Since early Chinese history, human excreta was commonly used in agriculture to complement farm manure in improving soil fertility. Farmers owned ‘Outhouses’ where they invited visitors to leave behind their ‘valuable’ excreta. In early Europe, Greek and Roman societies collected human excreta and used it as fertilizer. The Romans found that urine contained high value nutrients and collecting it was a good business. Emperor Vespasian introduced a ‘urine tax’ along with the proverb pecunia non olet (Money does not smell).
In Britain, Queen Victoria used an earth-closet at Windsor Castle, although many types of water-closet were available. Henry Moule in 1840’s was the champion of the earth-closet and backed up his belief with a scientific experiment where he persuaded a farmer to fertilise one half of a field with earth from his closet, and the other with an equal weight of superphosphate. Swedes were planted in both halves, and those nurtured with earth manure grew one third bigger than those given only superphosphate. For many years, the earth- and water-closets were rival systems with champions and detractors on both sides.
The nutrition value of urine and faeces as fertilizers
|Fertilizer||500 litres of Urine||500 litres of Faeces||Total||Fertilizer needs of 250kgs of cereal|
(500 litres of urine and 50 litres of faeces are about the amounts produced by one adult in a year)
Note that most of the nutrients are in the urine, though the vast majority of the pathogens are in the faeces. Although faeces has a lower nutrient content, its high organic matter aids water retention and is a good soil improver.
Ecological latrines can be divided into two main types: (i) dehydrating urine separating toilers and (ii) composting toilets.
(i) Dehydrating urine separating toilets
The urine and faeces are collected and stored separately by the use of specially designed pedestals and slabs. The urine is collected and stored until it can be used as a fertilizer on plants or crops. The faeces drops into a pit, vault or container to which a handful of either ash or lime is added. This has the effect of drying the faeces and increasing the pH which has a positive impact on reducing smell (less ammonia emission) and destroying pathogens . After 12 months of storage the resulting ‘humanure’ can be applied to the land. Some form of alternating double or multiple storage system is required to avoid mixing fresh and composted manure.
(ii) Composting toilet
The double-pit or vault composting latrines do not separate the faeces and urine, so that both enter the same vault or pit. A handful of a mixture of soil and ash is added to the pit after each use which has the effect of keeping the pit contents relatively dry and aerobic, as opposed to anaerobic and smelly. ‘Composting’ is not technically the correct name as the temperatures never rise high enough to create themophilic composting conditions. After 12 months of storage the resulting ‘humanure’ can be applied to thet land as a fertilizer and soil conditioner. The simplest form of composting latrine is called the Arborloo or ‘walking latrine’ (see below).
Arborloo A shallow (1-1.5m) unlined pit covered by a concrete slab and a movable simple superstructure. Once the pit is 2/3 filled (usually after some 4-6 months), the superstructure and slab are removed to a new pit. The old pit is further filled up with soil and a young tree is planted in the pit. Banana and Paw Paw grow particularly well in the old pit.
In many Developing Countries poor soil fertility and the increasing cost of artificial fertilizer is making it difficult for subsistence farmers to grow enough food to feed their families. Survival becomes more perilous as population growth means new land to cultivate is not available. The fertilizer producing qualities of ecological latrines can help the household economy of poor families. These farmers allude not only to the nutrient quality of the ‘humanure’, but also how the organic matter from the faeces improves soil structure.
The act of adding ash and/or soil and separating the urine has the effect of drying the faeces and the possibility of pathogen transmission to the water table is eliminated. This makes eco sanitation a particularly good option in areas where contamination of groundwater is a sensitive issue.
In water stressed or arid areas, ecological sanitation (which needs no water for flushing) can help save this valuable resource. In the developed countries of the north it has been estimated that use of ecological sanitation could reduce domestic water consumption by 20-40%.
Conventional sewage systems effectively remove faecal material and the pathogens it contains from the immediate household and community environment and deliver it to a sewage treatment works. In many countries the sewage works are incapable of effectively treating the waste as the volume entering the plant exceeds its design capacity (either because of population growth, the high cost of electricity or the mixing of sewage with storm water). The result is that poorly treated sewage is discharged into streams and rivers with detrimental effects on the rivers’ flora and fauna. It is argued that if eco-sanitation was more widely used, the need to build and operate expensive sewage works would diminish and the water quality in the rivers would improve.
In developing countries, areas with high groundwater tables and collapsing sandy soils are notoriously difficult in which to build permanent traditional latrines. Ecological latrines with their shallow pits or vaults can provide good, sustainable affordable solutions.
The debate about the safety of ecological sanitation often occurs in isolation of the context in which it is being practiced and the larger question of whether the introduction and practice of ecological sanitation will improve the overall health of a community is never addressed. Generally speaking, from a health perspective an ecological latrine is better than no latrine at all and any possible health risks must be weighed against the potential improvement in the household economy and a family’s ability to feed themselves.
‘Humanure’ has been used since ancient times for fertilizing crops. ‘Long-drops’ or latrine pits are common in South Africa but the simple act of planting a fruit-bearing tree on old, covered-over pits is perhaps not common knowledge. With modern knowledge and technology, the eco-sanitation concept can be refined and made more convenient (and safer). This could be part of the solution to recycling phosphorus which is a non-renewable resource (and vital for continued life on Earth). Waterless toilets are an ideal solution where water is scarce. It doesn’t seem logical to use perfectly good drinking water to flush toilets! Ecological sanitation is ultimately the way all human waste should be dealt with but it will take a while before the mechanisms are modernized and it becomes socially acceptable in the developed world. In the mean time, you should consider recycling grey water for toilet flushing. This also reduces the load on our over-capacity sewage works. Catching rainwater and storing it in rain water tanks also reduces stormwater runoff that often ends up in our sewage plants. Rainwater and greywater can be used for household- and garden use- saving water, saving money and saving the environment.