Recycling animal and human dung is the key to sustainable farming

By Kris De Decker
Low-tech Magazine

Flushing the water closet is handy, but it wreaks ecological havoc, deprives agricultural soils of essential nutrients and makes food production dependent on fossil fuels. For 4,000 years, human excrements and urine were considered extremely valuable trade products in China, Korea and Japan. Human dung was transported over specially designed canal networks by boats.

Thanks to the application of human “waste” products as fertilizers to agricultural fields, the East managed to feed a large population without polluting their drinking water. Meanwhile, cities in medieval Europe turned into open sewers. The concept was modernized in late 19th century Holland, with Charles Liernur’s sophisticated vacuum sewer system.


© Illustrations in red & black: ddidak for low-tech magazine.


If we recycle our own waste products, fertilizer production would automatically keep up with population growth


The innocent looking water closet breaks up a natural cycle in our food supply. Basically, it turns extremely valuable resources into waste products. When we grow crops, we withdraw essential nutrients from the soil: potassium, nitrogen and phosphate, to name but the most important. During the greater part of human history, we recycled these nutrients through our bodies and returned them to the soil, via excreta, food trimmings and the burial of dead. Today, we flush them mostly into the sea (see the infographic below, source).

Nutrients cycle humanure

This is problematic and unsustainable, for three main reasons.

To start, dumping sewage in rivers, lakes and seas kills fish and makes fresh water undrinkable. This can only be avoided by extending the water closet and the already very costly sewerage network with an equally expensive infrastructure of sewage stations (which does not completely eliminate the detrimental effect on water life).

Secondly, we need artificial fertilizers to keep our soil fertile. In 2008, almost 160 million tonnes of inorganic fertilizers were used worldwide (1 & 2). Without these, our agricultural soils would lose their fertility in just a few years time, followed by an inevitable collapse of food production and human population. A third problem is that the water closet logically consumes large quantities of fresh water to flush everything “away”.

Read full post at Low-tech Magazine

3 responses to “Recycling animal and human dung is the key to sustainable farming

  1. Excellent article with the simple answer that has been with us all along. Paul

  2. As Wendell Berry once wrote : ‘Modern agribiz takes a solution and divides it neatly into two problems.’

    Excellent, excellent article.

    Two modern problems (rampant waste/pollution and the persistent need for fertilizer/quality soil), awaiting one old-fashioned solution.

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