Green hydrogen. Hydrogen production from renewable sources. To Cyrus Smith, the engineer in Jules Verne’s book “The mysterious island”, this was clearly the energy source of the future:

One day, water will be used as fuel. Hydrogen and oxygen will be used separately or together to provide an inexhaustible source of heat and light.

Jules Verne (1874). “The mysterious island”.
The engineer Cyrus Smith from Jules Verne’s “The mysterious island”. Cyrus Smith (on the right) talked about how hydrogen, generated from water, will be the energy source of the future. Image from Wikipedia.

That was in 1874. It is now 2020.

In 2020, according to Wikipedia, 95% of all hydrogen is produced from fossil fuels (natural gas, oil, and coal). Not from water, as envisioned by Cyrus Smith.

Currently, 95% of all hydrogen is not green hydrogen. Instead, it is made from fossil fuels.

Obviously, if we want hydrogen to be a renewable source of energy, this will have to change.

Apparently there is growing interest in green hydrogen. You can see this in Google Trends, for example:

Google Trends shows growing interest in “green hydrogen” over the past five years.

And recently, the German government announced a €9 billion funding program for hydrogen technologies, the National Hydrogen Strategy.

So there is interest, and there are substantial resources. But what’s the progress thus far on making green hydrogen? Does the level of activity match the level of interest?

First, let’s see what the different ways of making green hydrogen actually are. Then, we can explore the current status of each of these methods, across R&D and business.

Methods for green hydrogen production

The US Department of Energy lists several ways of making hydrogen. Three of these ways are not based on fossil fuels. In other words, they could be considered “green hydrogen production”:

1. Electrolytic water splitting

In electrolytic water splitting, electrolyzers split water into hydrogen and oxygen. This process requires a lot of electrical energy. On the positive side, electrolytic water splitting is available commercially. By contrast, the other two methods listed below are not yet really.

2. Solar water splitting

Solar water splitting directly uses light energy to split water into hydrogen and oxygen. But according to the DoE, this is still “in the very early stages of research”.

3. Biological or microbial processes

In biological hydrogen production, microbes produce hydrogen. They do this either using sunlight or biomass. Similar to solar water splitting, the DoE says that this is still “at an early stage of research”.

The current state of green hydrogen production, according to Mergeflow

Using Mergeflow’s tech discovery software, we can now explore the current status of each of these three hydrogen production methods. More specifically, for each method, we want to know what’s happening currently in R&D and business activity.

First, we need to define queries for all three methods. The queries I made here are rather specific. My goal here was to really only get information that’s relevant directly, not other things in the vicinity. For example, I excluded hydrogen purification technologies from my search. If you have a Mergeflow account, you can explore my queries yourself if you like. Of course, you can also modify the queries then. After all, please keep in mind that I am no hydrogen tech expert by any means. So if you are, your queries might look different than mine. Anyways, here are interactive 360° reports for my queries:

Electrolytic water splitting

Solar water splitting

Biological or microbial processes

Create a Mergeflow account

If you don’t have a Mergeflow account but would like to see more details behind these 360° reports, you can get a free trial for Mergeflow. Then come back here and open the links above.

Now, let’s start with a high-level comparison of the three approaches to green hydrogen production.

High-level-comparing the three approaches to green hydrogen production

Here are some very general observations about the three green hydrogen production methods:

Venture capital fundings

Depending on how we frame our search, there are one or two companies here.

Sierra Energy

A Sierra Energy waste gasification facility. Image from

We wrote about Sierra Energy previously, in an article on e-waste recycling technologies. Sierra Energy is a waste gasification company. Hydrogen is one of the products they can make from waste. They describe their hydrogen production process on their website. In 2019, they received $33M Series A from Breakthrough Energy Ventures, Cox Investment Holdings, BNP ParibasTwynam InvestmentsFormica Ventures, and The March Fund.

Sierra Energy is also one of the Efficient Solutions labeled by the Solar Impulse Foundation. The Efficient Solutions label is awarded to “efficient, clean and profitable solutions with a positive impact on environment and quality of life”.


A Solugen mini-mill facility. Image from

Solugen is a synthetic biology company that makes hydrogen peroxide. So it is not a hydrogen producing company. But depending on the hydrogen peroxide -> hydrogen process, it could still be relevant. I’d group them into the “biological or microbial processes” category above. In 2019, Solugen raised $32M Series B from Y Combinator, Refactor Capital, Fifty Years, and KdT Ventures.


Electrolytic water splitting seems to be the only green hydrogen production method that’s on the radar of market analysts. That is, there are market estimates only related to electrolytic water splitting.

The size estimates for the water electrolysis market differ widely. One estimate puts it at $11,426M in 2023, whereas another estimate assumes $390M in 2024. Wow. Both estimates are pre-COVID. So this does not explain the difference. But we have another article on how you can use simple, back-of-the-envelope methods to check the plausibility of a market estimate.

In terms of market players, the market estimates mention Areva H2Gen, Hydrogenics (acquired by Cummins), and Nel Hydrogen, for example.

Public R&D funding

Above I mentioned the German government’s €9 billion hydrogen tech funding initiative. How does this compare to public R&D spending on green hydrogen production technologies so far?

I used Mergeflow’s Funded Research Projects data set to address this question. This data set has updates on EU CORDIS, Innovate UK, NIH, NSF, and SBIR research fundings.

Over the past five years, using my three queries above, I came back with the following total numbers of funding per technology:

Sums of public research funding per hydrogen production technology.

So, $10M for electrolytic, $13M for solar, and $2-3M for microbial hydrogen production. Let’s put this into perspective. Let’s look at all research projects that have to do anything with hydrogen. Over the past five years, Mergeflow’s “public research funding” data set has more than 700 such projects, totaling more than $870M.

Compared to $26M public research funding on green hydrogen production, Mergeflow’s public R&D funding data set has more than 700 projects on hydrogen in total for the past five years. The sum total of all these projects is more than $870M.

If you look at these green hydrogen production funding levels, you can get the impression that the “microbial” technology is just getting started.

Now, as a next step, let’s make all of this more concrete. Let’s look at some individual findings for each of the three green hydrogen production methods. Of course, in order to do this, I had to make a selection on what to include here. And my selection may differ from yours. But, like I said above, you are more than welcome to explore my queries for yourself.

Zooming in on individual findings

Electrolytic water splitting

Toshiba Energy Systems and their solar powered hydrogen production plant

For electrolytic water splitting, I started by looking at patents. There, Toshiba Energy Systems was a prominent player. They recently started operating their solar-powered hydrogen production plant at Fukushima, according to an Australian clean energy news source.

Toshiba Energy Systems’ solar-powered hydrogen production facilities at Fukushima. Image from Renew Economy.

As I mentioned above, electrolytic water splitting requires a lot of energy. So the combination with solar makes sense because then this energy is renewable.

Using spinel oxides to improve the energy efficiency of electrolytic hydrogen production

Since I’m no hydrogen tech expert, I initially skipped research publications. They are outside my area of expertise. Instead, I went to Mergeflow’s technology blogs and news data set. The advantage of tech blogs is that they are easier to understand, and at the same time often reference scientific papers. So you can use them as a “bridge” into the more specialized world of “real” R&D.

Here is a recent article from this data set:

Scientists break “bottleneck” in hydrogen electrolysis technology

These scientists, led by Xu Zhichuan from Nanyang Technical University, used machine learning to identify new spinel oxides that make water electrolysis more efficient. Spinel oxides here act as catalysts, and help reduce energy loss in electrolytic hydrogen production.

Now I went back to Mergeflow’s scientific publications data set. There, I simply searched for “spinel oxides AND hydrogen” and made a “authors and R&D organizations” network graph. Here is the part of the network graph around Xu Zhichuan:

Some of the authors and R&D organizations investigating spinel oxides for electrolytic hydrogen production. Screenshot from Mergeflow.

As you can see, this is quite an international network, involving Nanyang Technical University, the University of Cambridge, Lanzhou University, and Oregon State University.

Now, let’s move on to solar water splitting.

Solar water splitting

Solar-powered electrolysis uses solar power to provide the energy required for the electrolysis process. By contrast, solar water splitting uses sunlight directly to split water into hydrogen and oxygen.

SABIC’s solar water splitting technology

As with electrolytic hydrogen production, I first looked at patents. SABIC featured prominently there. A prolific inventor at SABIC is Hicham Idriss. He also works at University College London.

Hicham Idriss and his co-inventor network at SABIC. Screenshot from Mergeflow.

In addition to patents, Hicham Idriss co-authored several publications. For example, this paper describes an efficient and lower-cost method for solar water splitting.

On a side note, we wrote about SABIC in another article, in a different context. That context was strategies in additive manufacturing.

Using perovskite for new solar water splitting technologies

Next, I used Mergeflow’s ‘Emerging Technologies’ tags to explore tech blogs. An algorithm in Mergeflow generates these emerging technology tags. This algorithm matches the contents that Mergeflow collects against semantic models of emerging technologies.

Here are the emerging technologies for my search:

Emerging technologies identified by Mergeflow in tech blogs on solar water splitting. Screenshot from Mergeflow.

From the tag cloud, I zoomed in on “perovskite”. Here is an article I found:

New material for splitting water

This article looks at using perovskite for solar water splitting.

Illustration of perovskite for solar water splitting. Image by George Volonakis, taken from innovations-report.

The researchers behind this work say that perovskite could make solar water splitting more efficient. This is important because solar water splitting enables storage of solar energy (you could also use batteries). And you need to be able to store solar energy because you can only make solar energy when the sun is shining.

OK, now as a final step, let’s look at example findings on microbial hydrogen production.

Biological or microbial processes

Of the three green hydrogen production methods that I look at here, biohydrogen production seems to be the one with the lowest level of activities. Remember that above I wrote that so far it has received the smallest amount of public research funding.

There are also fewer patents, science publications, and news on biohydrogen production.

But here is something that I found particularly interesting:

Engineered enzymes for hydrogen production

In Mergeflow’s technology licensing data set, I found one offering available via RAMOT, the tech transfer office of Tel Aviv University:

Harvesting solar energy: Hydrogen production by a semi-artificial photo-system

The goal of this work is to get algae to produce hydrogen, via an engineered enzyme. Apparently, this work by a group around Iftach Yacoby has been in the making for quite some time. When I dug a little deeper in Mergeflow, I found a stream of publications and patents by the Yacoby lab, starting in 2007 with this patent…

Photocatalytic hydrogen production and polypeptides capable of same

…leading to this 2019 publication…

Re-routing photosynthetic energy for continuous hydrogen production in vivo

…and this 2020 tech news article:

Scientists say they’ve figured out how to get usable energy from plants

The Yacoby Lab for Renewable Energy Studies at Tel Aviv University. Image from

So, how far along is green hydrogen?

Again, I’m no hydrogen tech expert. But here are some things that I picked up during my search:

  • There are now venture-backed companies, such as Sierra Energy, that build facilities for green hydrogen production.
  • From what I can tell, there is research now that focuses not just on “is this possible at all?”, but also on “how can we make this more efficient?”.
  • Big corporations such as Toshiba are building some of the first larger-scale facilities.

These three things started happening over the past 2-3 years. They don’t just seem to be “more of the same” of what happened before.

We could also apply our back-of-the-envelope method for estimating tech maturity (as of September 2020):

Electrolytic water splitting

According to Mergeflow, electrolytic water splitting is present in Markets and Industry News. This suggests a “Mature” technology readiness level. Also, there are many Scientific Publications, Technology Licensing, and Research Projects. This suggests that electrolytic water splitting is not “Hype” but backed up by R&D.

Solar water splitting

Solar water splitting, according to Mergeflow, is not really present in Markets (there is no “solar water splitting” market estimate; just a related market estimate, on “cerium oxide nanoparticles”). It is present in Industry News, but not in Venture Capital. This suggests that solar water splitting is probably not at “Mature” but at “Intermediate” tech readiness. As for electrolytic water splitting, the presence of Scientific Publications, Technology Licensing, and Research Projects suggests that solar water splitting is not “Hype”.

Biological or microbial processes

According to Mergeflow, green hydrogen production based on biological processes is present in Industry News but neither in Markets or Venture Capital. This suggests that the “biological processes” technology is not at the “Mature” stage. There are Technology Licensing and Patents though, suggesting an “Intermediate” technology readiness level. It is present in Science Publications, so it is probably not “Hype”.

Would you like to do tech maturity estimates for your own topics? Try our software for free, no commitment, and sign up for a trial by clicking here.

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