If you’ve bought all the squiggly light bulbs and reusable hemp grocery bags you can handle, but you’re still looking for ways to “go green,” try taking a look at your investment portfolio. Screening for eco-friendly companies is becoming more common as the socially responsible investing phenomenon continues to gather steam.

Socially responsible investing refers to the practice of investing in financially strong companies that also make positive contributions to society in terms of environmental, social, and governance issues. For example, Dell (NASDAQ:DELL) offers its customers free equipment recycling and has been influential in the passage of legislation mandating recycling programs in several states.

Open-source leader Red Hat (NYSE:RHT) was recently recognized by Network World as having a “greener” operating system versus the competition, based on its lower power consumption. In addition to a more efficient operating system, the company’s virtualization technology can help customers reduce the amount of energy needed to power and cool data centers by enabling server consolidation.

Chip manufacturer Intel (NASDAQ:INTC) has been addressing climate change since 1993 through its efforts to reduce ozone-depleting substances, as well as its advocacy of environmental initiatives in the semiconductor industry. Earlier this year, the EPA recognized Intel’s support of renewable energy, placing the company at the top of its Fortune 500 Green Power Purchasers list.

While there is certainly a “feel-good” element to engaging in environmentally friendly business practices, there is also a more practical reason for publicly traded companies to follow the lead of Dell, Red Hat, and Intel: money. Lots of it.

According to Social Investment Forum, in 2007, more than $2.7 trillion was invested using socially responsible criteria. That’s more than 10% of all assets professionally managed in the U.S. With invested assets in socially responsible programs increasing by 27% compounded annually over the last six years, companies can’t afford to ignore this large and growing source of capital.

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