Experiments using urine and humus derived from ecological toilets

as a source of nutrients

for growing crops.








Peter Morgan







Experiments using urine and humus derived from ecological toilets

as a source of nutrients for growing crops.


Peter Morgan


The need to improve home-based agriculture, in a world which lacks sufficient food and where top soils are often leached out and infertile is a pressing challenge - but where will the nutrients and humus come from? Commercial fertilizers are beyond the means for huge numbers of people who grow food in their own back yards, and animal manures may also be out of reach for those living in the peri-urban fringe. Home made compost is one realistic possibility, and the great wealth of nutrients known to be present in human excreta, another. Perhaps the best is when compost and processed human excreta are mixed and added to the soil. Currently however, most human excreta is completely lost to agriculture. It  finds its way into deep pit latrines or into sewer pipes or septic tanks – and has little chance to add new life and vitality to the topsoil where plants grow. 


Fortunately the world of ecological sanitation is rising to meet this immense global challenge, where the nutrients available in human excreta, representing a huge and as yet almost untapped source of “plant food,” are processed in such a way that they can have enormous potential to benefit agriculture and food production. 


Those who believe in permaculture and organic farming are well aware that plants enjoy growing in a living fertile soil and not one that lacks life and is just fed nutrients alone. Fortunately human faeces can change into a remarkably fertile humus, which can act as an excellent soil conditioner, improving the texture as well as nutrient levels held in the soil. The urine itself is known to be filled with nutrients useful for plant growth. But even the use of urine requires that the soil contains humus, if the nutrients it contains are to be released in a form which the plant can use for growth. If we are serious about utilising the precious nutrients which arise from human excreta in agriculture, we must also take into account the nature of the soil itself. Thus in forming links between ecological sanitation and improved food production, good agriculture practice and a culture of soil improvement must be encouraged.


Most eco-toilets used throughout the world today employ the concept of urine diversion, where the urine and faeces are separated and processed independently, making them easier to process. Popular and successful as this method is, it is by no means the only method of effectively recycling the nutrients held in our excreta. In a revival of a traditional technique used for generations in many countries in Africa and elsewhere, the ancient concept of planting trees in decomposing excreta held in pit latrines is once again becoming more popular. This simple yet elegant technique is now accepted as belonging to a family of alternative ways of recycling nutrients held in human excreta and has enormous potential for the future, especially in poor developing countries.  


Recycling nutrients by growing trees in shallow pits - the Arborloo method. 


The Arborloo refers to a simple, low cost, shallow pit toilet where the toilet slab and structure are portable and move from one pit site to the next at about one yearly intervals. Thus a new, shallow, (0.6m – 1m deep) pit is dug every year. Once nearly full, the used pit is topped up with soil and a young tree is planted and protected. Sounds all too simple, and yet it is a most effective way of recycling the nutrients held in human excreta. The tree roots invade the organic material once converted into humus and take up the nutrients and convert them into vegetative growth and fruit.


Under suitable planting conditions most trees can grow well on latrine pits

Vigorous banana growth on Arborloo pit in Zimbabwe


The Arborloo method differs somewhat from the more traditional method of planting trees in old abandoned deeper pit latrines. With the Arborloo, both soil and wood ash are regularly added to the pit contents during the year of use. These additional ingredients hasten the production of humus and prepare a “pit soil” which is very suitable for tree growth and more so that composted raw excreta alone. Also the pits are dug deliberately shallow, which makes them easy to excavate for the family, but perhaps more importantly, also distances them more from the underground water table, thus reducing the risks of underground water contamination. In addition, the more rapid formation of humus in shallow pits which have a mix of ingredients may also reduce the potential risks of pathogens contaminating underground water. The composting process is aerobic, and not so anaerobic as in the deep pit latrines, where excreta may remain unchanged for years, especially in the deeper zones.  So, to put it simply, trees have an easier time of penetrating shallow Arborloo pits with their humus and can utilise most of the nutrients which become available. The young trees are planted in a layer of soil about 10cm – 15cm deep placed above the pit contents. Trees die if they are planted directly in excreta.


The Arborloo is a portable toilet structure placed over a shallow pit. It moves on a “never ending journey” through the lands, a tree being planted in soil placed over the pit contents. This example comes from Malawi, where arborloo’s are very popular

(Photo: Jim McGill)


Obviously this technique is most suited to places where there is space to plant a tree. The method is becoming very popular in countries like Mozambique, Malawi, Zambia, Kenya and Zimbabwe, and is being tested in South Africa. Its low cost and forgiving nature and the fact that the excreta is never touched by human hand are seen as important features. The growth of a new tree every year, which can turn into fruit orchards or wood lots is seen in a very positive light by the users.  There are reports from a number of countries of the fruits being larger and the trees altogether more healthy than similar trees planted nearby in the topsoil.


Another important feature is that this method is, in essence, a revival of an established concept. Mbachi Msomphora (pers.comm. 2001) reports of the frequent planting of banana trees on old latrine pits in Malawi. She also reported of  the Cham’mwamba tree (Moringa oliefera) and Mtumbu tree (Kirkia acuminata) being planted on abandoned full pit latrines in Malawi. The practice is also quite widespread in Africa (Rwanda , Kenya, Mozambique, Malawi, Zambia and even Zimbabwe). It was used by the Pilgrim Fathers when they arrived in the New World (Steve Esrey. pers. comm. 2001) The fact that it is so widely practiced means that it is logical and acceptable from the users point of view.


Nutrient levels in Arborloo soil


Analysis of Arborloo pit soil shows significantly elevated levels of all the major nutrients required for good plant growth, compared to normal topsoil, as the table below shows. In this case Arborloo pit soil was a combination of faeces, urine and poor topsoil only, revealing the high source of all the major plant nutrients derived from the excreta alone.



Analysis of Arborloo pit soil compared to a mean of various topsoils


Soil source                                                      pH       N*       P*        K*       Ca*     Mg*


Local topsoils (mean of 9 samples)                  5.5       38        44        0.49     8.05     3.58

Arborloo  (one yr. after tree planting. N=2)      5.95     111      309.5   0.95     11.07   5.1


*Nitrogen (N*) and Phosphorus (P*) are expressed as ppm and Potassium (K*), Calcium (Ca*)

and Magnesium (Mg*) as ME/100gms.


The initial growth of tree roots takes place within the 0.6 cu.m. of this enriched soil formed each year, and normally ensures healthy root growth for the future tree. This may be due to the high levels of phosphorus present in the pit soil, a nutrient well supplied from human faeces. Tree root invasion of the organic soil may be slow at first, depending on the rate of humus formation, but inevitably tree growth becomes rapid. This process may take up to two years depending on the soil/excreta mix and the type of tree and level of watering and protection. Trees vary in their reaction to the humus and the proportion of soil to human excreta will also vary from one pit the other. The higher the soil content, the faster the conversion of excreta to humus. The inclusion of wood ash provides more potash and addition of leaves also improved the final texture and elevates nutrient levels of the processed “pit soil.”


Evidence of enhanced tree growth.


Quantitative evidence of enhanced fruit production in trees planted on Arborloo pits is not yet available, although there are numerous visual reports of healthy trees and vigorous fruit growth from many countries. Fruit trees like banana, mango, guava, mulberry, avocado, paw paw and several citrus species respond positively to the organic pit environment, provided they are planted in topsoil and not in the excreta itself.  A wide variety of indigenous trees also respond positively including such species as Brachystegia glaucescens (mountain acacia), Acacia abbyssinica (African thorn bush), Albizia  gummifera (peacock flower) and Swartzia madagascariensis (snake bean tree).  In Malawi the indigenous tree Kirkia acuminata, and the exotic and valuable “Moringa tree” (Moringa oliefera), are traditionally planted on old latrine pits (Mbachi Msomphora pers.comm.)  In Kenya the “Neem” tree (Azadirachta indica) which has so many valuable properties also grows well in this organic environment (Obiero Ong’ ang’a pers.comm.). The eucalyptus species also grow rampantly in this medium as well as many other tree species (see Vol. III of Ecological Sanitation by PRM).



A young tree has been planted in an Arborloo pit in Malawi

(photo: Jim McGill)


Citrus tree growing on Arborloo pit in Kenya


The Arborloo, is the simplest and cheapest eco-toilet system used within the technical range of systems possible under the eco-san umbrella. Because of its ease of use and maintenance it is ideal as an entry point into the world of eco-sanitation, and one of the best examples of “closing the loop.” But perhaps the most important aspect of this concept is its link to the tree. The world lacks trees and they have such a beauty and value of their own which adds to the world we live in. There is no part of the world that would not benefit by having more trees. The tree is one of Nature’s marvels. It can be the provider of food, fuel, building materials and medicine. It helps to stabilise the soil and offers shade. It provides leaf litter and thus provides additional fertility to the soil, It also provides beauty and richness to our environment.

Recycling nutrients by making humus in shallow pits – the Fossa alterna method.


In many ways this system, which also composts excreta in shallow pits, works like the Arborloo. The twin pits used in this system are shallow, usually about 1.2 metres deep and placed between 0.5m and one metre apart. Like the Arborloo, a combination of soil, wood ash and if possible, leaves, are added to the shallow pit in combination with urine, faeces and anal cleansing material. Unlike many double vault pit  systems, only a single latrine slab is used and this alternates every year from one pit to the other and then back again. The challenge of the Fossa alterna, as this system is called,  is to induce the rapid conversion of excreta into a safe and workable humus within the time it takes to fill the second pit with excreta and soil/ash. This would not be possible in the normal pit latrine, where only excreta are added. But where soil and ash are added regularly, and in sufficient quantity, the whole process of humus formation is accelerated. In small to medium sized families, (around 6 persons) humus is formed in well drained pits well within the filling time of the second pit. This being the case, it therefore becomes possible to alternate the use of the pit on a yearly basis. This effectively makes the system permanent, because every year a pit of valuable humus is formed, and is easily excavated, thus making available an empty pit for the next year’s use. This method has been particularly successful in Mozambique under a programme supported by WaterAid. In this programme the portable slab and twin pits are used within a single permanent superstructure.  Every year approximately 600 litres of fertile humus is formed in the composted pit and this can be used on vegetable gardens. Where the toilets are used by more people, the pits are dug deeper  - to 1.5 metres (Ned Breslin. pers. comm.) or a third shallow pit can be introduced.



In the Fossa alterna the use of the toilet alternates at 12 month intervals between two

shallow pits, which are protected with a ring beam or brickwork at the pit head. Soil and ash are added regularly to the pit contents, which helps to convert the excreta into humus.


Fossa alterna in an urban suburb of Harare


Interior of the Fossa alterna.

The bucket contains a mixture of dry soil and wood ash (4:1)




The Fossa alterna does not occupy much space and if correctly managed

provides many years of trouble free service and fertile humus every year




Fossa alterna in WaterAid’s successful programme in Niassa Province in Mozambique.

Here the structure is not portable, as in the Zimbabwe examples. The two shallow pits are placed within the structure. A bathroom is also provided. These are very popular.


Nutrient levels in Fossa alterna pit soil


Analysis of Fossa alterna pit soil reveals, like the Arborloo, a rich humus with high levels of all the major nutrients required for plant growth, compared to normal topsoil. Levels of the major nutrients: nitrogen are increased about 7 times, phosphorus about 6 times and potassium about 9 times in studies undertaken in Zimbabwe.


Analysis of Fossa alterna pit soil compared to a mean of various topsoils


Soil source                                                      pH       N*       P*        K*       Ca*     Mg*


Local topsoils (mean of 9 samples)                  5.5       38        44        0.49     8.05     3.58

Fossa alterna pit soil (mean of 10 samples)    6.75     275      292      4.51     11.89   5.14


*Nitrogen (N*) and Phosphorus (P*) are expressed as ppm and Potassium (K*), Calcium (Ca*)

and Magnesium (Mg*) as ME/100gms.  1 ppm = 1 mg/kg. To obtain ppm from ME/100gms multiply

by 10 and the atomic number (39.1 for potassium). 


These figures, taken from 10 different Fossa alternae, reveal how rich the mix of human excreta and topsoil can be. “Fossa soils” are characteristically high in all the major plant nutrients, notably phosphorus. In each of these tested cases only poor local topsoil was added, without the inclusion of either wood ash or leaves. The addition of wood ash, in addition to elevating the level of potash, also helps to reduce odours and fly breeding in the pit. It also makes the reaction slightly more alkaline. The addition of leaves greatly improved the texture of the final product as well as elevating nutrient levels. This humus has a good balance of nutrients and plants grow well in it. Normally it is mixed with an equal volume of topsoil before planting vegetables. 


Plant trials with Fossa humus 


The value of Fossa  humus, dug out of fully composted pits was studied by mixing it with an equal volume of very poor sandy top soils taken from a peri-urban settlement called Epworth, close to Harare, and also a rural location called Ruwa. These are areas of exceptionally poor topsoil, typical of so many locations in Africa. Without soil enhancement few plant can grow in such soils.  Soil analysis of the poor soils (Epworth and Ruwa) enhanced with Fossa alterna humus are shown below.


Analysis of poor soils (Epworth and Ruwa) with Fossa alterna pit soil


Soil source                                                      pH       N*       P*        K*       Ca*     Mg*


Epworth soil                                                    4.1       23        54        0.07     1.72     0.50

Fossa alterna pit soil                                     6.4       197      299      2.94     26.64   4.77

Resulting mix of Epworth and FA soils         6.4       78        356      1.01     15.75   1.78


Ruwa soil                                                        5.5       27        5          0.29     10.23   4.11

Fossa alterna pit soil                                     6.5       319      196      3.26     13.70   7.26

Resulting mix of Ruwa and FA soils 6.4       91        247      0.88     3.05     2.49


*Nitrogen (N*) and Phosphorus (P*) are expressed as ppm and Potassium (K*), Calcium (Ca*)

and Magnesium (Mg*) as ME/100gms.

Evidence of enhanced vegetable growth.


In a series of simple experiments vegetables like spinach, covo, lettuce, green pepper, tomato and onion were grown in 10 litre buckets or basins of Epworth or Ruwa soil and their growth was compared with plants grown in similar containers filled with a 50/50 mix of Epworth  (or Ruwa) soil and Fossa alterna soil. When Fossa soil is excavated from the pits it is normally mixed with an equal volume of local topsoil to prepare beds or containers for planting vegetables. In each case the growth of the vegetables was monitored and the crop weighed after a certain number of days growth. The following chart showed the results of these trials. FA* denotes soil taken from Fossa alterna pit. The extra growth is due to FA enhancement.


Plant. Top soil type.

Growth period.

Weight at cropping

Top soil only

Weight at cropping

50/50 mix topsoil/FA*soil

Spinach on Epworth

30 days.

72 grams

546 grams (7 fold increase)

Covo on Epworth

30 days.

20 grams

161 grams (8 fold increase)

Covo 2. on Epworth

30 days.

81 grams

357 grams (4 fold increase)

Lettuce on Epworth.

30 days

122 grams

912 grams (7 fold increase)

Onion on Ruwa

4 months

141 grams

391 grams (2.7 fold increase)

Green pepper on Ruwa

4 months

19 grams

89 grams (4.6 fold increase)

Tomato on Ruwa

3 months

73 grams

735 grams (10 fold increase)


All these results clearly show a dramatic and meaningful increase in vegetable yield resulting from the enhancement of poor spoil (Epworth and Ruwa) with the Fossa alterna humus.


In similar trials with maize, three seedlings were planted in 2 buckets containing Epworth soil and also 2 containing the Epworth/Fossa mix. After 3 months a total cob weight of 110 gms (6 cobs) was recorded for 6 maize plants growing on Epworth/Fossa  soil, but only 2.5 gms for the 6 plants growing on the plain poor Epworth soil alone. Although this is a huge increase, the Fossa alterna humus contained in the buckets did not provide sufficient nutrients to take the maize to full yield. Urine was necessary in these trials to provide the maize with sufficient nutrient to gain full cob weight which can exceed 300 gms per cob (see later).



Spinach growing on poor sandy soil (left) and the same soil enhanced with an

equal volume of humus taken from a Fossa alterna pit (right).




Lettuce growing on poor sandy soil (left) and the same soil enhanced with an

equal volume of humus taken from a Fossa alterna pit (right).







Covo growing on poor sandy soil (left) and the same soil enhanced with an

equal volume of humus taken from a Fossa alterna pit (right).



Onion growing on poor sandy soil (left) and the same soil enhanced with an

equal volume of humus taken from a Fossa alterna pit (right).



Recycling nutrients derived from the urine diversion method.


There are many systems of urine diversion used throughout the world. Most separate urine from the faeces in a urine diverting pedestal or squat platform. In most cases the urine is fed into a tank where it is stored for later use. The faeces invariably fall into a vault where lime or wood ash is also added leading to desiccation Where there are twin vaults, the pedestal is moved from one vault to the other at approximately one year intervals to allow the faeces to dehydrate. However urine can be collected in a variety of ways other than in urine diverting toilets. Men can urinate into bottles direct or into “desert lilies” (a funnel over a container placed in some discrete place) and women into a variety of “potties” both separate from and attached to the conventional flush toilet. 


In a system called a skyloo used in Zimbabwe, a urine diverting pedestal is mounted over a single vault and the faeces fall into a 20 litre bucket, followed by a mixture of soil and wood ash (mix 4:1). Urine is diverted to a plastic container. The bucket of faeces, soil and ash is allowed to fill up and is then transferred to a “secondary composting site” which may be a shallow pit, trench or jar, where more soil is added. The most interesting system for secondary composting is the 30 litre split cement jar, where the mix of faeces, soil and ash are transferred, with more fertile being added after every application. 3 or 4 bucket fulls will fill the jar which is then watered down and left to compost for about 4 months. At the end of this period a very rich humus is formed. Vegetables (particularly tomatoes) grow very well in this humus, as do flowers and a wide variety of trees (which can be started off in the jars). Soil analyses of this humus formed in the jars shows a well balanced and high level of nutrients. Experience has shown that this humus is an excellent medium for growing a wide range of plants.




Urine diverting toilet used by the writer





The urine diverting pedestal. Urine passes down the front through a plastic pipe into a

20 litre plastic container. Faeces drop down vertically into a bucket held in the vault

beneath. Dry soil and ash (and toilet paper) are also added to the bucket.



Urine is collected in this 20 litre plastic container.



The brick built vault houses the bucket. The rear has a ferrocement

Door to gain access to the vault.



Rear vault access door removed. The 20 litre bucket is inside.





Emptying bucket contents into a 30 litre split cement jar



Several jars in which the mix of faeces, soil, paper and wood ash are

Composting. Plants like tomato thrive in such jars and often grow spontaneously.



   Analysis of “skyloo” humus composted in 30 litre cement jars


Soil source                                                      pH       N*       P*        K*       Ca*     Mg*


Skyloo humus (faeces, soil, wood ash)            6.72     232      297      3.06     32.22   12.06

Fossa alterna pit soil (mean of 10 samples)  6.75     275      292      4.51     11.89   5.14

Local topsoils (mean of 9 samples)                  5.5       38        44        0.49     8.05     3.58


*Nitrogen (N*) and Phosphorus (P*) are expressed as ppm and Potassium (K*), Calcium (Ca*)

and Magnesium (Mg*) as ME/100gms.


In many ways the humus formed in the jars is similar to Fossa alterna humus, and has a well balanced mix of nutrients. It has proved to be an excellent medium in which to grow seedlings as well as mature plants. The living content of the “jar humus” is very high – it is a most valuable product and enjoyed by many plant species grown in it. These results testify to the great value of faeces without the inclusion of urine. In fact both products are very valuable, the urine best as a liquid feed applied diluted with water.


Using the nutrients in urine to enhance the growth of plants.


Each of us excretes about 580 kg urine per year (for adults) - about 1.5 litres per day, and this contains many nutrients useful to plant growth. In recent figures released in China  by Gao, Shen and Zheng (2002), urine contains 96.98%water, 0.53 % (3.08 kg/yr) nitrogen (mostly urea), 0.04% (0.23 kg/yr) phosphorus, and 0.14% (0.81 kg/yr) potassium. By comparison 113.7 kg of human faeces are produced per year containing 80.7% water, 1.16% (1.31 kg/yr) nitrogen, 0.26% (0.29 kg/yr) phosphorus and 0.03% (0.03 kg/yr) potassium (a low figure for potassium compared to other analyses).  Thus the urine produces 4.12 kg/yr NPK compared to the faeces which produces 1.63 kg/yr. (thank you  Xiao Jun for offering this valuable information). Overall most nutrients are released in the urine, but these new figures indicate that the annual production of phosphorus is greater in faeces than in the urine.



Two 10 litre basins planted with rape and spinach. The basin on the left

has been fed with a 3:1 mix of water and urine, three times per week interspersed

with normal watering. The basin on the right has been irrigated with water only.


A problem faced with urine when used as a feed for plants is that it has a very high proportion of nitrogen and salt (Na Cl) compared to phosphorus and potassium. Most garden fertilizers for vegetables contain more phosphorus than nitrogen. Phosphorus is valuable for root growth, nitrogen for vegetative growth like leaves and potassium helps the ripening and fruiting process. The great value of urine lies in its universal availability and zero cost. Consequently it has immense potential value and has been used for many generations as a plant food in some countries, notably in the Far East. Because of its high nitrogen content it is particularly useful for feeding leafy vegetables, which enjoy a high nitrogen diet.

Plant trials with urine


The following trials were performed on a variety of vegetables and maize using urine diluted with water at a ratio of three parts water to one of urine as a liquid feed.  Seedlings were planted in containers, either 10 litre buckets or10 litre cement basins and irrigated with water first for a period (1 – 4 weeks) to stabilise in their new environment. Fast growing vegetables like lettuce, spinach, covo and rape were irrigated with water first for 1 – 2 weeks before urine application after transplant and tomatoes were watered for a period of one month before urine application. Thereafter 0.5 litres of a 3:1 water/urine mix. was applied to the buckets or basins on each urine application, this being the volume that the 10 litres of soil could absorb. The 3:1 mix was applied three times per week in this trial interspersed with regular watering at other times to keep the plants turgid and healthy. Young seedlings do not tolerate the 3:1 mix well and need to stabilise before the water/urine mix applied. They tolerate a 5:1 mix better. When the plants are very young diluted urine can retard plant growth or even kill the young plants.


For the maize trials, carried out mostly in 10 litre cement basins, the urine was diluted in the range 3:1, 5:1 and 10:1 with water. The plants were fed with urine either 3 times per week with the 3:1 mix (U1 application), once per week with the 3:1 application (U2), once a week with the 5:1 application (U3), once a week with the 10:1 application or with water only. Plants being fed the water/urine mix were also watered regularly at all other times to keep the plants healthy and turgid. After a specified growing period, the crop was harvested and weighed. A chart showing these various trials are given below. All watering was by hand - using a watering can – the old and reliable method.


Plant trials with urine for various vegetables, tomatoes and maize.


Plant and container

Urine/water application

Duration of growth


Lettuce (10 litre bucket)

water only

30 days

230 gms

Lettuce (10 litre bucket)

3:1 urine. 0.5 li X 3 per week for 3 plants  

30 days

500 gms (2 fold increase)

Lettuce (10 litre bucket)

water only

33 days

120 gms

Lettuce (10 litre bucket)

3:1 urine. 0.5 li X 3 per week for 3 plants  

33 days

345 gms (2.8 fold increase)

Spinach (10 litre bucket)

water only

30 days

52 gms

Spinach (10 litre bucket)

3:1 urine. 0.5 li X 3 per week for 3 plants  

30 days

350 gms (6 fold increase)

Covo (10 litre basin)

water only

8 weeks


Covo (10 litre basin)

3:1 urine. 0.5 li X 1 per week for 3 plants  

8 weeks

204 gms (1.5 fold increase)

Covo (10 litre basin)

3:1 urine. 0.5 li X 3 per week for 3 plants  

8 weeks

545 gms (4 fold increase)

Tomato (10 litre bucket)

water only

4 months

1680 gms ( 9 plants)

Tomato (10 litre bucket)

3:1 urine. 0.5 li X 3 per week for 3 plants  

4 months

6084 gms ( 9 plants) (3.6 fold increase)

Maize (M8 trial)

(10 litre basins)

water only

3.25 months

21 gms (mean 3 cobs)

Maize (M8 trial)

(10 litre basins)

3:1 urine. 0.5 li X 1 per week for 3 plants (U2)

3.25 months

135 gms (mean 3 cobs)

(6.4 fold increase)

Maize (M8 trial)

(10 litre basins)

3:1 urine. 0.5 li X 3 per week for 3 plants (U1)

3.25 months

318 gms (mean 3 cobs)

(15 fold increase)

Maize (M14 trial)

(10 litre basins)

water only

3 months

6 gms (mean 9 cobs)

Maize (M14 trial)

(10 litre basins)

10:1 urine. 0.5 li X 1 per week for 3 plants  u4

3 months

62 gms (mean 8 cobs)

(10 fold increase)

Maize (M14 trial)

(10 litre basins)

5:1 urine. 0.5 li X 1 per week for 3 plants  u3

3 months

138gms(mean 16 cobs)

(23 fold increase)

Maize (M14 trial)

(10 litre basins)

3:1 urine. 0.5 li X 1 per week for 3 plants  u2

3 months

169gms(mean 18 cobs)

(28 fold increase)

Maize (M14 trial)

(10 litre basins)

3:1 urine. 0.5 li X 3 per week for 3 plants  u1

3 months

211gms(mean 19 cobs)

(35 fold increase)




Urine has a pronounced effect on maize, especially when grown in containers

In the trials, maize plants were grown in 10 litre cement containers and fed with

varying amounts of urine. In this case the plant on the right is being fed with a

3:1 mix of water and urine (0.5 litres) three times per week. The maize on the

left is irrigated with water only. The difference is striking.









Total yield of cobs from maize planted in 3 -10 litre basins. On the left the maize was fed 1750mls urine per plant over the 3.5 month growing period, resulting in a crop of 954 gms. A reduced crop resulted from reduced input of urine (middle). Maize plants on the right were irrigated with water only. This produced a very poor yield.


A single photo shows the effect of different amounts of urine applied to maize plants over a 3 month period. On the left (U1) the plants have been fed a 3:1 water/urine mix three times per week (125 mls per plant per week). This has led to a mean cob weight of 211 gms. The 3:1 mix was applied to the U2 group once a week (40 mls per plant per week) and has led to a mean cob weight of 169 gms. A 5:1 mix was applied to the U3 group once a week (27 mls per plant per week) and has led to a mean cob weight of 138.2 gms. A 10:1 mix was applied to the U4 group once a week (15 mls per plant per week) and has led to a mean cob weight of 62 gms. Those plants fed water only produced a mean cob weight of only 6 gms. 99.4% of the total cob mass shown in this photo is derived from the nutrients provided by the urine.



These various trials reveal the great value of urine when used as a liquid feed for various plants, and particularly for leafy vegetables (lettuce, spinach, covo). The application of urine at the rate of 125mls per plant per week when diluted with 3 parts of water (U1) increased the yield of lettuce by 2 – 3 times, spinach by 6 times, covo by up to 4 times. Even for tomatoes which prefer a better balance of nutrients and certainly more potassium, crop output was enhanced by a factor of 3.6 times compared to plants irrigated in containers with water only. Maize too, responded very well to urine application when grown in basins, under experimental conditions. Compared to maize grown in basins without urine application the yield increases by factors which ranged between 6 and 35 times when fed urine. These are significant improvement in crop yield with the only source of available extra nutrients being released from the urine.


These and other results from an extensive series of maize trials reveal that the production of maize could be increased on poor sandy soil, by the application of urine alone, but that if the sandy soil had humus added, then the production went up further. Mean maize cobs yields of 4.3 gms for poor sandy soil (Epworth) irrigated with water only went up to 82.3 gms when soil was treated with urine only (125mls per plant per week) and to 131.28 gms when the poor sandy soil was mixed in equal proportions with Fossa alterna humus and also treated with urine. This increase is partly due to the presence of the nutrients in the Fossa alterna soil, but also due to the increased number of nitrifying bacteria present in the humus which converts the urea and ammonia in urine into nitrate ions which can be taken up by the plants. The addition of Fossa alterna humus to poor Epworth soil in equal proportions, but without urine treatment, only increased mean cob weights from 4.3 gms to 27.9 gms. This indicates that the presence of humus is an import requirement if the nitrogen in urine is to be converted into a usable form which  the plants can take up.


Efficiency of use of urine


In all cases the yields of both vegetables and maize was the highest when the highest dose of urine was applied, but these were wasteful of urine. The results reveal that a lower dose of urine was more effective in terms of gms of cob weight in relation to mls of urine applied. These are best revealed in maize trial M14, where a total of 70 plants were examined.    Figures are given below for urine application to maize with corresponding cob yield and also mls of urine required per gm. of cob yield.


Urine application to maize with corresponding mean cob yield


Liquid feed     No. weeks                   Total urine applied per plant Mean cob weight


Water               12                                none                                                     6gms

U4*                 12                                180 mls                                                62 gms

U3*                 12                                324 mls                                                138.18 gms

U2*                 12                                480 mls                                                169.61 gms

U1*                 12                                1500 mls                                              211.25 gms


These figures reveal, as in the M8 trial, that the maize cob output is related to the urine input and that the highest urine input results in the highest output of cobs in terms of overall yield. However the figures also reveal that the most effective use of urine is not found in this highest dose rate as the chart below shows.


Mls of urine required per gm weight of cob yield


Liquid feed       Urine input per plant per week  Mls urine required per 1 gm cob yield


U4                   15mls                                                   2,90 mls per gm cob

U3                   27mls                                                   2,34 mls per gm cob

U2                   40mls                                                   2,83 mls per gm cob

U1                   125mls                                                 7.10 mls per gm cob


Thus in terms of the most effective use of urine, the U3 treatment was the most effective, as this used 20% of the maximum urine dose to produce 65% of the maximum cob output. The U2 treatment used 33% of the maximum urine dose to produce 80% of the maximum cob output. These figures indicate that high doses of urine are not the most effective way of using this liquid feed. But cob size is a factor of importance considered by the consumer, and cobs produced in the U3 trial might have been considered undersized. Thus one looks at the U2 treatment as the guide. If the same amount of urine used to feed the U1 application was used to feed three times the number of plants at the U2 application rate (about 40mls per plant per week diluted with 3 X water), then the overall yield of cobs would have been increased by a significant 2.4 times. In fact heavy doses of urine are wasteful and not efficiently converted.  If urine is available in sufficient quantity, then an effective treatment for maize would be U2 treatment for the 1st and 3rd third months and U1 treatment for the second month. This regime would use a total of  820mls urine per plant with the possibility of little wastage of urine and producing a good cob weight per plant. The largest cob produced in the trial weighed 356 gms. Remarkably the plant grew 2.1 m high on just 100mm depth of soil.


Maize trials with urine application on the fields are ongoing. Here the urine is applied neat in small hollows made close to the plant, and the natural rainfall dilutes and flushes it into the soil. These are complex experiments where the reaction of maize to the urine depends on many factors including rainfall patterns, competition with weeds and vegetables which are often planted next to the maize. Too much rain and the nitrogen may be lost deeper down, too little rainfall and the urine may not reach the roots. Also different soils react differently to the application of urine, with some being better converters of the nitrogen than others. It is hoped to report on urine trials on maize grown in fields at a later date.   



Experimental maize field currently under investigation


Overall conclusions


These various experiments reveal how valuable human excreta can be when used as a humus derived from faeces or from a faeces/urine mix (Fossa alterna). They also reveal the value of the urine when applied in a diluted form to a wide variety of valuable crops.


Fossa alterna humus when added to barren soil can provide an excellent medium for growing vegetables in the back garden. Using the results from the trials, the annual production of Fossa humus from the family toilet (approximately 600 litres/yr) when mixed with poor local topsoil might produce: 27 kg spinach (first crop only – at least 2 crops can be reaped) or 17 kgs of covo (first crop only – covo can be cropped for an extensive period) or 37 Kg rape or 45 kg lettuce or 41 kg green pepper or 73 kg tomatoes or 40 – 50 kg onion. Obviously there would be a mix of these crops produced in practice. As can be seen from the equivalent weight of vegetables grown on poor soils alone, this is a remarkable enhancement in vegetable production. What the eco-humus does in addition to providing nutrients is to add humus to the soil, which has a great value in its own right for increasing the effectiveness of urine application.  Urine application is much less effective in barren soils which do not contain humus.


In terms of urine output, an annual production of at least 1 000 000 mls (1000 litres) is possible from a family of two adults and three children, even with some wasteage. There are many ways of collecting urine in the homestead, filling bottles and potties perhaps being the most likely in the absence of a urine diverting toilet. It is interesting to speculate how much vegetable growth and maize cob yield would result from the application of this annual production every year. The following figures are calculated using data from the experiments described in this paper.

Potential yield of vegetables and maize using annual family urine production


Crop                mls urine required per gm of crop.                Potential annual crop


Lettuce 5.5  mls per gm of crop                         181 kg/yr         or

Spinach            5.0  mls per gm of crop                                     200 kg/yr         or

Covo                7.3 mls per gm of crop                          137 kg/yr         or

Tomato            4.1 mls per gm of crop                          243 kg/yr         or

Maize               2.8 mls per gm of crop (U2 application)            352 kg/yr


Obviously urine would have to be stored and made available for use at certain times of the year when specific vegetables were growing. Also urine would be used for a variety of applications by the enthusiastic gardener, which may include the enhancement of flower beds as well as vegetables and trees. Whilst these figures are not likely to be realised fully in practice they do reveal the huge potential of urine application as an enhancer of vegetable and crop growth based on actual results from the plant trials with urine.


The annual production of both eco-humus from the family latrine (Fossa alterna or urine diverting) and urine from various family sources, is only sufficient to enhance the back yard family vegetable garden or a small maize field and no more.  But this may represent, for each family, a huge increase in vegetable production, especially in areas where the soil is poor or access to manure or commercial fertilizer is difficult or expensive. Barren gardens may be turned into gardens of plenty over the years.


The potential for increased crop production is only one benefit to be gained from the introduction of this new series of eco-toilets. The cheapness and ease of construction of both the Arborloo and the Fossa alterna, makes possible the construction of a family latrine at the home by the homesteaders themselves. This has been well demonstrated in WaterAid’s excellent eco-san programme in Mozambique and also in Malawi and Zambia. The construction of a simple concrete slab, using cement and river sand is perhaps the most challenging technical difficulty. Yet in Zimbabwe schoolgirls can perform this task with great ease, having been shown the method. There is little very skilled workmanship required or heavy labour needed to dig the shallow pits and the superstructures which are designed to provide privacy only.


At a time when rural, urban and peri-urban sanitation is in need of a practical uplift, and perhaps a broader outlook is required, these eco-solutions may offer a ray of hope, for they provide each family with a lot more than just a dumping ground for excreta and garbage, which has been the case in the past. The links formed between sanitation and the worlds of agriculture and forestry are practical and exciting. They may have arrived just in time to give the sanitary world the boost and novelty it now requires.




The writer wishes to thank the following people for their support, advice and encouragement or for promoting the concept of low cost eco-san in the field. The staff of the Friend Foundation, in particular Mrs Christine Dean and  Baidon Matambura, Moses Nyapokoto of Fambidzania, Marianne Knuth of Kafunda Village, Annie Kanyemba, Jim and Jill Latham of the Eco-Ed Trust and Ephraim Chimbunde, Edward Guzha and David Proudfoot of Mvuramanzi Trust in Zimbabwe. Ron Sawyer, George Anna Clark and Paco Arroyo from Mexico. Ned Breslin, Steven Sugden and John Kelleher and other colleagues in WaterAid, from Mozambique, Malawi and Zambia and also Mbachi Msomphora from Malawi and Xiao Jun from China. Obiero Ong’ang’a and Kinya Munyirwa from Kenya. Aussie Austin, Richard Holden, Dave Still and Stephen Nash from South Africa. Almaz Terrefe and Gunda Edstrom from Ethiopia – thanks for the early enlightenment. Uno Winblad for pioneering this ecological view on sanitation and for his long experience and valuable input. Many thanks to Paul Calvert for his valuable insights and encouragement from India. Many thanks to Arno Rosemarin and staff of SEI, Stockholm, who have supported the agricultural research sited in this paper as part of the new EcoSanRes research programme. Many thanks also to Håkan Jönsson and Björn Vinnerås for important inputs on the agricultural side and urine use. Sincere thanks and much gratitude to the late and much missed Steve Esrey from the USA. Ingvar Andersson and Rolf Winberg are much thanked for their long support and personal encouragement. Also to Bengt Johansson and Sida for their support which has made this new venture into ecological sanitation possible. Finally to my wife Linda thanks for every possible support.




Breslin, E. D., (2001). Introducing ecological sanitation: Some lessons from a small town pilot project in Mozambque. Stockholm Water Symposium, 201.


Esrey S.A., Gough, J., Rapaport, D., Sawyer, R., Simpson-Hebert, M., Vargas, J., Winblad, U.,(ed). 1998. Ecological Sanitation. Sida. Stockholm.


Esrey S.A. (1999). Nutrition - Closing the Loop. Proceedings of the Workshop on Ecological Sanitation. Mexico. October 1999.


Esrey S.A. & Andersson, I., (1999) Environmental Sanitation from an Eco-Systems Approach.  Proceedings of the Workshop on Ecological Sanitation. Mexico. October 1999.


Gao, XZh, Shen, T., Zheng Y., (2002) Practical Manure Handbook. Chinese Agricultural Publishing House. Beijing.


Hills, L. D. (1981). Fertility Gardening.  Cameron & Tayleur. London.                                


Howard, Sir Albert, (1943). An Agricultural Testament. Oxford University Press. London.


Jenkins, Joseph, C. (1994)   The Humanure Handbook. Chelsea Green Publishing Co. PO Box 428, White River Junction, VT. USA.


Jonsson H. (1997) Assessment of sanitation systems and reuse of urine. Ecological alternatives in sanitation. Publications on Water Resources. No.9. Sida. Stockholm.


Jonsson H.  Stenstrom TA, Svensson J. and Sundin A. (1997). Source Separated urine - nutrient and heavy metal content, water saving and faecal contamination. Water Science and Technology, 35 (9).


Manson. T. (1991) Garden Book. Roblaw Publishers, Harare.                                  


Morgan, Peter R. (1990). Rural Water Supplies and Sanitation. Macmillans. London.


Morgan,  Peter R., (1999). Ecological Sanitation in Zimbabwe. A compilation of manuals and experiences. Vols. 1, II, III and IV. Aquamor Pvt. Ltd. Harare. 


Saywell, D. (1999) Pollution from on-site sanitation - the risks? what risks? Waterlines. Vol. 17. No. 4. 22 - 23.


Simpson-Hebert, M & Sara Wood, (1997). Sanitation Promotion Kit. WHO. Geneva.


Stenstrom, Thor-Axel, (1999). Health Security in the Re-use of Human Excreta from on-site Sanitation. Proceedings of the Workshop on Ecological Sanitation. Mexico. October 1999.


Strauss, M. & Blumenthal U. J. (1990). Use of the human wastes in agriculture and aquaculture - utilization practices and health perspectives. IRCWD, Dubendorf, Switzerland.


Vinneras, Bjorn, (2002).  Possibilities for sustainable nutrient recycling by faecal separation combined with urine diversion. PhD thesis. Swedish University of Agricultural Science. Uppsala, Sweden 


Winblad U. & Kilama W. (1985) Sanitation without water. MacMillan. London.


Winblad, U. (1996). Towards an ecological approach to Sanitation. International Toilet Symposium. Toyama. Japan.