Biodegradable waste


Biodegradable waste includes any organic matter in waste which can be broken down into carbon dioxide, water, methane or simple organic molecules by micro-organisms and other living things by composting, aerobic digestion, anaerobic digestion or similar processes. 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 organic sulfates which can decompose to yield hydrogen sulphide 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.

Climate change impacts

The main environmental threat from biodegradable waste is the production of landfill gases. Landfill gas is generated by degradation of the biodegradable waste fraction, and is influenced by waste physicochemical composition and environmental variables. Studies have shown that the actual rate of gas production in a landfill is a function of waste composition, age, climate variables, moisture content, particle size, compaction and buffering capacity. LFG mainly consists of carbon dioxide, methane and numerous trace components. Methane is the second most important anthropogenic greenhouse gas after CO2 and is responsible for approximately 40% of global warming over the past 150 years. Further, for the past 25 years, global anthropogenic methane emissions have exceeded those from natural sources. Emissions from landfill sites account for 30% of the total anthropogenic methane emissions in Europe, 34% of those in the US, and 10% of anthropogenic methane emissions worldwide. Landfill gas emissions are one of the largest anthropogenic sources of methane especially because of food waste. Globally, if food waste couple be represented as its own country, it would be the third largest greenhouse gas emitter, behind China and the U.S. It has become important to reduce food waste related emissions by distinguishing between waste arising at two different stages in the food system: pre-consumer waste and consumer waste. A distinction is also made between two different types of emission; embedded emissions and waste disposal.