In a time when oil supplies are beginning to be depleted, the need to have alternate or renewable fuel sources is beginning to have an effect on the kinds of cars being offered for sale to the public. There are very few in the public today who have not heard the terms “biodiesel fuel” or “waste vegetable oil” in regards to renewable energy sources that are currently being researched to try and find answers to the shrinking supplies of petroleum-based fuels.
Technically speaking, waste vegetable oil is a biodiesel fuel because biodiesel fuels are any fuels that are derived from vegetable oils or animal fats that run a “diesel” or compression ignition engine. The term Biodiesel is currently used almost exclusively for the product made by combining chemically-reacting lipids like vegetable oil or animal tallow and alcohol.
One important difference between biodiesel and waste vegetable oil is that biodiesel is formulated to be used alone or with petrodiesal blends in “standard” diesel engines and is different from the new vegetable and waste oils which are used to power diesel engines that must be converted specifically to do so.
To produce biodiesel fuels, the oils must undergo a process known as “alcoholysis” (sometimes called “transesterification”). In this process vegetable oils have the fatty acids separated from the glycerol components using ethanol (and sometimes methanol) to replace the glycerol with specific types of alcohols known as short linear alcohols. In its purest form, biodiesel has the designation (B100) or it can be blended with petroleum diesel at any concentration for use in most modern diesel engines.
Because of the different solvent properties that biodiesel has versus petrodiesel, biodiesel will cause damage to natural rubber gaskets and hoses in vehicles made prior to 1992. For this reason, these parts in older cars must be replaced with a kind which is nonreactive to biodiesel.
An unexpected plus is that biodiesel has been known to break down and clear out deposits of residue left in fuel lines where petrodiesel has been used before. Fuel filters in the engine might become clogged with particulate matter as a result, especially if a quick switch to pure biodiesel is made. Mechanical experts recommend that the fuel filters on engines and heaters be changed not long after first switching to a biodiesel fuel blend.
Additional advantages to the use of biodiesel fuels include the fact that water will not mix with it; biodiesel has a higher boiling point and flash point of (less than 266 ° F for biodiesel as compared to 147 °F for petroleum-based diesel or -52 °F for gasoline. It has practically no sulfur content and is often used as an additive for Ultra-Low Sulfur Diesel (ULSD) fuel.
Waste vegetable oil (WVO), unlike pure plant oil (PPO) or straight vegetable oil (SVO) is a byproduct of other industries such as the deep fryers used in industrial potato processing plants, factories that produce snack foods and fast food restaurants. A majority of the enthusiasts who use it prefer to call the vegetable oil used for fuel as waste vegetable oil (WVO), particularly if it is the discarded oil recycled from a restaurant to better distinguish it from pure plant oil (PPO) or straight vegetable oil (SVO) commonly thought of as standard biodiesel
As of 2000, industry experts estimate that the United States was producing an amount in excess of 11 billion liters or 2.9 billion U.S. gallons. If this entire amount could be gathered up and used, it could be used to replace the equivalent amount of fossil-based petroleum, totaling almost 1% of the oil consumption in the US. The only theoretical drawback here is that the production of waste vegetable oil is limited by the amount that the industries can make as a byproduct versus pure or straight vegetable oil which is limited only by the farm production capacity of any given national economy.
Like the straight vegetable oil used as an alternative fuel for diesel engines, the viscosity of waste vegetable oil must be lowered so the proper atomization of fuel will prevent the incomplete combustion of the oil and the build-up of carbon that can ultimately damage the engine. Additionally, the free fatty acids (FFAs) found in WVO can have an adverse effect on metals. Copper and the alloys derived from it, like brass, are affected. Zinc and Metals like zinc, or those galvanized by zinc-plating are stripped by FFAs. In addition, tin, lead, iron, and steel are all susceptible, too. Stainless steel and aluminum are the only metals that seem to be immune to the effects of FFAs.
Ideally the engine on a car should be converted before using vegetable oil as a fuel. Most diesel car engines can use WVO, if fit with suitable modifications. One common solution is to reduce the viscosity and surface tension of the oil by preheating it, by the addition of a heat exchanger, and an additional fuel tank for “normal” diesel fuel (petrodiesel or biodiesel). It will contain valves to switch between this additional tank and the main tank which contains the vegetable oil. This tank and valve system is an aftermarket modification which costs around $1200 USD.
The engine is initially turned on with diesel, switched over to the vegetable oil when it is warmed up and changed back to diesel fuel shortly before turning it off to make sure that no vegetable oil remains in the engine or fuel lines so that it is read you start when it is cold again. For durability that is more long term, it has been discovered that it is best to increase the frequency of oil changes and to pay increased attention to engine maintenance, particularly when it comes to the fuel injectors, cooling system and glow plugs.
Although initially a little more expensive, as you can see, there are several advantages to using biodiesel or waste vegetable oil as fuels for vehicles. In addition to being a renewable resource, unlike fossil-based petroleum, these fuels also release fewer pollutants into the atmosphere which can worsen global warming.