Outcomes of E-Conference on Resource Recovery from Sanitation for Food Security and Soil Health
From Wednesday, February 19th, to Friday, February 21st, the SDSN Sustainable Agriculture and Food Systems hosted an online, virtual conference on recovering nutrients from sanitation for use in agriculture.
Why Nutrient Recovery from Sanitation?
Our global food system has created a number of challenges at the nexus of agriculture, sanitation, and water quality. Many soils are in poor health; mined of nutrients from decades of farming, or lacking them to begin with. This is particularly true for sub-Saharan Africa where poor soils throughout the region are a driver of low yields and resultant undernutrition (SDG 2) and poverty (SDG 1). Yet the high costs of fertilizers (African farmers pay two to six times the global average for fertilizer) mean that African farmers can only apply 17 kg of fertilizer per hectare, relative to a global average of 135 kg.
In other parts of the world, notably North America and China, overuse of chemical fertilizers leads to runoff that pollutes lakes and rivers. When combined with nutrients released in treated sewage from cities, this influx of nutrients causes anoxic “dead zones” in aquatic ecosystems (SDG 14). In 2019, the US National Oceanic and Atmospheric Administration (NOAA) predicted the dead zone in the Gulf of Mexico to be notably large, as the area received excess nutrients from the Mississippi, North America’s largest river.
One innovative solution to both these problems is to recapture nutrients lost as human “waste” and properly treat them for use in agroecological systems. In the context of sub-Saharan Africa, container-based sanitation offers many co-benefits. First, it is a modern way to provide sustainable sanitation systems to 319 million people currently lacking it (SDG 6), with the potential to be deployed both in cities and rural areas. Secondly, it offers a new growth sector for the economy, with waste collection and treatment potentially employing a large number of people (SDG 8), while supplying a more affordable, locally produced source of greatly needed fertilizer. In addition to fertilizer, waste-to-value chains can produce other outputs, such as energy and insects for animal feed.
In wealthy countries, existing sewer system infrastructure is expensive to run and maintain. It intentionally combines waste with vast amounts of potable fresh water, and then further combines household effluents with toxic runoff from industrial facilities and storm water. As climate change (SDG 13) reduces the availability of freshwater, water-scarce cities like Los Angeles, El Paso, and Phoenix rely more and more on water recovered from treated sewage for drinking, industrial uses, and agricultural uses, again with great costs to build and maintain the required infrastructure. Alternative innovations in managing human “waste” and recovering what is valuable is therefore relevant for all countries.
Conference Summary
All sessions were moderated by Rebecca Nelson , Professor at Cornell University in the United States and Co-Chair of SDSN Sustainable Agriculture and Food Systems.
On the first day of the conference we heard two presentations. Tom Wassenaar of CIRADin France gave a great overview of the topic ( slides ). He summarized some of the key challenges of chemical fertilizers, including depletion of the resource and eutrophication caused by runoff. He also looked at some of the advantages of recovering nutrients from human and livestock wastes, in particular that this could be a critical source of high quality, affordable, organic fertilizer in resource-poor settings.
Johannes Lehmann of Cornell Universityin the USA looked at several opportunities to recycle wastes to produce biochar ( slides ), including bones from slaughterhouses, manure from dairy operations, and human waste collected in cities. The gasses produced during the processing of these wastes into useable nutrient products can also be used to generate electricity.
The second day of the conference opened with a presentation from Sasha Kramer of SOIL in Haiti ( slides ). Today around 6,500 people are using toilets provided by SOIL’s growing urban sanitation service. Using toilets that separate liquid and solid wastes, they deliver clean containers to users and pick up waste to be processed centrally. They estimate that 510 tons of waste has been transformed into agricultural grade compost in 2019, with co-benefits including improvement of Haitian soil quality and increased resilience to climate change.
Our second speaker presented a very different example from that of Haiti. Jennifer McDonnell from the New York City Department of Environmental Protection shared New York's experience managing 152 miles of sewers and 14 sewage treatment plants with a combined capacity of over 1,400 million gallons daily (MGD) ( slides ). She shared that challenge for New York City is that they have a high concentration of nutrients which can be recovered, but are located a relatively great distance from the farms that could best handle biosolids in such large proportions.
Following Jennifer, Renzo Akkerman of Wageningen University and Research in the Netherlands shared some key challenges in building value chains to support resource recovery ( slides ). He shared a number of examples from around the world, including using GIS tools to optimize the location of a biogas installation in Amsterdam and a pilot to recover orchids after blooming to be cared for and sold again at the next bloom.
On the final day of the conference we heard from four speakers, with an emphasis on experiences in Africa. Davis Ireri shared the story of Sanergy 's work providing sanitation to persons living in slums and informal settlements in Nairobi, Kenya. They use handcarts to deliver clean containers and collect full ones, and process the wasted into high quality organic fertilizer. The organic fertilizer they produce sells for roughly half the costs of the same weight of chemical fertilizer, and is high in organic matter, helping farmers raise yields.
Complementing this example, Jane Wambui Mugo shared Sanivation 's work in Naivasha and Kakuma, Kenya ( slides ). Since launching 6 years ago, Sanivation has reached approximately 20,000 people, treated over 150 tons of waste, reduced diarrheal disease in localities served by about half, and produced 1,500 tons of fuel briquettes, reducing the pressure on trees and forests. The presentation also detailed some of the challenges they have faced in scaling up, including recruiting new customers.
David Berendes of the US Centers for Disease Control ( CDC ) shared the health benefits and risks of effective sanitation. Daily, over 800 children die from diarrhea which can be prevented with modern sanitation. This presentation also looked regional differences in sewage treatment, and shared some frightening statistics on the amount of untreated waste released into the environment.
Closing out our final session was Adama Hilou , a Professor at the University of Ouagadougou in Burkina Faso. His talk focused on the different waste streams in West Africa ( slides ), including organics and non-organics, and solutions for effective reduction and reuse of waste. He shares examples of waste re-made into useful items, such as plastics melted and molded into paving "stones," as well as opportunities for organics to be collected, treated, and turned into valuable resources.