Lesson 30. Storage and Handling of Biodiesel

30.1. Storage of Biodiesel

During storage, all the fuels are subject to degradation over time due to various reasons such as microbial action, water intrusion, air oxidation, etc.  Hence, it is recommended to store bio-diesel in clean, dry and appropriate tanks.  During storage, the prarameters of biodiesel such as acid number, water and sediment, viscosity etc. will be changed.  Though the flash point of bio-diesel is high, still storage precautions somewhat like that in storing the diesel fuel need to be taken.  

Underground storage is preferred in cold climates with proper precautions and equipment.  The 20:80 (B 20) blend fuel can be stored in above ground tanks depending on the pour point and cloud points of the blend. 

Biodiesel will be readily oxidized while storage.  Hence, long storage will lead to the deterioration of quality.  The presence of moisture in biodiesel will react with the esters to make free fatty acids and can support microbial growth in storage tanks.  This biological growth can be mitigated by using biocides in small concentration. 

The storage considerations are given as follows.

Exposure temperature

The temperature at which the biodiesel is being stored has significant effect on the quality of biodiesel.  Generally the diesel fuels have the tendency of gelling at low temperatures.  Similarly, biodiesel also has the problem of gelling during storing at low temperatures.  Temperature required to gelling is more for biodiesel than diesel.  To avoid formation of gel in biodiesel at low temperatures, additives can be used.  In general, biodiesel has to be stored at temperatures 15°F higher than pour point of fuel. 

Oxidative stability

This is the ability of the biodiesel to be stored for extended periods without degradation.  This particular degradation is due to reaction of the fuel with oxygen and catalysts.  The instability of fuel is correlation with number of C = C bonds in the fuel.  It is assessed that the instability is 50% for two C=C when compared to one C=C bond.  The instability may be estimated by iodine number and which is evident by high acid number, higher viscosity and formation of gums and sediments.  It is recommended that a safe storage period of 6 months and with suitable anti-oxidant additives may be stored for longer periods.   

Fuel solvency

The solvent properties of biodiesel plays major role in the selection of storage tanks and storage period.  Biodiesel has higher enzyme hydrolysis properties than diesel fuel.  If biodiesel is stored in old tanks, biodiesel dissolve the sediments due to the mild solvent nature.  Hence, the blend of biodiesel and diesel is stored in tanks, residual sediments in diesel storage tanks or vehicle fuel tanks can be solvated by biodiesel.  The 20:80 (B 20) blend fuel can serve the purpose.

Material compatibility

The material compatibility deals with the interaction of the biodiesel with materials of construction for storage tanks, seals, and gaskets during storage.  It is recommended to use stainless steel or aluminum equipment in the processing of biodiesel.  Normally during storage of blends of diesel and biodiesel, oxidation and sediment production in either biodiesel or diesel can be initiated by contact with brass, bronze, copper, lead, tin and zinc.  Hence, generally the acceptable materials for biodiesel storage are aluminum, steel, Teflon, fluorinated polyethylene or polypropylene etc.

30.2. Handling of Bio-Diesel

Generally, biodiesel blends are considered as petrodiesel for handling.  Though biodiesel contains no hazardous materials, it should be handled in well ventilated areas.  Care should be taken during handling of biodiesel, there should not be heat, spark, or flames sources in the nearer sources.  If biodiesel is stored in drums, proper drum handling procedures such as free from drum puncturing, no dragging or sliding should be followed.

Biodiesel does not contain volatile organic compounds which will cause the release of poisonous or noxious fumes. Biodiesel do not contain aromatic hydrocarbon (benzene, toluene, zylene) or chlorinated hydrocarbons also.  There is no lead or sulfur to react and release any harmful or corrosive gases from biodiesel.

While handling, safety glasses or face shields should be used to avoid mist or splash on face and eyes. Fire fighting measures to be followed as per its fire hazard classification.  It is recommended that PVC-coated gloves as well as safety glasses or goggles should be used when handling biodiesel.

Last modified: Wednesday, 9 April 2014, 4:50 AM