Carmageddon : Part A

Cars Make Cities Impossible

A simple consideration of the total number and type of car sales each year, compared to the total number of vehicles on the road, indicates that the average age of a car is high, and that there are vastly more internal combustion engine (ICE) vehicles than electric models, and that therefore there will continue to be a need for liquid vehicle fuels for several decades to come. Turnover in the global fleet is not high, and anticipated conversions of vehicles to electric drive are not expected to be significant, or at least, not early on, so the high volume production of diesel-like and gasoline-petrol-like fuels remains a necessity.

There is the question of whether fuel refining can be sustained over this period, which is likely to be a time of upheaval in terms of technology. But the key question is whether the continued use of ICE vehicles will make life in cities progressively impossible. Will the continued use of internal combustion engines render cities unliveable, owing to issues of climate change and air pollution ?

Whilst it might be possible to reduce the amount of net carbon dioxide being emitted from motorised vehicles by substituting increasing levels of biomass-derived feedstock, whether in final blending, or as drop-in to various refinery processes, will this still contribute to falling exhaust toxins mandated by increasingly stringent air quality regulations ?

It is perhaps instructive to consider what has happened in the area of marine fuels. As recently reported to the IMO International Maritime Organization, VLSFO, Very Low Sulfur Fuel Oil, or other low-sulfur grades, developed to replace higher sulfur fuel oils for marine vessels, may be responsible for an increase in air pollution emissions of Black Carbon. The reason for this is that the processes of reformulating and blending that reduce sulfur from the final products potentially include a higher level of aromatic hydrocarbon compounds. It has been known for some time that this has the potential to lead to higher carbon particulate emissions (see here, for example).

Marine fuel oil is largely composed of gunk from the bottom of the barrel of crude petroleum oil – residues and the heaviest distillates. This fraction of the oils is where the most complex hydrocarbons generally lurk. The aim of the refiner is to reduce waste by blending otherwise unusable fractions of oils into final fuel products. As the higher sulfur streams have been barred, highly aromatised substitute streams have been brought in. This is one step forward, two steps back.

If refiners were to try to displace some of their fossil fuel feedstocks with biomass-derived feedstocks, this may introduce certain combustion inefficiencies, and lead to a rebalancing of problem exhaust species, but not reduce them.

Adding biomass-derived feedstocks at various drop-in points in refinery can lead to additional processing requirements, such as isomerisation and alkylation, to reestablish the regulated specification of the final fuels, leading to inherent inefficiency, and also to the presence of esoteric hydrocarbons (unnatural to nature, or unknown in such high quantities) in both fuel and exhaust.

Whilst biodiesel may contribute towards lubricating vehicles, obviating the need for engine improver detergents, does it lead to higher unwanted exhaust emissions ?

Also, although fuels are regulated at refinery dispatch, many companies are advising customers to add their own fuel improvers – sold as engine protection. How does this alter the profile of emissions ? And how many metals are present – which will inevitably end up in the lungs of citizens ? And how much sulfur in the form of sulfonates, which will end up as sulfur dioxide in the air ?

Oxygenates added to fuels certainly improve the efficiency of combustion, but do they lead to higher unwanted emissions – or do they rebalance exhausts to be more dangerous ?