If you are looking for ways to put a little green in your wallet by putting some green in your portfolio, you might be surprised at the wide range of offerings available for your consideration. Let’s take a look at 10 interesting areas, which are highlighted below.

Wind

Windmill farms are sprouting up around the world. Australia, Europe and the United States are all investing in wind as a leading source of renewable energy. The business of wind not only includes the generation and sale of power, but also the design and construction of wind turbines. Few countries rely on wind for more than a tiny fraction of their power generation needs, but many countries are interested in the possibility.

If this is of interest to you, look for wind farm companies that sell wind-generated energy or companies that produce the windmill technology. There are few pure play stocks that deal in wind in the U.S. which will likely change over time, but companies like General Electric (NYSE:GE ) have a presence in this market.

To see the power of water, one needs look no further than China’s massive Three Gorges Dam project. While this $25 billion structure on the Yangtze River will be the largest hydroelectric power station in the world, it’s sure not the only one. Hydropower involves a lot of technology, a lot of infrastructure and a lot of power-hungry customers. Every one of those areas holds potential opportunities for investors. On the power side, two publically traded producers include PG&E Corp. (NYSE:PCG ), which has one of the largest hydro operations and Idacorp (NYSE:IDA ), which has 17 hydro projects. (For related reading, see Water: The Ultimate Commodity .)

Solar Energy

Solar energy is powering homes, buildings and a variety of other items from lights to radios. As the cost of fossil fuels continues to rise and their availability continues to decline, the future looks bright for solar energy.

If you think the sun is just starting to rise on this industry the companies to look at are those that produce solar energy panels, which will benefit if homeowners and businesses adopt solar technology. Two of the leading producers of solar panals are Evergreen Solar (Nasdaq:ESLR ) and Sunpower Corp. (Nasdaq:SPWR ), which both develop, manufacture and sell panels and components and will directly benefit from the increased adoption of solar power.

Fuel Cells

On a smaller scale, researchers are working with fuel cell technology to develop an alternative method of powering automobiles. The U.S. government hopes that hydrogen powered cars will be commonplace by 2020. If this technology works, there are millions of cars — and millions of consumers — waiting for it.

If you think this is the type of energy is the wave of the future there are a few companies that operate in the space and and develop fuel cell technology. For example, some of the largest producers include Ballard Power Systems (Nasdaq:BLDP ), which produces cells that can be used in from cars to power plants, and Fuel Cell Energy (Nasdaq:FCEL ), which focuses on providing power options to commercial and industrial facilities. (For related reading, check out Getting A Grip On The Cost Of Gas .)

Efficiency

Just about every aspect of efficiency is good for the environment. Energy efficient construction and appliances reduce home energy use and energy efficient cars reduce our dependence on oil. From efficient lighting to creating the paperless office, innovative companies are developing innovative products that maximize the benefit that we get from the resources that we use. Efficiency is the watchword of the day and a developing field that will create the technologies that we will use tomorrow. (For more insight, see For Companies, Green Is The New Black .)

This area is a little more difficult to invest in as there are no real pure play companies dealing strictly in efficiency. However, there are some companies that have done a great job at leveraging efficiency such as General Electric with its Ecomagination business unit.

Pollution Controls

Reduction is the key term here. From reducing green house gas emissions on industrial power plants to minimizing the emissions that come out of the tailpipe of your car, the pollution control industry is on the rise. Every time legislation mandates an improvement in the amount of some harmful chemical that can be released into the environment, the pollution control industry responds.

If this is something you are concerned about, look for companies that develop pollution control technologies such as Fuel-Tech (Nasdaq:FTEK ) and Versar (AMEX:VSR ).

Waste Reduction

Recycling has become a standard practice for many people in recent decades. The stuff that was formerly thrown away and trucked off to the landfill is now turned into useful products. Most people are aware that household products such as paper, metal and glass are reprocessed and reused, but they never stop to consider the business behind these endeavors. Of course, these aren’t the only items that are reused; waste oil, vegetable oil, batteries, cell phones, computers and even parts from cars can have a second life. Recycling these items involves a business enterprise humming along in the background. (To learn more, see Less Trash For More Cash .)

In terms of your portfolio, waste management companies with a large base of recycling facilities may be of interest including companies such as Allied Waste Industries (NYSE:AW ) and Waste Management (NYSE:WMI ).

Organics

Organic farms eschew the use of pesticides, engage in sustainable farming practices and sell products that are often healthier to eat than the stuff composed of three-syllable words that you can’t pronounce and a shelf-life measured in decades. They also engage in animal management practices that avoid the use of hormones and antibiotics, keeping those chemicals out of the food chain and out of the ground and water surrounding the farms. It’s good food — and good business.

With U.S. organic food sales reaching $17 billion in 2006, there is a huge market for organic food producers and grocery stores. Some of the biggest organic food companies include Whole Foods Markets (Nasdaq:WFMI ), United Natural Foods (Nasdaq:UNFI ) and NBTY (NYSE:NTY ) among others.

Best In Class

For many companies, the urge to go green is a relatively recent phenomenon. Like change everywhere, some firms adapt and some don’t. Investment managers in the green space have begun to categorize firms by the place they hold along the green spectrum. Take oil companies for example. One would be hard pressed to think of these firms as green, and for the most part, they aren’t. But if you take a closer look at their business models, it is easy to see that some are greener than others. Choosing the firms with the best environmental records and practices is another way of looking at green. (To learn more, read Can Business Evolve In A Green World? and Change The World One Investment At A Time .)

How to Grow a Green Portfolio

Editor’s Note. Please note that the companies mentioned in this article are examples to help you begin your research, not investment recommendations.