Turning a profit from human waste

Irrigation systems that channel waste water from people’s homes into agricultural fields have dramatically improved crop yields in Yaoundé, Cameroon. The water mitigates the effects of drought and allows farmers to continue harvesting during the dry season and, as a result, get up to five harvests a year. In 2016, the irrigation is estimated to have raised annual vegetable production by about 37,000 t, as well as increase annual income per producer to €545 from €380 in 2013, for an area of about 200 m².

With rain-fed agriculture becoming increasingly unreliable, the irrigation systems are enabling around 300 members from Buyam Sellam women’s groups and 3,500 agricultural labourers to grow assorted vegetables, including cabbage, cucumber, and tomato. “In the absence of rain we can have food on our tables and raise much needed income to send our children to school,” explains Anita Nveng, a Buyam Sellam member. The use of waste water irrigation is not only helping to increase the incomes of farmers, but has also succeeded in bridging the supply gap in vegetable production during the dry season so that production now satisfies 95% of demand rather than just 15%, as was previously the case.

According to UN-Water, 80% of all waste water, including faecal sludge, gets dumped without treatment, leading to a range of health and environmental risks. The problem is of particular concern in low-income countries where only 8% of waste water is treated. A field report carried out by the University of Youndé noted that crops irrigated with waste water from the river Avo’o in Youndé showed the best growth rates in the area. However, the investigation also highlighted the health risks associated with using waste water in urban agriculture, particularly if the water has high levels of pathogenic microorganisms, and recommended that laws ensuring the treatment of faecal sludge before discharge be properly enforced by the government. To address concerns over the health risks and environmental hazards of using waste water to produce food, the International Water Management Institute (IWMI), in collaboration with the World Health Organization (WHO), has helped to update guidelines on the safe use of waste water in irrigation and the 2015 Sanitation Safety Planning Manual to facilitate implementation of the WHO guidelines. 

In Ghana, a new treatment plant is the first commercial scale project in West Africa to produce high quality, safe fertiliser from treated human waste. The facility is operated by a public-private partnership (PPP) and, when fully operational, will process 12,600 m³ of waste a year to produce 500 t of pathogen-free organic fertiliser under the trademarked name ‘Fortifer’. The PPP to commercialise Fortifer was initiated by IWMI after pilot projects in Ghana showed the product to be safe and, when compared to inorganic fertilisers, improve agricultural yields by 20-50%. Market research revealed a widespread demand for the product among farmers in West Africa. “Turning faecal sludge into a fertiliser is an enormous development opportunity, with the potential to benefit millions of farmers while reducing the world’s most pressing sanitation problem in growing towns and cities,” says Pay Drechsel, IWMI’s theme leader on water quality, health and environment.