Editor's Note: Jon D. Markman writes a weekly column for CNBC on MSN Money that is republished here on TheStreet.com.

Even though the market is throwing a temper tantrum this summer over the concurrent bursting of the private-equity bubble, the credit bubble and the real estate bubble, at least one truth remains self-evident: The world is still running out of oil, and the one-two punch of rising Asian demand and broadening environmental restrictions make both alternative and "clean" energy look increasingly like a sure bet.

To be sure, the alternative-energy field is filled with rogues, bogus elixirs and questionable technologies, including such weird ideas as harvesting the power of algae grown in giant plastic baggies. Yet there are quite a few serious efforts in the marketplace today that are well-grounded and potentially very profitable.

Over the next year, I'm going to try to guide you to the intersection of investment opportunity and the future of energy. We will try to make money by taking positions in companies with real-world solutions and also save money by exposing charlatans.

Cleaning Up

First up this week, let's take a look at a totally down-to-earth and already almost profitable idea -- developing and expanding the use of compressed natural gas (CNG) and liquefied natural gas (LNG) as a fuel for corporate and municipal trucks, buses and cars.

These fleets, which focus on making round trips every day between a central parking lot and a couple of nearby destinations, are called "return to base" vehicle applications in the trade, and account for a vast portion of total corporate and government driving, something like a $21 billion business in the U.S. alone.

Compressed natural gas is an exceptionally efficient fuel for return-to-base fleets, as analysts believe it produces 50% to 70% fewer pollutants and saves $5,000 to $20,000 in fuel costs annually per vehicle than diesel, the fuel most commonly used today.

There's just one company focused on this market, and it went public a month ago,

Clean Energy Fuels

(CLNE) - Get Clean Energy Fuels Corp. Report

of Seal Beach, Calif.

Founded 10 years ago by energy industry icon T. Boone Pickens, the company designs, builds, finances and operates fueling stations that supply CNG and LNG to fleet operators. It also helps customers buy and finance natural-gas vehicles and ensure that they get their full measure of government incentives for doing so. Through 168 stations, it already serves 200 fleets that operate 13,000 CNG vehicles.

The company makes money mostly by selling CNG and LNG and running fueling stations. It's a volume business, and Clean Energy aims to become the brand and sales leader. The plan is attractive in its simplicity. By leveraging the country's vast network of gas pipelines, Clean Energy just buys supercooled liquefied natural gas from local utilities and then compresses and transports it to its fueling stations via tanker trucks.

Last year, Clean Energy lost $4.7 million on $91.5 million in revenue, but it appears to be right on the verge of a material ramp in profitability. It did earn money in the first quarter of this year, and if it wins a couple of contracts that are currently on the table with

Waste Management

( WMI) and the Port of Los Angeles, it could earn as much as 3 cents a share in the current fiscal year, 23 cents in 2008 and 60 cents to 84 cents in 2009.

If these estimates are anywhere near correct, we're talking about a little-known but well-established company led by a much-respected energy pro that dominates a niche where growth is likely to exceed 100%. And yet it trades at a price-earnings multiple, on 2009 estimates, of just 20. That seems a bit too good to be true, but what do you expect on the fringe? You're allowed to dream a little as long as you've got a firm foundation.

Good News for T. Boone

Now if you don't already know, Pickens is by no means a flower-powered Earth child. He launched his $2.5 billion fortune as a high-profile energy company takeover maven in the 1980s and more recently has run one of the nation's most successful commodities-focused hedge funds.

Pickens has been on a crusade of sorts lately, speaking out about the decline of fossil-fuel resources -- a topic known broadly as "peak oil" -- and the desirability of natural gas as an alternative.

With production at mature oil fields from the North Sea to Mexico seriously shrinking, and the lack of any recent significant oil finds, those warnings have hit home.

Just last month, the International Energy Agency announced its belief that crude oil will undergo a supply "crunch" after 2010 as production slows among non-OPEC nations. At the same time, global demand will continue to grow.

It doesn't hurt Pickens' position that other alternative fuels have experienced setbacks, as detailed in a recent WR Hambrecht analyst report.

Corn-sourced ethanol is struggling to account for 10% of the nation's fuel supply and has already inflated grain, meat and dairy prices. There are a lot of questions whether ethanol is even an alternative energy, since so much fossil fuel is required to grow and refine corn.

Biodiesel could work, but it still produces a lot of nasty nitrous-oxide emissions, and it is not likely to pass stringent new federal clean-air regulations set to arrive in force in 2010. Electric and gasoline hybrid engines remain expensive, and battery-life issues are unsolved. Hydrogen, while promising, remains in the pie-in-the-sky category, and it requires a lot of natural gas as a base fuel.

Efforts toward energy independence also help point the way toward natural gas. The U.S. imports three-fifths of its crude oil, and 90% of it is used in transportation. Natural gas is hard to transport overseas, so most of ours comes from domestic, Canadian and Mexican sources.

According to the U.S. Bureau of Transportation, there are 7.5 million fleet vehicles operating across the nation. Considering that three-quarters of them operate on a "return-to-base standard," Clean Energy's target market is potentially worth $20 billion per year in revenue.

TheStreet Recommends

Natural-gas vehicles are rare in private use here but much more common overseas. The International Association for Natural Gas Vehicles estimates that there are nearly 6 million NGVs worldwide, but only 150,000 or so are in the U.S. International popularity for the vehicles has been cultivated through a combination of clean-air mandates, high gasoline prices and large supplies of natural gas.

It's not hard to imagine, with a spate of clean air initiatives being proposed by individual states, along with calls for energy independence, that NGVs will gain popularity.

Moving forward, the big catalyst for Clean Energy will be the Port of Los Angeles' push to replace 5,300 of its oldest diesel trucks with ones powered by natural gas over the next two years.

Clean Energy has already won three out of the four contracts that the port has awarded for LNG terminals, and it is considered likely to win the fourth as well. The deal would boost annual gas volume by 32% in 2008 alone.

Other West Coast ports are said to be considering similar initiatives to help them comply with state regulations aimed at reducing carbon-dioxide pollution by 10% over the next 10 years.

When you add it all up, CNG looks like a promising transportation fuel for the next decade, and Clean Energy is emerging as its leading brand. My target for next year is $20, which would be a 40% move from the current quote.

But don't go wild with this stock or any others in this emerging field, and use a protective stop in case its promise doesn't materialize. Many new companies have tried to break the major oil companies' hold on transportation fuel, and most litter the roadside with failure.

Fine Print

Clean Energy buys gas from its own plant in Texas,

Williams

(WMB) - Get Williams Companies, Inc. Report

and

Exxon Mobil

(XOM) - Get Exxon Mobil Corporation Report

. The new California plant's supplier will be

Royal Dutch Shell

(RDS.A)

,

BP

(BP) - Get BP p.l.c. Sponsored ADR Report

or

Sempra Energy

(SRE) - Get Sempra Energy Report

.

At the time of publication, Markman was long Exxon Mobil, although positions may change at any time.

Jon D. Markman is editor of the independent investment newsletter The Daily Advantage. While Markman cannot provide personalized investment advice or recommendations, he appreciates your feedback;

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