Field and seed crop residues are the materials remaining above the ground after harvesting, including straw or stubble from barley, beans, oats, rice, rye, and wheat, stalks, or stover from corn, cotton, sorghum, soybeans, and alfalfa. The moisture content (wet basis) of these residues ranges from 8 to 80%. The typical bulk density of loose straw and stover varies from 1 to 3 lb/ft3 and the bulk density of baled straw and stover varies from 7 to 12 lb/ft3. If pelletized, the bulk density increases to 35 to 45 lb/ft3.
Fruit and nut crop residues include orchard pruning residues and brushes. The types of fruit and nut crops include almonds, apples, apricots, avocados, cherries, dates, figs, grapefruit, grapes, lemons, limes, olives, oranges, peaches, pears, plums, prunes, and walnuts. The moisture content (wet basis) of these residues ranges from 35 to 55%. Hammer-milled orchard pruning residues have a bulk density of from 9 to 12 lb/ft3.
Vegetable crop residues consist mostly of vines and leaves that remain on the ground after harvesting. The types of vegetable crops include such plants as artichokes, asparagus, cucumbers, lettuce, melon, potatoes, squash, and tomatoes. The moisture content (wet basis) of these residues is usually greater than 90%.
Nursery crop residues include the pruning residues and trimmings taken from the plants during their growth and in the preparation for market. There are more than 30 different species of nursery crops (such as flowers and indoor plants) that are grown. The moisture content of these residues is usually dependent on the type of crop that is being grown.
Quantifying the amounts and types of agricultural residues generated in each of the crop categories is extremely difficult, as it would require conducting comprehensive research throughout the state with continuous updates to the compiled data. Without ongoing data collection, any quantification estimates would only be valid for the time frame that the study was done and would be susceptible to ongoing market changes. Any quantification of agricultural residue tonnages should be viewed with these inherent limitations in mind and the tonnages quoted should not be considered absolute values.
See also: Agricultural Residues, Agricultural Waste, Residues, Rice Straw, Wheat Straw.
Agricultural Waste
Agricultural waste is the waste material remaining after processing crops to a marketable material or as a result of various agricultural operations. Agricultural wastes, which may include horticultural and forestry wastes, comprise crop residues, animal manure, diseased carcasses, as well as other wastes from farms, poultry houses and slaughterhouses, harvest waste, fertilizer run-off from fields, pesticides that enter into water, air, or soil; and salt and silt drained from fields.
The composition depends on the system of agriculture. Estimates of agricultural wastes are rare, but they are generally thought of as contributing a significant proportion of the total waste matter in the developed world. Since 1960, as a result of huge rises in productivity, there have been corresponding increases in the volumes of crop residues and animal manure requiring disposal. There is likely to be a significant increase in agricultural wastes globally if developing countries continue to intensify farming systems.
Agricultural wastes include both natural (organic) and non-natural waste materials. The main non-natural wastes include packaging, non-packaging plastics (such as silage and horticultural films); agrochemicals; animal health products (such as used syringes); waste from machinery (such as oil, tires, and batteries) and building waste (such as asbestos sheeting). Common wastes are sugar cane bagasse and cotton gin trash. Many agricultural wastes are sold as animal feed and materials unsuitable for use as animal feed are typically burned on site as fuel, thereby giving some processing plants the potential for being self-sufficient in energy.
See also: Agricultural Residues, Residues, Rice Straw, Wheat Straw.
Agrofuel
An agrofuel is a type of biofuel which is solid, liquid, or gaseous fuel and is obtained from relatively recently lifeless or living biological material. An agrofuel is a fuel that is obtained as a product of agriculture biomass and by-products at farming level, and/or industrial processing of raw material (agro-industries). The term covers mainly biomass materials derived directly from fuel crops and agro-industrial and animal by-products (Table A-8).
The three main types of biofuel are: (i) agrofuels, (ii) wood fuels, and (iii) municipal waste (sometime referred to as municipal by-products) which include gas, liquid, and solid products derived from processing activities (Table A-8) in which the major consideration is to identify the basic site where biomass production takes place. It is often necessary to distinguish whether the biofuel was connected to forest, agricultural, or municipal activities. The inclusion of a group on the use of agrofuels aims at distinguishing classical biofuels (generally related to forest exploitation) from those oriented toward annual or pluri-annual plantation.
Table A-8 Types of renewable fuel sources and products.
| Source | Phase | Products |
|---|---|---|
| Agrofuels | Gas | Biogas, producer gas, pyrolysis gas from agrofuels |
| Liquid | Ethanol, vegeTable oil, methanol, pyrolysis oil | |
| Solid | Straw, stalks, husks, bagasse, charcoal | |
| Woodfuels | Gas | Products from gasification and pyrolysis gases |
| Liquid | Black liquor, methanol, pyrolysis oil | |
| Solid | Fuelwood (chips, sawdust, pellets), charcoal | |
| Municipal waste | Gas | Landfill gas, sludge gas |
| Liquid | Sewage sludge, pyrolysis oil | |
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