Environmental Engineering Reference
In-Depth Information
OH
NHOAc
O
HO
O
O
O
Chitin
HO
O
NHOAc
n
OH
OH
NH
2
O
HO
O
O
O
HO
Chitosan
O
NH
2
n
OH
OH
OH
O
HO
O
O
O
HO
Cellulose
O
OH
n
OH
FIGURE 2.7
Molecular structures of chitin and chitosan in comparison with cellulose.
2.3.1 Oils and Fats
There are many different plants and animals that store oils and fats in their structures.
These compounds are similar in structure, but their aggregation state is different;
oils are liquid and fats are (partly) solid. The basic molecular structure is that of a glyc-
erol backbone with ester bonds to three carboxylic acids (called
). The
plant-derived oils can be used as a fuel in diesel engines, but they are viscous and
cause specific problems (e.g., interaction with lubrication oils). Therefore, via the
process of transesterification using methanol, resulting in fatty acid methyl esters
(FAMEs), or ethanol, they are converted into biodiesel with improved properties, such
as lower viscosity. Examples of oils that are used as raw materials are rapeseed, soy-
bean, canola, sunflower, sesame, palm, and coconut oils. There is much debate about
this way of utilizing vegetable oils as these can also be used for feeding humans and
animals. The entire picture, though, is somewhat more complicated.
Jatropha
oil, e.g.,
is a specific case where the food/feed versus fuel aspect does not play a role, as the
fruit of the
Jatropha curcas
plant cannot be used for human/animal consumption
due to the presence of certain poisons (the contents of which vary so as to result in
either a nontoxic or toxic fruit). The plant is cultivated in Central and South America,
Southeast Asia, India, and Africa. It is easy to grow on widely differing and difficult
soils, such as gravelly, sandy, and saline soils, that are not suitable for most other crops
“
fatty acids
”
Search WWH ::
Custom Search