The latest government brain wave (sarcasm) is hydrogen: Ministry of business, innovation & employment ARUP, published a paper full of happy talk, but lamentably little evidence of scientific understanding.
practicalities
The link between CO2 and global warming is far from established fact and the predictions are not born out by actual data (see graph), but let's just assume it was as they say.
Burning hydrogen may well not produce CO2, but instead it produces a lot of H2O (clouds). We all know that a clear sky means a cold winter night and the reality is that water vapour contributes most of the green house effect to our atmosphere. Thus for instance, burning hydrogen as a jet propellant will make things worse, rather than better.
Hydrogen is much more difficult to manage as a fuel, as it needs extreme pressure to contain any significant amount and it's more difficult to distribute and use than just filling the tank with petrol or even LPG.
brown and grey hydrogen
Hydrogen can be produced from fossil fuels by high temperature steam reformation. In that case the carbon component gets wasted and we end up producing just as much CO2 as we would have done by burning the fossil fuel in the first place as well as significant overhead the reformation process as well as it's byproducts such as residual methane (a far more potent green house gas than CO2).
Rather than venting CO2 to the atmosphere it can be dissolved in water (think of fizzy carbonanted drinks) but it then leaves us with acidified water to dispose of which will exchange CO2 with the atmosphere eventually anyway.
green hydrogen
"Green" hydrogen OTOH is produced by electrolysis of water and this consumes at least 3 times as much energy than you can ever get back from using the hydrogen as a fuel. Thus at best, it acts as a very inefficient battery.
ARUP suggests using "spare electricity capacity" to produce hydrogen for export. This is the very same hypothetical spare electricity that we will be using to recharge electric vehicle batteries: It's going to have to become a lot cheaper than our "spare capacity" (night time rate) to produce "green" hydrogen that can compete internationally in price with other fuels.
Such hypothetical "spare capacity", is going to require a lot more investment in electricity generation from "renewable" resources and I think the government owes us a proper cost analysis so that we, the electricity users don't end up subsidizing their virtue signaling climate propaganda stunt.
Investment Hype
Hydrogen fuel cells for cars and airplanes - seriously, do they understand that a fuel cell simply turns fuel into electricity (and rather inefficiently at that)?
So... having used electricity to make hydrogen (inefficiently from water) and then storing and transporting this far less convenient fuel and using a fuel cell to turn it back into less electricity... we end up with an electric car or an electric air plane perhaps (WTF?!) that we could have simply used batteries to power with the electricity we had in the first place... I see no investment potential there.
Stupidity and ignorance on a grandiose international scale! Hydrogen economy is the buzz word of -current year- politicians.
More virtue signalling is in the paper as it pontificates on the involvement of Maori issues in the exciting new hydrogen economy (sarcasm). To be honest I'm just sick of the systemic race BS in this county: Hydrogen has no racial bias. Let's keep it that way.
Conclusion
It's hard to believe, but we appear to be electing idiots to lead our country to self destruction.