Diesel Fuel You Grow on the Farm
Ohio State University (OSU) in Columbus,
Ohio, transports students around its spread-out
campus using a fleet of buses. Nothing unusual
in that. But, this year (1980) OSU is using soybean
oil as fuel.
Over the past decade, various student projects
at the OSU engineering school have shown
that vegetable oils can be used as fuel for diesel
engines. For a full year the university has run
a large, 60-passenger bus partly on soybean oil.
The experiment proved so successful that in
September the whole university fleet was
switched to the new fuel.
The soybean oil is collected from deep-fat
fryers in cafeterias and kitchens across the
University, filtered through muslin cloth by the
engineering students to remove gunk and
solids, and blended into diesel fuel.
A ratio of
one part soybean oil to four parts diesel was
settled on as it gave a stable mixture, lowest
fuel consumption, and actually smoked less
than diesel fuel alone.
The first bus maintained its normal 40 hour
a week schedule.
After 4,5oo miles on the soydiesel
blend the engine was taken apart and inspected.
Little or no abnormal wear had occurred.
The engine was actually in such fine
shape that it was merely reassembled and
returned to service without further attention.
...
Of all the research laboratories testing diesel
engines fueled by vegetable oils, the South African
government’s Division of Agricultural Engineering
has the most experience. At its laboratory
near Johannesburg it is running 10
tractors on sunflower oil. Fiat, International
Harvester, John Deere, Landini, Massey Ferguson,
and Ford tractors are being used, With
two exceptions the tractors started satisfactorily
on undiluted sunflower oil, All operated
normally, delivered almost full power, and
had virtually the same fuel consumption as on
diesel fuel.
A Ford 7000 tractor has run troublefree
for almost 1,400 hours of operation on a
farm using a blend of 20 percent sunflower oil
and 80 percent diesel fuel. At the end of this
time it was found that deposits in the combustion
chamber, cylinders, and piston ring
grooves were no worse than those formed
burning normal operation on diesel fuel. On
the other hand, carbon deposits on the injector
nozzles were worse and contributed to an
eventual 4 percent power loss and serious gumming
of the crankcase oil.
The rapid compression of fuel and air in the
cylinder of diesel engines generates enough
heat to ignite the mixture and power the engine.
Unlike a gasoline engine, no spark is
needed. Injecting the fuel into the combustion
chamber is the most crucial step in a diesel engine.
The fuel must be forced in against the
pressure of the compressed air and to make this
doubly difficult, the fuel has to be in the form
of mist. If not atomized, the fuel burns slowly
and unevenly, reducing engine efficiency, raising
unburned pollutants in the exhaust and the
lubricating system, and even forming deposits
of solid carbon in the engine itself.
Vegetable oils are more viscous and less easily
atomized than diesel fuel and are therefore
more difficult to inject successfully. This is
probably why the injector tips suffered buildups
of carbon. Coking and the resulting incomplete
combustion diluted the lubricating oil and
gummed it up because vegetable oils will polymerize
when they are hot and next to metal.
The South African engineers, however, have
found a way that seems to avoid these difficulties,
They slightly modify the sunflower oil in
chemical reactions using small amounts of
ethanol or methanol. The resulting ethyl or
methyl esters derived from sunflower oil
caused much less coking than diesel fuel itself.
Furthermore, they produced much less exhaust
smoke, and the engine ran quieter so that the
characteristic diesel knock was less audible,
And, against all expectations, the engine gave
more power with the new fuel than with diesel
fuel. Thus tractors were running on a renewable
fuel grown by farmers and achieving better
results than on diesel fuel, Much yet remains
to be done to test the widespread
applicability of these results, but it is a line of
research that is bright with promise,
from:
Innovative Biological Technologies for
Lesser Developed Countries
p46-47
http://www.fas.org/ota/reports/8512.pdf