Probably without really thinking much about it, we have pretty much engineered our entire society around the distillation curve of a barrel of crude oil – or at least the barrel that was easy to find in the 1950s or there abouts.
Most of our cars run on gasoline, largely because of the invention of the spark ignition internal combustion engine, where the fuel is a compromise between one that is volatile enough to vaporize but not too volatile to result in pre-ignition.
Rudolf Diesel originally designed his engine to run on peanut oil in the 1890’s, so it then found a home with the heavier distillates from crude oil. Since then it has become the backbone of heavier forms of transport such as trucks, ships and industrial vehicles. It is also making significant inroads into the passenger vehicle segment given its high efficiency (50% in the EU but much less in the USA).
A jet engine can run on a wide variety of fuels, but owing to the shortage of gasoline during the second world war, illuminating oil (kerosene) was the chosen product. Since then we have optimised this engine for this type of fuel and built a wealth of infrastructure at airports to support its use. Even its flashpoint specification was in part due to the need for safe handling on an aircarft carrier.
We have also optimised at the bottom of the barrel, using heavy fuels in ships and putting bitumen on our roads.
So as we seek lower carbon emission fuels for transport, do we try to replicate the exisiting approach or develop alternatives? Picking and choosing may not be an option here. For example, if we were to move away from deisel and gasoline for personal road tranport but decide to retain kerosene for aviation it unbalances the product slate that is produced by refineries. But the aviation sector is pretty much locked into kerosene, with no immediate developments on the horizon for alternative fuels. That then points to a solution which replicates kerosene from bio-sources, thereby utilising all the existing infrastructure. Alternatively, we continue to extract kerosene from crude oil and use the remaining products in gasifiers, combined with CCS, to make hydrogen and electricity. Interestingly, the very early use of crude oil also focussed on this cut of the barrel. The illuminating oil was extracted as an alternative to whale oil and the remaining distillates were “disposed” of.
Just looking at road transport alone, the future could well become quite complex. As other forms of transport are included it is not difficult to see that the relatively simple energy supply route we enjoy for transport today is going to change.