For tonnage applications in the UK and elsewhere, a role for blue hydrogen is recognised in the national hydrogen plan. In North East England, for example, there are sources of natural gas, via pipeline, offshore CO₂ storage or sequestration facilities and a local network of actual or potential chemicals and high temperature heat users. With a well-structured regulatory framework, this is a clear win for fossil fuel hydrogen – although there is one cloud on the horizon. It concerns fugitive or upstream methane emissions.
A recent paper from Cornell University claims that blue hydrogen may be worse than gas or coal. On closer inspection it seems that, from a European viewpoint, the American assumptions about leaks and cycle efficiencies are too pessimistic and blue hydrogen should be seen as a low-but-not-zero emissions hydrogen source.
Another possibility is to compress and flash the resulting CO₂ to liquid and transport it to collection hubs by trucks, trains or ships. This broadens the reach of blue hydrogen and overcomes the apparent lack of accessible, large-scale gas fields that are suitable for sequestration.
An emerging role for hydrogen is for energy storage. Not the hour-by-hour or multi-day storage that batteries or ‘liquid air’ systems address, rather the inter-seasonal storage that would have been so helpful as the industrial world emerges from the pandemic amidst climate change-induced ‘blocking’ events of the kind we have seen with the big freezes in Texas and China, or the extreme heat in California and Oregon.
With green hydrogen, the goal is to achieve fossil-free hydrogen, that much is clear, but where will all the water come from in a climate-stressed future? Supposing seawater could be used too, there will still be vast, arid regions that will remain inaccessible to green hydrogen. Even if its costs reduce, there is a risk that green hydrogen will be a niche, local solution. Yet here is point worth making. Locally sourced hydrogen avoids the need for top-down conversion of natural gas grids to hydrogen. Even if that were technically possible, the costs, business risk and disruption may be insurmountable. All that adds weight to the view that low carbon intensity electricity is the new natural gas. The big challenge with that idea is heat pumps; they are neither cheap nor simple to install.
Pyrolysis, hydrogen’s ‘ugly duckling’?
In a recent edition of the Institution of Civil Engineers’ Energy Journal, Alberto Abánades, Professor and pyrolysis expert at ETSII-UPM, Universidad Politécnica de Madrid and I have attempted to articulate a role for methane pyrolysis. In ‘Briefing: Pyrolysis of natural gas to hydrogen: a key energy transition tool’ we examine the crucial role of hydrogen to act as bridge between high-emissions fossil energy and low carbon energy.
From the outset, whatever the merits of pyrolysis, it is clear that while it is not grey, it is not truly green either. If the ugly duckling is to emerge into a swan, we propose that hydrogen derived from methane pyrolysis should be re-badged ‘white hydrogen’. So, what is the story here and does it have a chance?
This form of pyrolysis is not new. First championed in the 1960’s, the catalytic, fluidized bed processes of that time suffered severe coking problems that disabled the catalysts. Later, the European Union revived the pyrolysis idea and the 2006 SOLHYCARB project investigated the use of solar heat to split natural gas into hydrogen and elemental carbon (carbon black). Promising hydrogen yield and costs spurred further work. A breakthrough came in a 2016 study, DECARGAS, and that has German industry intrigued. Several, further pilot scale projects are underway, for example at BASF. In the DECARGAS project, of which Professor Abánades was part, hot metal (molten tin) pyrolysis was found to deliver competitive costs and a coke-free, high yield of hydrogen. A further extension of that idea is to use molten metal combinations or alloys that catalyse the methane splitting reaction. Unlike the 20th century versions, these catalysers are inert to the solid carbon nano-particles that emerge during the reaction.
Not only is the carbon successfully removed in the molten metal processes, it has value too – for use in grid scale batteries and tyres or, if necessary, it can be sent to landfill where it will remain passive. However, the real prize is graphene and there are early signs that the form of carbon black that pyrolysis produces may be suitable as a precursor for industrial graphene production. This is a point that Rice University Professor Matteo Pasquali and Dr. Carl Mesters of the Shell Technology Center in Houston have picked up in their PNAS article Opinion: We can use carbon to decarbonize—and get hydrogen for free. They make the case that the possibility of deriving graphene from methane pyrolysis is a game-changer.
In a review of the available processes for pyrolysis, Dr. Stefan Schneider and colleagues at the Karlsruhe Institute of Technology (KIT) explain that plasma-driven pyrolysis is another promising route to hydrogen. It is a big challenge but, it seems to this writer at least, there is a real need for an ultra-local solution. If plasma pyrolysis could be made to happen safely, reliably and cheaply in a small-sized hydrogen maker that would turn Western Europe’s home heating conundrum on its head. Is anyone up for leading such a mission – a big, perhaps ARPA-funded challenge to convert natural gas to hydrogen in homes?
About the author
Richard H. Clarke is a Fellow of the Institution of Chemical Engineers and Senior Consultant on Climate Risk and Energy at Ortec Finance, Rotterdam and London.