[fathead_glacier]

The article misses an often overlook but important point: burning hydrogen in air produces NOX which can be a more potent greenhouse gas than CO2. The solution to reduce the amount of generated NOX exists but the resultant engine is larger and consumes more fuel for the same power output.

Further, as stated hydrogen is typically produced by steam reforming which generates greenhouse gases. The alternative of using electrolysis requires electricity generated from carbon neutral sources.

Taking all this into account:

- making steel requires electricity, the carbon neutral source can be used here directly;

- land vehicles already have a proven alternative with electric engines;

- naval vehicles do not have the luxury of easily recharging electric batteries.

As a summary I think the solution already exists for steel making and land based transport the problem is widespread adoption and politics rather than technology. Naval based transport can benefit from hydrogen as a fuel source but it comes at the engineering challenge of transport/storage and the associated safety concerns.