Evolution of alcohol fuel blends towards a sustainable transport energy economy

Work undertaken by Lotus Engineering and partners has shown that the miscibility of the low-carbon-number alcohols with gasoline provides a powerful tool to enable the introduction of methanol as a transport fuel in a wholly evolutionary manner. This is primarily facilitated by the fact that the CAFÉ regulations in the US (together with other incentives in other countries, such as Sweden) have created a situation in which there are 7-8 million E85/gasoline flex-fuel vehicles on the roads there, for which insufficient E85 can be provided at an affordable price. This paper will show that the introduction of methanol (which can be made extremely simply and cheaply from natural gas) into gasoline-ethanol mixtures, can be used to create drop-in fuels equivalent to E85 and can bring the price of an alcohol-based fuel for spark-ignition engines down to less than that of gasoline (on a per-unit-energy basis, before tax is applied). It can thus more than compete with that fuel. This opens up the possibility of using the US’s reserves of naturally gas (be it conventional or unconventional types such as shale) immediately to manufacture methanol to displace gasoline, as a bridge to a broader energy economy based on higher concentrations of methanol made from renewable sources. The vehicle work conducted has shown the possibility of realizing this state of affairs, and related laboratory tests on some of the potential fuel blends have similarly demonstrated that they possess some of the necessary characteristics to be truly ‘dropin’ alternatives to E85. These necessary characteristics are considered to be equal volumetric energy content (to enable compliance with on-board diagnostics requirements), equal octane numbers and latent heat (to provide invisibility to the combustion and air handling systems), and inherent miscibility with gasoline (to avoid the requirement to change the fundamental nature of the vehicle fuel system). A further requirement in practice is that the vehicles still be of adequate performance with regard to tailpipe emissions standards using the existing exhaust after treatment systems fitted to them. In the present work this is demonstrated by reporting data for oxides of nitrogen emissions (NOx) taken from a standard production Saab 9 certified to the EU5 emissions standard using ternary blends (such NOx emissions being especially important from a human health point of view in built-up areas), which shows that generally such emissions are significantly lower for all of the alcohol blends than for gasoline. All results are found to be well within the EU5 limits, with the gasoline results showing that the after treatment system was indeed functioning correctly.