Farming with raw sewage
Farming with raw sewage is a common practice, particularly in areas of the world where water is scarce, but has risks to human health. About 10% of crops worldwide are fertilised using human effluent, and in some countries, such as Pakistan, the figure is closer to a quarter of all yields. Farmers in developing nations sometimes fertilise their crops using raw human waste, or allow material from nearby piping to irrigate their fields, because sewage is rich in nitrates and phosphates. Worldwide, the practice is typically illegal, but continues to occur since well-nourished crops are more profitable. Countries such as Mexico and Tunisia generally treat the waste before applying it to crops, but in other countries, such treatment is rare. Worldwide, 200 million farmers use sewage on about 20 million hectares of land, and it is valuable enough that auctioneering of sewage to farmers is not unheard of - for example, in the city of Faisalabad, Pakistan.
Using raw sewage is generally unacceptable because dangerous micro-organisms such as the E.coli bacteria can survive for months in it. However, treated waste, or 'biosolids', can be used to produce natural gas for a population's energy needs, as well as for farming.
- New Scientist: 'World's farmers turn to raw sewage for irrigation', 18th August 2008, and 'Sewage waters a tenth of world's irrigated crops', 18th August 2004.
- National Geographic: 'Human waste used by 200 million farmers, study says'. 21st August 2008.
- New Scientist: 'World's farmers turn to raw sewage for irrigation', 18th August 2008.
- New Scientist: 'Waste not'. 29th August 1998.
- Reuters: 'Texas city plans to convert human waste to energy'. 9th September 2008.