August 21, 2008

Purdue report: Switching to biodiesel benefits Indianapolis buses

The report also suggests introducing more diesel-electric hybrid buses and a fuel containing 20 percent biodiesel would further reduce emissions and petroleum consumption.

"There are many reasons an organization would want to move toward biodiesel, including environmental benefits and reducing consumption of imported petroleum," said Gregory Shaver, an assistant professor of mechanical engineering.

Shaver prepared the report with doctoral student Dave Snyder and undergraduate Chris Satkoski.

The university's Technical Assistance Program at the Purdue Research Park arranged for the engineers to prepare the study for IndyGo Public Transportation Corp., which provides mass transit in Indianapolis. The report was presented to Indianapolis Mayor Greg Ballard earlier this month at Purdue's Ray W. Herrick Laboratories in a visit organized by the university's Energy Center.

The report compared bus operations in April 2006 and April 2007 to determine the impact of switching from standard diesel fuel, referred to as B0, to B10, which contains 10 percent biodiesel. IndyGo switched its entire fleet to B10 in 2007.

Officials wanted to know the impacts of switching to B10 and whether it would be advisable to replace B10 with B20, which contains 20 percent biofuel.

"In our assessment, we would recommend going to B20," Shaver said. "We also saw a significant benefit to using the diesel-electric hybrid buses, so we would recommend increasing the number of hybrids in the fleet. The best bang for your buck might be running B20 in hybrid buses, depending on the initial cost of hybrids compared to standard buses."

The researchers found that the 280-bus fleet's two diesel-electric hybrid buses increased miles per gallon by 30 percent compared with the conventional buses.

Going from B0 to B10 had virtually no overall effect on mile-per-gallon fuel economy in the fleet, said Shaver, whose research is based at Herrick Labs.

IndyGo buses consumed about 1.8 million gallons of fuel in 2007.

"Changing to B20 could potentially save IndyGo 360,000 gallons of fuel per year in foreign and non-renewable sources," Shaver said. "That equates to 770,000 gallons of crude oil needed to produce the fuel."

Modern engines in buses and cars do not need to be modified to use fuels containing less than 20 percent biofuels.

"Biodiesel is more environmentally friendly than standard diesel, 100 percent renewable and domestically available," Shaver said. "It can be made from different types of animal fats and oils from plants, including soybeans."

The fuel also is "nearly carbon dioxide neutral," meaning the amount of carbon dioxide absorbed from the atmosphere by the growing plants is nearly equal to the combined carbon dioxide released during combustion of biodiesel and the carbon dioxide emitted by vehicles transporting the fuel.

"If you switched over completely to biodiesel, you would see about a 50 percent reduction in carbon dioxide emissions, which is pretty substantial," Shaver said.

Biodiesel also is nontoxic, biodegradable and burns cleaner than standard diesel fuel, reducing unburned hydrocarbons, pollutants called particulate matter and carbon monoxide. Using B10 generally reduces particulate matter and carbon monoxide by 5 percent and unburned hydrocarbons by 10 percent. Switching to B20 would likely cut particulate matter and carbon monoxide by12 percent and unburned hydrocarbons by 20 percent.

Researchers also noted that biodiesel mixes well with conventional diesel.

The report does indicate that one anticipated negative environmental impact to burning B10 fuel is a modest increase - from1 percent to 3 percent - in the emission of pollutants called nitrogen oxides, which cause smog. These nitrogen–oxide emissions increase further for higher biodiesel blends.

"It is a concern, and it's one of the things we are working on in our research team for blends higher than 20 percent," Shaver said.

Engineers in Shaver's research group are working to develop engines that efficiently combust fuels that contain higher concentrations of biofuels, aiming to reduce nitrogen oxides and fuel consumption.

Shaver's research group sponsors include Cummins, the National Science Foundation and the U.S. Office of Naval Research.

Writer: Emil Venere, (765) 494-4709, venere@purdue.edu

Sources: Gregory M. Shaver, (765) 494-9342, gshaver@ecn.purdue.edu

Purdue News Service: (765) 494-2096; purduenews@purdue.edu

To the News Service home page