The world is going green, from recycling and power generation to organic groceries and sustainable fisheries. Everyone, it seems – including climate change scientists, businesses, consumers and politicians – is interested in easing the burden humanity places on the environment.

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 available offerings. Here is a look at 11 top green investment areas, starting with various forms of renewable energy.

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

Green Power Investments

Green energy is a hot topic in a world concerned about the growing impact of climate change. Power generation that doesn’t rely on the burning of fossil fuels to heat our homes, fuel our vehicles or generate our electricity is the focus of a lot of attention and is creating a growing number of investment opportunities. Water, wind and solar are the current top contenders.

Water Stocks

One of the most important natural resources we have is water, a necessity for our survival. There is considerable fear that we are running out of clean water sources as the global population continues to grow. Cape Town, South Africa, is the first major metropolitan area predicted to run dry.

The European Environment Agency has also expressed concerns about the availability of water. The Agency notes that “Some 20 European countries depend on other countries for more than 10% of their water resources,” and five (the Netherlands, Hungary, Moldova, Romania, and Luxembourg) rely on rivers that flow in from other countries to provide more than 75% of their water. In the U.S., cities from Los Angeles to Miami are concerned about water scarcity as population growth and climate change take a toll on water resources.

These issues have created a clear opportunity to invest in companies that collect, clean and distribute water. The largest water utility company in the U.S. is American Water Works (AWK) and it has plenty of company. Aqua America (WTR) supplies water to nearly 3 million people, while ITT Industries (ITT) produces purification systems that help to make water drinkable. And, sticking with our water theme, these firms are just the tip of the proverbial iceberg.

If picking stocks is too much hassle, mutual funds provide additional ways to invest in water. The Calvert Global Water Fund (CFWAX) and the AllianzGI Global Water Fund (AWTAX) tap into water-based opportunities across the globe.

Exchange-traded fund offerings include the

  • PowerShares Water Resource Portfolio ETF (PHO)
  • PowerShares Global Water Portfolio ETF (PIO)
  • First Trust ISE Water Index Fund (FIW)
  • iShares Dow Jones U.S. Utilities Index ETF (IDU)
  • Summit Zacks Global Water Index (ZAXWTRX)
  • Invesco S&P Global Water Index ETF (CGW)

Water has also been the go-to resource for renewable energy for a very long time, beginning with the first-known water-powered grist mill in the 3rd century BC. Today, thanks to projects like China's massive Three Gorges Dam – a $25 billion structure on the Yangtze River that features the largest hydroelectric power station in the world – water is the world’s number one renewable energy source, according to the International Renewable Energy Agency (IRREA).

Hydropower involves a lot of technology, a lot of infrastructure and a lot of power-hungry customers. Each of those areas holds potential opportunities for investors. While there are few pure-play stocks in the hydro business, three publicly traded energy producers with notable amounts of hydropower in their portfolios include PG&E Corp. (PCG), which has one of the largest hydro operations; Idacorp (IDA), which has 17 hydro projects; and Brookfield Renewable Partners LP (BEP), a major renewable energy firm headquartered in Toronto, Canada.

Wind Power

After hydropower, the wind is the next most common source of renewable energy, according to the IRREA. Wind-generation farms are sprouting up around the world. Australia, Europe, and the United States are all investing in the 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. Currently, few countries rely on wind for more than a tiny fraction of their power generation needs, but many are interested in the possibility.

If this renewable interests you, look for wind farm companies that sell wind-generated energy or companies that produce wind turbine technology. Here again, there are few pure-play stocks that deal in the wind, but quite a few companies have a presence in this market. Some interesting companies include:

  • General Electric (GE)
  • NextEra Energy Partners LP (NEP)
  • Siemens Gamesa (GCTAY)
  • Vestas Wind Systems (VWDRY).

Further, the First Trust ISE Global Wind Energy Index Fund (FAN) provides a passive way to invest in wind energy.

Solar Energy 

Energy from the sun is powering homes, buildings and a variety of other items from lights to radios. As concern about fossil fuels continues to rise, the future looks bright for solar energy.

If you think the sun is just starting to rise in this industry, focus your attention on companies that produce solar energy panels, which will benefit as homeowners and businesses increasingly adopt solar power. Leading producers of solar panels include First Solar (FSLR), JinkoSolar Holding Co. Ltd. (JKS) and Sunpower Corp. (SPWR), which develop, manufacture and sell panels and components.

Of course, there’s more to solar than panels. From components to installation, a wide variety of businesses present investment opportunities, including:

  • Enphase Energy, Inc. (ENPH)
  • Sunrun (RUN)
  • Vivint Solar (VSLR)
  • Guggenheim Solar ETF (TAN)

Pollution Controls

The reduction is the key term here. From reducing greenhouse 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. This is the industry that responds every time legislation mandates an improvement in the amount of some harmful chemical that can be released into the environment. Companies that develop pollution control technologies include:

  • Fuel-Tech (FTEK)
  • Versar (VSR)
  • Market Vectors Environmental Services ETF (EVX)
  • PowerShares Cleantech (PZD)

Green Transportation

When it comes to transportation, Tesla (TSLA) is the first name on many people’s lists. While an attention-grabbing leader and exciting technology have kept this company in the news, it’s not the only game in town.

On a smaller scale, researchers are working with fuel-cell technology to develop an alternative method of powering automobiles. If this technology works, there are millions of cars – and millions of consumers – waiting for it.

Companies that operate in the space include Ballard Power Systems (BLDP), which produces cells that can be used in everything from cars to power plants, and Fuel Cell Energy (FCEL), which focuses on providing power options to commercial and industrial facilities.

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 businesses 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.

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 (AW) and Waste Management (WMI). Covanta Holding Corp. (CVA) takes a different approach, generating power by incinerating waste.

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 makes for good food – and good business.

Some of the biggest organic food companies include:

  • Whole Foods Markets (WFMI)
  • United Natural Foods (UNFI)
  • NBTY (NTY)

Aquaculture

Sustainable fishing is another food-related investment opportunity that is generating attention as the plight of the world’s overfished oceans impacts the human food chain. Marine Harvest ASA (MNHVF), a Norwegian firm with global operations, is an interesting play in this space. Australia has nearly a dozen publicly traded companies working in the area. Go fishing for an opportunity to invest.

Geothermal

Geothermal energy uses heat from the earth to produce clean energy.

  • Calpine Corp. (CPN)
  • Ormat Technologies Inc. (ORA)
  • U.S. Geothermal Inc. (HTM)

Top Environmental Policies

For many companies, the urge to go green is a relatively recent phenomenon. As with 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. In fact, several large oil companies are among the global leaders in promoting a tax on greenhouse gases and investing in energy sources that will help the world transition away from oil. Choosing the firms with the best environmental records and practices is another way of looking at green investments.

Green Up Your Portfolio

If a green investment catches your eye, there are plenty of ways to find a place for it in your portfolio. You don't have to choose individual companies to get into the area. Mutual funds, exchange-traded funds, stocks, bonds and even money market funds that focus on the environment are all available.