There are a number of obstacles that keep fleets from “going green.” Chief among them is “sticker shock.” Many alternative-fuel systems add a substantial, budget-busting up-front cost to a vehicle’s purchase price, ranging from $10,000 to $20,000 or higher, per unit to convert vehicles to run on a particular form of clean energy, including compressed natural gas (CNG), propane autogas, hybrid-electric, or all-electric power. These conversions not only take money, but time as well.

While many OEMs and upfitters can handle a conversion relatively quickly, it can add to the time it takes to be delivered to a fleet, delaying the time it takes to get the vehicle into productive, money-saving operation.

Even if a fleet manager and company management are willing to bear this up-front expense, often there isn’t the infrastructure to support the fleet, adding additional expense and time to install a fueling infrastructure for such fuels as CNG and propane autogas.

What if a fleet could transition to cleaner-burning fuel, with little (if any) extra cost? Would that make “greening” the fleet financially feasible?

For proponents of biodiesel the answer is a resounding “yes.” The alternative fuel can operate in most existing diesel engines without expensive conversions.

What is Biodiesel?
Simply put, biodiesel is an alternative, renewable fuel produced in the U.S. from plant oils (such as soybeans), animal fats, algae, or used cooking oil. The term “biodiesel” technically refers to pure fuel known as 100-percent biodiesel or B-100 before blending with conventional diesel fuel.

However, fleets that operate biodiesel don’t usually use pure B-100, but blends from B-5 (5-percent biodiesel-to-diesel ratio) to B-20 (20-percent biodiesel), which is the range many diesel engine manufacturers have approved for use in their engines.

As more engine OEMs have accepted biodiesel, so have more fleets, contributing to an upward growth in production, from 500,000 gallons in 1999 to 1.1 billion gallons in 2011, though production dipped from 2008 through 2010 during the height of the recession, before ramping back up to historic levels.

What do fleets that operate biodiesel think about the fuel? What has their experience been? What are their future plans?

Lambert St. Louis International Airport
● Sector: Government.
● Fleet Manager: Mike Bernich.
● Vehicle Types Using Biodiesel:
Includes more than 600 hp aircraft
rescue and firefighting (ARFF)
units, including specialized runway
snow removal equipment.
● Number of Vehicles Using
Biodiesel: 250.
● Biodiesel Blend: B-20.

Between 1987 and 1988, Lambert St. Louis International Airport launched an experimental biodiesel program using 20 test vehicles, with blends ranging from B-5 to B-40. Based on the results, Lambert fleet management determined B-20 was the best blend for optimal performance in the St. Louis climate. The program has since expanded to cover every piece of Lambert’s 250-unit diesel fleet.

Fleet Manager Mike Bernich discussed Lambert’s switch to biodiesel, and some of the unexpected challenges and benefits derived from the alternative fuel.

GRN: Why did you switch to biodiesel?

Bernich: For diesel engines, biodiesel was the logical choice because we did not have to convert any vehicle fuel delivery systems. Biodiesel is readily available, and we did not have to install any specialized pump dispensers.

GRN: What have been the results?

Bernich: To our operators, it was a seamless conversion. We haven’t heard complaints of power loss, and the slight drop in fuel economy is very negligible, offset by increased life of expensive components. Also, the drivers no longer complain about exhaust fumes (from conventional diesel) when starting vehicles in semi-closed buildings. They say it now smells like someone is cooking french fries in their vehicles.

GRN: What challenges have you

Bernich: The only challenge we have had was older equipment that was first run on [conventional] diesel. When biodiesel was introduced — due to the soot accumulating in the fuel system from the original fuel — the biodiesel flushed and cleaned the entire fuel system, initially requiring filter changes more frequently than a vehicle that was started on biodiesel. After several scheduled filter changes, we were able to return to manufacturers’ recommended filter change intervals.

For fleets with a higher-mileage or higher-hour unit that they’re considering moving to biodiesel, one of the key things you have to remember is that biodiesel is going to clean the soot out of the system. You’ll want to have extra filters available during initial changeover — depending on how much soot has accumulated in the system.

GRN: What are your future plans regarding biodiesel?

Bernich: As long as it is available and cost effective for us, our plans are to continue using biodiesel. It has reduced our overall maintenance costs due to longer wear life and it assists us in keeping emissions at a lower level than standard diesel. With federal mandates to lower the sulfur content of diesel, the use of biodiesel helps compensate for the loss of lubrication from the lower sulfur content, which we’ve seen helps increase engine life.


Enterprise Holdings
● Sector: Automotive.
● Fleet Contact: Lisa Martini.
● Vehicle Types Using Biodiesel:
Medium-duty shuttle buses.
● Number of Vehicles Using
Biodiesel: 500.
● Biodiesel Blend: B-5 through B-20.

In 2010, Enterprise Holdings, owner and operator of the Enterprise Rent-A-Car, National Car Rental, and Alamo Rent A Car brands, began converting its fleet of shuttle buses to biodiesel at airport locations in more than 50 North American markets. Overall, more than 70 percent of its buses now run on biodiesel, with approximately 50 percent using 5 percent biodiesel (B-5), and more than 20 percent using B-20. By the end of 2012, the company’s older buses will be replaced with new B-20-compatible models and more than 80-percent of its total shuttle bus fleet will run on biodiesel.

Lisa Martini, spokesperson for Enterprise Holdings, discussed why the company pursued biodiesel as an alternative fuel and the benefits it has derived from the switch.

GRN: Why did you commit to biodiesel?

Martini: It’s a commitment to our customers and our business to help build the clean-fuel market, embracing clean fuels and engine technologies to give it greater opportunity to become commercially viable. We’re testing a number of clean-fuel technologies, but biodiesel is one that is certainly becoming more available. We’re able to get it out there and make it available in many of our markets.

GRN: What have been the results?

Martini: Overall it has been positive. There hasn’t been any noticeable loss in power. In terms of fuel economy, the difference is negligible.

GRN: What challenges have you experienced?

Martini: We’re at the mercy of retail availability of fuel. So, availability in terms of retail and having suppliers to be able to provide us the fuel is really the biggest obstacles to transitioning our entire fleet.

GRN: What are your future plans with biodiesel?

Martini: We definitely want to transition all of our shuttle buses to B-20. So, we’ll continue to purchase chassis with B-20-compatible engines. We’ve made the commitment to biodiesel, and we plan to stay with that in our shuttles as part of our sustainability commitment.


The Biodiesel Standard (ASTM D 6751)

All engines are designed and manufactured for a fuel that has certain characteristics. In the U.S., the industry organization that defines the consensus on fuels is the American Society for Testing and Materials (ASTM). In the case of diesel fuel (and biodiesel), the responsibility for setting standards lies within ASTM Committee D02 on Petroleum Products and Lubricants. To assure that the standards are rigorous and robust, ASTM committee D02 is comprised of fuel producers, engine equipment manufacturers, and third-party interests (users, government agencies, consultants, et al). ASTM also uses a complicated ballot process in which a single negative vote is enough to defeat a ballot, so it is a true consensus organization.

An ASTM standard is not easily achieved. Some standards can take more than 10 years to gain agreement and be issued by ASTM.

ASTM fuel standards are the minimum-accepted values for properties of the fuel to provide adequate customer satisfaction and/or protection. For diesel fuel, the ASTM standard is ASTM D 975. All engine and fuel injection manufacturers design their engines around ASTM D 975. In cooperative discussions with the engine community early in the biodiesel industry’s development, engine manufacturers strongly encouraged the biodiesel industry to develop an ASTM standard for biodiesel fuel, which would allow them to provide their customers with a more definitive judgment on how the fuel would affect engine and fuel system operations compared to ASTM D 975 fuel for which an engine was designed.

In June 1994, a task force was formed on Burner, Diesel, Non-Aviation Gas Turbine, and Marine Fuels, with the expressed objective of developing an ASTM standard for biodiesel. The biodiesel standard, ASTM PS 121-99, was approved, and subsequently issued in June 1999 (See the ASTM website at In December 2001, ASTM approved the full standard for biodiesel, with the new designation of D-6751.

This standard covers pure biodiesel (B-100), for blending with petrodiesel in levels up to 20 percent by volume. Higher levels of biodiesel are allowed on a case-by-case basis after discussion with the individual engine company, since most of the experience in the U.S. thus far has been with B-20 blends.

The approval of this biodiesel standard, and the technical reviews necessary to secure its approval, has provided both the engine community and customers with the information needed to assure trouble-free operation with biodiesel blends.
Source: National Biodiesel Board

For Further Research

Check out these online resources on biodiesel to learn more:

● Biodiesel Basics:

● U.S. Department of Energy, Alternative Fuels Data Center:

● National Biodiesel Board:

About the author
Sean Lyden

Sean Lyden


Sean Lyden was a contributing author for Bobit publications for many years.

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