Environmental Engineering Reference
In-Depth Information
Energy crops can be classified into three groups based on the part of the plant material
utilized and the conversion process (Sims et al., 2006):
1. Sources of sugars (e.g., sugar beet, Jerusalem artichoke, sugarcane, and sweet sorghum),
and starches (e.g., barley, wheat, oats, corn, and rye).
2. Sources of lignocellulosic materials (e.g., straw and wood), short rotation crops, and solid
energy crops (e.g., whole crop maize, reed canary grass, miscanthus, short rotation trees,
and eucalyptus).
3. Sources of vegetable oils (e.g., rapeseed, linseed, soybean, sunflower, safflower, castor
oil, olive, palm, and coconut).
A different type of classification groups energy crops depending on their origin in:
Woody plants,
●
Herbaceous plants and grasses,
●
Aquatic plants,
●
Manures (McKendry, 2002).
●
Regardless of classification, ideal energy crops should produce a high yield, have a low
cost, require low energy inputs, demand low nutrients and water, and have a composition with
low level of contaminants (McKendry, 2002).
Matching the conversion technologies, feedstocks are also classified in three generations:
First-generation feedstocks are corn and sugarcane for ethanol and soybeans for
biodiesel.
●
Second-generation feedstocks are crop residues.
●
Third-generation feedstocks are dedicated energy crops, which include lignocellulosic
materials such as perennial grasses, fast growing trees, and algae (Biomass Research and
Development Initiative [BDRI], 2008).
●
Table 14.5
Composition of biomass for selected materials.
Biomass source
Composition of biomass (wt%, dry basis)
Sugars
Cellulose
Hemicellulose
Lignin
Others
Bagasse
3
38
27
20
12
Molasses
61
—
—
—
39
Sugarcane prepared
43
22
15
11
9
Sugarcane leaves
—
36
21
16
27
Sugarcane whole
33
25
17
12
13
Napier grass
—
32
20
9
39
Sugarcane hybrids
28
37
14
15
6
Sweet sorghum
34
36
16
10
3
Eucalyptus grandis
—
38
13
37
12
Eucalyptus saligna
—
45
12
25
18
Leucaena leucocephala
—
43
14
25
18
Municipal solid waste
—
33
9
17
41
Newspaper
—
62
16
21
1
Reproduced from Saxena et al., 2009, with permission from Elsevier.
