An oil and gas private-equity investor used the expression “light green” recently to describe a type of alternative energy. The firm is also investing in that space. What is light green? It is, for example, investing in natural gas exploration in China with a goal of contributing to getting China off coal. It’s a hydrocarbon investment but it’s greener than coal. Thus, it is “light green.” This “light green” expression has been possibly the most helpful way to define the alternative-energy space. In 2006, Oil and Gas Investor noticed that many upstream-energy capital providers were also arranging financings for alternative-energy companies, such as Energy Capital Solutions‘ capital raises for Panda Ethanol. An “Investor’s Guide to Alternative Energy” (which is under way) and The Alternative Energy Investment Symposium (this Nov. 27-28 in NYC) were borne from that observation and Oil and Gas Investor’s experience in putting energy capital users in front of energy capital providers, and vice versa, plus parent Hart Energy Publishing’s downstream expertise with advising energy conglomerates (International Fuel Quality Center) and with advising on biofuels (Global Biofuels Center). In developing the Investor’s Guide and the Symposium, analysts, investors and capital providers alike have expressed difficulty with categorizing the myriad forms of alternative energy. In the “light green” example, natural gas can be an alternative energy. In the U.S., natural gas is considered cleaner than coal and some other forms of fuel and power generation. Yet, it is a hydrocarbon and not as clean as the sun and the wind. Generally, alternative energy is what it is: Energy that is an alternative to what is less-clean. Here are some more types of green. –Uber Green: Solar, wind. –Makes-Me-Feel-Better Green: Ethanol, which consumes natural gas in production, has a lower energy content than real gasoline and drives up the price of food but makes Americans feel they’re impowering Willie Nelson’s farmers and being socially conscientious. –Prius Green: This is an alternative energy that doesn’t make any noise. Celebrities once liked this but the paparazzi could not find them. –Goober Green: Methane gas from landfills. –Last-Week’s-Pizza-Under-The-Bed Green: Alt energy that was good last week but out of favor now, like nuclear power. –Green-Tea Green: Liquefied natural gas from Australia that is destined for Asian markets. –Ben & Jerry’s Green: Hand-crafted ice cream for which no fuel was used to make. Very trendy. –Golf Green: Rechargeable batteries. What types of green would you add? Meanwhile, make plans to join us at The Alternative Energy Investment Symposium this Nov. 27-28 in NYC at the Sheraton Towers in Times Square for both capital providers’ and capital users’ views of viable alternative-energy investment opportunities.