Where's the steel?

A blast furnace in operation

From the discovery of iron working techniques, about 3,200 years ago, up until the widespread exploitation of fossil fuels, about 250 years ago, iron and steel were rare, precious materials. The average person, across the whole world, almost certainly had less than 500 grammes of it. A knife, probably; some tool of their trade, possibly. Even members of the elite -- warriors who fought in full armour, for example -- probably owned no more than 30kg of iron and steel.

The use of fossil fuel changed all that, of course. There's about one car for every two people in the UK, and the average car now weighs 1857Kg, so that's almost a ton per person in cars alone, not to mention all the steel we now have in buildings and infrastructure. But it's fossil fuels that have made that possible. In future, we can't use them. So how much steel will we have?

Steel costs about 4MWh/ton to make. Current production of steel is about 1.8 billion tonnes per annum.That's about 7.2 billion MWh, or 7.2 million GWh, or 7,200 terawatt hours per annum -- which is 23% of total world industrial energy consumption.

Total world electricity production is around 27,000 terawatt hours So making all our steel electrically would take one third of our total electricity generation capacity. But only 28%, or 7560 TWh, of this is renewable. In other words, if we converted all our current steel making capacity ro electric arc, it would use virtually all of the world's production of renewable energy.

About 260GW of new renewable generating capacity is being added annually, but that figure is a bit misleading, since renewable plant cannot operate at full capacity all the time. Solar panels only operate during hours of daylight, and at full capacity only when the sky is cloudless and the sun significantly above the horizon. Wind turbines operate at full capacity only in a fairly narrow band of wind speeds. So 260GW of capacity does not translate into 2 277 TWh of electricity actually produced per year, but much less. How much less? I don't know, but about a third, or 0.7 TWh, seems a reasonable guess.

However, only a proportion of steel is made using electric arc furnaces; the rest is made using fossil fuels, largely coal. The exact proportion is hard to establish, since especially in the West new electric arc capacity is being built quickly. But the best figure I can get is around 29%. That means, of course, that of that 29% of steel that is made electrically, only 28% – or 8% of total steel making – is carbon neutral.

It also means that, disregarding the proportion of existing electric arc furnaces which are using fossil-fuel generated electricity, it would take seven years of our total new renewable energy capacity to replace existing fossil fuel steel making capacity with renewable. And that's before a single joule of electricity becomes available to power any of the new electric cars, electric trucks, electric trains, etc, that we want to build with that steel.

Except we couldn't build the new capacity that quickly, because it takes (a lot of) steel to build both new steelmaking plant and new renewable electricity generating capacity. We are going to have to shut down the approximately 70% of steelmaking capacity that is fossil fuel powered, and we're going to have to shut it down soon. And in a world which is critically short of a strategic material as critical as steel, making the right choices about how to allocate that steel is going to be hard and contentious.

So no. We're not all going to have electric cars. We're going to have a lot less steel