Urban Farmers Gain from Waste Water
The global food crisis continues to fuel food price inflation and send many into hunger and despair. Around the world, solutions are being sought to the urgent need for more food and cheaper food. U.N. Secretary General Ban Ki-moon has called for food production to increase 50 percent by 2030 just to meet rising demand - and right now there are 862 million people undernourished (FAO).
One fast-growing solution is bringing farming to urban and semi-urban spaces, where the majority of the world’s population now lives.
Urban farmers can take advantage of their close proximity to consumers, keeping costs down and profits up. They can also solve one of agriculture’s enduring problems - where to find water for irrigation by using existing waste water. Waste water is plentiful in urban environments, where factories usually pump out waste water into streams, rivers and lakes.
The amount of urban farmed agriculture is still small, about 10 percent of the world’s agricultural production, but is a potential growth area if handled well. In 53 cities surveyed by the International Water Management Institute, 1.1 million farmers - some 200 million worldwide - are now using recycled or waste water to irrigate their crops.
In Accra, Ghana, more than 200,000 people depend on food grown with wastewater. In Pakistan, a full quarter of the grown vegetables use wastewater.
The use of waste water comes with its ups and downs. While the World Health Organization rightfully points out that waste water can be a source of disease and pollution, cities also face a dilemma: diverting fresh water to irrigate crops means less for people to drink. Out of the 53 cities surveyed by the International Water Management Institute, 85 percent dumped their raw sewage and wastewater into streams and lakes. With this in mind, the WHOhas altered its stance on wastewater, and now supports its use for irrigating farmland as long as all efforts are made to treat wastewater and that people are warned to thoroughly wash food before eating it.
Pay Drechsel, who heads the IWMI’s research division based in Accra, Ghana, studying safe and productive use of low-quality water, says sophisticated systems to use waste water have developed in Vietnam, China and India, “where this practice has been going on for centuries.”
“People know how to avoid health risks, like thorough cooking of vegetables,” he said. “In Vietnam and China, waste from households (fecal waste, solid waste and wastewater from household use) have always been effectively recycled in ‘closed systems’ at a household level where the waste/nutrients are recycled into the food chain and so return for human consumption.”
Drechsel cites examples like Calcutta, where a large wetland is being used for treating and recycling wastewater for beneficial uses such as fish farming. In Northern Ghana, fecal sludge from septic tanks is spread on fields that are later used to grow cereals.
“The risk for the consumer is extremely low, a waste product is productively recycled, the farmer has a good harvest and the city gets rid of their waste,” Drechsel said. “A multiple win-win situation.
“Depending on the local situations such models can be widely used, provided they are documented and the risk factors are controlled,” he added.
Farmers use various methods to reduce the risk of contamination, including drip irrigation where the water does not touch the crop.
The risks for both farmers and consumer can be managed with the right protocols. For farmers, Drechsel recommends wearing of rubber boots and careful hand washing to avoid skin diseases. He points out that these farmers usually make more money than those who do not use waste water, and thus can afford the extra cost of precautionary measures, like de-worming tablets. They can quickly get out of poverty by using this water.
For consumers, the risk is from diarrhoea, typhus or cholera if raw food is eaten unwashed or poorly washed. The best solution is to turn to the WHO’s guidelines and proven local practices and tested techniques developed by researchers.
“Here more awareness creation on invisible risks through pathogens is needed. Perception studies in West Africa showed that nearly all households wash vegetables but they target visible dirt. Thus, the methods used are not effective. Best would be therefore a combination of risk reducing interventions from farm to fork, as none alone is 100 percent efficient. This is also what the new WHO guidelines promote: a flexible approach, reducing in each country the health risks as far as it is possible and feasible.”
Drechsel sees an opportunity for water treatment plants to seize: “What is missing so far is a ‘design for reuse.’ If treatment plants would be designed to serve farmers they could be less sophisticated and easier to maintain. Farmers could be involved in this, maybe a win-win situation.
“The environment benefits too. Spreading wastewater over fields, and allowing it to leach back through the soil into local waterways, turns out to be a reasonable way to purify it. The process filters out all the organic contaminants, and much of the nitrogen and phosphates that would otherwise contribute to algal blooms and dead zones further downstream. It is certainly preferable to dumping wastewater straight into the nearest big river or lake.”
- Vertical farming, where hothouses are piled one on top of the other, is an option being promoted as a solution to the food needs of urban dwellers.
- Extensive photographs of vertical farm project concepts by Chris Jacobs in cooperation with the grandfather of skyscraper farm concepts: Dr. Dickson Despommier of Columbia University. His ideal: all-in-one eco-towers would actually produce more energy, water (via condensation/purification) and food than their occupants would consume. His mission: to gather architects, engineers, economists and urban planners to develop a sustainable and high-tech wonder of ecological engineering.
- Urban Gardening News, a news service providing a review of daily news targeting everyone involved in planning & practicing alternative farming in cities. Great updates on how things are progressing across the South.