Hydrogen is often touted as being a cleaner alternative to burning fossil fuels. One reason for this is that hydrogen burns without the emission of carbon dioxide (CO2). Yet hydrogen, at present, is predominantly manufactured using fossil fuels, including steam methane, reforming resulting in significant CO2 emissions.
However, we know it is possible to produce hydrogen, almost entirely carbon-free, mainly by using either renewable power from solar and wind farms or using a process known as methane pyrolysis. In these instances hydrogen gas can be extracted from water via electrolysis or from natural gas via high temperature heating.
While the processes underlying these hydrogen generation techniques are not new, the commercial technologies deploying these hydrogen generation methods have only recently been deployed at application scale. This means only 0.1% of global hydrogen in 2019 was produced using electrolysis. In 2020 we saw a record increase in production of what was labeled “green hydrogen”, but in reality, there is still a long way to go before hydrogen production (not to mention transportation and storage) is truly green.
So, the question is, if major industrial sectors like power generation, transportation, and others adopted hydrogen on a significant scale, how would all that demand be fulfilled?
What can we do until green hydrogen electrolysis-based production (and the corresponding volume of renewable electricity needed to power green electrolysis) is ready to carry us into the green future? We need a stopgap to help pick up the slack at a scale that’s needed right now.
At the moment, significant policymakers such as the European Commission are, in addition to encouraging green hydrogen production, also promoting “blue” hydrogen products, sometimes referred to as traditional gray hydrogen with added carbon capture and sequestration.
This blue hydrogen system combines the use of fossil fuels with expensive carbon capture and sequestration (CCS) techniques to remove CO2 from the atmosphere and lower the carbon impact..
The Promise of Turquoise Hydrogen
As the term suggests, an alternative hydrogen production method known as “turquoise” hydrogen uses a process referred to as methane pyrolysis. The process splits methane, which is the main molecule in natural gas, into solid carbon and hydrogen in an environment without oxygen. Carbon in this state does not become carbon dioxide or carbon monoxide, but remains pure carbon and is referred to as “carbon black”. This carbon black has numerous industrial applications, including the manufacture of car tires, batteries, plastics, and various coatings. Interestingly, carbon black is a critical raw material needed at scale.
The splitting of methane isn’t new, and several commercial-scale plants do it in North America today. But cracking methane in turquoise hydrogen production is different from traditional methane splitting. Old fashioned methane splitting releases high volumes of CO2 and CO because the traditional process happens in air. Similarly the heat required to generate pyrolysis temperatures typically comes from burning hydrocarbons (which generate even more emissions). A number of startups in the USA, Australia, and Europe are working to scale a number of different turquoise hydrogen production technologies.
Readily available natural gas is mainly used for turquoise hydrogen feedstock. The most common source of energy for heating and splitting methane comes from electricity. USA-based Modern Electron uses hydrogen derived from natural gas to generate the heat necessary for pyrolysis. Both the hydrogen approach and the electrical approach (when/if the energy comes from renewable sources) deliver carbon neutral hydrogen. Many experts including researchers at the US Department of Energy and Stanford Universityare excited about the potential for large-scale and distributed production of hydrogen using methane pyrolysis.
Is Turquoise Hydrogen A Game Changer?
Thanks to the hydrogen produced being environmentally friendly while still reliant on fossil fuels, turquoise hydrogen has been touted as a game-changer The significant distinction here is that when done correctly, methane pyrolysis does not inevitably result in carbon emissions. This means that you can leverage the convenience of natural gas but not need to invest in carbon capture technologies or finding places to store CO2.
While we wait for green electrolyzer capacity worldwide to increase in availability and decrease in price, methane pyrolysis is poised to become a practical and economic route toward generating clean hydrogen without carbon dioxide as a byproduct. This will help to accelerate the build-out of the hydrogen value chain. In other words, low coast turquoise hydrogen will help make the production of both hydrogen and systems that use hydrogen more available, more viable, and more profitable.
Carbon black production will undoubtedly be apart of this value chain. There is the potential to change the overall economics of hydrogen production by selling carbon black materials alongside hydrogen. Future developments in the use of carbon black in construction materials will also likely further adds to the attractiveness of turquoise hydrogen.
The turquoise process requires heat that can be generated from electricity derived from renewable sources, or directly from hydrogen split from natural gas. One rate limiting step for all renewables-powered hydrogen production techniques is that that renewable power generation capacity and the supporting electrical infrastructure will need to be significantly increased (over 10x). However, the pyrolysis process is ideally suited for countries with large reserves of natural gas. Especially when deployed with “continuous combustion pyrolysis”, renewable electricity resources aren’t even needed to deliver low carbon intensity and carbon neutral hydrogen.
This will give countries with the required resources a commercial advantage and the ability to produce both clean hydrogen and responsibly sourced carbon black.
How Far Along Are We?
Pyrolysis is under development in the USA, but several gas utilities including NW Natural in the Pacific Northwest are piloting distributed methane pyrolysis technologies. Many technological hurdles in the way of scaling the technology have been solved, but there are challenges.
The first small (distributed) commercial turquoise units are expected to deliver approximately 5kg of hydrogen per day. The first large (centralized) turquoise units are expected to consume 20,000 tons of natural gas to produce around 5,000 tons of hydrogen. In other words, there is a broad spectrum of potential production scenarios for both hydrogen and carbon black.
Some natural gas-based hydrogen production methods are economic without monetizing carbon black. Other hydrogen production methods require monetize sales of the carbon byproduct to be cost effective.
As mentioned earlier, this carbon black is used for tire manufacturing. Keep in mind that a tire contains around 30 percent of carbon, which helps to improve its wear and raises heat resistance and UV radiation.
In upcoming stages, we will see hydrogen becoming more prominent economically, and eventually, carbon-free hydrogen will be commonplace.
Today, most pyrolysis technologies are optimized for black carbon production (see Monolith); some companies like Modern Electron optimize solely to produce hydrogen with a high degree of efficiency.
At present, there is a clear need to develop new uses and applications for the carbon produced. It could, for instance, be used in construction materials, agricultural soil amendments, and building road infrastructures. Not to mention the fact that carbon black is far cheaper to store than large quantities of CO2.
As an interesting side note,, if the methane fed into turquoise hydrogen is derived from biogas, it contains CO2 captured from the atmosphere. So, if pyrolysis is used to create hydrogen using biogas or RNG, the resulting hydrogen is actually carbon negative. This could reduce the quantity of atmospheric CO2 significantly over time, helping us transition to a hydrogen economy without the looming threat of greenhouse gasses.
Takeaways
It is worth mentioning that hydrogen is seen as a key fuel as governments and the energy sector race toward net-zero targets worldwide. The use of turquoise hydrogen may offer another way of reaching those targets sooner while giving sustainable businesses what they need to grow and thrive.