Germany, annoyed with Russia, has halted the 750-mile-long Nord 2 Stream gas pipeline that was built to transport 55 billion cubic meters of gas a year from Russia’s north west to north Germany. Presumably, on the back of this experience, Europe will wean itself away from Russian energy. When that happens what will Russia do with all the natural gas?
Quantum has, in the past, brought to readers several age-old technologies that are now getting mainstreamed in the wake of the climate change crisis (‘switched reluctance motors’ and ‘co-electrolysis’, to name two.) Now, another well-known but shelved technology is making a stuttering come back, which could answer Russia’s problem of what to do with the natural gas. Indeed, this technology is taking root in India too.
We are talking of ‘natural gas pyrolysis’, which is one of the ways of producing green hydrogen, ignored until recently because there was no need for it. But now, given the emphasis on green hydrogen, NGP is sprouting up here and there.
Simply put, NGP involves heating natural gas (which is mostly methane) to above 1,000 degrees Celsius, which breaks the bond between the carbon and hydrogen atoms. The hydrogen is collected for use. The carbon is left behind in solid form; it can be collected and used or disposed off. Hydrogen produced by NGP is labeled ‘turquoise hydrogen’.
There are several methods of doing NGP. One that seems to be more popular than the rest is pyrolysis of methane in a liquid metal. The molten metal, which can also act as a catalyst, retains heat longer and acts as an effective heat transfer media, says a publication of the Office of Scientific and Technical Information, part of the US Department of Energy. Further, because the carbon does not dissolve in the liquid metal, it is easy to skim off, it says, adding that molten metal systems are “routinely used in industry.”
However, the ‘industry’ is still in its nascent stages. There are not too many companies in business, though evidently many are thinking of jumping into the fray. One company that is operating a commercial-scale NGP plant is Monolith, based in Nebraska, USA, whose Co-Founder and Director, Pete Johnson, says that NGP is “a less understood way of producing hydrogen”. In a 2021 presentation, Johnson says that if the energy for the process comes from renewable energy sources, the net greenhouse gas emissions from NGP is zero.
Experts say that NGP is a promising technology. Hemant Mallya, Senior Programme Lead with the Council for Energy, Environment and Water (CEEW), a Delhi-based think-tank, tells Quantum that NGP could be “a good interim solution” before green hydrogen from water electrolysis becomes economically viable.
While the technology is quite mature, there is scope for improvements. Researchers at IIT Madras, Prof R Vinu of the Department of Chemical Engineering and Prof R Sarathy of the Department of Electrical Engineering, have achieved success in NGP at much lower temperatures, of around 120 degrees Celsius, using ‘non thermal plasma’. The system they have designed shows “high hydrogen selectivity” (produces more hydrogen), Prof Vinu tells Quantum.
Prof Vinu says that NGP does not necessarily need natural gas—any gas containing hydrocarbons, like biogas or land-fill gas, would do just as well. In fact, using biogas, which is essentially a mixture of carbon dioxide and methane, you can produce ‘syn gas’ (carbon monoxide and hydrogen). Syn gas is a ‘platform chemical’, using which one could produce an assortment of chemicals, including hydrogen.
One Indian company from a large group that today produces carbon black (which has requested not to be named) is mulling entry into NGP. Interestingly, one can play around with the process so as to get the desired form of carbon as the residue—for instance, graphene, a versatile, new-age material.
Prof Vinu says that with the NGP technology that IIT Madras is developing, it is possible to produce hydrogen locally at a small level, making way for decentralized hydrogen production.
NGP is today not competitive with SMR-based hydrogen in the absence of a carbon tax, but Prof Vinu says it is on par with electrolysis. But even that is because NGP requires feedstock such as natural gas or biogas, whereas electrolysis needs only water. However, Johnson says that in terms of energy consumption, NGP needs seven times less energy than electrolysis—the bond between carbon and hydrogen is easier to break than that between hydrogen and oxygen.
So, if Russia finds itself with a lot of natural gas and no takers, it can use the gas in a NGP process and produce hydrogen. But what to do with the hydrogen? Well, it is not difficult to make ammonia from the gas. Ammonia can be stored or transported easily. While ammonia can be produced cheaper using the natural gas, the process emits carbon dioxide. It is better to produce hydrogen from the gas and make ‘green ammonia’ using the hydrogen. Ammonia is easy to store and ship around the world.