We took some time out lately to talk about moves in natural gas. Yet, as our eye always remains on the current diesel price, there are other options out there as well. Of course, natural gas does remain at the top of the “alternative fuel” heap for trucks, electric drive and fuel cell technologies continue to show promise. Could we see one of these forms of energy rise as a worthy alternative for good ole’ diesel?
So, what are the alternatives? For commercial motor vehicles, the options mainly include propane, or autogas, biodiesel, renewable diesel and dimethyl ether (DME). Much like any other choice-based option, each has its detractors and advocates.
While propane has been in use for a long, long time, and the two diesel variants can be used simply by filling up with them, DME is more of an outlier. It seemed to pique a lot of fleet’s interest some time ago, but doesn’t be appearing to make a huge splash on the fuel scene.
According to Kenny Vieth of ACT Research, “Because each company’s goal for its fleet is different, even two similar fleets may make different fuel choices. Each fleet will assess its own corporate goals, the local/regional availability and price of the respective alternative fuels, and any regulations and incentives for the areas in which the fleet operates before making the fuel decision. Cost, range, weight, performance, and time will all factor into each fleet’s decision.”
In the lower GVH classes, propane autogas makes a good value proposition. As an alternative to standard diesel, renewable diesel demonstrates nearly the same level of performance while simultaneously allowing fleets to burnish their “green” cred.
Biodiesel is especially useful because of its versatility. It can be blended into many difference forms, whether the truck needs to focus on performance or fuel efficiency. Biodiesel also offers innovation in how it is acquired. New companies are bringing new methods to bear and the line on what a biofuel is becomes increasingly blurred.
DME is still a bit of a black swan. Currently, DME is used mainly by Volvo. According to John Moore of Volvo Trucks, “Sustainable sources of energy are the future and Volvo will continue to research and invest in the sources of energy that provide the best value for our customers.”
The main problem with DME is that – because of its outlier status – there is very little infrastructure support or performance or engine-durability testing, to-date.
So, with all these options on the table, which ones might be best for your fleet? The best way to answer that question is by looking at each one individually, by strength and weakness. We’ll start with Autogas.
The Story of Autogas
Propane, otherwise known as liquified petroleum gas, is only referred to autogas when it is used in the context of a motor vehicle fuel. Across all quarters autogas is considered a viable, competitive alternative for light-, medium- and in some cases, heavy-duty commercial motor vehicles (CMV).
Compared to other fuels, autogas is ideally suited for more sustainable operations. It significantly reduces harmful emissions, is more affordable than traditional gasoline and can be produced almost entirely right here in America.
But what kind of fleet would be suited for this sort of fuel? Autogas is ideal for fleets that are centrally fueled. They can also be used in application where refueling stations are shares. Autogas infrastructure is quite built out across the country, with a few options.
Finally, a point of major desirability, autogas is considered a non-contaminant. When it comes polluting the air, land or water resources, autogas meets EPA the same requirements as those in place for gasoline and diesel infrastructure.
The one area where autogas may be deficient is for long-haul applications. Still, fleets can opt for bi-fuel vehicles, which are built with gasoline back-ups within their propane autogas infrastructure.
A Look at Biodiesel
Biodiesel has come a long way in the past few years. Today, biodiesel can be produced domestically using renewable sources such as vegetable oil, animal fat or restaurant grease. The federal Renewable Fuel Standard sets stringent requirements and biodiesel meets all of them.
Although biodiesel does emit CO2, it does so at a far lower rate than standard gasoline or diesel engines. Still, that doesn’t mean biodiesel is not without its flaws. The major complaint users have is that biodiesel performance suffers in cold weather. This drawback is typically the result of the blend being used.
Biodiesel can count several different sources in its main component. Feedstocks, oils, agents and other factors can change the composition of the biodiesel one way or another. Conventional wisdom says that regular number 2 diesel should be combined with a blend of 5% to perform well. Since both diesel and biodiesel can crystallize in cold weather, fuel blenders must take great care to ensure they get the blend right.
One way to combat fuel crystallization is to add a cold flow improver or other heater of some type. Fortunately, there are plenty of aftermarket options for ensuring your fuel doesn’t crystallize.
While some may get confused, biodiesel and renewable diesel are two totally different fueling options. The two terms should not be considered interchangeable. Rather than being derived from cooking oil or something else, renewable diesel is derived from biomass, meaning some sort of plant-life.
For a fuel to be classified as such, renewable diesel must meet the registration requirements established by the EPA as stated under section 211 of the Clean Air Act. More recommendations can be found in the American Society of Testing and Materials specifications. The specific verbiage can be found under sections D651 and D975.
Renewable diesel also goes by hydrogenation-derived, or “green diesel.” It can also be produced with animal fats and oils, but in this format, it is used either alone, or blended with a little petroleum. The petroleum must be refined to a certain ASTM specification as stated by the Department of Energy.
Doing it this way allows renewable diesel to be used within existing diesel infrastructure and applications. In fact, according to the Department of Energy (DOE) fuel producers have begun designing an HDRD substitute that the hope will be a substitute for just about any straight-petroleum based blend on the market. Ideally, the goal is to get the vehicles to function optimally using the fuel without having to invest significantly in changing or updating their internal components.
Renewable diesel also has benefits beyond its green cred. It also meets quality standards for new diesel engines and – for the most part – is compatible with current diesel fueling standards and infrastructure. The fact is, high combustion/high quality renewable diesel offers the same vehicle performance while making great strides to keep its footprint as “green” as possible.
What Is DME?
Sitting at the bottom of this list is Dimethyl ether or DME. This fuel first hit the scene back in the early-2000s, though at the time development was happening primarily across the pond. Motivating the development of these vehicles was Europe’s aging fleet. Europe has been at the forefront of studying and implementing green technologies for a long time.
Yet, for some reason DME never made it big here in America. The main reason for this can be found in the fact that over the past decades, diesel fuel has done a good job cleaning up its emissions profile. Compounding the problem, diesel prices are far too attractive.
Competing which more popular natural gas and autogas alternatives have also taken a chunk out of DME’s appeal. Since DME is a synthetic product, it could be produced in the U.S. on a large scale using natural gas feedstock.
Manufacturing infrastructure for DME is already in place, since CMVs using autogas must likewise be handled the same way, in a pressurized storage container at an ambient temperature. DME also doesn’t emit particulate emissions the same way conventional engines do, meaning less components installed on the truck. There is a serious weight and cost saving advantage to these engine types.
With a very high cetane number, DME can match diesel in energy efficiency and power, yet can all but eliminate emissions since its combustion does not release carbon-to-carbon bonds. A downfall? DME has only half the energy density of diesel fuel, which means it will need to be stored in tanks that are twice the size of normal variants.
While plenty of DME demonstrations have taken place in both Europe and America, it remains to be seen if this promising alternative fuel will catch on. The big elephant in the room. DME is not commercially available yet in the Unites States, but will it be in the coming future? Only time will tell.
The fact is, as more and more fleets and consumers turn to alternative fuels and sources of energy, expect things like renewable diesel, biofuels, DME and other synthetic options to flood the market. Although we certainly haven’t seen diesel’s last days, that’s not to say diesel’s days are not numbered.