Plant oil as fuel: Difference between revisions

Diesel engines can be modified to run on straight vegetable oil or waste vegetable oil (used cooking oil). Problems can occur with some engine types when operated for extended periods at idle or low load as vegetable oil does not burn well in these conditions. Suitable engine modifications along with attention to fuel quality, ambient temperatures and operating regime generally avoids these issues.

Quality biodiesel, which is typically a modified vegetable oil, does not have these effects to the same degree, but some engines, oil types, and ambient conditions can cause similar problems.

Why

Biofuels are not made from petroleum; not purchasing petroleum products allows you to avoid supporting business practices such as oil drilling that are harmful to the environment and human rights.

Waste cooking oil is discarded by restaurants and other businesses and can be obtained for free or very cheap. This allows you to recycle something that would otherwise go to waste. Since the vegetable oil is not produced in respond to an economic demand for fuel, using it is carbon neutral.

History

Theory

Vegetable oil is too thick to burn well in the engine unless it is hot. To deal with this problem, some vehicles use a two-tank system: one tank for biodiesel or petrodiesel, and one for vegetable oil. The engine is started on diesel and run until it heats up, then the driver switches to the vegetable oil tank. When done driving, the vehicle must be switched back to the diesel tank in order to get the vegetable oil out of the fuel lines; otherwise, the lines will still be full of vegetable oil when the car is next started, and it will be difficult to start.

Oil that is not hot enough when it enters the engine will not burn properly and will cause buildup that will damage the engine.

Waste vegetable oil must be filtered and water must be removed before it can be used as fuel, or it will damage the engine.

Process

Modifications are done on a diesel vehicle; if the vehicle is not already diesel, it has to be converted to run on diesel before it can run on vegetable oil.

Two-tank system

Processes for converting to vegetable oil vary. One process is outlined below.

In the two-tank system, the following modifications are made:

• A second gas tank is added; this can be a purchased gas tank or another receptacle that can hold fuel, such as a bucket.
• The new tank is installed somewhere on the vehicle, e.g. in the trunk.
• A valve is installed that allows the driver to switch from one tank to the other. It uses electricity from the vehicle's battery, and a switch is installed in the vehicle that the driver can switch.
• An extra fuel filter is installed in the vehicle to filter particles and water out of the vegetable oil. Hoses can be spliced from the coolant system and run to this filter; this brings hot coolant to the filter and heats it up, in order to get the oil hotter.
• Fuel lines are run from the tank that will hold diesel to the valve that allows switching between tanks.
• Fuel lines are run from the tank that will hold vegetable oil to the new filter, and from there to the valve that allows switching between tanks.
• A heater is installed near the fuel injectors to ensure that oil is as hot as possible before it enters the engine.
• Fuel lines are run from the valve to the vehicle's fuel pump, then to the heater, then to the fuel injectors.
• Return lines are added that return unused diesel to the diesel tank.
• A buzzer is installed that sounds when the vehicle is turned off and the tank is still set to vegetable oil. This warns the driver that they forgot to purge vegetable oil from the fuel lines and the vehicle may not start next time. When this happens, the driver turns the vehicle back on (possible since the engine is still hot) and switches to the diesel tank and runs it long enough to replace the oil in the fuel lines with diesel.

External links

• Biogas and liquid biofuels (original)
• Making Biodiesel
• Wikipedia:Straight vegetable oil
• Pure plant oil fuel technology at the Open Biofuel Engine Development (OBED)wiki - Information about running vegetable oils in Diesel engines
• 10 steps to converting to wvo...the basic process
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