"The Future of Pittsburgh," the ball that marked off the final seconds of 2006 as it rose above Penn Avenue and Stanwix Street last night, made its climb up the 74-foot pole using clean renewable energy.

That means the 6,000 watts of energy needed to lift and light the half-ton ball, and the resulting carbon dioxide, were symbolically offset by the purchase of renewable energy credits by two groups, Sustainable Pittsburgh and Citizens for Pennsylvania's Future, or PennFuture.

The groups made the purchase for less than $100, with the money going toward the purchase and operation of methane digesters for use on farms.

"We want to show people how easy it is to buy clean energy and make your life greener," said Jeanne K. Clark, spokeswoman for PennFuture.

They bought their credits through NativeEnergy, a renewable energy company, but Ms. Clark said homeowners usually can do the same through their electric company.

"What we hope will happen is that by buying renewable energy credits, you're supplanting some of the dirty energy," she said.

The ball, which is made of recycled materials, has 48 surface strobe lights, 72 internal halogen bulbs and 1,100 light emitting diodes.

The groups say the credits offset greenhouse gases associated with the energy used to light and raise the ball.