Joe McElvaney, a Phoenix fire protection engineer, said the city requires a permit to handle the flammable and combustible materials used in biodiesel. But many home brewers ignore zoning regulations and waste-disposal requirements.
http://www.azcentral.com/news/articles/2008/11/22/20081122biodiesel1122.html
The story has also been picked up by the New York Times:
http://www.nytimes.com/2008/11/23/us/23arizona.html?_r=1&oref=slogin