Agricultural Waste Generation Sources and Characteristics

Agricultural waste is defined as unwanted waste produced as a result of agricultural activities (i.e., manure, oil, silage plastics, fertilizer, pesticides and herbicides; wastes from farms, poultry houses and slaughterhouses; veterinary medicines or horticultural plastics).

The by-products of agricultural activities are usually referred to as “agricultural waste”. These wastes take the form of crop residues (residual stalks, straw, leaves, roots, husks, shells etcetera) and animal waste (manures).

Agricultural wastes are widely available, renewable and virtually free, hence they can be an important resource. They can be converted into heat, steam, charcoal, methanol, ethanol, biodiesel as well as raw materials (animal feed, composting, energy and biogas construction etcetera).

Compositions of agricultural wastes depend on the system and type of agricultural activities. They can be in form of liquids, slurries or solids. Agricultural wastes include: animal waste (manure and animal carcasses), food processing waste (only 20% of maize is canned and 80% is waste), crop waste (corn stalks, sugarcane bagasse, drops and culls from fruits and vegetables, pruning) and hazardous and toxic agricultural waste (pesticides, insecticides and herbicides, etc.).

Expansion of agricultural production has naturally resulted in increased quantities of agricultural wastes such as livestock waste, crop residues and agro-allied industrial by-products. There is therefore significant increase in agricultural wastes globally as a result of intensification of farming systems.

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It is estimated that about 998 million tons of agricultural waste is produced yearly (Agamuthu, 2009). It was also reported that organic wastes amount to 80% of the total solid wastes generated in any farm (Brown and Root Environmental consultancy, 1997).

Agricultural Waste Generation Sources

1. Waste from application of chemicals during Cultivation practices

Most crops in tropics do well because of the favorable weather conditions. Likewise generation and development of insects and weeds are also favored by the tropical climates.

As a result, there is high demand for pesticides and insecticides as well as herbicides in order to kill insects and protect plants against the spread of epidemic diseases and weed infestation.

These needs often lead to the abuse of the chemicals by farmers. After use, most of the containers holding these chemicals are usually pitched into fields or surrounding water bodies.

These wastes have the potential to cause environmental hazards such as food poisoning and contamination of the farmland due to their potential to last in the soil.

Also, application of fertilizers plays an important role in maintaining the productivity and quality of plants. However, most farmers apply more fertilizer to their crops than recommended rate in order to boost production (Hai and Tuyet, 2010).

The implication of such excessive application of fertilizer is that portion is retained in the soil, a portion enters in to water bodies as a result of either surface runoff or the irrigation system (which results in the pollution of surface water); while portion enters ground water and a portion escapes into atmosphere and denitrified thus causing air pollution.

2. Waste from livestock production

Waste from livestock activities include solid waste such as manure and organic materials in the slaughterhouse; wastewater such as urine, cage wash water, wastewater from the bathing of animals; from maintaining sanitation in slaughterhouses; and air pollutants and odors.

The pollution caused by livestock production is therefore a serious problem since most of them are usually built around residential areas. Air pollution includes odors emanating from cages resulting from the digestion process of livestock wastes; the putrefaction process of organic matter in manure; animal urine, and/or from redundant foods.

This untreated and non-reusable waste source can generate greenhouse gases while also having negative effects on the fertility of the soil and causing water pollution.

In livestock waste, water volume accounts for 75–95% of total volume, while the rest includes organic matter, inorganic matter, and many species of microorganisms and parasite eggs (Hai and Tuyet, 2010). Those germs and substances can spread diseases to humans and cause many negative effects on the environment.

3. Waste from Aquaculture

Aquaculture production requires the use of inputs, especially feed per unit area of land (Henriksson et al., 2018) leading to an increase in waste generation from the production systems.

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These wastes have little or no economic value and are often a nuisance to the environment. The waste generation from aquaculture has made its sustainability a public concern (Martins et al., 2010).

Reports indicated that metabolic wastes discharged by 63,000 tons of fish produced in Japan in 1999 were equivalent to the waste generated by 5 million people (Suzuki et al., 2003). This underscores the need for proper methods to ensure the sustainable intensification of aquaculture.