Productive reuse of wastes & wastewater

Urban agriculture plays an important role in transforming urban wastes and wastewater into valuable resources. Many cities have growing problems to dispose of all solid wastes and wastewater generated in the city. The fast growth of the urban population growth leads to a substantial increase in the volume of urban organic wastes and wastewater produced. Collection and disposal of solid wastes can consume up to 50% of the operating budget of a Municipality Therefore, Municipalities seek to reduce the costs on wastes management. 

Also the treatment and disposal of wastewater is a growing problem for many cities in developing countries (and not only there). Wastewater treatment is very costly, and even those cities that are able to procure funding to build treatment plants only treat a small percentage of the total volume of wastewater produced in the city. The rest is left to flow into natural water bodies contaminating the waterflows that downstreams are used in agriculture and other uses. Meanwhile fresh water scarcity is quickly growing and water price is quickly rising, the demand for food by the cities is quickly increasing and the farmers in the city region are in need of organic matter, fertilisers and irrigation water. Solid wastes and wastewater contain high amounts of organic matter and nutrients that can be reclaimed and used as a resource in urban agriculture. Intensive vegetable growers, plant and tree nurseries and pig growers are among the sectors that are using large quantities of urban organic wastes. Especially in cities in arid and semi-arid areas, productive reuse of urban wastewater for irrigation water and nutrients is rapidly gaining importance.

The socio-economic advantages for the intra- and peri-urban farmers and environmental and economic gains of these practices for the city have to be weighed against the potential health risks associated with the reuse of urban organic wastes and wastewater. Such risks have to be actively managed in close cooperation between all stakeholders involved and a combination of regulatory, economical, technical and educational measures have to be drawn up in a collaborative manner based on thorough understanding of the transfer mechanisms involved in each of these health hazards

For an extensive introduction and review of literature on the reuse of urban organic wastes in urban agriculture please go to State of the Art on Wastes. This paper discusses the benefits of composting, presents a framework for analysis and planning of composting interventions and reviews common constraints. Composting the large quantities of organic matter provides a win-win strategy by reducing waste flows, enhancing soil properties, recycling valuable soil nutrients and creating livelihoods, but there remain several constraints that explain why this opportunity is not yet widely exploited..

For an extensive introduction and review of literature on the productive reuse of urban wastewater please go to State of the Art on Wastewater. This paper discusses the use of urban wastewater a resource in intra- and peri-urban agriculture: for crop production, which includes fodder grasses, vegetables, cereals, ornamental plants, trees and flowers, timber crops and fruit trees, as well as for aquaculture and related benefits for the farmers, consumers and the city management. Also potential negative impacts on human health and the urban environment are reviewed and risk management strategies are discussed. 

Go to RUAF publications for an overview of RUAF publications on this topic (most of which are available online). 
You may also view the articles in the Urban Agriculture Magazine on this topic or use the Search option.

PDF icon Organic wastes.pdf423.16 KB
PDF icon WW Use for UA.pdf368.52 KB