Waste valorization in the context of "Non-biodegradable"

Biodegradable waste includes any organic matter in waste which can be broken down into carbon dioxide, water, methane, compost, humus, and simple organic molecules by micro-organisms and other living things by composting, aerobic digestion, anaerobic digestion or similar processes. It mainly includes kitchen waste (spoiled food, trimmings, inedible parts), ash, soil, dung and other plant matter. In waste management, it also includes some inorganic materials which can be decomposed by bacteria. Such materials include gypsum and its products such as plasterboard and other simple sulfates which can be decomposed by sulfate reducing bacteria to yield hydrogen sulfide in anaerobic land-fill conditions.

In domestic waste collection, the scope of biodegradable waste may be narrowed to include only those degradable wastes capable of being handled in the local waste handling facilities. To address this, many local waste management districts are integrating programs related to sort the biodegradable waste for composting or other waste valorization strategies, where biodegradable waste gets reused for other products, such as using agricultural waste for fiber production or biochar.

Scrap consists of recyclable materials, usually metals, left over from product manufacturing and consumption, such as parts of vehicles, building supplies, and surplus materials. Unlike waste, scrap can have monetary value, especially recovered metals, and non-metallic materials are also recovered for recycling. Once collected, the materials are sorted into types – typically metal scrap will be crushed, shredded, and sorted using mechanical processes.

Metal recycling, especially of structural steel, ships, used manufactured goods, such as vehicles and white goods, is an industrial activity with complex networks of wrecking yards, sorting facilities, and recycling plants. The industry includes both formal organizations and a wide range of informal roles such as waste pickers who help sorting through scrap.

In mining, tailings or tails are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different from overburden, which is the waste rock or other material that overlies an ore or mineral body and is displaced during mining without being processed. Waste valorization is the evaluation of waste and residues from an economic process in order to determine their value in reuse or recycling, as what was gangue at the time of separation may increase with time or more sophisticated recovery processes.

The extraction of minerals from ore can be done two ways: placer mining, which uses water and gravity to concentrate the valuable minerals, or hard rock mining, which pulverizes the rock containing the ore and then relies on chemical reactions to concentrate the sought-after material. In the latter, the extraction of minerals from ore requires comminution, i.e., grinding the ore into fine particles to facilitate extraction of the target element(s). Because of this comminution, tailings consist of a slurry of fine particles, ranging from the size of a grain of sand to a few micrometres. Mine tailings are usually produced from the mill in slurry form, which is a mixture of fine mineral particles and water.