Oil, and its major liquid-fuel derivatives (petroleum [gasoline], diesel, kerosene and aviation fuel), are incredibly convenient energy sources. They are energy dense, easily combustible yet relatively stable, and represent an abundant, naturally available energy carrier. Oil underpins our massive modern transport fleet. But what do we do when the oil runs dry (or, indeed, as prices rise following the plateau/peak that we may have already reached), and carbon restrictions tighten?
Well, there’s no other obvious natural energy carriers for use in transport. But we can make them, by drawing on natural processes (biodiesel and bioethanol), or using stationary energy inputs to create chemical-electric batteries, hydrogen fuel cells, purified metals, etc. In the former case, the enegy input comes from a solar source in the form of biomass (via photosynthesis), and in the latter, it must come from technosolar, nuclear, or fossil fuels such as coal and natural gas.
Hydrogen is often touted as the obvious future energy carrier (other than electricity), but it faces substantial technological and logistical obstacles, such as high conversion losses (60 to 80% reduction compared to original energy input), extreme volatility, energy required for compression to a liquified form, piping embrittlement and leakage, storage volume problems, the need to construct a new, massive distributional network, and so on. The problems are detailed here and here (but for a counter-critique of some points, see here).
I should note that hydrogen is NOT an energy source, despite the oft repeated allusions in the media, because hydrogen does not occur naturally on Earth). Some are optimistic that storage of hydrogen in metal hydrides will solve some major problems, but that requires considerable R&D. I’m cautiously optimistic of metal hydrides, electrochemical compression, and proton exchange membrane fuel cells and parallel path magnetic technology, in particular. But they’re not ready and proven — yet another area where a massive investment in energy technology and engineering development is needed NOW, if we are to have readily exploitable fossil-fuel-free energy systems in the medium- to long-term.
But speaking the other day with an engineer from one of Australia’s largest steel manufacturers (OneSteel Whyalla), he raised an interesting issue regarding hydrogen that is quite separate from its use as an alternative transport fuel. I was previously quite unaware of this remarkably important role for hydrogen.
Steel making is responsible for about 7% of global CO2 emissions — a remarkable number for a single industry — which shows how dependent our modern society is on steel. Look around you — tables, chairs, cars, building frames, lamps, doorknobs, rubbish bins, etc., etc. It’s everywhere. Although 80% of steel is recycled (and this can be done via electric-arc-furnaces that don’t rely on fossil fuel combustion), demand is rising fast. As such, most steel produced today is still made from iron ore. Primary steel production requires a reductant during smelting, and at feasible temperatures, coking coal has historically been by far the best choice for this role (a tonne of coke for 2 tonnes of iron ore). Thus about 80% of the CO2 emissions from steel manufacture come not from it’s power demand (which could be replaced by electricity from carbon-free sources such as technosolar or nuclear), but from the chemical requirements of the steelmaking process. To cite Wiki:
Although the efficiency of blast furnaces is constantly evolving, the chemical process inside the blast furnace remains the same. According to the American Iron and Steel Institute: “Blast furnaces will survive into the next millennium because the larger, efficient furnaces can produce hot metal at costs competitive with other iron making technologies.” One of the biggest drawbacks of the blast furnaces is the inevitable carbon dioxide production as iron is reduced from iron oxides by carbon and there is no economical substitute – steelmaking is one of the unavoidable industrial contributors of the CO2 emissions in the world.
But wait. There is one other element that can be used as a reductant in steel manufacture (driving off the oxygen from iron ore) at practical temperatures, and the process is well proven. That is… hydrogen.
So I can see a great role for high temperature fast spectrum nuclear reactors such as the lead-cooled variety, for CO2-free thermochemical production of hydrogen, for the critical iron-steel making industry (or the Integral Fast Reactor via electrolysis). This is yet another advantage of Gen IV nuclear that I’d not previously considered — build a reactor next to each major blast furnace and pipe the hydrogen directly and simply, over short distances (so avoid issues with hydrogen storage and long-distance piping). This honestly seems to offer the only feasible way to get rid of coking coal and the 7% of global anthropogenic carbon emissions that this process causes. The steelworks at Whyalla in South Australia, is an obvious place to demonstate this potentially superb synergy.
So, whilst the ‘hydrogen transport economy’ may still be a long way from reality, its major use in industrial applications like steelmaking may be much closer than many might have imagined. Time to start re-hyping hydrogen!