for National Geographic News
Facing water shortages and escalating fertilizer costs, farmers in developing countries are using raw sewage to irrigate and fertilize nearly 49 million acres (20 million hectares) of cropland, according to a new report—and it may not be a bad thing.
While the practice carries serious health risks for many, those dangers are eclipsed by the social and economic gains for poor urban farmers and consumers who need affordable food, the study authors say.
Nearly 200 million farmers in China, India, Vietnam, sub-Saharan Africa, and Latin America harvest grains and vegetables from fields that use untreated human waste.
Ten percent of the world's population relies on such foods, according to the World Health Organization (WHO).
"There is a large potential for wastewater agriculture to both help and hurt great numbers of urban consumers," said Liqa Raschid-Sally, who led the study published by the Sri Lanka-based International Water Management Institute (IWMI) and released this week at the World Water Week conference in Stockholm, Sweden.
Health Risks
The report focused on poor urban areas, where farms in or near cities supply relatively inexpensive food. Most of these operations draw irrigation water from local rivers or lakes. Unlike developed cities, however, these areas lack advanced water-treatment facilities, and rivers effectively become sewers.
When this water is used for agricultural irrigation, farmers risk absorbing disease-causing bacteria, as do consumers who eat the produce raw and unwashed. Nearly 2.2 million people die each year because of diarrhea-related diseases, including cholera, according to WHO statistics. More than 80 percent of those cases can be attributed to contact with contaminated water and a lack of proper sanitation. But Pay Drechsel, an IWMI environmental scientist, argues that the social and economic benefits of using untreated human waste to grow food outweigh the health risks.
Those dangers can be addressed with farmer and consumer education, he said, while the free water and nutrients from human wastewater and feces can help urban farmers in developing countries to escape poverty.
Waste Into Water
Agriculture is a water-intensive business, accounting for nearly 70 percent of global fresh water consumption.
In poor, parched regions, untreated wastewater is the only viable irrigation source to keep farmers in business, according to Drechsel. Mark Redwood, a senior program officer with the Canadian International Development Research Centre, said that in some cases, water is so scarce that farmers break open sewage pipes transporting waste to local rivers.
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