18.1.2 Solid waste
Solid waste is defined as any waste that is dry in form and is discarded by people as unwanted. You can describe the solid waste from general housekeeping as residential waste, refuse, household waste or domestic waste. Waste produced in other areas is defined as industrial, commercial, institutional or agricultural waste, or street sweepings, depending on its source. In urban settings, municipal waste refers to the solid waste that is collected by local government (the municipality) and may include household, commercial, industrial waste and street sweepings. The solid waste that is produced as a result of food preparation, or any foodstuff leftover after eating, is called kitchen waste or garbage.
Understanding the appropriate methods for the management of solid waste is closely related to the characteristics of the waste and therefore to its source. Considering the sources one by one:
- a.Residential waste or domestic waste is generated from households. It is mostly characterised as non-hazardous wastes, especially in rural households. It may include rubbish, such as packaging materials, kitchen wastes, ash, etc.
- b.Agricultural solid wastes could include food residues, animal dung, crop residues, grass and leaves. Such wastes are mostly non-hazardous and biodegradable in nature. However, containers for used or obsolete pesticides, herbicides and rodenticides could be a health hazard to families and sprayers. Therefore, these items should be safely removed in collaboration with the agricultural development extension agents in your kebele.
- c.Commercial wastes are those generated from business establishments, food and drink service establishments, shops, or open market places. These vary a great deal but may include packaging paper, cardboard, electronics, timber, wire, metals, plastic bags (festal), tin cans, garbage and other wastes that are generally of non-hazardous nature.
- d.Industrial waste can be produced from small, medium or large-scale industries. The type of waste produced may vary depending on the raw material used and the product of the industrial process. These wastes may be hazardous or non-hazardous, depending on the process. The solid waste produced could contain chemicals, wood, metal, ceramic or other components.
- e.Institutional solid waste is produced from public or government institutions, offices, schools, universities, religious institutions, sporting fields, etc. It can be very mixed in its components.
- f.Healthcare waste is produced from healthcare facilities such as Health Posts, health centres and hospitals. This category of waste is composed of both hazardous (infectious) and non-hazardous wastes (also referred to as general waste). The management of healthcare waste needs special attention and is discussed in Study Session 23.
The rate of production and characteristics of residential or domestic solid waste depends on cultural habits, urbanisation, season of the year and the agro-ecological zone of the area.
Can you think of some differences in the kitchen waste produced in the dry and wet seasons?
Your answer will depend on where you live and the type of foodstuff that is ripe during that particular season but you may have answered leaves of maize and maize husk, peelings of potatoes or sweet potatoes during the wet seasons and pods of chick peas (shimbra tirtir) during the dry season.
Urban and affluent societies tend to produce greater quantities of solid waste than rural communities. Rural waste comes from households and agricultural activities and is mostly organic and biodegradable in nature. This makes it suitable for making compost. Compost is a mixture of decomposed organic matter, mostly of plant origin, that can be used to improve soil structure and to return nutrients to the land.
Solid waste generated from households in your community will consist mostly of organic decomposable matter that will be broken down through bacterial action. In urban areas, where there is a large amount of solid waste, it is usually taken to a landfill site for disposal. Landfill sites, also known as dumps or rubbish dump sites, are sometimes located in places such as former quarries where the waste can be used to fill in a hole in the ground, hence the name ‘land fill’. In landfill sites and some community waste disposal sites, the solid waste decomposition process will produce leachate. Leachate is formed when the liquid fraction from a mixed solid waste is separated by gravity from the solid component. Unless controlled, the leachate will seep out from the bottom of the waste tip and can pollute surface and groundwater. It may contain toxic chemicals in addition to pathogenic microorganisms. The biosolids (the solid fraction) as well as the leachate formed in this process need to be disposed of safely in a way that will not affect the environment or human living conditions.