Fuel: Diesel & Beyond

The days are gone when “Fill 'er up” meant fuel up with good old #2 Diesel and be on your way .

Already, some fleets are running on once-exotic fuels like biodiesel and ethanol and turning to advanced hybrid technologies to help power their trucks more efficiently and “greenly.”

Yes, the future is in sight but it is not at all clear which alternatives beyond diesel are the best choices to power trucks.

The staggering rise in the cost of fossil fuels — be it the ultra-low sulfur diesel that powers most medium- and heavy-duty trucks or the unleaded gasoline that light trucks and cars use — along with the swelling tide of public and private environmentalism and the desire of developed nations like ours to be more energy-independent, coupled with technological breakthroughs, are driving the development of a rich menu of alternative ways to power vehicles.

The trick is figuring out not just which new fuel — or fuels — are appropriate for a given fleet right now but also which might deliver better results in a few to some years down the road.

In terms of dealing with the plethora of choices emerging, one positive to bear in mind is that trucking has historically been adept at working with — and taking advantage of — equipment options that are not one-size-fits-all solutions.

Zeroing in on all this choice, it would be nice to state that pumping biodiesel into medium and heavy trucks and ethanol into light trucks would amount to a magic potion for trucking, allowing fleets to be green and save green while running fuels that seem little different than what they have burned for decades.

But, again, things are not that simple. Both biodiesel and ethanol (collectively they are biofuels) hold great promise but they're not expected to win converts without a fight. There remains plenty of opportunity for natural gas vehicles (NGVs) too.

And gaining attention in just the past few years are medium- and heavy-duty hybrid powertrain setups. Much further down the developmental highway are hydrogen-powered fuel cell and full electric power.

FARM-GROWN

What are biofuels and why are they all the rage? Biodiesel and ethanol are derived from biomass energy, gained from plants and plant-derived materials. Wood is the oldest and still the largest biomass energy resource; other sources include food crops, grassy and woody plants, residues from agriculture or forestry, and the organic component of municipal and industrial wastes, including the fumes known as methane gas.

According to the U.S. Dept. of Energy's National Renewable Energy Laboratory (NREL), tapping biomass energy can greatly reduce greenhouse gas emissions.

The key thing about biofuels is they can be mixed with diesel or gasoline, to create biodiesel and ethanol respectively, to lower exhaust pollution by up to 30%, states a recent Michelin report on “sustainable mobility.”

What's more, NREL says using biofuels can reduce dependence on foreign oil because they are the “only renewable liquid transportation fuels available.”

The real kicker, and this is where agronomics comes into play, and farm-belt politicians step right in, is that “biomass energy supports U.S. agricultural and forest-product industries.”

The “feed stocks” in this country that make up biomass fuels are corn (for ethanol) and soybeans (for biodiesel), which NREL calls “surplus crops.”

The laboratory adds that in the near future “with NREL-developed technology” agricultural residues such as corn stover (the stalks, leaves, and husks of the plant) and wheat straw will also be used.

“Long-term plans include growing and using dedicated energy crops, such as fast-growing trees and grasses, that can grow sustainably on land that will not support intensive food crops,” states NREL. Translation: A new industry has been born that not only benefits large-scale farmers, but also communities where biofuel plants are sited. This is the kind of progress that won't be easily stopped let alone slowed.

That in a soypod (or cornhusk) is why trucking is hearing so much about biofuels. However, whether you can fuel your truck or car with a biofuel at this time depends on where you are. Think corn, think soybeans. If your trucks are in the Farm Belt or traveling through it, chances are you can. If not, well, then no.

If you can access them, the good news about biodiesel and ethanol is these fuels can be used by fleets with essentially no extra investment because they will power existing equipment with few if any modifications and no new fuel-distribution infrastructure is needed.

In addition, a lot of spadework has already been done by advocacy groups and pioneering users that indicate that biodiesel and ethanol blends are most effective, with B20 (80% diesel) and E85 (15% gasoline) most commonly cited.

According to the National Biodiesel Board (NBB), “biodiesel blends operate in diesel engines, from light to heavy-duty, just like petroleum diesel. B20 works in any diesel engine with few or no modifications to the engine or the fuel system, and provides similar horsepower, torque, and mileage as diesel.”

NBB also points out that in its pure form or in blends, biodiesel can be stored wherever petroleum diesel is stored, except in concrete-lined tanks. The fuel should be stored in a clean, dry, dark environment. At higher blend levels, biodiesel may deteriorate natural rubber or polyurethane foam materials. “Biodiesel also has a higher flash point, handles like diesel and is safe to transport,” states the board.

Fuel quality, however, remains a concern for biodiesel users. Biodiesel that does not meet strict quality standards can clog filters and injectors and even increase emissions. NBB advises fleets to be sure they are purchasing biodiesel that meets the American Society of Testing and Materials (ASTM) Specification D 6751, which was released back in 2002. A copy of the D 6751 spec can be purchased for $35 at www.astm.org.

As for ethanol, the gasoline substitute, the American Coalition for Ethanol (ACE) makes similar claims for the straight gasoline substitute: “Ethanol is a clean, renewable, high-performance fuel… up to a 10% blend of ethanol (E10) is covered under warranty by every auto manufacturer that sells vehicles in the U.S. for every make and every model of vehicle. E85 (85% ethanol/15% gasoline) is for use in Flexible Fuel Vehicles (FFVs), which can operate on gasoline or any blend of ethanol up to 85%.”

ACE adds that since ethanol has a lower Btu value than gasoline, it “burns cooler and is gentler on the vehicle's engine — less wear and tear leads to longer engine life.”

BLUE FLAME

The alternative fuel with the longest continuous track record in trucking is natural gas, in both its compressed (CNG) and liquefied (LNG) forms

Just because biodiesel and ethanol appear here to stay does not mean natural gas vehicles (NGVs) are going away. On the other hand, unless there are major technological breakthroughs to increase their range dramatically or a colossal nationwide effort to expand the fueling infrastructure, they'll remain a primary choice only for fleets that are centrally fueled at their own pumps or that have ready access to public fueling facilities.

Natural Gas Vehicles for America (NGVA) points to these key facts:

• Over 150,000 NGVs now on U.S. roads

• Over 1,500 NGV fueling stations in the U.S. — over half available for public use

• Over 50 different manufacturers produce 150 models of light-, medium- and heavy-duty natural gas vehicles and engines

• About 22% of all new transit bus orders are for NGVs.

The fundamentals of NGVs are fairly straightforward — they operate on the same basic principles as gasoline-powered vehicles. Fuel is mixed with air and fed into the cylinder where it is then ignited by a spark plug to move a piston up and down.

Natural gas can power the same vehicles currently powered by gasoline and diesel — be they light-, medium- or heavy-duty. But because natural gas is a gas rather than a liquid at standard pressure and temperature, some modifications are required for an NGV. These changes mainly involve the fuel storage tank, fueling receptacle/nozzle and the engine.

Most NGVs use CNG, which is stored onboard under high pressure in tube-shaped cylinders attached to the rear, top or undercarriage of the vehicle. These cylinders meet rigorous safety standards, states NGVA, and are made of high-strength materials designed to withstand impact and puncture. In the case of fire, they are fitted with pressure relief devices (PRDs) to provide a controlled venting of the gas rather than letting the pressure build up in the tank.