I’m guessing that if you polled self-described “green” advocates about their least favorite green technology, biofuels would be at the top of the list. Out of all the forms of renewable energy, biofuels are the most controversial from an environmental perspective, mainly because every drop now available to global markets comes from food crops like corn, sugarcane and soy. It would be nice if cellulosic biofuel — the stuff made from non-food plant materials — could step up and provide at least a fraction of the potential market. But that just hasn’t happened the way the industry and its government backers have hoped. In fact, commercial-scale cellulosic ethanol production is so far behind schedule in the United States, the Environmental Protection Agency has had to slash its targets twice, from an original hope for 100 million gallons by 2010 and 250 million gallons by 2011 to a bare 12.9 million gallons by next year — and even that pathetically small figure will be a challenge for the industry to manage. Looks like we’ve got awhile to perfect cellulosic biofuel’s technology, and the business model, and the feedstock issues, and all the other problems that have limited its development to date.