Forget noxious fumes and choking smog. Feed your car soy sauce, and the streets will be filled with the aromas of home cooking. That's the message US soybean growers are trying to promote as they urge drivers to embrace soy-based biodiesel fuel as an environmentally friendly alternative to stinky petroleum, the Reuters news agency said.

"The exhaust smells like cooking French fries or tempura," commercial consultant Greg Olwig told a symposium in Tokyo on Tuesday organised by the American Soybean Association, Reuters said.

According to the news agency, Olwig was in Tokyo to sing the praises of a renewable fuel that is biodegradable, non-toxic and free of sulphur. Soy-based biodiesel is said to offer similar fuel economy, horsepower and torque to petroleum-based diesel.

"Biodiesel is not a new idea," Olwig reportedly said. "When Dr. Rudolph Diesel developed the diesel engine over 100 years ago, it ran on vegetable oil."

Reuters noted that biodiesel use across the United States swelled to about 60 million litres (13.2 million gallons) last year from 2.3 million litres (500,000 gallons) in 1999 as producers promoted home-grown energy sources over foreign oil.

The fuel can be made from any fat or vegetable oil, but about 90% of US biodiesel comes from soybean oil, the report said.