More than just a deliverer of parcels, the United States Postal Service (USPS) is recognized as an innovator in fleet management, automotive technology and alternative fuel use. At the same time, however, the Postal Service has a reputation for being a tremendous consumer of fuel. It currently operates the largest motor vehicle fleet in the nation, consuming approximately 93.5 million gallons of gasoline and 34 million gallons of diesel fuel per year.

Searching for ways to offset emissions and cut back on its consumption of petroleum fuels, the USPS began operating flexible fuel vehicles (FFVs)-cars and trucks designed to run on ethanol-gasoline blends as high as E85-in the early 1990s. Today, the Postal Service operates the largest FFV fleet in the world.

Riding on its success with ethanol-blended gas, the USPS established an aggressive strategy for evaluating and implementing the use of biodiesel blends. The Postal Service started using biodiesel blends in its fleet vehicles in 2000, in part to assess the viability and cost effectiveness of the fuel and in part to comply with the federal Energy Policy Act of 1992 (EPAct). EPAct required that by 2004, 75 percent of all new light-duty vehicles acquired by U.S. government agencies be capable of operating on-but not necessarily using alternative fuels. In 2004, the USPS met and exceeded that requirement with 79 percent of its fleet vehicles running or able to run on alternative fuels. "The USPS has met or exceeded the requirements of EPAct every year-a fact that we're very proud of," said Han Dinh, USPS program director for vehicle engineering.

With biodiesel playing a significant role, ethanol, compressed natural gas and electric-powered vehicles were also large factors in meeting the requirements set by the federal government.

Since 2000, USPS fleets have steadily increased their collective use of biodiesel by using B20 in heavy-duty fleet vehicles in various regions of the country. In fact, over 941,000 gallons of B20 were used to fuel USPS fleet vehicles in 2004, compared to roughly 400,000 gallons of B20 in 2000.

Biodiesel research
In an effort to evaluate the performance of biodiesel, the USPS teamed up with NREL in 2004, conducting a research project designed to critically evaluate the effects of using B20 on engine systems. The results were compared to the effects of conventional petroleum diesel use.

Primarily, the USPS wanted to document the effects of biodiesel's enhanced lubricity characteristics and how that might lessen mechanical wear on engine components, in addition to evaluating B20's compatibility with non-metal engine parts, its solvent characteristics, deposit-forming tendencies and corrosive potential. Throughout the duration of the project-which was the first of its kind performed in the United States-NREL's primary role was to handle the assessment and evaluation of test vehicles. "This study has been very important," Dinh said. "It is the first [fleet study of its type] where engines have been completely torn down and evaluated."

Four fleet vehicles, all from the Miami area, were used in the project. The vehicles involved were two identical 1996 Mack Tractor semi trucks and two identical 1993 Ford nine-ton cargo vans. These vehicles all had similar mileage and had been operating on conventional diesel until 2001 when they started running biodiesel blends. The test vehicles were compared to four other identical vehicles, which had been operating exclusively on conventional diesel in similar conditions. The Mack semi trucks used in the study were used to pull full-size trailers from airports to local distribution centers; the routes were mainly short, resulting in mostly city highway miles. The Ford cargo vans were used to transport items between major USPS facilities. These routes were long, resulting in mostly interstate highway miles.

As part of the analysis process, the engines from the B20-fueled trucks and the petroleum-fueled trucks were removed from their chassis and evaluated using defined protocols. After each engine was disassembled, they were inspected for wear, breaks and other structural/mechanical damage. Each engine was also checked for any accumulation of dirt, sludge and carbon deposits.

Project findings, which were finalized in the first quarter of 2005, found "mixed results," Dinh said, but were fundamentally positive. In fact, the only negative effects associated with B20 stemmed from what the USPS believes was a case of fuel contamination.

In biodiesel's favor, initial results indicated that there were no significant mechanical issues or adverse operating conditions resulting from the use of B20 in the Ford cargo vans. "We didn't see any major differences … between the cargo vans," Dinh said.

The Mack semi trucks also showed no signs of any mechanical issues; however, some fuel system issues did arise during the study. "The Mack [trucks] using biodiesel had issues with the fuel system plugging," Dinh said. "We will be researching this problem further, but believe that there was some sort of fuel contamination in the [vehicle] fuel tanks that caused the clogging." The USPS has since been working with Mack engineering to work on solutions to correct the problem.

Another upshot for biodiesel was the fact that the report categorized conditions of engine wear on all the tested vehicles as "normal" for the length of service and accumulated mileage of the vehicles.

After the testing was complete, the Mack semi trucks were rebuilt and put back into service. The Ford cargo vans, which were at the end of their life cycle, were torn down and scrapped.

A number of new cargo vans that will replace the ones used in the study and others like them will operate on B20, Dinh said. The cargo vans used in the study burned both B20 and conventional diesel during their life cycles, and were 10 to 12 years old. With the new vehicles, the USPS will be able to study how B20 would affect an engine from the beginning to the end of its life cycle.

Dinh presented the initial results of the project at the 2005 National Biodiesel Conference & Expo in February. "The results from this one-of-a-kind study have sparked a lot of interest in the biodiesel industry," Dinh said, adding that the Postal Service will continue to share the practical knowledge it gained through the study with other vehicle fleet operations, as well as the industry and the pubic.

The future of biodiesel and the USPS
The Postal Service expects its use of biodiesel to rise significantly in the coming years due to the recent federal biodiesel tax incentive, future prospects of lower biofuel costs and a more readily available commercial biodiesel refueling infrastructure. In 2004, the USPS consumed slightly less biodiesel than it did in 2003. But Dinh said the decrease was caused by a number of fleet trucks being taken out of service because they had reached the end of their life cycle, as well as the limited availability of biodiesel in some areas of the country. As the price of biodiesel becomes more competitive-especially in the face of record-high petroleum prices-USPS expects to operate more vehicles on B20 in additional sites across the nation. "We have a couple of new projects getting underway and more are sure to come," Dinh said.

While the latest study was conducted in the Miami area, and USPS fleet use of B20 has been largely confined to the Manhattan, Detroit and St. Louis areas, Dinh said the next USPS biodiesel project will be open to the entire nationwide fleet. The project will seek USPS fleet managers willing to run biodiesel blends in their vehicles for a certain amount of time. The USPS Vehicle Engineering Department will then run tests on the vehicles used in the program. Tests would include taking oil samples, inspecting fuel tanks containing biodiesel blends, and checking engine wear. "There has been a very receptive response so far," Dinh said. "Many areas such as Denver, Oklahoma and Alabama have shown interest in participating."

In addition, the USPS and NREL are planning to team up again soon on a biofuels emissions study involving both biodiesel- and ethanol-blended fuels.

Dinh said the USPS is also interested in testing the effects of biodiesel blends in smaller vehicles. To date, most biofuels-related fleet testing has been performed on relatively large trucks and vans. The smaller home and business delivery trucks have reportedly not been studied in the same way. The USPS has recently purchased 10 new Jeep Liberty CRD sport utility vehicles for residential mail delivery and, in the future, these or similar diesel-powered vehicles could be evaluated.

In the not-to-distant future, the USPS hopes to see most of its massive fleet using alternative fuels. It's an ambitious objective that would take years to achieve. "It is a major challenge," Dinh said.

But then again, so is delivering 206 billion pieces of mail per year.

Kory Wallen is a Biodiesel Magazine staff writer and photographer. Reach him by e-mail at kwallen@bbibiofuels.com or by phone at (701) 746-8385.