Resource recovery is using wastes as an input material to create valuable products as new outputs. The aim is to reduce the amount of waste generated, thereby reducing the need for landfill space, and optimizing the values created from garbage. Valuable resources can be recovered from wastewater, sewage sludge, faecal sludge and human excreta. These include water, energy, and fertilizing nutrients nitrogen, phosphorus, potassium, as well as micro-nutrients such as Sulphur and organic matter.
Anaerobic digestion of the organic fraction of municipal solid waste (MSW) is more environmentally effective than landfill, incineration or pyrolysis. Waste to energy achieves a reduction of greenhouse gas emissions through three separate mechanisms: (1) by generating electrical power or steam, waste to energy avoids carbon dioxide (CO2) emissions from fossil fuel-based electrical generation; (2) the waste to energy combustion process virtually eliminates all potential methane emissions from landfill, thereby avoiding any possible release of methane in the future; and (3) the recovery of ferrous and nonferrous metals from the municipal solid waste by waste to energy is more energy-efficient than production from raw materials.