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.