rel="nofollow" href="#ulink_50de99e4-2b8a-53a6-84f7-c6506fb4580a">Table A-6) that can potentially be used for energy applications, in a number of ways. Sources can include: (i) arable crop residues such as straw or husks, (ii) animal manures and slurries, and (iii) animal bedding such as poultry litter.
Table A-6 Examples of crops and crop wastes.
| Crops | Crop wastes |
|---|---|
| Barley | Straw, bran |
| Coco | Hull, fiber |
| Coffee | Pulp, husk |
| Cotton | Stalk, lint, hull |
| Groundnut | Shell, stalk, leaves |
| Jute | Stem |
| Maize | Stalk, leaves |
| Mango | Peel |
| Millet | Straw, bran |
| Palm oil | Shell, fiber, fruit bunches |
| Rice | Straw, husk, bran |
| Sorghum | Straw, bran |
| Tomato | Stem |
| Wheat | Straw, husk, bran |
Forest litter is mainly constituted of dry fallen leaves. Plantations of those species widely used for reforestation or soil conservation/sand fixation such as Eucalyptus and Casuarina equisetifolia, provide an important biomass litter yearly. Animal garbage is livestock manure. Generally, dry animal wastes directly used as fuel are cow and camel dung, and sometimes that of horse and sheep. The quantity of manure produced depends on the amount of fodder eaten, the quality of fodder, and the live weight of the animal. The excrement-yield values vary among the species.
In many developing countries, most agricultural residues burned as fuel are used in their natural state with some pre-treatment like drying, and cutting, and compacting in rare occasions. Crop residues are characterized by its seasonal availability and have characteristics that differ from other solid fuels such as wood, charcoal, and char briquette. The main differences are the high content of volatile matter and lower density and burning time.
The moisture content make wet residues energetically inefficient to use for combustion or gasification. It is preferable to process them close to production, and to use processes that can make use of biomass in an aqueous environment. Any moisture content must be driven off before processing (such as combustion) can take place, either in advance before storage or as part of the combustion process (which then uses part of the energy of the fuel). Gasification also requires relatively low moisture content (<10-15%).
Many of the above agricultural residues may have alternate uses or markets, and any decision to use them for energy must be made in the context of these renewable sources. In particular, many such residues are presently widely used for soil nutrient recycling and improvement purposes and may therefore be displacing significant quantities of synthetic fertilizers or other products. As the manufacture of many of these products entails significant carbon dioxide emissions and energy inputs, their substitution for agricultural residues should not be undertaken without caution.
See also: Agricultural Waste, Biomass, Residues, Rice Straw, Wheat Straw.
Agricultural Residue – Types
The four main types of agricultural residues are (i) feed and seed crop, (ii) fruit and nut crop, (iii) vegetable crop, and (iv) nursery crop and vary in composition (Table A-7).
Table A-7 Properties of various agricultural residues.
| Agricultural residues | Volatiles (%) | Fixed carbon (%) | Ash (%) | HHV (Kj/kg) | LHV (Kj/kg) | Density (%) |
|---|---|---|---|---|---|---|
| Arhar stalk | 83.47 | 14.76 | 1.77 | 15.00 | 14.85 | |
| Bagasse | 75.10 | 16.87 | 8.03 | 19.50 | 19.37 | 40 – 60 |
| Bamboo dust | 75.32 | 15.59 | 9.09 | 16.02 | 15.87 | |
| Cotton stalk | 70.89 | 22.43 | 6.68 | 18.26 | 17.85 | 10 – 20 |
| Coconut coir | 70.30 | 26.77 | 2.93 | 18.20 | 17.79 | 7 – 8 |
| Corn cob | 80.20 | 16.20 | 3.60 | 15.58 | 15.23 | 10 – 20 |
| Dhaincha stalk | 80.32 | 17.01 | 2.67 | 19.63 | 19.43 | |
| Groundnut shell | 68.12 | 24.97 | 6.91 | 17.20 | 17.06 | |
| Jute stick | 75.33 | 19.00 | 5.67 | 19.45 | 19.01 |
