@urlyman There is a hell of a lot of scrap available that we're not using right now. The total UK scrap supply is about 10 million tonnes per annum, of which we use about 2.5. Most of the rest is exported, sure. But we could build several more arc furnaces.
Steel for rails in particular is often made via arc furnaces, while some other uses need "virgin" steel.
Meanwhile, where you actually need virgin steel, large scale direct reduction from hydrogen, using electricity from renewables, is not only possible, there are at least four plants under construction.
Granted there are difficulties with hydrogen; electrolysis doesn't like running below 50% capacity, for instance, and most of the H2 leaks (greenhouse gas) come from starting and stopping.
In any case annual demand for steel for rails is about 80,000 tonnes (UK). That's a fraction of overall steel demand.
Steel is indeed a problem. But we can provide the steel needed for rail.
The problem with building new rail lines is that 1) it tends to go through important habitats, 2) it tends to take decades, 3) it tends to cost tens of billions and 4) if any modal shift actually occurs, it can lead to further emissions in other sectors (i.e. we need to close down airports at the same time).
If it's done right it can still make a meaningful contribution to the transition. For instance we need a low-speed line from Birmingham out to Crewe to make HS2's capacity gains on rail freight actually materialise.
