Many cities are short of water and subject to critical environmental degradation. Their peri-urban areas are among the worst polluted and disease ridden habitats of the world. Sewage discharges from centralised waterborne collection systems pollute surface waters and seepage from sewers, septic tanks and pit toilets pollute groundwater. Conventional sanitation technologies based on flush toilets, sewers, treatment and discharge cannot solve these problems in urban areas lacking the necessary resources such as water, money and institutional capacity. The range of policy options in sanitation should be widened to include ecological alternatives.
Ecological sanitation technologies take the principle of environmental sanitation a step further: Environmental sanitation means keeping our surroundings (the environment) clean and safe and preventing pollution. It includes wastewater treatment and disposal, vector control and other disease-prevention activities. Ecological sanitation, on the other hand, is structured on recycling principles. It means keeping the eco-cycle in the sanitation process closed. It is also a low-energy approach that uses natural processes.
Ecological sanitation (also called “ecosan”) is a cycle, or closed-loop system, which treats human excreta as a resource. In this system, excreta are processed on site until they are free of pathogenic (disease-causing) organisms. Thereafter the sanitized excreta are recycled by using them for agricultural purposes. Key features of ecosan are therefore:
- Prevention of pollution and disease caused by human excreta;
- treatment of human excreta as a resource rather than as a waste product; and
- recovery and recycling of the nutrients.
Conventional approaches to sanitation misplace these nutrients, dispose of them and break this cycle. The very idea that excreta are waste with no useful purpose is a modern misconception. It is at the root of pollution problems that result from conventional approaches to sanitation. In nature there is no waste – all products of living things are used as raw materials by others. Recycling sanitized human urine and faeces by returning them to the soil serves to restore the natural cycle of life-building materials that has been disrupted by our current sanitation practices.
These principles are not new. In some cultures, for example in parts of East Asia, ecological sanitation systems have been widely used for hundreds of years, and in the case of China, for a few thousand years. It is important, however, that these systems are not regarded merely as a second-rate solution for poor people. Ecosan principles may be applied across a range of socio-economic conditions.
The excellent fertiliser value of human excreta has been well established. Humans excrete, on average, sufficient plant nutrients in the forms of nitrogen, phosphorus and potassium to grow the 230 kg of crops they need each year, with approximately 65 to 90% of the nutrients being found in urine. Furthermore, these nutrients are in chemical compounds easily accessible to plants.
In most countries of the world, use of human excreta as fertiliser has been implemented only to a very limited extent. Rather, they have been flushed out into the rivers with consequent growth of algae, etc, resulting in a lack of oxygen in the aquatic resources. These resources have also been polluted with pathogenic microorganisms to the extent that many rivers have become virus infected more or less permanently. It is thus better to create a closed system, with no pollution from bacteria or viruses and where human fertilisers are harvested and used to grow the following year's crops.
If ecological sanitation could be adopted on a large scale, it would protect our groundwater, streams, lakes and seas from faecal contamination. Less water would be consumed. Farmers would also require less commercial fertilisers, much of which washes out of the soil into water, thereby contributing to environmental degradation.