Oilseeds
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Wikipedia-Article "Oilseeds"
Vegetable oil or vegoil is fat extracted from plant sources, known as oil plants. Although in principle other parts of plants may yield oil, in practice seeds form the almost exclusive source. Vegetable oils are used as cooking oils and for industrial uses. Some types, such as rapeseed oil, cottonseed oil, or castor oil, are not fit for human consumption without further processing.
Like all fats, vegetable oils are esters of glycerin and a varying blend of fatty acids, and are insoluble in water but soluble in organic solvents.
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Sources
Common sources of vegetable oil include:
Oilseeds:
- cashew
- castor bean - castor oil
- flax seed - linseed oil
- grape seed - grape seed oil
- hemp (cannabis)
- mustard
- poppy seeds - poppyseed oil
- rapeseed
- safflower
- sesame seed
- sunflower
Other vegetable oils:
- almond
- apricot
- avocado
- corn (maize) - corn oil
- cotton plant seed - cottonseed oil
- coconut - coconut oil
- fusarium - actually a fungus
- hazelnut
- neem oil
- olive - olive oil
- palm - palm oil - from the fruit of the African palm tree -
- palm kernel oil - from the seed of the African palm tree
- peanut - peanut oil
- pumpkin seed
- rice bran - used also in paints[1]
- soybean - soybean oil is sometimes marketed simply as "vegetable oil" in American grocery stores
- walnut
According to the USDA, the total world consumption of major vegetable oils in 2000 was:
| Soybeans | 26.0 million metric tons (MMT) |
| Palm | 23.3 MMT |
| Rapeseed | 13.1 MMT |
| Sunflowerseed | 8.6 MMT |
| Peanut | 4.2 MMT |
| Cottonseed | 3.6 MMT |
| Palm Kernel | 2.7 MMT |
| Olive | 2.5 MMT |
Note that these figures include industrial and animal feed use. The majority of European rapseed oil production is used to produce biodiesel, or used directly as fuel in diesel cars which may require modification to heat the oil to reduce its higher viscosity. The suitability of the fuel should come as little surprise, as Rudolph Diesel originally designed his engine to run on peanut oil.
Use of vegetable oil directly as a fuel is one of the most environmentally friendly sources of power, as it is carbon neutral, and unlike biodiesel does not require energy input to perform transesterification or produce glycerine as a waste product. The use of waste vegetable oils is obviously greener, but requires filtering, settling, and some waste, may not be suitable.
Sunflower oils are also used for this purpose and with a seven degree centigrade lower freezing point can provide slightly better cold weather starting. It is worth mentioning some indirect injection diesel engines will run happily without alteration, especially in warmer climates or summer. The French XUD series of engine is a good example. One caveat is the injection pump should not use vegetable oil as a lubricant, as due to the higher viscosity when cold it can fail to lubricate and cause premature failure. Inline injection pumps, and mechanical Bosch pumps work well, however CAV/Rotodiesel and similar can fail if run on relatively low vegetable oil to diesel ratios. Petrol may be added as a thinner to the fuel, as most manufacturers recommend this for winter up to ten percent. In practice many people may add slightly more, as the problems of vapour locks are less likely at low temperatures. However, excessive thinning can cause a lack of lubrication in injectors, resulting in their overheating.
Extraction
- One can use the "modern" way of processing oil by chemical extraction, using solvent extracts, which produces higher yields and is quicker and less expensive. The most common solvent is petroleum-derived hexane.
- Another way is the "physical extraction", that does not use solvent extracts. It is made the "old" way by several different types of mechanical extraction. This method is frequently used to produce cooking oil, since it is preferred by most customers (at least in Europe). Expeller-pressed extraction is one type. There are two other types that are both oil presses. The screw press and the ram press.
Industrial uses
- Vegetable oils are increasing being used in the electrical industry as insulators as vegetable oils are non toxic to the environment, biodegrade if spilt and have high flash and fire points. However, vegetable oils have issues with chemical stability (there has to be a tradeoff with biodegradability) so are generally used in systems where they are not exposed to oxygen and are more expensive than crude oil distillate. Three examples are Midel 7131 by M & I materials, FR3 by Cooper Power and Biotemp by ABB. Midel 7131 is a synthetic oil, manufactured by an alcohol + acid reaction.