The last 12 months has seen the debate around hydrogen grow from a whisper to a shout.
What was once merely a discussion is now becoming policy. Something which was a niche feedstock product serving heavy industry is now very much at the forefront of decarbonising the transportation and shipping world.
Hundreds of billions of dollars are being invested into projects aimed at helping achieve net-zero targets and creating zero-emission fuel.
Against that backdrop, let's take a closer look at the different options available.
The most common form of hydrogen, it's created from fossil fuels and the process releases carbon dioxide which is not captured.
The process used to create hydrogen from natural gas is called steam methane reforming (SMR), where high-temperature steam (700°C–1,000°C) is used to produce hydrogen from a methane source, such as natural gas. In steam methane reforming, methane reacts with steam under 3–25 bar pressure (1 bar = 14.5 pounds per square inch) in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relatively small amount of carbon dioxide. Steam reforming is endothermic — that is, heat must be supplied to the process for the reaction to proceed.
There is also a gasification process which uses coal as a feedstock, creating brown hydrogen, which also releases carbon dioxide and can be put in the same category as grey.
The head of business development at the renewable energy giant Enel has described hydrogen as a "climate killer" as it stands right now due to almost all of it being grey: “98% of it is produced from steam reforming and gasification, which equates to yearly carbon emissions comparable to that of Indonesia and the UK combined," he said. "Just 2% is produced from electrolysis.”
Clearly then, grey hydrogen is not a long-term solution.
Blue hydrogen uses the same process as grey, except this time the carbon is captured and stored. This makes it much more environmentally friendly, but comes with added technical challenges and a big increase in cost.
Carbon capture and storage (CCS) has been around a while, with the technology being used by heavy industry and power generation companies burning fossil fuels. The technology can capture up to 90% of the CO2 produced, so it isn't perfect but clearly a massive improvement.
Most of the time, this CO2 is then transported by a pipeline and stored deep underground, often in salt caverns or depleted oil and gas reservoirs.
Countries which do not have access to such underground options will find it very challenging to establish a blue hydrogen industry, and it may be more cost-effective to develop green hydrogen as their primary solution.
Some forward thinking organisations like Drax in the UK have been combining CCS with biomass fuels, aiming to become carbon negative — removing more carbon dioxide from the atmosphere than it produces.
When it comes to hydrogen production, blue hydrogen is often seen as a stepping stone from grey to green, and it's proven to be divisive among industry professionals.
On one hand, it is relatively easy to scale up from existing grey hydrogen production and requires less electricity. It is also not dependent on the rapid & continuous growth in renewable energy sources such as offshore wind & solar.
On the other, think tanks and green hydrogen advocates argue that blue hydrogen goes against the goals and principles of net-zero, as well as being more expensive than green in the medium term.
The utopian vision of the future is a net-zero world where all our electricity and fuel is produced by emission-free sources.
In the context of this piece, that means a fully-scaled green hydrogen industry on a global scale.
It has the potential to be a major part in solving the intermittent generating capacity of most renewable energy sources. Excess electricity can be used to create hydrogen, which is then stored as a gas or liquid until needed.
It faces many challenges, but the momentum behind it is growing with governments around the world recognising the potential benefits and developing policies to help drive development and adoption.
So, what exactly is green hydrogen?
Rather than using fossil fuels, green hydrogen is made by using a process called electrolysis to split water into hydrogen and oxygen.
If that process is powered by a renewable energy source, such as wind or solar power, then the hydrogen is referred to as being green.
What are the challenges?
Green hydrogen needs electrolysers to be built on a scale larger than we've yet seen.
Transportation and Storage
Either very high pressures or very high temperatures are required, both with their own technical difficulties.
To become competitive, the price per kilogram of green hydrogen has to reduce to a benchmark of $2/kg, with Bloomberg New Energy Finance reporting that $1/kg is achievable by 2050. At these prices, green hydrogen can compete with natural gas.
“Costs for producing green hydrogen have fallen 50% since 2015 and could be reduced by an additional 30% by 2025 due to the benefits of increased scale and more standardized manufacturing, among other factors,” said Simon Blakey, a senior adviser for global gas at IHS Markit.
Creating green hydrogen needs a huge amount of electricity, which means a mind-blowing increase in the amount of wind and solar power to meet global targets.
Some current estimates are that that we need to install more offshore wind capacity than in the previous 20 years, every year for the next 30 years.
These are all major challenges, but a lot of them are already being overcome by incredible engineers and scientists.
With the right backing, we can be confident that green hydrogen will prove itself to be the amazing energy solution we need.
Scaling up around the world
In February, the Hydrogen Council released a report which outlines the scale of growth.
Over 200 projects have been announced by over 30 countries, with investment totaling over $300 billion.
The main players at the moment are Australia and Europe, with each adopting a slightly different approach.
The European Union has a clear strategy, has formed a clean hydrogen alliance and is developing "hydrogen valleys" which use the offshore wind capacity of the North Sea to power electrolysers. The longer term plan is to use the existing natural gas pipeline network to enable the transportation of hydrogen across the continent.
Saudi Arabia recently announced its intention to enter the market, bringing to bear their enormous solar power potential and expertise in the development of major energy projects.
Japan have developed a project which could have wide-ranging potential: turning sewage into hydrogen via a carbon-neutral process. This could be adopted in every country with sewage treatment facilities, opening up the possibility of producing hydrogen locally and reducing the need to transport it.
The US is lagging a little behind in some respects, with a report commissioned last year urging policymakers to "follow the lead of the European Union".
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