Abstract
Key words:
Alternative fuel, Bio-diesel, high free fatty acid, Soapstock, acid oil.
Abstract:
Bio-diesel is an alternative fuel for diesel engines, produced from vegetable oils or animal fats. Most of the bio-diesel that is currently made uses semi-refined and refined vegetable oils as the predominant feedstock. The high value of edible grade vegetable oils such as soybean and rapeseed oil in most countries makes production of bio-diesel a cost effective very challenging. However there are large amounts of vegetable oils refining byproducts, known as soapstock, available at low cost that could be converted to bio-diesel economically competitive. The problem with processing these low cost feedstock is that they often contain large amount of free fatty acids( FFA) that can not be converted to bio-diesel by using a conventional alkaline catalyzed transestreification process. At the University of Zimbabwe, we are working on alternative renewable fuels, especially biodiesel from cheap feedstock. The study includes the identification of basic feedstock, their availability in this country and the exploration of issues associated with the economic production of biodiesel. In this study, 100 liters of soybean acid oil was collected from National Food Industries Harare, Zimbabwe. A technique was used to reduce the FFA content of the feedstock by using an acid catalyzed pretreatment to esterify the free fatty acids before transesterifying the triglycerides with an alkaline catalyst and fuel grade bio-diesel was produced about 25% cheaper than petroleum based diesel.