What are agriculture residues?
Agriculture residues directly burnt as fuel in developing world include crop residues, forest litter, and also grass and animal garbage. Crop residues are more widely burnt than animal waste and forest litter.
Crop residues encompasses all agricultural wastes such as straw, stem, stalk, leaves, husk, shell, peel, lint, stones, pulp, stubble, etc. which come from cereals (rice, wheat, maize or corn, sorghum, barley, millet), cotton, groundnut, jute, legumes (tomato, bean, soy) coffee, cacao, olive, tea, fruits (banana, mango, coco, cashew) and palm oil.
|Crops||Crop wastes||Residues production|
|Rice||Straw, husk, bran||1.5t of straw and 0.2t of husk from 1t of rice|
|Wheat||Straw, husk, bran||2t of residues from 1t of wheat seed|
|Maize||Stalk, leaves||6t of waste from 1t of maize (leaves + stalks 4t)|
|Sorghum||Straw, bran||2.5t of residues from 1t of sorghum seed|
|Barley||Straw, bran||1.5t of straw from 1t of barley|
|Millet||Straw, bran||2t of residue from 1t of millet produced|
|Cotton||Stalk, lint, hull||0.2t of waste from 1t of cotton seed|
|Groundnut||Shell, stalk, leaves||25% of shell weight from non husked|
|Coffee||Pulp, husk||3.6t of waste from 1t of green coffee|
|Coco||Hull, fibre||0.9t of waste from 1t of coconut|
|Palm oil||Shell, fibre, fruit bunches||75% waste from weight of fruit bunch|
Sources: (1) Memento de l’agronome : quatrième edition 1640 pages (2) J lamptey and al – 1990- bioenergy – IDRC/UNU - 210 page (3) CowiConsult – 1984 – Etude d’une utilisation efficace des déchets agricoles comme fuel domestiques au Sénégal 250 pages
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.
|SPECIES||Daily manure yield as % of liveweight||Animal liveweight (Kg)||Animal liveweight (Kg)||Dung yield (Kg/day)||Dung yield (Kg/day)|
Source: (1) Memento de l’agronome : quatrième edition (2) GTZ – 1989 – biogas plants in animal husbandry – 134 pages
Agricultural residues characteristicsIn the developing world, most agricultural residues burnt 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, char briquette. The main differences are the high content of volatile matter and lower density and burning time.
|Agricultural residues||Volatiles (%)||Fixed carbon (%)||Ash (%)||HHV (Kj/kg)||LHV (Kj/kg)||Density (%)|
|Bagasse||75.10||16.87||8.03||19.50||19.37||40 - 60|
|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|
|Sal seed leaves||60.03||20.22||19.75||18.57||18.42|
|Sal seed husk||62.54||28.06||9.40||20.60||20.13|
Concerning animal waste, the calorific values of cow dung and chicken droppings are respectively 16 – 19 Mj/kg and 14 - 16 Mj/kg. Cow dung calorific value is more important than the one of wood.
Who uses them?The rural families in the villages who own agricultural land use their own agricultural residues which varies throughout the year as per the crop planted. They use it as a household fuel for cooking, heating water and for space heating in colder climates.
Agricultural wastes are directly burnt to meet the need of cooking. Crop residues are yet used to light wood and charcoal.
West African potters burn a large amount of agricultural residues in their traditional pottery pit in order to produce their canaris, earthenware jars, ceramic stoves and other pottery.
In the part of the world faced by the scarcity of woodfuel and the cost-effective fuel substitutes, agricultural waste (owing to its high potentiality) may play a major role on sustainable energy. However the traditional use of crop residues and the lack of information on modern technologies such as briquetting, pelleting, and bioconversion, limit the development of large scale use which leads to increase the value of agricultural output.
Agriculture as a biomass supplier is yet affected by soil quality. Agricultural wastes can be used as either fuel or fertilizer. So the bio digestion of agricultural residues leads to provide both energy (biogas) and upgraded fertilizer than raw waste.
Agricultural residues potentiality in developing worldAgricultural wastes potentiality can be estimated by the following formulae:
means the potentiality of crop residues where “a” represents the crop production; “b” designs the crop residue yield production, and “i” the type of crop. when the calorific value of each type of crop is used the potentiality can be calculated in TOE (ton crude oil equivalent).
means the potentiality manure production where “alpha” represents the number of animal head; “b” designs the garbage yield production, and “i” the animal species.
means the potentiality of crop residues where “S” represents the area of plantation; “R” designs the residue yield production per unit of surface, and “i” the type of crop.
The statistical data about agricultures production are available for any country in the FAO website.
Example: the Senegal crop residues production
|CROP||'CROP PRODUCTION ( tonnes ) 1999'||'CROP PRODUCTION ( tonnes ) 2000'||'CROP PRODUCTION ( tonnes ) 2001'||'CROP PRODUCTION ( tonnes ) 2002'||'CROP PRODUCTION ( tonnes ) 2003'||'CROP PRODUCTION ( tonnes ) annual production'|
|Groundnut||1 014 250||1 061 540||943 837||501 298||900 000||884 185|
|Oil palm||64000||65000||65000||65000||70000||65 800|
|Cotton||14 649||20 411||34 237||33 913||34 000||27 442|
|Rice||239 786||202 293||243 907||177 756||177 756||208 300|
|Coco||4 700||4 700||4 700||4 700||4 700||4 700|
Crop residues productions
|Crop||Residues||Calorific value (KJ/Kg)||Annual crop production (tonnes)||Waste yield (%)||Annual residues production (tonnes)||Energy (TOE)|
|Oil palm||Wastes||16||65800||72.5%||47 705||18.2|
|Millet||Wastes||18||522002.6||200.0%||1 044 005||447.4|
|2830511.2||2 848 107||1171.2|
In Senegal the total of annual crop wastes equals 2 848 107 tonnes or 1171.2 TOE, which represents the amount of imported oil consumed. However the quantity available and exploited is low, under 40%. Bagasse and groundnut shell are widely burnt by industries to meet their energy need in the factories.
- Agricultural residue is a fuel which is available free of cost to the poor rural families.
- It is also a useful way to dispose of the crop residues in the field, instead of burning them in situ.
- Agricultural wastes remain safer than LPG which poses some safety concerns in local transport and use;
- It is easy to handle and transport;
- Low impact on women’s time for harvesting
- Agricultural wastes are much easier to light than wood and charcoal.
- It is responsible for extreme cases of air pollution when it is burned in open fires? or traditional or Improved stoves?.
- It is very bulky and has to be carried to the homes.
- The seasonal availability of crop residues can be limit for its use.
- Its burning time is worse.
- Its storage requires more space in house.
Although the world rice production is important, particularly in developing countries, where it is cropped by family exploitation, its residue is widely used as fuel for cooking. In countries where rice production is important, such as Thailand and the Philippines, improved cooking stoves are made.
Improved cooking stoves used in Thailand : the Meechai, improved rice-husk stove without chimney.
The mayon turbo stove disseminated by REAP Canada
External links and references
ContributorsGrant Ballard-Tremeer 1 September 2003
Dr Karabi Dutta 11 September 2003
Mamadou Fall 12 July 2007