Ecological sanitation
Ecological sanitation, commonly abbreviated as ecosan, and also known as circular sanitation as a reference to the circular economy, is an approach to sanitation provision which aims to safely reuse excreta in agriculture. It is an approach, rather than a technology or a device which is characterized by a desire to "close the loop", mainly for the nutrients and organic matter between sanitation and agriculture in a safe manner. One of the aims is to minimise the use of non-renewable resources. When properly designed and operated, ecosan systems provide a hygienically safe system to convert human excreta into nutrients to be returned to the soil, and water to be returned to the land. Ecosan is also called resource-oriented sanitation.
Definition
The definition of ecosan has varied in the past. In 2012, a widely accepted definition of ecosan was formulated by Swedish experts: "Ecological sanitation systems are systems which allow for the safe recycling of nutrients to crop production in such a way that the use of non-renewable resources is minimized. These systems have a strong potential to be sustainable sanitation systems if technical, institutional, social and economic aspects are managed appropriately."Prior to 2012, ecosan has often been associated with urine diversion and in particular with urine-diverting dry toilets, a type of dry toilet. For this reason, the term "ecosan toilet" is widely used when people mean a UDDT. However, the ecosan concept should not be limited to one particular type of toilet. Also, UDDTs can be used without having any reuse activities in which case they are not in line with the ecosan concept.
Use of the term "ecosan"
The term "ecosan" was first used in 1995 and the first project started in 1996 in Ethiopia, by an NGO called Sudea. A trio, Dr Torsten Modig, Umeå University, Almaz Terrefe, teamleader, and Gunder Edström, hygiene expert, chose an area in a dense urban area as a starting point. They used urine diverting dry toilets coupled with reuse activities.In the ecosan concept, human excreta and wastewater is regarded as a potential resource – which is why it has also been called "resource oriented sanitation". The term "productive sanitation" has also been in use since about 2006.
Comparison with the term "sustainable sanitation"
The definition of ecosan is focusing on the health, environment and resource aspect of sustainable sanitation. Thus ecosan is not, per se, sustainable sanitation, but ecosan systems can be implemented in a sustainable way and have a strong potential for sustainable sanitation, if technical, institutional, social and economical aspects are cared for appropriately. Ecosan systems can be "unsustainable" for example if there is too little user acceptance or if the costs of the system are too high for a given target group of users, making the system financially unsustainable in the longer term.Overview
The main objectives of ecological sanitation are to reduce the health risks related to sanitation, contaminated water and waste; to prevent groundwater pollution and surface water pollution; and to reuse nutrients or energy contained within wastes.Resource recovery
The statement in the definition of ecosan to "safely recycle" includes hygienic, microbial and chemical aspects. Thus, the recycled human excreta product, in solid or liquid form, shall be of high quality both concerning pathogens and all kind of hazardous chemical components. The statement "use of non-renewable resources is minimized" means that the gain in resources by recycling shall be larger than the cost of resources by recycling.Ecosan is based on an overall concept of material flows as part of an ecologically and economically sustainable wastewater management system tailored to the needs of the users and to the respective local conditions. It does not favor a specific sanitation technology, but is rather a certain philosophy in handling substances that have so far been seen simply as wastewater and water-carried waste for disposal.
Reuse as fertilizer
The first proponents of ecosan systems had a strong focus on increasing agricultural productivity and thus improving the nutritional status of the people at the same time as providing them with safe sanitation. Disease reduction was meant to be achieved not only by reducing infections transmitted via the fecal–oral route but also by reducing malnutrition in children. This link between WASH, nutrition, a disease called environmental enteropathy as well as stunted growth of children has risen to the top of the agenda of the WASH sector since about 2013.Agricultural trials around the world have shown measurable benefits of using treated excreta in agriculture as a fertilizer and soil conditioner. This applies in particular to the use of urine. Reuse trials in Zimbabwe showed positive results for using urine on green, leafy plants such as spinach or maize as well as fruit trees. Another study in Finland indicated that the use of urine and the use of urine and wood ash "could produce 27% and 10% more red beet root biomass". Urine has been proven in many studies to be a valuable, relatively easy to handle fertilizer, containing nitrogen, phosphorus, potassium and important micro-nutrients.
Phosphorus recovery
Another aspect that ecosan systems are trying to address is the possible upcoming shortage of phosphorus. Phosphorus has an important role for plant growth, and therefore in fertilizer production, but is a limited mineral resource. The situation is similar for potassium. Known mineral phosphate rock reserves are becoming scarce and increasingly costly to extract – this is also called the "peak phosphorus" crisis. One review of global phosphate supply suggested that if collected, phosphate in urine could supply 22% of the total demand.Benefits
Benefits of ecosan systems include:- Minimizing the introduction of pathogens from human excreta into the water cycle - for example groundwater pollution by pit latrines.
- Conservation of resources through lower water consumption, substitution of mineral fertilizer and minimization of water pollution.
- Less reliance on mined phosphorus and other non-renewable resources for fertilizer production.
- Reduced consumption of energy in fertilizer production: Urea is a major component of urine, yet we produce vast quantities of urea by using fossil fuels. By properly managing urine, treatment costs as well as fertilizer costs can be reduced.
Challenges
Some proponents of ecosan have been criticized as being too dogmatic, with an over-emphasis on environmental resource protection rather than a focus on public health protection and provision of sanitation at a very low cost.
The safety of ecosan systems in terms of pathogen destruction during the various treatment processes is a continuous topic of debate between proponents and opponents of ecosan systems. However, the publication of the WHO Guidelines on Reuse, with its multiple barrier concept, has gone a long way in establishing a common framework for safe reuse. Nevertheless, the question remains whether ecosan systems can ever be scaled up to reach millions of people and how they can be made sufficiently safe to operate. The initial excitement in the early 2000s by the ecosan pioneers has changed into a realization that changing attitudes and behaviors in sanitation takes a lot of patience.
Acknowledgement for ecosan came with the awarding of the Stockholm Water Prize in 2013 to Peter Morgan, a pioneer of handpumps and ventilated pit latrines in addition to ecosan-type toilets. Peter Morgan is renowned as one of the leading creators and proponents of ecological sanitation solutions, which enable the safe reuse of human excreta to enhance soil quality and crop production. His ecosan-type toilets are now in use in countries across the globe, centred on converting a sanitary problem into a productive resource.
Also many of the research projects that the Bill and Melinda Gates Foundation have been funding since about 2011 in sanitation are dealing with resource recovery – this might well be a legacy of the ecosan concept, even if the term "ecosan" is not used by these researchers.
Technologies used in ecosan systems
Ecosan offers a flexible framework, where centralized elements can be combined with decentralized ones, waterborne with dry sanitation, high-tech with low-tech, etc. By considering a much larger range of options, optimal and economic solutions can be developed for each particular situation. Technologies used in ecosan systems often - but not always - include elements of source separation, i.e. keeping different waste streams separate, as this can make treatment and safe reuse easier.The most common technology used in ecosan systems is the urine-diverting dry toilet, but ecosan systems can also use other technologies, such as vacuum toilets coupled with biogas plants, constructed wetlands, composting toilets and so forth.
Examples of ecosan projects worldwide can be found in a list published by GIZ in 2012, as well as in those case studies published by the Sustainable Sanitation Alliance that are focused on reuse activities.
History
Excreta reuse in dry sanitation systems
The recovery and use of urine and feces in "dry sanitation systems", i.e. without sewers or without mixing substantial amounts of water with the excreta, has been practiced by almost all cultures. The reuse was not limited to agricultural production. The Romans, for example, were aware of the bleaching attribute of the ammonia within urine and used it to whiten clothing.Many traditional agricultural societies recognized the value of human waste for soil fertility and practised the "dry" collection and reuse of excreta. This enabled them to live in communities in which nutrients and organic matter contained in excreta were returned to the soil. Historical descriptions about these practices are sparse, but it is known that excreta reuse was practiced widely in Asia but also in Central and South America. However, the most renowned example of the organised collection and use of human excreta to support food production is that of China. The value of "night soil" as a fertilizer was recognized with well-developed systems in place to enable the collection of excreta from cities and its transportation to fields. The Chinese were aware of the benefits of using excreta in crop production more than 2500 years ago, enabling them to sustain more people at a higher density than any other system of agriculture.
In Mexico the Aztec culture collected human excreta for agricultural use. One example of this practice has been documented for the Aztec city of Tenochtitlan which was founded in 1325 and was one of the last cities of pre-Hispanic Mexico : The population placed the sweepings in special boats moored at docks around the city. Mixtures of sweepings and excreta were used to fertilize the chinampas or to bolster the banks bordering the lake. Urine was collected in containers in all houses, then mixed with mud and used as a fabric dye. The Aztecs recognized the importance of recycling nutrients and compounds contained in wastewater.
In Peru, the Incas had a high regard for excreta as a fertilizer, which was stored, dried and pulverized to be utilized when planting maize.
In the Middle Ages, the use of excreta and greywater in agricultural production was the norm. European cities were rapidly urbanizing and sanitation was becoming an increasingly serious problem, whilst at the same time the cities themselves were becoming an increasingly important source of agricultural nutrients. The practice of directly using the nutrients in excreta and wastewater for agriculture therefore continued in Europe into the middle of the 19th century. Farmers, recognizing the value of excreta, were eager to get these fertilizers to increase production and urban sanitation benefited. This practice was also called gong farmer in England but carried many health risks for those involved with transporting the excreta and fecal sludge.
Besides direct use, excreta was also processed to produce pure chemicals. Using nitraries and nitre beds, one extract the nitrogen within as potassium nitrate, a key ingredient in gunpowder. KNO3 was also responsible for the discovery of nitric acid in the 17th century.
Traditional forms of sanitation and excreta reuse have continued in various parts of the world for centuries and were still common practice at the advent of the Industrial Revolution. Even as the world became increasingly more urbanised, the nutrients in excreta collected from urban sanitation systems without mixing with water were still used in many societies as a resource to maintain soil fertility, despite rising population densities.