Many contractors prefer diesel trucks. Gary Gerber is no
exception — his service truck has a diesel engine. But
Gerber never takes his truck to the gas station. It runs on
biodiesel fuel made from used cooking oil.
The only thing special about this truck
is that it uses biodiesel fuel produced and stored in the
This is not as strange as it sounds. Early models of the
diesel engine — which was invented in the 1890s —
ran on vegetable-oil fuel. Most modern diesel engines will run
on biodiesel without being modified, but since biodiesel can
eat through certain kinds of rubber, engines built before 1995
may need new fuel-line parts.
For Gerber, biodiesel is just another way to avoid using
fossil fuels. He is the founder of Sun Light & Power, a
Berkeley, Calif., company that designs and installs alternative
energy systems like photovoltaic power and solar water
At first, Gerber purchased biodiesel from a supplier who
delivered it to a storage tank in his shop. Recently, however,
he began making his own. Acquiring the raw materials is easy.
In the past, local restaurants paid a rendering company to haul
used oil away. Now, Gerber takes it away for free. Well, almost
free. They have to give him lunch.
Converting used vegetable oil into
biodiesel is a fairly simple process: The oil is mixed with
catalysts and heated in a tank (left). The finished product
(right) is amber brown and chemically similar to No. 2 heating
When the oil arrives at the shop, warehouse manager Karl Tupper
processes it for use as fuel. Processing is necessary because
plain oil is viscous and contains compounds that will gum up an
engine. Converting the oil into biodiesel is a relatively
simple process, thanks in no small part to Tupper's graduate
degree in chemistry.
Tupper filters out the food debris, adds lye and methanol to
act as catalysts, and then pumps the mixture through a heated
tank. This cracks the oil molecules into shorter chains,
producing biodiesel plus a residue of glycerin. The glycerin is
drained off, and after further purification the biodiesel is
ready for use as fuel.
Other than the energy that went into the lye and ethanol, no
fossil fuels are expended to process the oil. Heat for the
reaction is generated by burning biodiesel from previous
batches, and the electricity that runs the pumps comes from a
photovoltaic power system. Glycerin is the only waste product,
and some of it goes to a local mechanic who is trying it out as
an engine degreaser.
Commercially produced biodiesel is available at a small number
of gas stations around the country. Since Berkeley has a mild
climate, Gerber can run his truck on pure biodiesel. But the
substance gels up in very cold weather, so in other parts of
the country it's blended with conventional diesel fuel or other