Berkeley has ended its six-year attempt to save the world by burning biodiesel in its trucks and machinery amid concerns it actually increases greenhouse gases worldwide and exacerbates hunger.

The city stopped receiving shipments of biodiesel derived from soy bean crops last month.

The City Council will consider formalizing its policy on the matter in September.

"Four years ago we looked at this and thought it was a really good idea to do biofuels when there were no crop-based biofuels, but the situation has changed beneath us," said Robert Clear a member of the city's Community Environmental Advisory Commission which recommended the city change its policy on biofuels.

In 2003, the city started using 100 percent biodiesel in its more than 100 cars and trucks that run on diesel fuel. But that biodiesel was derived from recycled frying grease. Over the years, the supply changed to a crop-based biofuel.

New thinking on that product and its implications for global warming have changed for the worse.

Although biodiesel pollutes less than regular diesel when it comes out of a tail pipe, the farming involved to produce crop-based biofuels actually increases pollution worldwide, city officials say.

Clear said American farmers who are now converting their crops to grow soy beans to meet the biodiesel demand are decreasing the amount of land used to grow food for people and cattle.

That in turn has caused an increase in demand for land to grow food in South America and South East Asia where farmers are burning down virgin forests. The burning of the forests releases carbon into the atmosphere and there is a decrease in the amount of carbon the plants suck out of the atmosphere: two big negatives for global warming.

Add that to the fact that American farmers are growing less food because they are using their land for biodiesel production and you have a crimp on worldwide food supplies that contributes to global hunger problems.

Both of those issues are something Berkeley policy makers don't want on their save-the-world agenda even though local pollution is reduced when their trucks are burning biodiesel.

"It no longer looks like a thing to encourage," Clear said. "It's really too bad, because we'd love to see some magic bullets."

One option is going back to using biodiesel from recycled fryer grease, but there just isn't enough of it to go around and it's hard on the engines, said Deputy Public Works Director Andrew Clough.

In 2005 the city had two diesel truck engines explode when the city got a bad batch of biodiesel made from recycled fryer grease.

"Right now it doesn't sound like there is a good option," Clough said. "What seemed like a really good idea maybe isn't such a good idea as we thought because of all the considerations."

Reach Doug Oakley at doakley@bayareanewsgroup.com