On the fringes of green technology

During the first oil shocks in the early 1970s, some inventors began to tout cars running vegetable oil. They were looked at with benign amusement but largely swept to the side when the price of oil dropped again in the '80s.

Now, biodiesel refiners are erecting refineries that produce 100 million gallons a year. So you never know. The following is a list of products and concepts emerging on the fringes of green tech that one day may be mainstream, or still outlandish.

The Segway and the NMG (pictured here) from Myers Motors have the same goal: to allow people to travel alone in small-energy efficient vehicles. They have a point--government stats say that roughly 77 percent of car trips in the U.S. involve only one passenger, said Howard Levine, CEO of Venture Vehicles, which is coming out with two-seater plug-in hybrids and electric cars.

But then there are the practical problems. Like, where do you put groceries? How do you convince buyers that they are safe? Who buys a car that can't give a group of people a ride? And with an obesity epidemic, do you want things like the Segway to displace walking? Oh, and check out the I-Unit, a motorized chair from Toyota's tech showcase in Nagoya.

While Segway has foundered, the world will see how the faster, more robust vehicles from Venture and others fare in the next few years.