End of Project ReportThe use of recovered vegetable oil (RVO) and tallow as vehicle fuels was
investigated. Two options were considered; use in unprocessed form in specially
adapted engines, and the production of biodiesel for use in unmodified engines.
Two vehicles were modified to allow the use of RVO as fuel. Their performance in
terms of power and fuel economy was acceptable, but fuel filter blockage problems
would need to be resolved and long-term effects on engine life investigated before
this approach could be recommended.
Tallow with high free-fatty-acid content was esterified by a two-stage process that
could be used in a simple plant and produce biodiesel of reasonable quality. High
ester yields were obtained in laboratory and pilot-scale trials. Problems of layer
separation remain to be resolved, and the process needs to be streamlined to allow
a high throughput to be achieved.
In comparing the costs of these fuels with each other and with mineral diesel,
allowance must be made for any differences in fuel economy and for the cost of
engine conversion kits. Including these items, the use of RVO in a converted
engine would have a slightly lower cost than its use as biodiesel. Biodiesel from
tallow is likely to be more expensive than from RVO if either ester yield or plant
capacity is significantly reduced
