If the game-changing energy potential of green hydrogen wasn’t enough for you, a new breed of fuels is emerging that utilise the green gas in replacing fossil fuels. We already put one of these hydrogen-derived power fuels — green ammonia — under the spotlight last year, and it’s high time to look at its power-to-X sibling, green methane.
It goes under many aliases: renewable methane, solar power fuels, Renewable Natural Gas (RNG), biomethane, electromethane, Substitute or Sustainable Natural Gas (SNG), e-Fuel. Regardless of the name, its supporters underline one thing: its decarbonisation potential.
But before we get to that, we have to clear the air on non-green methane.
The non-green methane
Methane is, like hydrogen, a colourless gas and is likewise extremely useful. It’s been used as a fuel and, later, a chemical feedstock since it was discovered and isolated in the 18th Century by Alessandro Volta while studying marsh gas at Lake Maggiore, Italy. (Incidentally, just a few hundred km away from where Enapter produces AEM electrolysers in Pisa).
The normally odourless methane is the key component of natural gas (90%), where an additive gives that distinctive smell we know from gas stoves. Despite taking a hit due to COVID-19, the methane and natural gas markets look set to rebound, driven by use in residential heating, switches from coal to gas-driven power plants, transport use and many industrial applications – including steam methane reforming to create grey hydrogen.
And the latter starts to hint at the problem. Although burning methane or natural gas results in fewer emissions of air pollutants and CO2 than coal or petroleum products – leading many to dub it a “transition fuel” between its fossil fellows and renewables – methane is still a greenhouse gas, one with an initial global warming impact 84-86 times stronger than CO2.
Farming is often painted as the main methane emitting culprit but its emissions are only about 20-25% of the global total. Traditionally, methane is taken either directly from natural gas fields or as a by-product of other fossil fuel extraction, with a similar but increasing amount of “fugitive gas” escaping here or from gas pipes, contributing to global warming.
Thankfully, methane doesn’t have to come from fossil fuel sources.
Biomass, biogas and methanation
Another tried and tested way of sourcing methane today is biomass gasification, in which biomass is fed into an airtight system where bacteria digest it and give off biogas – a methane-rich mixture of gases from which biomethane can be extracted.
This anaerobic digestion (without oxygen) is the same that causes methane production (methanation) in the bowels of cows, in landfills, in sewage sludge digestion and in the formation of natural gas from the decay of buried animal life over millennia.
Biomass reactors and digesters are sprouting up around the world due to their usefulness in repurposing all sorts of organic material to make gas, avoid methane emissions from uncovered decomposition – and replace fossil fuel methane.
And another industrial waste can also become a resource for making methane: CO2.
That’s the approach taken by Germany’s bioCO2nvert project, which pairs CO2 released through the large-scale bioethanol brewing process of Südzucker AG and combines it with green hydrogen made onsite from excess renewable energy with an Enapter electrolyser.
At this point, we’re not talking about methanation of carbon-based biomass (all known life is carbon-based) but methanisation of pure carbon monoxide or dioxide itself.
Next level: Biocatalysis
When the captured CO2 is introduced to green hydrogen, a catalyst takes action – in this case, a living catalyst known as methanogenic archaea. Under anaerobic conditions, these microorganisms metabolise CO2 and H2 to methane, which the bioCO2nvert project run by Technische Hochschule Ostwestfalen-Lippe and partners uses as an energy storage medium.
A similar approach will be rolled out on a larger scale in Belgium by 2025, where a lime kiln with intensive CO2 emissions will capture these and use biocatalysis to convert 75 MW of green hydrogen and carbon dioxide into e-methane to be fed into the gas grid.
While large-scale industrial projects have a role to play, smaller flexible solutions will also be needed to bring renewable methane to all those who need it (just as with green hydrogen).
The Austrian firm Krajete GmbH is another company that uses methanogenic archaea to catalyse the conversion of green H2 and CO2 to methane, with inputs sourced partially using AEM electrolysers. Based on their extensive experience in providing methanation technology to customers and integrators, the biological methanation specialists see serious potential for the on-site production of green methane for residential use – by using a modular solution that, like Enapter’s, can help serve decentralised users.
And looking beyond biocatalysis, there’s yet another way to create methane from green H2.
Pulling CO2 out of fresh air
Metal catalysts can also be used to methanise CO2 with hydrogen via the Sabatier Process, with this “electrocatalysis” technology soon to produce electromethane in Australia.
The company behind this, Southern Green Gas, is laying the groundwork to not only produce power fuels from Australia’s renewable electricity at scale – but to do it using carbon dioxide directly captured from the air.
Its demonstration plant in Wallumbilla, Queensland is expected to start operation early 2022. It will produce around 320 kg of green hydrogen annually with AEM electrolysers, bringing it together with Direct Air Capture CO2 and converting into 32 gigajoules of methane.
Southern Green Gas is partnering with energy infrastructure company APA Group on the project, in recognition of the huge potential of renewable methane for immediate use in existing infrastructure: The e-methane made in Wallumbilla will be injected directly into an APA gas line, with a larger pilot project foreseen as part of a commercial feasibility project.
Australia is excited about the potential of such e-fuels production, with gas networks keen to future-proof their networks and pipe green methane to liquefied natural gas (LNG) plants that can prop up the country’s export markets in the post-fossil fuel future.
The road forward for green methane
Here is where we really get to the heart of green methane’s potential: Although burning methane releases CO2, it can be a “carbon-neutral” fuel via cases like direct air capture as the CO2 released to the atmosphere is equal to the amount taken from it.
And as the world looks to decarbonise natural gas and LNG-reliant sectors, more countries are turning to green methane for heating, as well as for the production of liquid synthetic fuels for aviation and shipping (for example, via conversion to methanol), with the biomethane market alone set to at least double by 2025.
China and Japan are launching a joint project to create one of the world’s largest methane plants, (using captured industrial CO2 and waste hydrogen), the U.S has at least 115 facilities producing RNG from landfilled waste, with predictions that this could eventually replace up to 11% of natural gas usage – but the U.S is still playing catch-up with Europe.
Europe’s biomethane plant headcount jumped from 483 to 729 between 2018 to 2020, including Danish anaerobic digesters that could fully replace the country’s natural gas with RNG within 20 years and Germany with the bulk of the plants. Green methane can even be carbon negative, if the CO2 is captured from the atmosphere – and if combusted CO2 can be captured through pyrolysis or chemical looping combustion and sequestered or reused.
But for green methane to reach its full decarbonisation potential, it has to deal with its greenhouse gas issues. While technical solutions like improved satellite monitoring can help diminish fugitive methane and quickly address leaks, an additional approach can help:
The modular, distributed creation of renewable electricity and green hydrogen for renewable methane allows power fuels to be produced as close as possible to where they’re needed, minimising risk of methane leaks while replacing fossil fuel natural gas. With this – and the chance to use waste CO2 and curtailed green power where it arises – green methane can be a safe, cost-effective solution for near-term decarbonisation.
Talk to our business development team to find out more about AEM eletrolysers for your green hydrogen and green methane needs.