Diesel will be around for a long time
Americans think of diesel fuel as the dirtiest, nastiest stuff available. It's associated with loud engines, black smoke, and slow big rigs on the highway. Environmental advocates often malign diesel as a dirty, polluting menace. Biodiesel is often lumped in with ethanol as a food-thieving green fuel.
For all of its bad publicity, however, diesel is the most common fuel in the world, dominating as the developing world's liquid fuel of choice and powering nearly half the automobiles in Europe and large percentage of those in Asia. In the United States, the bulk of our heavy machinery and freight hauling vehicles are diesel-powered. Tractor-trailers, trains, buses, earth movers, military machines, and many more are using diesel as their fuel source.
Despite calls to replace diesel and other petroleum fuels with alternatives, our world is powered by diesel fuel and will be for some time to come.
Two years ago, the U.S. Department of Energy commissioned the National Petroleum Council to report on what fuels will power America's foreseeable future. That report, delivered in August of this year, titled Advancing Technology for America's Transportation Future, finished a two-year study into fuels, technologies, industry practices, and government policies through to 2030 that are and could continue to reduce greenhouse gas emissions from American transportation by fifty percent by 2050.
The crux of its findings?
“Diesel engines will remain the powertrain of choice for HD vehicles for decades to come because of their power and efficiency. There are, however, opportunities to improve the technology. Significant fuel economy improvements in diesel powered trucks are possible. Indeed, the fuel economy (mpg) for new Class 7&8 HD vehicles, which consume more than 70 percent of the fuel in the trucking fleet, could be doubled.”
The report also found that market dynamics, not government, will contribute the most to how technology and future fuels are adopted and used.
“There is a great deal of uncertainty regarding which individual fuel-vehicle systems will overcome technology hurdles to become economically and environmentally attractive by 2050. Therefore, government policies should be technology neutral while market dynamics drive commercialization.”
Currently, and in the near future, there are no viable replacements for diesel in most heavy-duty markets and few that will suffice for medium-duty needs. Heavy transportation will be needed for a very long time and over-the-road (OTR) as well as rail-based cartage are the means of choice for most freight. Other options are either experimental or merely blueprints and will not replace these primary means of freight transportation for decades. So most of the changes we'll likely see in goods transportation will happen inside existing transport matrices rather than through the introduction of new ways of moving material.
This means diesel will continue to dominate. In the medium-duty market, some alternatives for vehicles are available and will continue to carve niches in the market. In heavy hauling, however, no feasible alternatives to diesel are being offered currently and known technologies are either not going to be viable for the market at all or are decades away from being implemented.
Particulate emissions, which are of concern in diesel engines, are dropping despite the growing number of diesel engines in use in the United States and Europe. In these developed countries, regulations and new technologies are lowering the amount of PM emitted by diesel engines and after-treatment options, once only popular in passenger cars, are now being used in many on- and off-road machines. In particular, the passenger fleet (buses, shuttles, etc) are often the highest source of urbanized PM emissions and are the focus of many of these upgrades.
Passenger vehicles may move away from gasoline, but the attraction of diesel will likely keep it viable for many years. With its very high efficiency (compared to gasoline), its robust longevity, and the relative ease of refinement for diesel (including biologic sources) mean it is a fuel that both burgeoning and established vehicle markets can and do embrace. The emissions from diesel is generally cheaper and easier to control than are those from gasoline as well.
So expect to see diesel as a primary fuel option for at least the next twenty to thirty years. Like it or not.