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Biodiesel is a renewable energy fuel produced from animal fats and vegetable oils by lipid transesterification. Chemically, it is a fatty acid mono alkyl[?] ester.

Biodiesel is nonflammable and non-explosive. It is biodegradable and nontoxic.

Production Biodiesel can be produced from virgin oil feedstock from such crops as mustard, rapeseed, and soybeans, as well as other crops. Waste vegetable oil (WVO) collected from restaurants can also be used.

According to a study written by Drs. Van Dyne and Raymer for the Tennessee Valley Authority, although the average US farm requires 33 litres (8.75 gallons) of fuel to cultivate 40 ares (one acre) of land, rapeseed produces an average of 420 l (110 gallons) of oil per acre. The average yield of high-yield rapeseed fields is 550 l (145 gallons) per acre. Unfortunately by themselves these statistics are not enough to show whether such a change makes economic sense. The issue is Malthusian: one of the exceptions Nassau Senior[?] noted to the idea that machines aren't harmful to wages is, where the machines themselves make demands on resources that would have gone into food production. So the important question isn't whether biodiesel can be produced as whether that would lead to a food shortfall - which in turn depends on food availability in relation to population levels. For third world countries biodiesel sources that use marginal land make more sense, e.g. Honge nuts grown along roads.

The direct source of the energy content of biodiesel is solar energy captured by plants during photosynthesis. The website http://www.biodiesel.co.uk/levington.htm discusses the positive energy balance of biodiesel:

When straw was left in the field, biodiesel production was strongly energy positive, yielding 1 GJ biodiesel for every 0.561 GJ of energy input (a yield/cost ratio of 1.78).

When straw was burned as fuel and oilseed rapemeal was used as a fertilizer, the yield/cost ratio for biodiesel production was even better (3.71). In other words, for every unit of energy input to produce biodiesel, the output was 3.71 units (the difference of 2.71 units would be from solar energy).

The production of biodiesel processors is measured in metric tonnes/year with a specific gravity of 0.89

Fuel properties When mixed with petrodiesel (the industry term for diesel produced from petroleum), biodiesel can be used at any concentration and is commonly referred to according to its "B factor": 20% biodiesel is called B20, and 100% biodiesel is called B100.

B100 can be used in any diesel engine. Because biodiesel is an effective solvent, it also cleans the fuel system. Fuel filters catch petrodiesel particulates when biodiesel is used, so clogging is not an issue once the precipitates have been removed. Biodiesel has the disadvantage of degrading rubber gaskets and hoses in older vehicles (prior to 1992), but not in newer vehicles.

Biodiesel reduces emissions of unburned hydrocarbons and carbon monoxide by approximately 50%. It also eliminates sulfur emissions, so that diesel vehicles burning B100 can use catalytic converters[?] to eliminate NOx emissions, which are somewhat elevated with biodiesel.

See also: hydrogen car, energy balance[?], renewable energy.

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