While there are no federal guidelines for the storage of biodiesel, individual states may have varying rules and regulations. Generally, it is acceptable to store biodiesel in any tank approved by the EPA for diesel storage. With that in mind, there are still some helpful dos and don'ts that should be followed in storing biodiesel.
When storing B100, a report prepared by the National Renewable Energy Laboratory for the Dept. of Energy report recommends use of a nitrogen blanket in fuel tanks and/or storing the biodiesel in sealed drums or totes for smaller amounts of fuel. Also, use of an antioxidant, either natural or as an additive, can be helpful, particularly if the fuel is stored for more than six months, after which time the degradation process can begin. An antioxidant can significantly increase the storage life and/or stability of B100. For any fuel stored longer than six months, the report suggests testing it periodically for acid number and sediments to ensure it remains in compliance with ASTM D6751 standards.
Storing B100 also comes with other challenges. For instance, putting the fuel in direct sunlight or under heat will accelerate the oxidation process. Oxygen also will speed that process, so keeping the tank or drum sealed and oxygen out is important. While B100 and lesser blends can be stored in most EPA-approved diesel tanks, storage in copper, brass, bronze, lead, tin or zinc containers is not recommended as these will accelerate the degradation process. Preferred storage tank materials include steel, aluminum, fluorinated polyethylene, fluorinated propylene and Teflon. ASTM D4625 data suggests a shelf life of eight months to one year for B100, while the National Biodiesel Board recommends a six-month storage life.
When dealing with B20 blends or lower, there are some storage differences. One of the most important is temperature control. Blends of biodiesel should be stored at temperatures at least 5-10 deg. F. above the cloud point of the blend, according to the EPA. Depending on cloud and pour points, most blends can be stored in either underground or above ground tanks.