It is in these crowded cities, too, that food security is weakened by the lack of clean, nutrient-rich soil as well as growing space available for local families.
But there is an inexpensive solution to both problems. A recent innovation, called the Peepoo, is a disposable bag that can be used once as a toilet and then buried in the ground. Urea crystals in the bag kill off disease-producing pathogens and break down the waste into fertilizer, simultaneously eliminating the sanitation risk and providing a benefit for urban gardens. After successful test runs in Kenya and India, the bags will be mass produced this summer and sold for U.S. 2-3 cents each, making them more accessible to those who will benefit from them the most.
In post-earthquake Haiti, where many poor and homeless residents are forced to live in garbage heaps and to relieve themselves wherever they can find privacy, SOIL/SOL, a non-profit working to improve soil and convert waste into a resource, is partnering with Oxfam GB to build indoor dry toilets for 25 families as well as four public dry toilets. The project will establish a waste composting site to convert dry waste into fertilizer and nutrient-rich soil that can then be used to grow vegetables in rooftop gardens and backyards.
In Malawi, Stacia and Kristof Nordin's permaculture project uses a composting toilet to fertilize the crops. Although these units can be expensive to purchase and install, one company, Rigel Technology, manufactures a toilet that costs just US$30 and separates solid from fluid waste, converting it into fertilizer. The Indian non-profit Sulabh International also promotes community units that convert methane from waste into biogas for cooking.
On a larger scale, wetlands outside of Calcutta, India, process some 600 million liters of raw sewage delivered from the city every day in 300 fish-producing ponds. These wetlands produce 13,000 tons of fish annually for consumption by the city's 12 million inhabitants. They also serve as an environmentally sound waste treatment center, with hyacinths, algal blooms, and fish disposing of the waste, while also providing a home for migrating birds and an important source of local food for the population of Calcutta.
Aside from cost and installation, the main obstacles to using human waste to fertilize crops are cultural and behavioral. UNICEF notes in an online case study that a government-run program in India provided 33 families in the village of Bahtarai with latrines near their houses. But the majority of villagers still preferred to use the fields as toilets, as they were accustomed to doing their whole lives.
'It is not enough just to construct the toilets,' said Gaurav Dwivedi, a Bilaspur District magistrate, in the UNCEF study. 'We have to change the thinking of people so that they are amenable to using the toilets.'
Molly Theobald is a research fellow with the Worldwatch Institute. She can be reached at firstname.lastname@example.org.
This article originally appeared on the Worldwatch Institute blog Nourishing the Planet. For permission to republish this report, please contact Juli Diamond at email@example.com.