When you pull the cord on the LEHR Eco Trimmer or Eco Blower, they sound much like your typical lawn implement. There is a bit of a buzz, but you will notice the lack of an overwhelming fuel smell and no smoke being emitted from the engine.

Those are two of the big selling points of the technology developed by Bernardo Herzer for his gas-powered yard tools.

"We're using propane to power small internal-combustion engines, which is a greener gas than other hydrocarbons like gasoline or diesel," Herzer told the Deseret News on Friday while standing on the exhibit floor of the True Value Fall 2009 Hardware Show at the Salt Palace.

"One of the great advantages of using a (fuel) like natural gas or propane is that (the vast majority of it) is made in this country," he said. "It absolutely reduces our dependency on foreign oil."

Herzer, a licensed sea captain, founded LEHR Inc. about five years ago and developed the small-engine technology after converting gasoline engines to run on propane while working aboard his research vessel in the North Sea.

He was awarded a patent for the technology to use propane to run small engines like the ones that power gasoline string trimmers and leaf blowers.

One of the major differences in the engines used in the LEHR tools is that they are four-stroke engines, rather than the less-efficient two-stroke engines often found in gasoline-powered, hand-held lawn tools.

"Two-stroke engines are not as sustainable as four-strokes," he said. "Thirty percent of the fuel in a two-stroke (engine) goes out of the tailpipe unburned."

He said the LEHR tools are about 35 percent more efficient than a comparable gasoline engine implements.

Though run on propane, the Eco Trimmer does require oil in the crankcase and has to be checked and refilled at periodic intervals.

LEHR trimmers cost about $200, while the blowers are about $235.

Herzer said that while two-stroke engines are still the predominant technology used in small-engine tools, he hoped to see a change in the industry because "(two-stroke engines) are the gross polluters of internal combustion engines today."

Technically speaking, two-stroke engines fire once every piston revolution, while four-stroke engines fire once every other revolution.

A "stroke" refers to the movement of the piston in the engine. Two-stroke means one stroke in each direction.

A two-stroke engine will have a compression stroke followed by an explosion of the compressed fuel. A four- stroke engine has one compression stroke and one exhaust stroke, with each followed by a return stroke.

Two-stroke engines do not use fuel efficiently and produce more pollution, he said.

Currently, the LEHR tools are sold in hardware stores nationwide and Herzer said he expects to introduce an environmentally friendly engine for lawn mowers and snow throwers sometime next year.

"By developing these technologies and bringing them up to market, today we give people the choice," he said. "Tomorrow, we won't have a choice.

"We have to do the 'green thing' or our children won't be here."

e-mail: jlee@desnews.com