Biodegradable waste

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. Biodegradable waste when not handled properly can have an outsized impact on climate change, especially through methane emissions from anaerobic fermentation that produces landfill gas. Other approaches to reducing the impact include reducing the amount of waste produced, such as through reducing food waste. Biodegradable waste can be found in municipal solid waste (sometimes called biodegradable municipal waste, or as green waste, food waste, paper waste and biodegradable plastics). Other biodegradable wastes include human waste, manure, sewage, sewage sludge and slaughterhouse waste. In the absence of oxygen, much of this waste will decay to methane by anaerobic digestion. In the UK, 7.4 million tonnes of biodegradable waste was sent to landfill in 2018 having reduced from 7.8 million tonnes in 2017. In many parts of the developed world, biodegradable waste is separated from the rest of the waste stream, either by separate curb-side collection or by waste sorting after collection. At the point of collection such waste is often referred to as green waste. Removing such waste from the rest of the waste stream substantially reduces waste volumes for disposal and also allows biodegradable waste to be composted.