Biodiesel - Production of Biodiesel - Base oils
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Production of Biodiesel - Base oils
Soybeans that can be processed to produce Biodiesel. Image from the National Biodiesel BoardA variety of biolipids can be used to produce biodiesel. These include:
Virgin oil feedstock; rapeseed and soybean oils are most commonly used, though other crops such as mustard, palm oil and even algae show promise; waste vegetable oil (WVO); Animal fats including tallow, lard, and yellow grease.
Many advocates suggest that waste vegetable oil is the best source of oil to produce biodiesel. However, the available supply is drastically less than the amount of petroleum-based fuel that is burned for transportation and home heating in the world. According to the United States Environmental Protection Agency (EPA), restaurants in the US produce about 300 million gallons of waste cooking oil annually.[1] (http://www.epa.gov/oswer/docs/iwg/2004_costilla_county_draft3.pdf) Although it is economically profitable to use WVO to produce biodiesel, it is even more profitable to convert WVO into other products such as soap. Hence, most WVO that is not dumped into landfills is used for these other purposes. Animal fats are similarly limited in supply, and it would not be efficient to raise animals simply for their fat. However, producing biodiesel with animal fat that would have otherwise been discarded could replace a small percentage of petroleum diesel usage. Providing a significant alternative is the Jatropha tree, providing significant fuel in India and aiding restoration efforts in Thailand and Bangladesh.
The estimated transportation fuel and home heating oil use in the United States is about 230,000 million gallons. (Briggs, 2004) Waste vegetable oil and animal fats would not be enough to meet this demand. In the United States, estimated production of vegetable oil for all uses is about 23,600 million pounds (12,000,000 t) or 3,000 million US gallons (11,000,000 m³)), and estimated production of animal fat is 11,638 million pounds (5,000,000 t). (Van Gerpen, 2004)
For a truly renewable source of oil, crops or other similar cultivatable sources would have to be considered. Plants utilize photosynthesis to convert solar energy into chemical energy. It is this chemical energy that biodiesel stores and is released when it is burned. Therefore plants can offer a sustainable oil source for biodiesel production. Different plants produce usable oil at different rates. Some studies have shown the following annual production:
Soybean: 40 to 50 US gal/acre (40 to 50 m³/km²)
Mustard: 140 US gal/acre (130 m³/km²)
Rapeseed: 110 to 145 US gal/acre (100 to 140 m³/km²)
Palm oil: 650 US gal/acre (610 m³/km²) [2] (http://www.journeytoforever.org/biodiesel_yield.html)
Algae: 10,000 to 20,000 US gal/acre (10,000 to 20,000 m³/km²)
The production of algae to harvest oil for biodiesel has not been undertaken
on a commercial scale, but working feasibility studies have been conducted
to arrive at the above number. Specially bred mustard varieties can produce
reasonably high oil yields, and have the added benefit that the meal leftover
after the oil has been pressed out can act as a effective and biodegradable
pesticide. There is ongoing research into finding more suitable crops and improving
oil yield. Using the current yields, vast amounts of land would have to be
put into production to produce enough oil to completely replace fossil fuel
usage.
Soybeans are not a very efficient crop solely for the production of biodiesel, but their common use in the United States for food products has led to soybean biodiesel becoming the primary source for biodiesel in that country. Soybean producers have lobbied to increase awareness of soybean biodiesel, expanding the market for their product. In Europe, rapeseed is the most common base oil used in biodiesel production.
From Wikipedia.