Paper Transport (PTI) is now testing two tractors equipped with prototype 12L compressed natural gas (CNG) engines supplied by Cummins.

One engine is installed in a Kenworth and the other in a Freightliner.

“The 12L CNG trucks are an important step forward for us as we look toward more widespread use of natural gas as a fuel for our trucks,” Jeff Shefchik, president of Paper Transport, said.

The engines offer horsepower and torque equal to commonly used Class 8 diesel engines, PTI said. The company said it expects the vehicles to be used in higher weight applications and environments where hills are common.

“The full use of CNG trucks had been somewhat limited by the fact that the 9L engine was all that was available for a 100% CNG power unit,” Shefchik said. “The 12L’s capability to handle steeper grades will be a nice feature.”

Full production of the 12L CNG model is not expected until the first quarter of 2013.

Earlier this year, PTI began testing a dual-fuel system from American Power Group (APG), a subsidiary of GreenMan Technologies.

APG’s dual-fuel system converts diesel engines to run on both diesel fuel and up to 60% of compressed natural gas, liquefied natural gas, well-head gas, or bio-methane. Paper Transport is testing the system on a 2009 Freightliner Cascadia running a 14.8L Detroit Diesel DD15 Series engine.

Paper Transport has been utilizing CNG tractors since February of 2010.

PTI is a Green Bay, WI-based truckload carrier offering dry van, dedicated operations, intermodal drayage, and brokerage services.