Environmental Engineering Reference
In-Depth Information
rice—one of the basic foodstuffs for a significant portion of humankind. The annual production of
rice in 1999 was approximately 600 million t (Gunstone and Harwood 2007 and references therein);
however, the production of rice bran oil is approximately 0.7-1.0 million t (Gunstone and Harwood
2007) with India, China, and Japan being the major producers of this oil. Rice bran, obtained after
removing the hull and abrading the bran layer, contains 18-24% oil and 4-6% free fatty acids, fibers,
protein, and carbohydrates. The major fatty acids in rice bran oil are palmitic, oleic, and linoleic
acids with smaller amounts of stearic and linolenic acids and traces of other fatty acids such as 14:0,
16:1, 20:0, 20:1, and 22:1. Rice bran oil contains a number of other constituents, including waxes
(2-4%; esters of saturated fatty acids with saturated alcohols), monomethylsterols, dimethylsterols,
and tocotrienols, the latter together with oryzanols imparting high oxidative stability to rice bran
oil (Gunstone and Harwood 2007). Numerous publications have dealt with biodiesel derived from
rice bran oil (Table 33.1).
33.2.5 o
livE
o
il
Olive oil is a commercialized oil of recognized nutritional value and is expensive compared with
other oils. It is therefore not listed in Tables 33.1 and 33.2. It can only be seen as an experimental
source of fuel, if at all, and it is only briefly mentioned in this section. It also appears that this oil
would be potentially strongly affected by the food-versus-fuel issue. A study has dealt with Turkish
sulfur olive oil as fuel source (Aksoy et al. 1988), and other reports have examined olive oil as a
supplement to petrodiesel fuel (Rakopoulos et al. 1992a, 1992b; Rakopoulos et al. 2006). Other
works have focused on used olive oil, which would be less affected by the aforementioned issues, as
a source of biodiesel (Dorado et al. 2003a, 2003b, 2004; Yuste and Dorado 2006).
33.2.6 o
ilS
with
v
arying
f
atty
a
cid
p
rofilES
Most commodity oils such as soybean and rapeseed (canola) oils as well as most lower-volume and
“emerging” oils such as those discussed in this chapter possess fatty acid profiles consisting largely of
the five major species—C16:0, C18:0, C18:1, C18:2, and C18:3. As a result, the biodiesels derived from
these feedstocks exhibit the common problems of poor cold flow and oxidative stability with varying
severity. Feedstocks with high amounts of C16:0 and/or C18:0 will demonstrate poor cold flow. The
presence of even longer-chain unsaturated fatty acids such C20:0 and C22:0 in some feedstocks will
exacerbate the cold-flow problem. For example, biodiesel derived from moringa oil, which contains
approximately 23.5% saturated fatty acids, 4% being C20:0 and 7% being C22:0, together with
approximately 72% C18:1, has a cloud point of 18°C (Rashid et al. 2008). Conversely, feedstocks with
high amounts of polyunsaturated fatty acids will possess insufficient oxidative stability. For example,
camelina oil (Chapter 2.8) used for biodiesel production had around 38.4% C18:3 (Bernardo et al.
2003; Froehlich and Rice 2005). However, it must be considered that small amounts of polyunsaturated
fatty acid chains may exert greater influence on oxidative stability than the small amounts indicate.
Some of the oils listed in a compilation of 75 nontraditional seed oils for potential biodiesel
use in India contain major amounts of fatty acids beyond the five most common ones (Azam et al.
2005). The biodiesel fuels from oils with significant amounts of eleostearic acid displayed low
cetane numbers, with the cetane number of biodiesel from
Aleuritis montana
(64.6%—eleostearic
acid = 9
t
,11
t
,13
t
-octadecatrienoic acid) reported as 20.56, that of biodiesel from
Aleuritis fordii
(tung oil; 81.5%—eleostearic acid = 9
c
,11
t
,13
t
-octadecatrienoic acid) given as 36.25, and that of
biodiesel from
Mallotus phillippinensis
(72% kamlolenic acid = 18-hydroxyeleostearic acid) listed
as 36.34. Biodiesel from tung oil displayed a relatively high viscosity of approximately 7 mm
2
/s
(Shang et al. 2010), a possible reason being its low stability which may lead to polymer formation.
Other authors reported some fuel-related properties of 17 untransesterified Kenyan vegetable oils
(Munavu and Odhiambo 1984) and of six other seed oils from tropical Africa (Eromosele and
Paschal 2003).
