I've been reading an interesting feature article in the New Scientist (dated 6th Feb 2021) about how hydrogen can help decarbonise the world economy. I knew quite a bit of it already, thanks to all the research I do for this blog, but there were a few eye openers in there.
Here are the headlines:
- Hydrogen is the most abundant element in the universe. It holds thousands of times more energy per kilo than the most efficient batteries, and three times as much as standard petrol. The only by-product of using it is is water.
- Not all hydrogen is carbon free however, because it can be produced in 3 distinct ways named grey, blue and green hydrogen respectively.
- Grey hydrogen has the largest carbon footprint as it's generated using natural gas (mainly), coal or oil, creating a great deal of CO2 in the process. This is the way 96% of hydrogen is produced and costs about $1 a kilo. The fossil fuel companies would love us to go with this as it means business-as-usual for them. In terms of the world going 'Net-Zero' by 2050 though, it's of no use at all.
- Blue hydrogen: Is where fossil fuels are still used to generate hydrogen but the CO2 is captured and 'buried' using Carbon Capture and Storage (CCS). Again the fossil fuel companies get to use their reserves but there's some added cost in using CCS, so blue hydrogen costs at least $2 per kilo. The biggest drawbacks here are that CCS has yet to be proven at scale (and it will have to be huge scale), and CCS doesn't capture all the CO2. From 10% to 50% is lost.
- Green hydrogen is produced using a process called electrolysis - Basically using electricity to split water into hydrogen and oxygen - It's only green if renewable energy is used though. Normal electric off the grid will have an element of fossil fuel in it. Around 4% of hydrogen is generated by electrolysis at a cost of $4 per kilo, but most of it isn't entirely green. So we'd need to decarbonise the grid AND massively increase the amount of renewables to power the grid whilst generating enough hydrogen to decarbonise the rest of the economy.
- It is therefore suggested that blue hydrogen will be a useful short term stepping stone to a greener future. It can be used to bury the carbon from gas and coal power stations, whilst paving the way for the infrastructure required to carry green hydrogen when we get there,
- When there's enough hydrogen being produced, it can be used to decarbonise areas which will otherwise be difficult to fully decarbonise e.g. Trucks, aviation, and trains (Where batteries are impractical), steel production and shipping.
- Hydrogen could also be used to heat homes. The existing pipework can be repurposed to carry it and our boilers could be replaced by hydrogen burning versions. However there are a number of other contenders for heating homes, so this one's not a given.
- There are many projects across the world being planned or actually underway that will generate green hydrogen at scale, so this is a technology that is coming of age and will therefore drive down the costs. However, there is a final problem to overcome: Hydrogen is difficult to transport as its molecules are so small they leak through the walls of most conventional containers. So, for the moment at least, supply will have to stay local to demand until the transport infrastructure has been upgraded to handle it.
