Managing human waste: Flushing away gold?

No one likes to talk about the management of human waste, but it’s a life-or-death matter that links human and environmental health. And at a time when freshwater and energy resources are diminishing, perhaps the discussion should focus on how not to waste our waste.

Until now, the primary aim of sanitation systems has been to keep excrement out of contact with human beings. Over the millennia there have been many variations on the toilet: in ancient Egypt sand was used in lavatories; on the island of Crete in around 1600 BC the Minoans had water-based sewerage systems; the Romans built sewers for the collection of waste and rainwater and pioneered public lavatories; and toilet paper was first used in China around 1,500 years ago.

When flush toilets and sewage systems became the standard in Europe, water was plentiful. On the principle that dilution made wastewaters safe, raw sewage was flushed into rivers, streams and oceans. It was only 150 years ago that it was fully recognized that waterborne pathogens cause disease, leading to the development of today’s wastewater treatment, which separates solids from liquids and cleans the liquids for reuse, while incinerating or burying the remaining sludge.

While this system has greatly reduced disease, sewerage systems need complex infrastructure and a lot of water: current systems require 50-100 litres of water to remove up to 1.5 litres of human excreta per day. Further, wastewater treatment requires energy, and while decontaminated water and sludge can be put to good use, we are producing more than we can manage. And remember, it costs around $1,000 per person to install and maintain sewers.

Today, more than a third of the world’s population, some 2.6 billion people, have no access to adequate sanitation and 1.1 billion people have no access to any sort of toilet. Instead, they have to defecate wherever they can, including in rivers and fields, polluting surface and groundwater and transmitting disease. Clearly, it’s time for a rethink.

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This post is also available in: French, Spanish