogen, by contrast, can be produced when surplus electricity at a wind or solar farm is used to power on-site electrolysis equipment that transforms water (H2O) into hydrogen (H2).

From sunlight to hydrogen—directly

Researchers at Kiel University’s Botanical Institute are developing a revolutionary method for producing hydrogen directly from sunlight. No need for a solar farm or electrolysis. “If we succeed in scaling up this process, it would be a much simpler way to make green hydrogen,” project director Dr. Kirstin Gutekunst says.

Dr. Kirstin Gutekunst

The key ingredient is a cyanobacterium (also known as blue-green alga), a microorganism that, like all green plants, carries out photosynthesis: it uses sunlight to synthesize water and carbon dioxide into food, in this case sugar. The research team has succeeded in fusing an enzyme called hydrogenase so that the cyanobacterium’s photosynthesis mainly yields hydrogen. Unlike previous experiments in test tubes, in the Kiel method the fusion takes place in the living cell, which enables hydrogen production to potentially continue indefinitely. This could make photosynthesis an important source of tomorrow’s energy.

Photosynthesis is already essential for all ecosystems: it feeds plants, which in turn feed animals. “Humans too live in part on the carbohydrates produced by photosynthesis,” Dr. Gutekunst emphasizes. “You and I are able to hold this conversation because photosynthesis provides us with the energy.” The Kiel University scientists merely want to extend this principle so that photosynthesis can also provide energy for industry, transport, and other applications.

Big potential—and question marks

That’s still a ways off. “We’re conducting basic research,” Dr. Gutekunst emphasizes. Several problems need to be solved before the process can be scaled up. For example, hydrogenase becomes inactive in presence of too much oxygen, which is a necessary byproduct of photosynthesis. Currently, the process has to be supplemented by a second, glucose-based process. To avoid this in future, the team is exploring whether the process works with less oxygen-sensitive variants of the enzyme.

This and other hurdles need to be overcome for the innovation’s benefits really to be assessed. Dr. Gutekunst is therefore cautious with predictions about the role hydrogen from photosynthesis could play in the decades ahead.

But the potential is doubtless huge: “We’re at a point where investing in more research definitely makes sense. In about ten years we’ll know whether and to what extent the process can be used for energy production.” She added that more staff focused entirely on this process would enable the team to make considerable progress in a relatively short time. That, however, will require more public funding of research.


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