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One-tenth of the world's irrigated crops--everything from lettuce and tomatoes to mangoes and coconuts--are watered by sewage. And much of that sewage is raw and untreated, gushing direct from sewer pipes into fields at the fringes of the developing world's great megacities, reveals the first global survey of the hidden practice of waste-water irrigation. And, however much consumers may squirm, farmers like it that way. Because the stinking, lumpy and pathogen-rich sewage is rich in nitrates and phosphates that fertilize crops free of charge. Other findings from the study:
- One-quarter of Pakistan's vegetables, including salad crops, are grown in sewage
- Farms hooked up to sewage pipes make big profits
- In Mexico, Jordan, Israel and Tunisia, sewage is specially treated to remove pathogens and make it safe for irrigation. But in India, China and Pakistan, the study found that treatment is rare. The sewage is added to fields complete with disease-causing pathogens and toxic waste from industry.
- Sewage is probably the biggest source of water for urban farming, which provides an estimated one fifth of the world's food
As if this isn't enough to make you grimmace, you can also read how rocket fuel has contaminated parts of the lettuce supply right here in the United States.
New Scientist August 18, 2004