Environmental Engineering Reference
In-Depth Information
Table 2.1. Global production of agro-crop residues as calculated by Tao et al . (2012a) using FAOSTAT
statistics (2009) and the residue-product ratio of Koopmans (1997).
Tg
Tg ∗∗
% of total
% of total ∗∗
Agrocrop
Residue
% accumulated
Maize
2020.7
30.2
30.2
Stalks
1634.2
24.4
Cob
223.1
3.3
Husks
163.4
2.4
Rice
1373.7
20.5
50.7
Straw
1192.5
17.8
Husk
181.2
2.7
Wheat
1193.4
17.8
68.5
Straw
1193.4
17.8
Sugar cane
992.7
14.8
83.4
Tops
504.8
7.5
Bagasse
487.9
7.3
Soybeans
777.9
11.6
95.0
Straw, pods
777.9
11.6
Groundnut
98.6
1.5
96.5
Straw
81.7
1.2
Husks
16.9
0.3
Oil palm
90.2
1.3
97.8
Bunches
47.7
0.7
Fibre
29.0
0.4
Shell
13.5
0.2
Millet
56.1
0.8
98.6
Stalks
56.1
0.8
Coconut
32.3
0.5
99.1
Husks
25.1
0.4
Shells
7.2
0.1
Coffee
17.3
0.3
99.4
Husks
17.3
0.3
Cassava
14.9
0.2
99.6
Stalks
14.9
0.2
Tobacco
13.8
0.2
99.8
Stalks, etc.
13.8
0.2
Jute
8.5
0.1
99.9
Stalks
8.5
0.1
Cocoa
4.2
0.1
100.0
Pods
4.2
0.1
Sum
6,694.3
6,694.3
100.0
100.0
million tonnes; 1 Pg
1000 million tonnes. ∗∗ accumulated.
=
1000 Tg
=
Including forestry residuals and manure, Woolf et al . (2010) calculated that around 5 Pg of
biomass is produced around the world annually that is suitable for energy conversion and could
be exploited without endangering food security, habitats, or soil conservation. Table 2.2 presents
a breakdown of this available biomass in terms of the feedstocks from which it derives.
There are some limitations that restrict the scope for growing biomass crops as feedstocks for
biofuel production. Some of these stem from the need for specific ecosystem services to maintain
crop growth (e.g. the availability of fresh water). Others relate to the need to conserve existing
habitats (i.e. biological conservation). Finally, most existing ecosystems have some quantity of
stored carbon that may be released into the atmosphere as CO 2 or methane (CH 4 ) in response
to land use changes, which would result in increased greenhouse gas emissions. Consequently,
 
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