Report 2 of 5: Divide and Spray - Sweden

Introduction

The use of human waste in agriculture has a long history. For example, the Romans used waste as a fertiliser. More recently, Sweden has taken the lead in recycling and reusing human excreta. The city of Stockholm has supported the introduction of ecological sanitation in middle class housing areas where the urine is centrally collected, stored and spread on farmland as fertiliser. A project funded by the Swedish International Development Cooperation Agency, Sida, and carried out by the United Nations Development Programme is promoting further development of ecological sanitation.

By failing to return natural fertilisers, such as human excreta, back onto the land, we are depleting soils of nutrients, resulting in the production and use of artificial fertilisers, and the increased use of pesticides to prevent the food supply from diminishing. For food security and agricultural purposes there is a need to utilise the valuable nutrients in human excreta. Furthermore, the practice of dumping human waste into water and off the land also destroys marine life, reducing food prospects from the sea.

Ecological sanitation aims to recycle nutrients from human waste back into the environment and into productive systems such as farming. Studies indicate that each person’s waste can provide enough nitrogen, phosphorous and potassium to grow a year’s supply of wheat and maize for that person. Recycled human waste is an affordable and environmentally sound alternative to chemical fertilisers. Applying human waste to crops is safer than spraying them with chemical fertilisers because it diverts raw sewage from rivers and can help improve agricultural production. It also costs only a fraction of sewage treatment plants.

Ecological sanitation around the world

Eco-sanitation is being tried and implemented globally due to high water tables, excessive water pollution, lack of fresh water, declining marine eco-systems and the high cost of commercial fertilisers. In El Salvador, a peri-urban community discovered that the diversion of urine eliminated flies and smells. In Mexico, people are experimenting with urine in urban agriculture as well as growing traditional Mayan food grains. In the Pacific, livelihoods were threatened by dumping into the coastal waters. Eco-sanitation solutions were implemented to reduce contamination and restore fish populations. In Kenya and Zimbabwe "arbor loos" are being used to plant trees for household use.

Conventional sanitation systems

About three billion people are today lacking safe sanitation. Conventional sewage systems, based on flush toilets, have failed to solve the sanitation needs for developing countries. Over 95% of sewage in developing countries is discharged completely untreated into surface waters, polluting rivers, lakes and coastal areas. The other conventional sanitation solution for poor people in developing countries, the pit latrine, also has its shortcomings in densely populated areas where space is limited. Groundwater is almost inevitably polluted thus threatening drinking water supply.

Conventional sanitation systems, based on flush-toilets, have focused on how to treat pathogens and/or keep human excreta away from people. In the process we have used and contaminated large quantities of fresh water, and destroyed land and marine ecosystems. Current sanitation solutions contribute, either directly or indirectly, to many of the problems faced by society today such as water pollution, scarcity of freshwater, food insecurity, destruction and loss of soil fertility, global warming and poor human health as well as loss of life.

Each person produces about 500 litres of urine and 50 litres of faeces each year. Once the faeces have been dehydrated, it is actually no more than a bucketful per person per year. The real problem is that in the flush and discharge system, faeces are not handled separately. They are mixed with urine. This means that instead of 50 litres of a heavily polluted substance, there are 550 litres. To flush away the 550 litres of faeces and urine in a flush toilet uses about 15,000 litres of water every year.

Ecological sanitation

Ecological sanitation is basically a way of bringing plant nutrients back to the soil. It is a system of dealing with human excreta that prevents disease, protects the environment, particularly our water resources and is affordable, acceptable and simple.

Urine makes up about 90% of human waste and contains about 80% of the fertiliser value of waste. Faeces contain the remaining 20% of waste’s fertiliser value but carry pathogens and may spread disease. The pathogens can be destroyed by dehydration, decomposition or heating. In order to prevent the "clean" urine from being contaminated by potentially pathogenic matter, firms all over the world are manufacturing special toilet seats and squatting slabs that separate the two forms of waste.

Compared to Western-type sewage systems, ecological sanitation systems are technically simple and can be built at low cost because they require no water supply, no sewers and no excavation. More importantly, human waste becomes part of a natural eco-system – recycled and returned to the land for food production and food security - rather than being dumped as a pollutant.

"Don’t mix"

The first principle of ecological sanitation is "Don’t mix". By keeping urine and faeces apart, problems of bad odours and fly breeding are reduced or even eliminated, and storage, treatment and transport are made easier. By not mixing human excreta and flushing water, the sanitation problem is limited to managing a comparatively small volume of urine and faeces. As a result a lot of water can be saved, expenditure on pipe networks and treatment plants is reduced and the environment is preserved.

There are three methods by which urine and faeces can be kept apart. The most straightforward method is never to mix the two. This way the urine remains sterile and can be used without any further treatment. Another possibility is to mix and then drain. The third possibility is to mix and then evaporate.

If urine is not going to be used, it can be soaked into the ground or evaporated. However, it is better to recycle urine because it contains nitrogen and phosphates in forms that are easily absorbed by plants. Urine diluted with water can be used directly in the garden or it can be stored and used at a later date. Faeces can, if necessary, be processed in several steps before they are reused. In an ecological toilet, that is a dry toilet with urine diversion, they are subject to primary treatment, basically dehydration, which also effectively destroys most of the pathogenic organisms.

Illustration: ©A.Hanæus, 1996 Design of a urine separating system with soil infiltration for treatment of faeces and greywater. From Hanæus and Johansson, 1996.

Urine separating wastewater systems

Source separation of human urine is based on toilets equipped with two bowls, a front one for the collection of urine and a rear one for faeces. It is possible to equip both dry sanitation toilets and water closets this way. The collected urine is lead through a sewer system to a storage tank. There may be a risk of cross contamination of the urine with faeces although this is more likely to occur with diarrhoea or improper use of the toilet.

Ecological sanitation is not only for poor countries. About 3000 water closets equipped with urine separation have been sold in Sweden. Almost all of these toilets have been delivered by BB Innovation & Co. (the model is called "Dubbletten") or by WM Ekologen (model DS-toilet). The systems are based on urine diversion and dehydration.

The urine is collected in the front of the toilet and led through a hose or a tube down to a urine storage tank. When the urine tank is full, a lorry comes and collects the urine by sucking it out using a pipe. The urine is then taken to be stored in special tanks where it is monitored. The present recommended storage time for source-separated urine is a minimum of six months. This is to ensure that all the bacteria have been killed before the urine is spread as a fertiliser on agricultural land. The faeces fall straight down into a bucket under the toilet seat. The system is usually combined with separate, on site treatment of greywater – bath, dish washing and laundry water.

The most important factor for a working urine system is that the components in such a system are well designed. But there may also be a need to inform the users about how to use the toilets in a manner that maximises the degree of separation.

Advantages of ecological sanitation

• Ecological toilets can be installed inside houses and on any floor.
• If they are properly managed they do not smell or produce flies.
• Ecological sanitation systems are independent of the groundwater and subsoil conditions.
• When applied on a large scale there are great advantages to the environment. No water is required for flushing, transportation and dilution of human excreta. The nutrients are kept out of the water and returned to the land where they are used to increase agricultural production.

Remember:

Don’t mix urine and faeces – keep separate!

Don’t flush away faeces – dehydrate!

Don’t waste a valuable resource – fertilise!
 

Intermediate Technology Development Group would like to thank Ingvar Andersson, who is a senior freshwater advisor in UNDP’s Sustainable Energy and Environment Division, and Uno Winblad for providing the original information on ecological sanitation.

This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.

TVE/ Practical Action gratefully acknowledge support for the HANDS ON programmes from the UK's Department for International Development (DFID), the European Commission (EC), the UN Foundation and UNDP/The Equator Initiative in collaboration with the Government of Canada, IDRC, IUCN, BrasilConnects and the Nature Conservancy.