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Human fertiliser - closing the nutrient loop

Carrots grown through a new composting scheme in Burkina Faso (Sandrine Tapsoba/CREPA)
Carrots grown through a new composting scheme in Burkina Faso
Sandrine Tapsoba/CREPA

"Carrots grown with human urine for fertiliser are so sweet," says Anselme Vodounhessi. "I've tried them!" A professional in ecological sanitation, Vodounhessi is in a tiny, unsqueamish, minority. For most people in Burkina Faso, where he works, the idea of using human excreta in food production would at the very least cause an internal shudder, if not an exclamation of disgust. But in four neighbourhoods of the capital, Ouagadougou, commercial production of sanitised human fertiliser is now a reality, and it could soon be part of strategic sanitation plans in towns and cities across the country.

A thousand households in Ouagadougou are currently supplying toilet waste for fertiliser production. Separated into its solid and liquid components, the waste is collected by a local private association, treated to make it pathogen-free, and sold to urban farmers as a cheap, but highly effective alternative to chemical inputs. Known as a 'closed loop' system, the scheme is ensuring that unused nutrients are recycled back into the urban food chain. Project staff of the implementing agency, CREPA (the West African centre for low cost water supply and sanitation) believe that it is the first of its kind in the region.

Safe and suitable

The closed loop system is ideal for Ouagadougou, where less than 20 per cent of households in the city have access to sanitation. Household pit latrines are emptied periodically by tankers, but this is expensive (US$65 per collection) and causes environmental damage and health risks in the rural areas where untreated faecal sludge is dumped. But risk management investigations by the CREPA project have found that urine placed in a dark container becomes bacteria-free in 30-45 days, largely through its own acidity. Faecal matter takes longer, but if it is kept dry - not flushed with water or mixed with urine - it becomes a safe, powdery, nutrient-rich compost within six months. Burkina Faso's hot, dry climate is perfect to speed the process.

Containers are collected and taken away for processing (Sandrine Tapsoba/CREPA)
Containers are collected and taken away for processing
Sandrine Tapsoba/CREPA

Using an Ecosan toilet that separates urine from faeces and does not add water is fundamental to ecological sanitation. Urine passed in the toilet is fed into 20 litre, yellow jerry cans, which are collected by donkey cart and taken to an 'eco-station'. Here the urine is decanted into large drums and stored for the necessary number of days before being sold in green jerry cans, as liquid fertiliser. The toilets are designed so that solid waste can be stored for six months before being collected, taken to the eco-station, quality checked and sold. In Ouagadougou, the design and manufacture of Ecosan toilets has involved about 100 local builders.

From the bottom up

Not surprisingly, gaining public acceptance and enthusiasm for excreta-based fertiliser has required extensive consultation and dialogue with householders, market gardeners and builders as well as municipal planners and national legislators. Learning from the experiences and opinions of each group has been paramount, guiding a baseline survey which canvassed views on the whole recycling process, from collection, transport and treatment of excreta to the sale and use of liquid and solid fertilisers. Householders were asked about their needs, their ability to pay for services and their preferences and expectations of a sanitation system. Market gardeners discussed their fertiliser requirements and their readiness to use inputs produced from human waste.

In addition to listening and learning, capacity building has also been key, enabling all the interest groups to participate in the project design and implementation. Burkina Faso is currently undergoing a decentralisation of power to municipalities, but municipal staff have limited capacity to assess sanitation needs or plan solutions. Support from project staff has addressed this, boosting needs assessment and strategic planning skills more generally in the municipal offices. A programme of awareness raising and training targeted the local private sector, highlighting business opportunities in closed loop sanitation systems. Households with Ecosan toilets pay a small charge per month to have their waste collected and farmers pay for the fertiliser. However, both services are cheap compared to the alternatives: refuse tankers and chemical inputs.

National strategy

Containers for urine collection, left, and Ecosan fertiliser from processed urine (Sandrine Tapsoba/CREPA)
Containers for urine collection, left, and Ecosan fertiliser from processed urine
Sandrine Tapsoba/CREPA

One of Ouagadougou's Millennium Development Goals is to provide sanitation facilities to 59 per cent of households. So far, the CREPA project, which is funded by the European Union, has only been implemented in four outlying suburbs, but it hopes that ecological sanitation will become part of national strategy. Intense political lobbying may be needed, but the municipal authorities are keen advocates of the system and government ministries are showing interest. Following a research study into sanitation and environmental risks, a scientific monitoring working group has been set up, which includes representatives from the environment, health and agriculture ministries. The value of nutrients contained in Ouagadougou's household excreta has been estimated by CREPA at US$22 million per year. Closing the nutrient loop would not only save money and boost the capital's food supply, but would help to resolve the serious and increasingly difficult problem of managing faecal waste in a fast-growing city.

Date published: November 2008

 

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