Solid Waste Management Methods: Segregation, Composting and Landfills

Once solid waste has been generated, how it is actually collected, sorted and disposed of determines whether it becomes a manageable resource or an accumulating environmental hazard. This section covers the practical, on-the-ground methods that put the 3R principle into effect for the waste that a household, institution or municipality actually produces.

The first and most important practical step is segregation of waste at source -- meaning that waste is sorted into separate categories at the very point where it is generated, before it is collected, rather than being mixed together in a single bin and sorted (imperfectly, at much greater cost and difficulty) afterwards. Waste is typically segregated into at least three streams: biodegradable waste (kitchen and food waste, garden trimmings, and other organic matter that decomposes naturally), non-biodegradable waste (most plastics, and other material that does not break down through natural biological processes on any reasonable timescale), and recyclable waste (paper, glass, metals and certain plastics that can be reprocessed into new material). Segregation at source matters enormously because it keeps biodegradable waste -- which can rot, produce foul odours and attract disease-carrying pests if mixed with other waste -- separate and available for composting, keeps recyclables clean and uncontaminated so they retain their value for recycling, and reduces the volume of genuinely unusable waste that must ultimately be sent to a landfill.

Biodegradable waste that has been separated out can be converted into useful manure through composting: organic waste is piled or contained under conditions that allow naturally occurring micro-organisms to decompose it aerobically (in the presence of oxygen) into a dark, crumbly, nutrient-rich material called compost, which greatly improves soil fertility and structure when applied to farmland or gardens. Vermicomposting is a related and increasingly popular technique in which specific species of earthworms (commonly red wiggler earthworms) are introduced into the organic waste; as the earthworms feed on the waste and pass it through their digestive systems, they accelerate decomposition considerably compared with ordinary composting and produce a particularly fine, nutrient-dense product known as vermicompost, along with earthworm castings that further enrich the soil. Vermicomposting is especially attractive at a household or community scale because it can be carried out in a relatively small space, requires no external energy input, and converts kitchen and garden waste that would otherwise go to a landfill into a genuinely valuable soil amendment. …