South African farmers are being urged to adopt the sanitation economy, recycling treated human waste into low-cost organic fertiliser and irrigation water to offset soaring input costs, improve soil health, and boost local enterprise.
Addressing grain producers and agricultural industry leaders in Bredasdorp in the Western Cape, deputy minister of water and sanitation Dr Jack Bloom highlighted the dual challenge of declining regional rainfall and skyrocketing farming expenses.
With Swartland rainfall down by 79% on average, wheat planting areas at a 97-year low, and Middle Eastern ammonia prices doubling within a single year, Bloom presented the safe recycling of human waste as a viable, locally produced solution to secure affordable nutrients and water.
“Right now, we treat what comes out of those toilets purely as a cost. I want us to turn that cost chain into a value chain: collect, treat, recover, manufacture, sell, use.
“That’s the sanitation economy. And agriculture sits right at the centre of it, because you are the biggest potential customer for what we recover,” Bloom said.
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Unlocking nutrients and alternative irrigation sources
Addressing input constraints, Bloom explained that safely treated human waste yields nitrogen, phosphorus, and potassium –the primary components found in commercial synthetic fertilisers. Because these products are manufactured domestically, they provide a natural buffer against severe global price fluctuations and energy shocks.
Beyond dry fertiliser, wastewater treatment offers a secondary benefit: clean effluent for crop irrigation. Bloom highlighted decentralised wastewater treatment systems, a chemical-free process using anaerobic tanks, microorganism filters, and reed bed wetlands to process waste.
South Africa currently faces a growing volume of municipal sludge, producing nearly 640 000 dry tonnes annually from large municipal wastewater treatment plants and an additional 378 000 to 567 000 dry tonnes from smaller plants and pit toilets.
“That’s not a stockpile. That’s a fertiliser factory’s worth of raw material, going into the ground instead of onto your fields every single year,” Bloom said.
Navigating technical realities and long-term soil health
As the agricultural sector explored the potential of the sanitation economy, environmental experts highlighted the importance of rigorous technical standards, site selection, and quality management when applying recycled effluent and sludge.
Environmental advisor Dr Anthony Turton noted that utilising wastewater effluent had well-established historical foundations in South Africa.
“The idea sounds good, and there is a lot of evidence that effluent was used to irrigate pastures and grow instant lawn.”
Turton referenced the Percy Stewart plant as an early example; however, he pointed out that past operational models also provided important lessons regarding long-term runoff and soil management.
“Another example is the old disposal site of AECI at Modderfontein. We have since learnt that it is the Modderfontein disposal site that is now a source of nitrates and phosphates for the Hartbeestring Dam, so it is not a good idea. We see the same at the Rooiwal WWTW, where a farmer adjacent to the plant is instituting legal action against the state because of the pollution of his land by sewage,” he said.
Turton outlined several key technical considerations that needed to be managed to safeguard agricultural soils.
“There are many risks. The major one is heavy metal contamination, mostly from eroding copper and lead-treated pipes. These are way above safe levels and eventually destroy the soil. The other risk is salinisation because the effluent has salts in it.
“The removal of salt is technically possible, but the disposal of the brine is a persistent problem not yet solved. There is technology at the Tweefontein Plant near Ogies that uses next-generation technology to concentrate the brine, but it has not resolved the disposal problem. This kills the business case,” he said.
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