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Difference between revisions of "Waste plant oil as fuel"

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Tags: ANON EDIT. To be patrolled., n
(we need article on VWO collection, so added link)
Tags: ANON EDIT. To be patrolled., n
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*[[PPO_single_tank_system|Single tank conversion systems for IC engines]]
*[[PPO_single_tank_system|Single tank conversion systems for IC engines]]
*[[PPO_two_tank_system|Two tank conversion systems for IC engines]]
*[[PPO_two_tank_system|Two tank conversion systems for IC engines]]
*[[VWO collection service in cities]]: collection of VWO for burning it at a central electricity production plant

Revision as of 12:57, 8 August 2012

Waste plant oil (WPO) or waste vegetable oil (WVO), is used cooking oil that is often discarded by restaurants and businesses that deep-fry a lot of food. It can be used to fuel diesel vehicles and for a variety of other purposes.

As the ethics of burning perfectly good oil (from human consumable plants) for transportation purposes are questionable, WVO is a good alternative lipid fuel. After that straight vegetable oil has been used to cook food, waste vegetable oil is produced which can still be used as fuel! Restaurants typically pay "recycling" companies to take away their waste oil, which is then used in animal food or cosmetics. This is not closed-end recycling, and is non-sustainable.

While not at first obvious, using WVO as a fuel is actually closed-end recycling, since the CO2 that is emitted is sucked up by the next year's oil crops.

WVO must be "cleaned" before using. This can be as simple as days to weeks of gravity settling, or it might be pumped through filters. Using cleanable, reusable filters eliminate the waste of replaceable filters.

Because WVO is gleaned from a wide variety of sources, it's energy content and pollution is impossible to characterize accurately, but it should be similar to SVO.


In vehicles

Diesel vehicles can be converted to run on vegetable oil. However, vegetable oil is thicker than diesel fuel and may not burn efficiently in the engine, leaving burnt residue in the engine that will eventually break it. Vegetable oil is thinner and less viscous when it is hot. In order for vegetable oil to burn efficiently, it must be hot when it enters the fuel injectors. Conversions employ various strategies to ensure this.

A drawback of running a vehicle on vegetable oil is that they may have trouble in cold weather. Even regular diesel vehicles have trouble starting when it is very cold, and vegetable oil is thicker than diesel. Vehicles employ various methods to heat up the oil, and vehicles used in cold climates can add extra heaters. One type of heater is called a "hot fox" which can be installed for example in the trunk; it heats up the oil before it gets to the front of the vehicle, where there is another heater that finishes the job before the fuel reaches the fuel injectors.

Another option is to turn waste vegetable oil into biodiesel. It must still be filtered for particles, but there is no need to convert the vehicle or add another tank if you are using biodiesel: you can just put it in your regular tank and drive. Biodiesel works like regular diesel. There are directions for making biodiesel here.


Particles (e.g. of food that was cooked in the oil) and water in the WVO will damage the engine—particles will create buildup in the engine, and water in the fuel can destroy the engine. Repairs to the engine can cost more than the price of the vehicle. Therefore WVO must be filtered and water must be removed before it can be used as fuel. Some people allow the oil to stand (e.g. in barrels) for about a week to allow water to separate from the oil; it can then be drained off through a spout at the bottom of the barrel. Standing also allows particles to separate out from the oil and drift to the bottom of the barrel; this is a first step in filtration. One method is to install two drains on the barrel: one that drains from the bottom, to drain off water and particles, and another higher up, to drain off (hopefully) clean oil. That way, clean oil can be drained off without disturbing it and mixing the contaminants back in.

The barrels must be left alone while the oil is standing—jostling will mix some of the water and particles back into the oil.

After standing, the oil is filtered, first through a large filter and then through filters with progressively smaller holes in order to get out small particles that would collect in the engine and damage it. The oil can be filtered multiple times.

The oil can also be heated to boil off water. One way to test whether standing has gotten rid of the water is to heat up frying pan on the stove until it is very hot and a drop of water skitters in the pan, then take a cup of the oil after it has been stood and pour it into the pan—if it boils and spurts and makes a fuss, there is still water in it.

So-called "straight vegetable oil" (SVO), store-bought oil, can be used instead of WVO at greater expense but with less filtration and purification hassle.

As Heating or Cooking Fuel

The oil can be absorbed using a special but inexpensive absorbent pad. The soaked pad can then be placed in a receptacle and burned. It can be used as cooking fuel in lieu of firewood or charcoal. It can also be used as a Firestarter for bonfires and fireplaces.

See also: Soak and Burn Pad


Some restaurants have to pay to have their grease hauled off, and they may be willing to let you take it away for them. Sometimes you'll be required to take all or nothing. Some restaurants are willing to put used oil back into the containers it came in, which makes it convenient for hauling away. Oil is discarded into barrels or large, rectangular grease traps usually located behind the restaurant, often near the dumpsters or the back door of the kitchen.

See also: Negotiating For Waste Vegetable Oil

Determining which oil is good to use

Grease from restaurants that fry red meat is not good to use in a vehicle—it is thick and will form solids, reducing flow and creating clogging. Asian and Mexican restaurants and vegetarian restaurants are better sources because they're frequently frying vegetable products. Chicken is also ok. A way to test whether oil is of good quality is to dip a piece of cardboard into it and watch it drip off—is it smooth and runny? Or is it thick and clumpy?

It is important to check to see whether water has gotten into the oil—if the containers were not closed, water may have gotten in.

Rancid oil cannot be used for fuel. [1]


Often, waste cooking oil is discarded by restaurants and other businesses and consumers can obtain them for free. In other cases, they can only be obtained for a sum, yet this sum is often very small. The sum probably depends on the region where it is obtained[2][3][4] (as local petrofuel prices dictate the price of biofuels in part) and also depends on the type of straight vegetable oil it was before being used to fry food (ie canola, peanut, ...). Finally, the freshness (freshly used, old, or rancid) will also be another factor determining the price. Since it is a recycled -or rather downcycled- product the price will be much lower than the local market price of the type of SVO it was made from (typically 1/3 or less[5].

See also


  1. Portions (cc) S.E.E.D.S. under Creative Commons
  2. VWO worth 1,4 RM to 2RM in Penang
  3. VWO worth 2 RM in Penang
  4. VWO thievery on the rise
  5. Biodiesel worth 0,18 pence made DIY, cheapest SVO worth 0,6 $, so a similar rate (1/3) will probably exist for WVO aswell

External links