Hitting another milestone, the U.S. Department of Commerce issued its 5 millionth patent Tuesday.

Patent No. 5,000,000 was awarded to the University of Florida for a process its researchers developed to turn organic waste into a clean gasoline substitute.Commerce Secretary Robert Mosbacher said the milestone comes "at a time when the technological innovation encouraged by patent rights is critical to our international competitiveness."

"All Americans should make a renewed commitment to creativity in order to ensure that our country continues to grow and prosper," he said.

Mosbacher issued the 5 millionth patent to university President John Lombardi, after it was signed by patent and trademark Commissioner Harry Manbeck Jr.

The 200th anniversary of the U.S. patent system was celebrated last year.

Past milestone patents include:

-Patent No. 4,000,000, issued to Robert Mendenhall of Las Vegas, Nev., in 1976 for developing a recycling system for asphalt used in road surfacing. The system is now used in many parts of the country.

-Patent No. 3,000,000, issued to Kenneth Eldredge in 1960, for an automatic reading device, which led to the electronic check-reading system now used by most banks.

-Patent No. 2,000,000, given to Joseph Ledwinka of Philadelphia, Pa., in 1935 for an automobile wheel rim that permitted tires to be more securely fastened.

-Patent No. 1,000,000, issued in 1911 to Francis Holton of Akron, Ohio, for a solid automobile tire thought at the time to be a possible replacement for air-filled tires.