While investors appear hungry for social networking IPOs — as seen with the LinkedIn (NASDAQ: LNKD) offering recently that was priced almost 85% below where it opened — there is another hot sector that is getting attention:  cleantech.  Of course, with persistently high oil prices and instability in the Middle East, the industry continues to attract capital.

And over the past year, there have been a couple strong IPOs in the sector.  Granted, they all have common issues.  For example, the losses are substantial.  What’s more, it is far from clear that the new-fangled clean energy technologies will be able to get adoption in the marketplace.

Then again, this is common for any new industry, right?  So if you want to get some exposure to cleantech and the emerging “green” companies of the alternative energy revolution, here are some options:

Solazyme

Solazyme (NASDAQ: SZYM) has a technology system that turns algae into high-value oils.  The applications are quite broad, such as fuels/chemicals, nutritional products and skin care.  No doubt, these markets represent trillions in value.

To produce its oils, Solazyme uses industrial fermentation equipment.  The company believes that this approach will be able to manufacture oils at $3.44 per gallon or $0.91 per liter.

Last year, Solazyme launched its first commercial products.  It was a line of dietary supplements, called Golden Chlorella, which you can find at places like Whole Foods (NYSE:WFM) and GNC (NYSE:GNC).

Solazyme has also been aggressive in forming partnerships.  These include deals with Dow Chemical (NYSE:DOW) and Chevron (NYSE:CVX).

Amyris Biotech

Amyris Biotechnologies (NASDAQ:AMRS) has systems that genetically modify microorganisms, such as yeast.  These become “living factories” that become target molecules.  One of the results is better medicines.  For example, Amyris is focusing on an anti-malarial therapeutic.  This is based on a grant from the Bill & Melinda Gates Foundation.

However, the company’s technology can be used for other areas.  These include cosmetics, perfumes and even transportation fuel.

Amyris system has several advantages.  First, it relies primarily on Brazilian sugarcane as the feedstock.  This is abundant and low cost.  Besides, Amyris has been striking contracts to lock-up supply.

Next, the company has a capital-light strategy.  That is, it uses existing infrastructure to produce its molecules, such as with Brazilian ethanol and sugar plants.

Gevo

Gevo (NASDAQ: GEVO) develops biobased products that are an alternative to petroleum products, with a focus on specialty chemicals.  The company thinks its offerings will be price competitive and more environmentally friendly.

The company’s system is called Gevo Integrated Fermentation Technology or GIFT.  It involves a complex process of biocatalysts, chemical separations and fermentation.  In fact, GIFT is made to be used in traditional chemical plants, which certainly helps with customer adoption.

Already, Gevo has signed contracts with a variety of major customers.  Some examples include Lanxess, Total Petrochemicals USA, United Airlines and Toray Industries.  The plan is to begin commercialization in the first half of 2012.

Tom Taulli’s latest book is “All About Short Selling” and he has an upcoming book called “All About Commodities.”  You can find him at Twitter account @ttaulli. He does not own a position in any of the stocks named here.