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What's happening: Shares of Clean Energy Fuels Corp (NASDAQ:CLNE) are rocketing up today, pushing a 20% gain already. The company's stock has been both up and down huge already in 2015: 

CLNE Chart

CLNE data by YCharts

After more than doubling from the beginning of the year through May 1, it would lose half of its value by the beginning of July. However, it has come roaring back this week, up nearly 27% since Monday. 

Why it's happening: Clean Energy Fuels issued a press release this morning, detailing the strong growth in new and expanded stations for the refuse business. The company said it has already built 14 stations for this industry this year, and expects to build another 22 before year-end. 

The bottom line is, the refuse business has been one of the company's strongest growth markets for years, and by all indications, that growth is continuing, and may even be accelerating. One of the key drivers, beyond cost (natural gas is cheaper than diesel) appears to be the environmental benefit.

Not only does natural gas produce fewer tailpipe emissions than diesel and gasoline, but it can also be produced as a byproduct from landfills, and there is a lot of evidence that this biogas -- which Clean Energy sources from the waste removal industry and other sources and sells under the trademark Redeem -- is 90% cleaner than traditional fossil fuels. Landfill operators also reduce the methane emissions from their landfills by capturing this biogas, both to resell and to use. In other words, it's a classic "win-win" (as annoying as that phrase is). 

But back to Clean Energy's huge run-up: This marks the second day this week the company's stock has shot up 10% or more, and it's likely that we see more days like this ahead -- as well as days it drops 10% or more of its value. 

The reason why? Clean Energy Fuels remains a relatively speculative and higher risk investment, due to the volatility of oil and gas prices, and the slow pace of adoption of natural gas as a fuel for transportation. The company's fuel sales have consistently grown much faster than the rate of adoption -- indicating the company's huge head start over its competitors in scale and size is paying off -- but a lack of profits after years of spending for growth make it ripe for opportunistic traders. 

And with almost 20% of its shares held short as of the most recent data, there's a lot of potential volatility baked in. Today's announcement was positive, but the market's big reaction is probably as much short sellers exiting their positions as exuberant buyers snapping up shares. 

Keep the long view, and don't get too caught up in "noisy" days like this. Earnings for the second quarter will tell us more. The company is scheduled to report in early August. Stay tuned here for more. 

Jason Hall owns shares of and options for Clean Energy Fuels. The Motley Fool recommends Clean Energy Fuels. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.