From the source cited, here is a breakdown per industry:

https://ourworldindata.org/ghg-emissions-by-sector

Energy usage for industry is 24%

Road travel is 11%

It seems aviation’s 2% is not the low hanging fruit.

But passenger road traffic is only 7%. The rest is freight which requires a completely different solution.

There is no low hanging fruit. We need to address every sector. No individual solution is going to cut more than a few percent of total carbon emissions.

24% industrial use is in my mind.

A buddy of mine worked for a startup a few years ago that promised to go into large plants and do some trickery with the harmonic losses with the very large AC motors in a lot of the big equipment. Apparently there is a lot of losses in such things. They would install equipment to improve the situation in exchange for a portion of the energy savings over time, which was considerable.

Except that also breaks down into 7% iron/steel, 3.6% chemical and oil, 1% food and tobacco and many other small categories.

Is the same solution that cuts down on carbon emissions in making steel going to cut emissions when making fertilizer?

Yes, because all those plants have big AC motors driving the machinery. Any place where there is a big AC motor can benefit from this. That means most of the applications you can think of.