Environmental Engineering Reference
In-Depth Information
place at approximately 70-80°C, but according to the European Advance Combustion Research for
Energy from Vegetable Oil, the viscosity of vegetable oil equals that of diesel oil at 150°C (http://
www.biomatnet.org/secure/Other/S1033.htm).
German manufacturers are also offering single-tank conversion kits that do not require the
driver to switch between the engine tanks (http://www.noendpress.com/caleb/biodiesel/biodiesel_
conversion_mercedes_booklet.pdf). These kits mostly use German produced rapeseed oil which
meets the German rapeseed oil fuel standards DIN 51605 and are suitably modified to operate
at subfreezing temperatures greater than -10°C. Experts recommend that users of these modified
engines should regularly change the oil and keep the engine well maintained. The most successful
prototypes of this experiment have been the pre-1990 Mercedes Benz models which are widely used
for experimentation in biofuel research.
It is evident that the replacement of petrodiesel fuel with SVO is a work in progress. Enthusiasts
and engineers continue to strive for perfection by testing a variety of apparatuses and vegetable
oil blends. The Vegetable Oil Fuel Database was produced by a diverse community of people
comparing actual road tests with laboratory research. According to the online database, almost 93%
of the vehicles have performed adequately in the short term whereas 16 of 341 vehicles observed
have logged over 50,000 mi using vegetable oil. Waste vegetable oil (WVO) can also be used in
diesel engines, but there are many theories of the best way of preparing it for fuel use. Most agree
that the oil should settle for at least two weeks to allow suspended sediments (food particles) and
water to settle to the bottom. After settling, a good filtration system in addition to the heating
system is all that is required to run most diesel engines on vegetable oil whether it is virgin, unused
oil, or waste vegetable oil (WVO). Both WVO and SVO are still experimental fuels (see review
by Jones and Peterson (2002); http://journeytoforever.org/biofuel_library/uidaho_rawoils.html) and
could be risky for the engine. Therefore they are exciting novel sources of bioenergy but may not
be commercially viable.
18.1.2.2 Biodiesel
Vegetable oil is the basis of biodiesel. Although similar to petrodiesel, some modifications are
required to utilize this fuel in standard diesel engines. The goal of much research has been the
production of an engine that runs on biodiesel without the need for modifications. The very first
account of the production of biodiesel traces back to 1937, when Belgian Patent 422,877 was granted
to G. Chavanne. He described the formation of biodiesel by separating the fatty acids from glycerol
and replacing glycerol with alcohols (Knothe 2001). Biodiesel is usually a blend of petro diesel and
vegeoil diesel with a B description. The “B” designation is used to describe the amount of biodiesel
present in a fuel mixture compound. A “B20” fuel is one that contains 20% biodiesel whereas
“B100” denotes 100% biodiesel. Currently a blend of 20% biodiesel and 80% petroleum diesel is
commonly used in large vehicles to reduce greenhouse gas emissions. Such a blend does not require
engine modifications. In contrast, use of a 100% biodiesel requires specifically modified engines to
provide the needed performance.
Research on biodiesel reveals that a blend of biodiesel and petrodiesel performs much better
than petrodiesel alone. The widespread use of biodiesel is limited by production costs and limited
availability of raw materials (Radich 2004). In his study, “BioDiesel Performance Costs and Use,”
Anthony Radich (Radich 2004) defines biodiesel as, “the monoalkyl esters of long chain fatty
acids derived from plant or animal matter which meet (A) the registration requirements for fuels
and fuel additives established by the Environmental Protection Agency under section 211 of the
Clean Air Act (42 U.S.C. 7545), and (B) the requirements of the American Society of Testing and
Materials D6751.”
The major drawback of using pure biodiesel is its tendency to gel at cold temperatures (-10°C
for canola-derived biodiesel), which can clog the fuel lines and filters in the vehicle's fuel system. It
is therefore suggested that the long-term efficacy of biodiesel blends remains controversial in low-
temperature zones such as in North America and Europe. In addition to low temperature concerns,
