DME can reduce emissions and pollution from heavy transportation, and also give a big boost to hydrogen vehicles

Can a new fuel for trucks that is clean, powerful, and easy to produce from local waste residues also get more zero-emission hydrogen vehicles on the road?

At Oberon Fuels, we are busy working with a global coalition to bring a new fuel, dimethyl ether (DME), to the trucking and heavy equipment industry. DME is not a household name, but it is known among those in heavy-duty vehicle applications because it is the best option to replace diesel amid rising demand for a more sustainable transportation infrastructure:

· DME burns cleanly and quietly and can reduce carbon dioxide emission by 68–101%, depending on which renewable feedstock is used.

· DME is a single molecule fuel with no impurities. It is sulfur-free and burns with no particulate matter, making it easier to control nitrogen oxides (NOx) pollution.

· It is also one of the few truck fuels that can truly be produced locally. Urban garbage streams, dairy manure, and other organic waste streams can be repurposed to make DME fuel for fleets of trucks and other vehicles.

· DME also meets tough performance requirements, a must for trucking and other heavy-duty applications that need the power and torque of compression-ignition engines.

· DME vehicles are less expensive to run over their lifetime given operational costs and lower weights; and DME infrastructure is easy to build and expand.

Oberon’s process for producing DME

At Oberon, we envision a future where locally-produced truck fuel is moving goods, providing jobs, cleaning the air, and making good use of waste streams that would otherwise contribute to climate change, water pollution, or other environmental problems.

Over the past eight years, we have partnered with Volvo Trucks, Mack Trucks, Ford, and a host of other manufacturers to build DME engines, test demonstration vehicles, get standards approved, and design infrastructure that can make DME a crucial component of global transport networks.

The first wave of demonstration vehicles has passed with flying colors, and large-scale rollouts are on the horizon.

And yet this vision does not tap the full potential of DME. In fact, this molecule may have an invaluable second act as a booster to the emerging hydrogen fuel infrastructure.

DME is an ideal carrier for hydrogen fuel

DME is dense in hydrogen. One DME molecule has six hydrogen atoms. DME’s lack of carbon-carbon bonds makes reforming DME into pure hydrogen a simple, cheap process that can occur at lower temperatures.

A DME molecule

DME’s liquid state under mild pressure would also help hydrogen fuel overcome one of its most intractable problems: transport. Hydrogen is notoriously difficult to compress, requiring pressures of up to 10,000 pounds per square inch, a dangerous level that requires expensive equipment. DME on the other hand, can be moved in modified propane trailers at pressures around 73 pounds per square inch.

These qualities give DME a unique dual-use potential with the rollout of DME trucks becoming an ideal way to push hydrogen infrastructure as well. It could happen a number of ways with DME being used to make hydrogen at fueling stations, on board vehicles, or even by powering a fuel cell directly.

DME is much easier to transport than pure hydrogen.

The pathway to safe, affordable hydrogen infrastructure.

DME could be used as a hydrogen carrier almost immediately. Oberon is already producing DME as a fuel, and hydrogen cars are on the road in select markets. A simple equipment upgrade would give any of today’s hydrogen fueling stations the ability to turn DME into truly renewable hydrogen.

Even more encouraging is that the infrastructure for both DME and hydrogen can be quickly expanded without unwieldy market disruptions or unexpected capital costs. In fact, DME and hydrogen infrastructure can work together as they grow.

DME is already taking the first steps to replace a portion of the diesel used in trucking. All of the pathways that are giving DME engines and fuel production a foothold can also lead to a more robust network of hydrogen fuel infrastructure.

For example, bi-fuel vehicles that can use up to 20% DME to displace diesel (these are called dual fuel vehicles in Europe) may be one of the easiest ways for a fleet to begin using locally produced DME, since inexpensive aftermarket add-ons allow existing diesels to adapt to using both fuels.

Conversions that can also be done on farm equipment, construction equipment, and other engines could add even more opportunity for DME production facilities.

Bi-fuel prototypes are already undergoing testing, and large-scale demonstrations could be seen as early as next year.

Another pathway for DME is running in parallel to bi-fuel systems. Vehicles that run on 100% DME continue to be tested and additional vehicle deployment is anticipated in 2019. These dedicated DME vehicles have already been successfully demonstrated, and multiple engine manufacturers have programs underway to perfect the technology further.

A fleet of new DME trucks would be a big incentive for more DME production and fueling infrastructure, yet the adoption of 100% DME doesn’t rely entirely on new OEM vehicles. Companies are also working on conversion kits that could modify existing fleets to switch entirely to DME as local fuel supplies become dependable.

A third pathway for expanding DME infrastructure can be found in hybrid-electric vehicles. Range extension with DME is ideal, since the gas is efficient, lightweight and clean. The similarity of DME engines and diesels mean that diesel-electric hybrids can easily give way to DME-electric hybrids, providing yet another push for regional DME fueling stations and production facilities.

A fourth pathway is where DME begins to play its double-duty role as a carrier for hydrogen fuel. This could unfold in a variety of ways.

Converting DME to hydrogen at the station

Non-toxic, easy-to-handle DME would be trucked to fueling stations for conversion into hydrogen fuel, using simple reforming equipment. Existing hydrogen dispensers, storage tanks and fuel cell vehicles would still be used.

No pipelines would be needed, which would cut down on methane leaks in transit, expedite project development, and result in locally-produced, truly green hydrogen fuel. Renewable methane molecules from local waste streams would be converted to DME and then hydrogen. It is not an accounting game of injecting in the pipeline and pulling out “bio”methane at a different location to make “renewable” hydrogen.

Converting to DME on board the vehicle

A second option would be to convert DME to hydrogen on board the vehicle. DME fueling equipment is basically modified propane fueling equipment, and so infrastructure expansion would still be relatively simple and low cost.

DME-powered fuels cell may one day compete with hydrogen

Finally, and perhaps most advanced, would be to use DME directly in a fuel cell. A DME fuel cell could provide the drivetrain power, skipping the need for conversion to hydrogen entirely. This is an advanced option that may not come until a large number of hydrogen powered fuel cells are on the road, but if DME is already used in hydrogen transport these vehicles would find a much easier path to market.

Magnifying investments already made

The most powerful aspect of developing DME and hydrogen fuels together is that they can both leverage the investments we have already made to clean up transportation the world over.

Engine manufactures are already busy making heavy trucks that run on DME, and European coalitions are forming to build the regulatory frameworks that can put DME trucks on the road. DME is already legal to use as a fuel across the United States. Oberon’s biogas-based DME qualifies for EPA Renewable Identification Number (RIN) credits.

International standards have also established DME as a legitimate vehicle fuel. In 2014, ASTM International developed technical specifications for fuel-grade DME that provide guidance for fuel producers, engine suppliers, and infrastructure developers. In 2015, the International Organization for Standardization (ISO) also specified DME characteristics for use as fuel.

In California, huge investments have been made to help a new generation of alternative fuels, including fuel cell vehicles. This year, the state doubled its construction goal for hydrogen stations, setting new targets of 200 stations by 2030 and 5 million zero-emissions vehicles in the same timeframe. Yet with all the expense and hurdles required to build an entirely new fueling infrastructure, even the most ardent supporters know more needs to be done to support truly renewable hydrogen.

If DME fuel were to be rolled out alongside hydrogen infrastructure, the two fuels could find a synergy that catapults transportation infrastructure faster, and further, than has previously been imagined.

An investment in a DME station or production facility would also be an investment in renewable hydrogen. DME production on a dairy farm or landfill would mitigate methane emissions and fuel heavy duty truck alongside fuel cell vehicles. The penetration of fuel cell vehicles into the market would also expend the DME fuel network, giving truck fleets the fuel they need to haul the heaviest loads. Technology improvements on a DME-powered vehicle would cascade into benefits for those running on hydrogen.

This opportunity might be missed if policy makers and vehicle developers do not align their strategies soon. DME engines are in development now, and hydrogen vehicles are pushing into the market, but there is no coordination between these two natural allies.

With the near-term opportunity for DME terminal construction aligned with the existing pathways for zero emissions vehicles, the time is now for strategic DME-hydrogen partnerships. They could unlock the long-sought dream of a transformed transportation sector; one that thrives on truly clean vehicles, recycled waste streams, and locally produced fuels.