A game-changing solution could unlock our hydrogen future

Hydrogen gas can be burned as fuel, along with oxygen, leaving only water as a byproduct. Usable in ordinary combustion engines, hydrogen fuel itself can be easily produced by methods such as water electrolysis. If this production is powered by renewable energy, carbon will not be involved at any stage of the process, making it entirely greenhouse gas free.

In addition to this, hydrogen fuel is currently being explored as a possible way to store excess renewable energy for longer term.

Hydrogen is one of the most promising paths to a carbon neutral economy.

When the production of wind, solar and hydroelectric facilities exceeds the demand for electricity, this energy could be used to produce hydrogen, which could be stored indefinitely. Then, if renewable energy production drops, the hydrogen could be converted back into clean energy on demand.

All of these factors have cemented hydrogen’s place as one of the most promising pathways to a carbon-neutral economy: a goal that is becoming increasingly urgent as climate change continues to accelerate.

However, the fuel’s global deployment still has a major hurdle to overcome.

The challenge (explosive): Since hydrogen gas is highly explosive, it must be stored and transported in highly secure fuel cells, where it is either pressurized or cooled to ultra-low temperatures.

Not only is this equipment too expensive for everyday users, but it could also cause catastrophic damage if it malfunctions, raising ongoing concerns about the safety of the technology.

The global deployment of hydrogen fuel still has a major hurdle to overcome.

One solution to the problem is chemistry: a reaction that converts hydrogen gas (H2) and carbon dioxide (CO2) in formic acid — a liquid that can be easily and safely stored over a wide range of temperatures and pressures.

However, the chemical catalysts involved in this process often require the use of rare metals or extreme reaction conditions, making the whole thing less economically attractive.

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Life finds a way: A group of biologists in Germany has now demonstrated a potentially revolutionary solution to this problem.

In their study, Volker Müller and his colleagues from Johann Wolfgang Goethe University in Frankfurt studied a species of bacteria that inhabits the deep ocean. To gain the energy it needs, this organism carries an enzyme that catalyzes the rapid conversion of H2 and co2 in formic acid.

The bacteria did not need extreme conditions to survive.

Normally, bacteria would continue to digest this compound, producing less useful acetic acid and ethanol. Yet, through genetic engineering, Müller’s team altered its metabolism to prevent this further reaction, and even completely reverse the initial reaction: converting formic acid back into CO2 and hydrogen fuel.

Crucially, these bacteria didn’t need extreme conditions to survive, steadily converting chemicals at temperatures of just 30°C (86°F) and steady atmospheric pressure.

The experience: Using a bioreactor, the researchers fed their modified bacteria hydrogen gas for eight hours during the day. This simulated how long hydrogen gas could realistically be produced using energy harvested from solar panels during the southern German summer.

For the remaining 16 hours, they shut off the hydrogen supply to the reactor, causing the formic acid produced during the day to reoxidize and release the hydrogen gas initially consumed by the bacteria.

At the same time, the CO2 released from the bioreactor could be recaptured, ready for use in the next storage cycle.

The bio-battery could be used to store excess renewable energy.

Müller’s team kept the experiment running for a total of 2 weeks, allowing them to evaluate the performance of their fuel cell over multiple day/night cycles.

Encouragingly, the amount of formic acid produced in the bioreactor remained constant for the first 4 cycles, before the unwanted production of acetic acid began to degrade its performance.

Storing hydrogen safely: The researchers describe their configuration as a “bio-battery”, in which the electrons carried by H2 can be stored inside formic acid indefinitely and then accessed whenever a user requires it.

With further improvements, they hope their bacteria will be able to maintain their levels of formic acid production over many day/night cycles, paving the way for the technology to be deployed on an industrial scale.

Technology could provide industries with stronger incentives to capture CO2 they produce.

If successful, the bio-battery could be used to store excess renewable energy and then release it again when customer demand begins to exceed supply.

This is particularly important in scenarios where the production of renewable energy is highly variable: for example, when the solar panels do not produce electricity at night; or at drier times of the year when less water is available to power hydroelectric generators. Wind power is also seasonally variable in different regions.

Since the process also involves the storage and recycling of CO2it could also provide industries with stronger incentives to capture CO2 they produce – potentially bringing a carbon-neutral economy closer to reality.

This article was originally published by our sister site, Freethink.

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