The Potentional of Recovered Vegetable Oil and Tallow as Vehicle Fuels

Abstract

The 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.