Course: BFM 202 Biodiesel Production

Lecture

Choosing Feedstock
Credits
BFM 202 Biodiesel Production Unit 4 Lecture has been adapted from "ENGY 131 Lesson 4 Alternate Biodiesel Feedstocks” by Southeastern Illinois College.

ENGY 131 Biodiesel Production course content by Southeastern Illinois College is licensed under a Creative Commons Attribution 3.0 Unported License. Except where indicated otherwise.

Unit 4 Alternative Biodiesel Feedstocks

Choosing Feedstock

Biodiesel is referred to as a green fuel and is fulfilling its promise
as a replacement for petroleum-based diesel.

In the last unit, we learned that the transesterification of triglycerides
produces biodiesel and its by-product, glycerol. We also learned that
excess free fatty acids (FFA) creates soap during the process and that
the goal is to have a highly-refined oil feedstock that contains less
than 1 percent FFA. In this unit, we look at the complexities involved in
choosing feedstock.

Cost and availability are the primary drivers in selecting a feedstock.
The less refinement and preparation a feedstock requires, the cheaper
the biodiesel becomes. This explains why rapeseed, soybeans, palm oil,
and jatropha are the most popular feedstock choices, globally. Each has
fewer free fatty acids and less moisture, therefore, requiring less preparation.

Mad Cow disease and biodiesel: A real controversy . . . or not

In the 1990s, there was concern regarding the use of bovine, or cattle,
lipids as a source of animal fat feedstock for biodiesel due to infectious
proteins present in the form of Creutzfeldt-Jacob, or mad cow, disease.
The issue was whether or not Mad Cow disease could be spread via the
exhaust emissions of diesel engines. The World Health Organization, the
U.S. Food and Drug Administration, and the Scientific Steering Committee
of the European Commission, have concluded that the tallow fraction of rendered
animals do not pose a health risk since the infectious proteins would separate
with the meat and bone rather than the lipids during processing.

Restaurant cooking oil waste and animal fat from slaughter processing
are cheap, low-quality oils used for feedstocks that can help to support
the economic feasibility of biodiesel. The problem with these low
quality oils is that the high FFA content causes soap to form, making
the separation of biodiesel and glycerin difficult and expensive. The
soap formation results in poor yields, therefore a pre-treatment for the
feedstock is necessary and expensive which increases the biodiesel price
at the pump.

There are acid catalysts that help reduce FFA's soap formation but they
aren't very effective in high moisture feedstocks and cause serious
environmental issues due to the corrosive properties of those acid-based
catalysts. This prevents them from being cost effective.

Crude vegetable oils with high FFA can be blended with diesel for use in
diesel engines. To this end, Jatropha Curcas L. (CJO) is being heavily
researched. Jatropha is a non-edible tree-based oil with a high FFA
content but still lends itself to being considered as a leading blending
source for diesel. Blended CJO is being analyzed for engine performance
and emissions properties in direct injection (DI) diesel engines. The
effect of FFA on other critical fuel properties is also being investigated.