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"Green"​ Hydrogen Should Play by the Same Rules as Renewable Natural Gas (RNG)

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Alan Rozich's picture
Director BioConversion Solutions

Providing quantitative sustainability insights using sound technical analyses with a management consulting approach to craft strategies that address the mega-trends that are occurring in the...

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  • Nov 29, 2021

Hydrogen is touted by some to potentially supply 14% of all US energy demand by 2050 by what the report authors characterizes as an "Ambitious" scenario.

It needs to be noted, however, that the same report opines that the base expectation is that hydrogen supplies a mere 1% of US energy demand. Is hydrogen in danger of becoming sustainability's version of the Dot Com Bubble?

In the 1990s, a bevy of internet companies saw huge valuations driven by aggressive speculation by a focused cadre of investors. In the fall of 2002, there was a precipitous crash resulting in numerous bankruptcies while surviving companies saw their market capitalization eviscerated. Interestingly, in 1996, six years before the crash, the former Chairman of the Federal Reserve, Alan Greenspan (the gentleman shown in the header), cautioned and forewarned investors against displaying what he termed, "irrational exuberance", regarding the high valuations of internet companies. History unfortunately proved Mr. Greenspan right concerning the consequences when a large cadre of investors artificially inflate and over-value a technology offering that had yet to undergo thorough market operational exposure.

It can be argued that hydrogen economy "hype" is currently in a similar circumstance as was the Dot Com space some years ago. There are high, perhaps too high, expectations that likely need to be tempered due to significant challenges that must be overcome. It is also painfully obvious that, inexplicably, hydrogen seems to be getting immunity from intense scrutiny. Clearly, hydrogen, like myriads of other technology platforms MUST play a role in sustainability and climate change endeavors. The determination for its specific fit remains to be seen and will evolve. However, over-promising and under-delivering on expectations could inadvertently damage hydrogen's appeal which would be egregiously unfortunate particularly since there already is a significant level of existing infrastructure in the US that can be used for launching a hydrogen economy.

Hydrogen's Curious Colorful Metamorphosis

The first rule for hydrogen that requires attention concerns its fit within accepted sustainability jargon.

Currently, it is not clear how hydrogen fits. In a nutshell, it is a renewable, sort of, but not really as positioned.

Previously, the sustainability and renewables space generally thought in terms of two types of resources:

Natural gas that is made using renewable resources is "renewable natural gas" or RNG. Plain, simple, and straightforward.

In contrast, hydrogen advocates, who apparently are concerned with the perceived difficulty of generating authentic green hydrogen, have attempted to "create" an elaborate alternative criteria and unique grading system. This stratagem currently consists of nine colors which assigns a color for hydrogen for different "levels" of sustainability attributes. Each color corresponds to the specific production methodology used to make the hydrogen presumably bestowing varying degrees of sustainability attributes. More details on this grading rationale are given elsewhere and a chart is shown below.

The detailed explanation for the color coding makes for interesting reading. As previously noted, the gist of the color-coding methodology is to assign a color for the hydrogen that is linked to the specific production methodology. Basically, as the hydrogen color chart segues from left to right towards white, ancillary schemes are introduced to the hydrogen production process to either capture or mitigate carbon dioxide production. These augmentations are increasingly more complicated technical assemblages that are a burden to efficient hydrogen production and costs.

Surprisingly, the "greenest" hydrogen being promoted in the color scheme is purportedly made using electrolysis that is powered by renewable energy systems such as solar and wind. Biohydrogen is not discussed and there is no mention of the use of biological processes which are suitable for making REAL green, non-color coded, hydrogen.

The color-coding scheme for hydrogen can be construed as a backdoor Byzantine strategy to enhance the appearance of the sustainability gravitas of hydrogen to the investment community.

It is suggested that an alternative to the color-coding arm waving is to generate meaningful case studies for the various hydrogen production scenarios complete with mass and energy balances. These data provide a better basis with which to quantify sustainability benefits, enhance transparency, and give potential hydrogen consumers a firmer technical and commercial basis for proceeding forward. The aggregate sustainability calculus can be estimated using substantive analyses.

The Case for Renewable Natural Gas (RNG)

RNG (Renewable natural gas) is readily produced by feeding biomass to anaerobic digesters. According the Union of Concerned Scientists, the US generates almost 700 million tons of renewable biomass annually. Additionally, consider the vast amount of installed assets and infrastructure in the US that are available for generating RNG:

As an example, Shell has recently installed and RNG system that is projected to make about 740,000 MMBTU per year of RNG. With high conversion technology, this system could produce about 1,200,000 MMBTU annually per installation.

The table above makes some interesting points. First, RNG production can be readily ramped-up in the US using a distributed resource model easily matching and also vastly exceed the 1% and 14% targets for US national energy demand proposed for hydrogen production. Also, the MMBTU/day production target can be readily increased with more feedstock and larger infrastructure size so more energy production per installation is feasible which lowers the number of installations required. Finally, it is important to note that production of RNG using anaerobic digestion creates the opportunity for manufacturing multiple renewable resources at one installation as depicted in a recent presentation. Water, fertilizer compounds, and RNG can all be manufactured which bolsters project financing attributes with multiple off-take contracts for renewable products.

RNG and Hydrogen

There are three other rules that hydrogen should follow:

  • Leverage existing infrastructure where feasible.
  • Use biological conversion systems when practicable.
  • Manufacture multiple renewable products at the same installation when practicable.

So, here's a thought. A major piece of the hydrogen puzzle could be solved by manufacturing the hydrogen in tandem with RNG using biological systems. This strategy produces hydrogen while addressing all four rules, the three above and the first rule. This approach enables RNG and other renewables to bolster the value proposition and project financing attributes by using a "plug 'n' play" approach and creating multiple renewables.

Additionally, the hydrogen is biologically generated and is thus genuine "green hydrogen." This feature has significant commercial implications as it enables project owners to dispense with the convoluted, color-coded branding pontification.


In summary, committing billions of dollars solely betting on hydrogen to guarantee that the Nation is to cover 1% of its annual energy demand seems fiscally extravagant at best. In contrast, using a multi-tasking renewable manufacturing INITIATIVE that leverages existing assets makes sense on many levels. Sustainability collaboration will expose the greater community to real green hydrogen projects at various levels of development which will propel deployment and adaptation. With the superior economics of manufacturing hydrogen using a multi-tasking technology architecture, hydrogen and other renewables such as RNG and green ammonia will all garner greater exposure, commercial acceptance and adaptation, and increased incorporation into the economy accelerating the transition to a profitable and greener economy.

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Matt Chester's picture
Matt Chester on Nov 29, 2021

The detailed explanation for the color coding makes for interesting reading. As previously noted, the gist of the color-coding methodology is to assign a color for the hydrogen that is linked to the specific production methodology. Basically, as the hydrogen color chart segues from left to right towards white, ancillary schemes are introduced to the hydrogen production process to either capture or mitigate carbon dioxide production. These augmentations are increasingly more complicated technical assemblages that are a burden to efficient hydrogen production and costs.

The potential for hydrogen seems to be shooting itself in the foot-- I understand the need to classify and discuss hydrogen by where it comes from, but it comes across as a lot of hand waving and almost being purposefully confusing. If there was a simple system of measuring/accounting for the carbon intensity of hydrogen, and even keeping track of that from production to consumption, then we could look at the numbers rather than have the ever-expanding rainbow. 

Bob Meinetz's picture
Bob Meinetz on Nov 29, 2021

Alan, how could going through the laborious process of synthesizing RNG possibly be more efficient that burning biomass (primarily, wood pellets) at a steam-turbine electricity plant?
Not that biomass represents any kind of solution, anyway. It's all essentially solar power - the more steps it goes through, the less efficient it is.

Alan Rozich's picture
Alan Rozich on Nov 29, 2021

“Laborious process of synthesizing RNG”? When did enzyme kinetics become laborious? They are the most efficient catalysts on the planet. The energy barriers of bioconversion system reactions which are catalyzed with enzyme kinetics are significantly lower than energy barriers for physical-chemical systems. The other point you need to appreciate is that when you biodegrade biomass, you also release green ammonia which is recoverable adding to the value proposition. 

Bob Meinetz's picture
Bob Meinetz on Nov 30, 2021

"The energy barriers of bioconversion system reactions which are catalyzed with enzyme kinetics are significantly lower than energy barriers for physical-chemical systems."

Bioconversion system reactions are physical chemical systems, so I'm not getting your point. Both energy barriers are the same, the only difference is energy efficiency of different pathways.

All renewable energy ultimately comes from the sun, which makes the wind blow and trees grow (photosynthesis). Assuming your biomass is old growth timber (more than 90% is), you're telling me that a tree that has gathered potential energy from the sun for 80-100 years can be chopped down, chipped, hauled to a digester (be it the world's most efficient digester, or not), and end-product can then be recovered and piped for consumer or industrial consumption - all, with with greater efficiency than a solar panel gathering electricity from the sun? It's not adding up.


Alan Rozich's picture
Alan Rozich on Nov 30, 2021


This was your original question: "Alan, how could going through the laborious process of synthesizing RNG possibly be more efficient that burning biomass (primarily, wood pellets) at a steam-turbine electricity plant?"


Perhaps there is a confusion with jargon. Once biomass is formed, it can be converted to energy. This process, as you note, is courtesy of the sun. You opine that burning biomass is efficient. That's not necessarily accurate. One must first deal with the latent heat of vaporization penalty that is associated with the water content of the biomass. Before the biomass will burn, the water must be driven off using evaporation. This process is a huge energy hog. For example, municipal WWTPs that used to incinerate sludge as a disposal technique had to ensure that water content of biomass was less than 75%. Otherwise, sludge incineration was expensive because so much fuel was needed to drive off the water.

In contrast to incineration, bioconversion systems use enzymes from microorganisms to make chemical reactions occur. Consequently, the latent heat of evaporation is not a factor. Other physical-chemical systems heavily rely on temperature, pressure, and other means to increase reaction kinetics while bioconversion systems can operate under conditions that do not require exotic materials of construction, etc that are common with high pressure, high temperature reaction scenarios. 


Your second, new question about solar panels is another topic. In that regard, you might also consider the overall sustainability calculus particularly with respect to sustainable land management practices. Large centralized wind and solar installations (not rooftop systems) are notorious for their poor sustainable land management features as discussed elsewhere. The Costa Rica debacle is an actual example where these considerations were largely overlooked by the UN and which sloppy deployment of renewables created problematic consequences for that country.

Bob Meinetz's picture
Bob Meinetz on Dec 1, 2021

Alan, we agree that solar farms constitute an abysmal use of land in terms of energy production. But here you propose another way to convert solar energy to useable form, i.e. "renewable natural gas", via...deforestation? What's sustainable about that?

I guess I was opining about burning wood in incinerators and didn't know it. My bad. But if we're waiting 80-100 years for our chopped-down forest to regrow anyway, another two years to allow cut wood to dry is not going to be a deal-breaker. No vaporization penalty. And you're ignoring two other penalties with your scenario:

1) Heat loss in anaerobic digesters. Anaerobic digestion not only produces methane, it produces heat. Unless you have some exotic way to capture that heat, it's energy wasted.

2) Losses associated with storing and pumping methane to point-of-use. Notwithstanding niche applications of digesters in the woods making methane for local consumption, to get the methane where it needs to go takes energy. One could argue pumping methane through underground pipes 10-50 miles to energy customers would be more energy efficient than transmitting electricity, but it would be a tough row to hoe.

The bottom line is this: there will never be a way to produce enough energy from the sun, quickly enough, to be competitive with fossil fuel extraction. The energy stored in fossil fuels originally came from the sun too, of course, but it wasn't stored over the timeframe of 80-100 years, like our tree. It was stored over millions of years, in trillions of trees. As those trees fell and were covered in sediments, it created a vast store of hydrocarbon energy. So we can roll the dice with different configurations of renewable energy, as many times as we like, but we'll never come up with roll of thirteen. It can't be done.

That's why I'm a nuclear energy advocate. To end fossil fuel consumption, we'll need to go even farther back in time, billions of years, to get to energy stored in the most fundamental building blocks of matter. There's a frightening amount of useable, carbon-free energy stored therein - and if our biggest hurdle is overcoming fear, maybe putting the brakes on climate change won't be as hard as we thought.

In practical terms, it really comes down to nuclear energy vs. fossil fuels. Everything else is a distraction.

Rick Engebretson's picture
Rick Engebretson on Nov 30, 2021

It is difficult trying to de-saturate closed minded criticism.

First, learn the difference between 19th century thermodynamics and 20th century statistical mechanics/quantum physics "physical chemistry."

Second, living in a dairy producing region, cow manure demanded what Alan now proposes. When the issue of plastic recycling gained public concern 35 years ago, it was natural to propose mass production of "recycled plastic livestock septic tanks." A scientist learns the hard way that politicians don't like science interfering with their money grab.

How long can we afford political failure?

Rick Engebretson's picture
Rick Engebretson on Nov 30, 2021

Delighted by your interests, Alan.

While doing some Ph.D. research (hydrogen exchange kinetics in proteins effected by high pressure, ultra-sound, electric field frequencies) I was also studying Solid State Physics. Some remarkable bio-physics exists in your approach. First, a chemical hydrogen ion is a physical fundamental particle, the proton. Acids bases are proton donors acceptors, and behave just like semiconductor electron donors acceptors. Molecular dipoles, symmetry, spectroscopy, structures were all ripe for exploring 40 years ago. I'm not sure science like that exists anymore.

So I'll just opine that enzymes exploit raw physics to perform chemistry. And I believe the best way to convert a pile of bio-MASS into useful "enhanced energy" fuel is concentrated solar photo-chemistry.

Mark Silverstone's picture
Mark Silverstone on Dec 1, 2021

«…the US generates almost 700 million tons of renewable biomass annually.»

May I ask what is the practicable yield of RNG (and ammonia) from this biomass?

What do we presently spend on responsible management of just the sludge from these waste streams?

Am I correct or oversimplying to say that the RNG process you are describing is the use of primarily (or totally?) presently existing various waste streams for NG production via microbial metabolism? I don’t think anyone is suggesting chopping down forests for the purpose. Rather, I think you are suggesting turning what is now an expensive to manage waste stream into a resource.

If so, RNG deserves a classification  quite distinct from the color coding «system» which, I agree, is less than constructive and more confusing than ever. 


Alan Rozich's picture
Alan Rozich on Dec 1, 2021


Thanks for the comment. The US biomass production number comes from the Union of Concerned Scientists and I believe the link is in the article.

If you’re interested, I can send you a PPT that quantifies the production of RNG and other renewables in a multi-tasking manufacturing mode.

Mark Silverstone's picture
Mark Silverstone on Dec 3, 2021

I would appreciate that. I would like to bring it to the attention of some local sludge generators, i.e. Municipal water treatment plants, farming interests, NG gas processors. Here, in Norway, the «Green» NG (please excuse the use of that term) industry is getting started. I would like to remind them of the potential of these sources.


Alan Rozich's picture
Alan Rozich on Dec 3, 2021

Can I email it to you? 


Alan Rozich's picture
Alan Rozich on Dec 3, 2021


Try this link to a preso: ECELSIOR Preso

The technology architecture is a version of bioconversion that gets almost 90% feedstock conversion and produces high grade fertilizers and water as renewable products. 


Mark Silverstone's picture
Mark Silverstone on Dec 10, 2021

Thanks very much Alan. Very interesting and useful presentation!

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