Odour from commercial piggeries can be highly offensive. Effluent from pig farms, which generally contain organic matter like faeces, urine, blood, and body parts is the main source of odour.
Wastes need to be treated to prevent it from entering waterways and to manage odour. Solid wastes are removed by screening and can either be composted or buried (for body parts). The remaining liquid waste is stored in lagoons or ponds for microbes to break down.
The treatment process that breaks down piggery wastes releases methane, which is a potent greenhouse gas. Although methane from piggeries can be turned into electricity in anaerobic digesters, methane produced from other livestock, such as cattle is released into the atmosphere.
Read more about how of animal agriculture contributes to global warming and climate change at Terrastendo.