U.S. rail operator Amtrak may have given the term "cattle car" a whole new meaning with the first test of a biodiesel train that runs on beef byproducts.

Operating on a $274,000 (£178,000) grant from the Federal Railroad Administration, the state-owned rail company has begun operating its daily Heartland Flyer train, traveling between Oklahoma City and Forth Worth, using B20 biodiesel fuel.

The fuel, which mixes 80 percent diesel with 20 percent biofuel, cuts both hydrocarbon and carbon monoxide emissions by 10 percent, according to the company, which said that the fuel also reduces particulates by 15 percent and sulphates by 20 percent compared to standard diesel fuels.

The biodiesel, which was refined from beef byproducts provided by a Texas supplier, will run as a 12-month experiment, during which Amtrak will collect data on emissions, and on the impact of the fuel on mechanical parts.

Although technically the fuel mix can run in unmodified trains, the locomotive was fitted with new engine assemblies so that detailed measurements could be taken to establish the effect of the fuel on the engine.

The impact of biofuel blends on engines can vary dramatically, with some biofuels leading to increased wear and tear, while others tend to burn cleaner and lead to improved engine performance and durability.

Amtrak is now promoting the biodiesel train to passengers with a 50 percent discount on a companion fare until May 28.

The biodiesel trial is the latest in a series of environmental initiatives from Amtrak designed to highlight the operator's position as a green alternative to domestic U.S. flights.

The company has switched from low-sulphur fuel to ultra-low sulphur fuel across the railroad to tackle air pollution, and has installed recycling receptacles in its trains and stations. It has also stepped up efforts to reduce idling times for its diesel trains, and has introduced regenerative braking systems for its electric trains similar to those in hybrid cars, such as the Toyota Prius.

In addition, the company is a member of the Chicago Climate Exchange and has a public commitment to reduce emissions by 7 percent in 2011 and 2012.

Image courtesy of Amtrak. This article originally appeared at BusinessGreen.com and is reprinted with permission.