I attended a Propane Alternative Energy conference here in Rochester, NY and want investors in CLNE to know that it is a formidable alternative to natural gas as automotive fuel. While natural gas has been touted as the fuel for America due to supplies in the ground and the infrastructure to deliver it, propane is a secret companion (about 15%) to natural gas, being separated at the well head in some cases or at a processing plant prior to feed the natural gas into the distribution system.

The principal arguments for propane is that it only requires compression to about 140 psi for storage in vehicles and is practically non-flammable should there be an accident that causes puncture to the tank. Should this happen, the gas is too concentrated to burn near the vehicle and disperses rapidly in the air. Its volumetric energy is about 60% that of gasoline, and the total volume of tanks that can conveniently be mounted in a car or light truck is 60 gallons, however, only about 60% of the propane can be removed as a liquid before there is only gas left in the tank. This making its range before refueling equal to what your car can get with 24 gallons of gas.

In contrast, natural gas is liquified at about 3000 psi, meaning the tanks have to be constructed of carbon fiber laminates that are costly, while propane tanks can be made from steel, albeit 1/4" thick.

The advantages of propane that it shares with natural gas also means an extremely clean engine with no dilution of the engine oil. If a longer lasting oil for viscosity reasons is used, it is easy to get 70,000 miles per oil change. Engines should routinely last for 300,000 miles before rebuilding.

Propane refueling stations will be showing up in Conoco=Phillips gas stations, but a person can also get refueled from a propane dealer. Fleets of trucks will be served by private refueling stations and FedEx is looking into converting to propane.

Therefore,I see the nation's fleet going into both natural gas conversion and propane. I am sure that Clean Energy Fuels is aware of these issues, but I would recommend they embrace propane, if nothing else as a backup fuel, since running out of fuel on the road can be a real problem for delivery by roadside assist vehicles while propane has the upper hand here as well.

While conversion of gasoline engines to propane is available in the after market, Ford is now offering trucks with the conversion already implemented. School bus propane fleets will crop up in the next 3-5 years as replacements are needed. I do not see the conversion of fleets to natural gas occurring as smoothly in the country driving situation. Therefore, we're seeing heavy truck fleets moving into natural gas with refueling occuring primarily on major expresswayps.

I have therefore decided to split my alternative energy investments between CLNE and FSYS and watch the race between these two fuels from a comfortable seat in the grandstand.