5.0 Toxicity of Biodiesel

Impacts on human health represent a significant criteria as to the suitability of the fuel for commercial applications. Health effects can be measured in terms of fuel toxicity to the human body as well as health impacts due to exhaust emissions. Tests conducted by the Wil Research Laboratories investigated the acute oral toxicity of pure biodiesel fuel as well as B20 in a single dose study on rats, which concluded that biodiesel is not a toxic and there is no hazards anticipated from ingestion incidental to industrial exposure. The acute oral LD50 (lethal dose) is greater than 17.4-g/kg-body weight, which by comparison is far safer then even table salt. According to NIOSH (National Institute for Occupational Safety & Human Health), a 96-hr. lethal concentration of biodiesel for bluegills was greater than 1000 mg/l and this aquatic toxicity is deemed as insignificant. Other related effects of biodiesel are given below:

• Very mild human skin irritation. It is less than the irritation produced by 4% soap and water solution.
• It is biodegradable. It degrades at least 4 to 5 times faster then conventional diesel fuel.
• Biodiesel has a flash point of about 300 F well above conventional diesel fuel.
• Spills of biodiesel can decolorize any painted surface if left for long.
• There is no tendency for the mutagenicity of exhaust gas to increase for a vehicle running on biodiesel (20%RSME80% diesel).

5.1 Storage & Infrastructure

In general, the standard storage and handling procedures used for petroleum diesel may be used for biodiesel. It is preferable to store the fuel in clean, dry and dark environment. Biodiesel may gel at low temperatures and care needs to be taken to avoid temperature extremes. Acceptable storage tank materials include mild steel, stainless steel, fluorinated polyethylene and fluorinated polypropylene. Biodiesel has a solvent effect, which releases the deposits accumulated on tanks and pipes, which previously have been used for diesel. These deposits can be expected to clog filters initially and precautions should be taken for this.

5.2 Materials Compatibility

Biodiesel over time will soften and degrade certain types of elastomers and natural rubber compounds. Materials like bronze, brass, copper, lead, tin and zinc may oxidize the diesel or biodiesel fuels and create sediments. Moreover, lead solders and zinc linings should be avoided, as should copper pipes, brass regulators and copper fittings. It is desirable to change all components, which are not biodiesel compatible to aluminum or stainless steel. The effect of B20 on vulnerable materials is diluted compared to higher blends. It may also be noted that most of the new generation vehicles can take biodiesel without any materials compatibility problems as they are already tuned to using low sulphur diesel, biodiesel etc. Compatibility of some materials with biodiesel is given in Table-9.

Table-9: Material Compatibility with Biodiesel Fuels

Source: National Renewable Energy Laboratory (NREL).

5.3 Solvency of Biodiesel

Biodiesel is a mild solvent. On prolonged contact with painted surfaces, it may deface some paints. Always wipe up spills and dispose of rags in a safe manner. Biodiesel soaked rags may self-combust if not handled properly. The most commonly encountered problem with solvency is biodiesel’s tendency to "clean out" storage tanks, including the vehicle fuel tanks and systems. Some type of diesel tends to form sediments that stick to and accumulate in storage tanks, forming layers of sludge or slime in the fuel systems. The older the system, and the poorer the maintenance, the thicker the accumulated sediments become. Biodiesel will dissolve these sediments and carry the dissolved solids into the fuel systems of the vehicles. Fuel filters will catch most of it, but in severe cases, the dissolved sediments have caused fuel injector failure. Few problems have been encountered with B20 in typical diesel storage situations. However, the solvency effect of the biodiesel in B20 is sufficiently diluted so that most problems encountered are minor and in general the problem goes away after the first few tanks of fuel.

5.4 Lubricity of Biodiesel

Biodiesel blends offer superior lubricating properties, which may reduce engine wear and extend the life of fuel injection systems. Tests with two leading lubricity measuring systems-the BOCLE machnine and the HFRR machine-show biodiesel blends offer better lubricating properties then conventional petroleum diesel. Lubricity is especially important for rotary/distributor type fuel injection pumps in which parts are lubricated by the fuel itself and not by the engine oil. The result of a lubricity test done by Exxon with petrodiesel and biodiesel blends is given in Table-10.

Table-10: Lubricity Results (HFRR Machine)

Source: Exxon & Interchem Environmental Inc.