Biodiesel fuel, a renewable energy source, is beginning to integrate into the U.S. farming and trucking industries, the San Francisco Chronicle says.

Production of biodiesel fuel, manufactured from animal fats or vegetable oils, tripled in 2005 to 75 million gallons, the Chronicle reported. The United States uses almost 140 billion gallons of gasoline per year.

Government subsidies and a nationwide increase in fuel plant construction have many business owners experimenting with biodiesel fuel for vehicles with diesel engines.

Once far more expensive than petroleum, a sharp price increase for regular diesel makes biodiesel more attractive. The average gallon of biodiesel fuel costs between $3.00 and $3.50, the Chronicle said.

Sixty-five biodiesel plants are operating in the United States, and fifty more are under construction, the newspaper said.

The National Renewable Energy Laboratory found in a study that pure biodiesel fuel releases 78 percent less carbon dioxide than regular diesel.

A federal tax credit for users of biodiesel fuel was introduced in January 2005, the newspaper said.