Bio diesel can be obtained from vegetable oil or animal fats (bio-lipids),
using transesterification. Biodiesel is a non-fossil fuel, cleaner burning
alternative to petrodiesel. It can also be mixed with petrodiesel in any
amount in some modern engines, but is 'strongly recommended against' by some
manufacturers.
Biodiesel has a higher gel point than petrodiesel, but is comparable to
diesel. This can be overcome by using a biodiesel/petrodiesel blend, or by
installing a fuel heater, but this is only necessary during the colder
months. A small fraction of biodiesel can be used as an additive in
low-sulphur formulations of diesel to increase the lubricity lost when the
sulfur is removed. In the event of fuel spills, biodiesel is easily washed
away with ordinary water and is non-toxic compared to other fuels.
Biodiesel can be produced using kits. Certain kits allow for processing of
used vegetable oil that can be run through any conventional diesel motor
with modifications. The modification needed is the replacement of fuel lines
from the intake and motor and all affected rubber fittings in injection and
feeding pumps a.s.o (in vehicles manufactured before 1993). This is because
biodiesel is an effective solvent and will replace softeners within
unsuitable rubber with itself over time. Synthetic gaskets for fittings and
hoses prevent this.
Chemically, most biodiesel consists of alkyl (usually methyl) esters instead
of the alkines and aromatic hydrocarbons of petroleum derived diesel.
However, biodiesel has combustion properties very similar to petrodiesel,
including combustion energy and cetane ratings. Paraffin biodiesel also
exists.
The use of biodiesel blended diesel fuels in fractions up to 99% result in
substantial emission reductions. Sulfur oxide and sulphate emissions, major
components of acid rain, are essentially eliminated with pure biodiesel and
substantially reduced using biodiesel blends with minor quantities of ULSD
petrodiesel. Use of biodiesel also results in substantial reductions of
unburned hydrocarbons, carbon monoxide, and particulate matter compared to
either gasoline or petrodiesel. CO, or carbon monoxide, emissions using
biodiesel are substantially reduced, on the order of 50% compared to most
petrodiesel fuels. The exhaust emissions of particulate matter from
biodiesel have been found to be 30 percent lower than overall particulate
matter emissions from petrodiesel. The exhaust emissions of total
hydrocarbons (a contributing factor in the localized formation of smog and
ozone) are up to 93 percent lower for biodiesel than diesel fuel. Biodiesel
emissions of nitrogen oxides can sometimes increase slightly. However,
biodiesel's complete lack of sulfur and sulfate emissions allows the use of
NOx control technologies, such as AdBlue, that cannot be used with
conventional diesel, allowing the management and control of nitrous oxide
emissions.
Biodiesel also may reduce health risks associated with petroleum diesel.
Biodiesel emissions showed decreased levels of PAH and nitrited PAH
compounds which have been identified as potential cancer causing compounds.
In recent testing, PAH compounds were reduced by 75 to 85 percent, with the
exception of benzo(a)anthracene, which was reduced by roughly 50 percent.
Targeted nPAH compounds were also reduced dramatically with biodiesel fuel,
with 2-nitrofluorene and 1-nitropyrene reduced by 90 percent, and the rest
of the nPAH compounds reduced to only trace levels.