I have three 55 gallon drums of biodiesel in my garage most times. It's highly adviseable to add some biocide if you're going to store the fuel more than a month or two. Racor makes biocide for diesel fuel as well as others. As posted earlier, yes, water in fuel breeds bacteria and microbes. For the small bung vents, 1 micron particle filters that are filled with dessicant are available. These allow the drum's necessary breathing(which happens no matter how you try to seal it, with changing temperatures) and do not allow dirt or moisture into the fuel. Its sure nice to be filling up in my garage at $1.55/gal with renewable domestically grown soybean based biodiesel, and not sending my fuel dollars to the middle east...not to mention the huge reduction in air pollution and 55 cetane index
