One of the easiest ways to help clean the air is to buy more environmentally friendly fuels, such as biodiesel or ethanol.

But doing so is not that easy -- at least not yet -- in North San Diego County and Southwest Riverside County.

For the moment, a filling station in central San Diego is the closest location in which alternative fuels are sold. That station is Pearson Fuels on 4001 El Cajon Blvd., off Interstate 15.

Biodiesel and ethanol typically are blended with conventional fuels.

Ethanol, an alcohol made from corn, is combined with gasoline. Biodiesel is a biodegradable fuel made from soybean and vegetable oils blended with petroleum-based diesel.

Most vehicles with conventional diesel engines are capable of running on biodiesel, said Mike Lewis, general manager and owner of Pearson Fuels. But vehicle owners must join a biodiesel users group before they can fill up.

As for the 85 percent ethanol blend Lewis sells, it is only supposed to be used in flex-fuel vehicles designed to safely switch between ethanol and gasoline, Lewis said. He said there are about 500,000 such vehicles on the road in California and 30,000 in San Diego County.

"We won't turn the pump on for you if you don't have the right car," Lewis said.

To be sure, driving to central San Diego to fill up on biodiesel or ethanol may not be all that helpful for the environment. Still, Pearson Fuels may be an environmentally friendly option for the many commuters who work in San Diego and have the ability to go there without wasting gallons of fuel.

In a few months, options closer to home may emerge for those who don't work in San Diego. That's because Lewis is planning to expand. Lewis said he has obtained the required permits to build an ethanol station in the Bressi Ranch area of Carlsbad. He is aiming to open in March.

Lewis also said he is preparing to build a similar station in Oceanside that could open next summer.

"I think ultimately these biofuels will take off," Lewis said. "When they do, everybody is going to be trying to build stations."

Ethanol also could be coming to Southwest Riverside County around this time next year.

"I am in final negotiations to put one on the freeway in Sun City," Lewis said.

At the San Diego station, Lewis sells a type of fuel called E85, so named because it is a blend of 85 percent ethanol and 15 percent gasoline. That particular blend, which is what he proposes to sell in Carlsbad, Oceanside and Sun City, is available to vehicles designed for it.

But the situation is different for truck owners who want to pour biodiesel into the tank.

"It is technically an experimental fuel," Lewis said.

One must first sign up with the Southern California Biodiesel Users Group through either the group's or station's Web sites, before fueling up at Pearson. Lewis said about 500 people have registered.

Unlike its ethanol product, Pearson doesn't sell a blended version of biodiesel. Rather, the liquid coming out of the nozzle is 100 percent biodiesel, and truck owners must mix it on their own with regular diesel.

Meanwhile, the local franchise of a Canadian company is gearing up to make a splash in biodiesel development.

The Oceanside branch of Vancouver-based 1-800-GOT-JUNK, a company that hauls junk from people's homes and takes it to recycling centers or a landfill, has signed on to test the fuel. Bill Cox of Oceanside, the franchise owner, said biodiesel will be used in one of eight trucks for the next six months.

Cox said his plan is to fill up the Oceanside-based truck regularly with a blend of 20 percent biodiesel and 80 percent diesel. He said he will track the mileage and watch for problems the fuel may cause, although he is confident none will surface.

"I don't think it's going to be any cheaper. It may even cost me some more money," Cox said. "But I don't even care at this point. It's going to be good for Mother Earth."

Lewis said biodiesel and ethanol are going to benefit Earth for years to come.

"There is a lot of talk about hydrogen, but it is so far down the road," Lewis said. "Ethanol and biodiesel are available right now."

Contact staff writer Dave Downey at (760) 745-6611, Ext. 2623, or ddowney@nctimes.com.