Waste is a byproduct of life and civilisation; it is the material that remains after a useful component has been consumed. From an economic perspective, waste is a material involved in life or technology whose value today is less than the cost of its utilisation. From a regulatory viewpoint, waste is anything discarded or can no longer be used for its original purpose. The term solid waste includes not only solid materials but also liquid and gases. If one reuses something, it may not be considered waste.
Domestic waste(also known as rubbish, garbage, trash, or junk) is unwanted or undesired material (although the old adage one man's waste is another man's treasure sometimes applies). Waste is the general term; though the other terms are used loosely as synonyms, they have more specific meanings: rubbish or trash are mixed household waste including paper and packaging; food waste or garbage (North America) is kitchen and table waste; and junk or scrap is metallic or industrial material. There are other categories of waste as well: sewage, manure, ash, and plant materials from garden operations, including grass cuttings, fallen leaves, and pruned branches.
Industrial waste is waste produced by factories, mills, and mines. Chemical waste and toxic waste(usually a subcategory of chemical waste) are two more specific designations of industrial waste.
Municipal solid waste(MSW) is a waste that includes predominantly household waste (domestic waste) with sometimes the addition of commercial waste collected by a municipality within a given area. They are in either solid or semisolid form and generally exclude industrial hazardous waste. The term residual waste relates to waste left from household sources containing materials that have not been separated out or sent for reprocessing.
In this chapter, the components of waste is be described. Then, the processes to generate fuels derived from various domestic, urban, forestry, farm, crop and agricultural wastes will be explained, and the associated fuels characterized.