The global oil supply is set to run dry 90 years before alternatives become available worldwide, a new study suggests.

The global oil supply is set to run dry 90 years before replacements such as renewable energy are ready to satisfy the same amount of demand, according to the study by researchers at University of California, Davis.

The researchers came to the conclusion after examining the following factors:

-- Activity from long-term investors as a predictor of whether and when the burgeoning technologies would go mainstream;

-- Existing public companies dealing in non-oil fuels such as BlueFire Ethanol Inc. of Irvine and Enova Systems Inc. of Torrance; and

-- The value and dividends of public companies in both the oil and alternative energy markets.

There are many predictions of when oil could run out, but also many, many factors that could feed into a timeline for depletion," said Deb Niemeier, a professor of civil and environmental engineering. "For example, whether consumption patterns stay at the level, whether new (oil) fields are found, how much technology improves for harvesting less accessible or economic fields now, and so forth."

Current policies that set targets for batteries, hydrogen, biofuel and other alternative energy sources won't be enough, the researchers noted.

The study was published in the Nov. issue of the journal Environmental Science and Technology.