"We have modest goals of replacing the whole petrochemical industry and becoming a major source of energy," Venter told an audience that included global warming fighter Al Gore and Google co-founder Larry Page.

"We think we will have fourth-generation fuels in about 18 months, with CO2 as the fuel stock."

Simple organisms can be genetically re-engineered to produce vaccines or octane-based fuels as waste, according to Venter.

Biofuel alternatives to oil are third-generation. The next step is life forms that feed on CO2 and give off fuel such as methane gas as waste, according to Venter.

"We have 20 million genes which I call the design components of the future," Venter said. "We are limited here only by our imagination."

His team is using synthetic chromosomes to modify organisms that already exist, not making new life, he said. Organisms already exist that produce octane, but not in amounts needed to be a fuel supply.

"If they could produce things on the scale we need, this would be a methane planet," Venter said. "The scale is what is critical; which is why we need to genetically design them."

The genetics of octane-producing organisms can be tinkered with to increase the amount of CO2 they eat and octane they excrete, according to Venter.

The limiting part of the equation isn't designing an organism, it's the difficulty of extracting high concentrations of CO2 from the air to feed the organisms, the scientist said in answer to a question from Page.

Scientists put "suicide genes" into their living creations so that if they escape the lab, they can be triggered to kill themselves.

Venter said he is also working on organisms that make vaccines for the flu and other illnesses.

"We will see an exponential change in the pace of the sophistication of organisms and what they can do," Venter said.

"We are a ways away from designing people. Our goal is just to make sure they survive long enough to do that."