Page 238 - Biofuels Refining and Performance

Chapter
8

Cracking of Lipids for Fuels

and Chemicals

Ernst A. Stadlbauer and Sebastian Bojanowski

8.1 Introduction
Lipids [1] in the form of fat and edible oils are important energy sources
for humans due to the high calorific value of triacylglycerols (~37 kJ/g, or
~9 kcal/g) and the nutritional benefits of both essential fatty acids and
phosphate. In addition, energy stored in lipids may be technically realized
by either direct use in combustion or by upgrading into a more versatile
fuel. In this respect, lipids play an important role for providing lighting
and warmth.
Historically, whale oil lamps and tallow candles were gradually dis-
placed by kerosene lamps and electric bulbs [2]. Nowadays, lipids are
attracting interest as a renewable source of fuels and chemical feedstock.
Therefore, segmentation in the marketplace for lipids is noticeable [3].
In emerging economies of eastern Asia, there is a demand for cheap,
edible commodity oils, such as soybean or palm oils. In developed
economies, a nutritionally led demand for niche oils, such as low-trans-
fat oils, high-omega-3 oils, and enhanced lipophilic vitamins (especially
A and E), prevails. More recently, nonedible uses of lipids arise from the
proliferating demand for alternative fuels [4] to substitute liquid hydro-
carbons derived from mineral oil [5]. Such strategies fall into four broad
categories. One is aimed at fueling diesel engines with pure vegetable oils
[6] or vegetable oil–fossil fuel blends [7]. The other focuses on biodiesel
(alkyl esters of fatty acids), which is mainly sourced from rapeseed and
palm oils [8–10]. Problems [11] associated with the more polar charac-
teristics of vegetable oil and biodiesel in comparison to conventional

221
Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.