“To justify that expense you have to drive a lot of miles every year and you probably need to have something that doesn’t have good mileage,” said Jack Falkenrath, product development manager for Go Natural.

In March 2011, the Environmental Protection Agency issued new rules for aftermarket conversion systems, expanding compliance options and making it less burdensome for manufacturers to get EPA approvals on systems for vehicles 2 years old or older. Those changes have led more companies to seek EPA approvals, giving fleets more choices. (See below.)

Kauss estimates it takes him 5 to 7 years to recoup his investment, but said the copper mine is turning to natural gas to reduce emissions and not to cut fuel costs. “By going from a gallon of gasoline to CNG, we’ve reduced emissions by 30%,” he said.

To convert vehicles to bi-fuel, Go Natural adds a dual injector system that fits into the factory injector ports on the engine, firing either gasoline or natural gas into the intake manifold. For dedicated systems they replace the fuel injectors with some that have more capacity. Go Natural also adds a wiring harness that snaps into the factory wiring harness to control the system, CNG tanks and a fuel interface module that houses a pressure gauge and emergency fuel shut off valve.