It's frustrating driving a fuel-efficient vehicle sometimes.
While you know you're just one small part of an effort to clean up transportation, seeing an 18-wheeler pumping clouds of black smoke into the air can make you feel like your efforts are going to waste.
Cleaning up trucks should be a high priority then, given the vital job they do and the numbers in which they can be found--and that's exactly what Dimethyl Ether (DME) promises.
It's the latest alternative fuel under consideration in the haulage industry, and according to Navigant Research there are several benefits over diesel, compressed natural gas (CNG) and liquid petroleum gas (LPG).
DME can actually be produced from natural gas or coal, but can also be produced from biomass--a much greener option as it makes further use of waste products. DME is converted into a liquid under "modest pressure"--around 5 bar, or 75 psi, and can then be stored at similar pressures--compared to the 3,600 psi for CNG.
Unlike the diesel fuel commonly used in trucks it produces no particulate matter--the microscopic particles often attributed to raising instances of heart and lung disease--though does produce carbon monoxide and nitrogen oxide. On the plus side, it's non-toxic and non-carcinogenic if ingested, though we'd not recommend it even so...
DME also has a high cetane rating of 60, compared to the 45-55 of diesel. This not only means it can be used like diesel--and works with modern direct injection technology--but also means quicker, cleaner ignition, leading to those low particulate figures and better economy.
Don't get excited just yet...
The perfect fuel for trucks then? Environmentally, it's hard to disagree. But economically, Navigant Research isn't so sure.
Like so many alternative fuels, there's little infrastructure for DME at the moment. The price isn't immediately attractive either, compared to CNG or LPG--it's around the same price as regular diesel, so there's no direct cost incentive for businesses to switch.
While early adopters of hybrids and electric vehicles are prepared to take an initial financial hit to improve their transportation, it's much harder for a cost-squeezed truck operator to do the same.
In the meantime then, it's incremental improvements we should all be hoping for--aero efficiency and engine tweaks, switching to cleaner natural gas, or retro-fitting parts to improve the emissions of existing trucks.
It's low-hanging fruit that we can all appreciate. When you're following a big rig up a long hill and not a speck emerges from its exhaust stacks, driving your EV or hybrid doesn't seem quite so futile.