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Gabinetti a secco
Perché usare un gabinetto a secco?

Il nostro rapporto con i nostri escrementi

Tre generazioni di gabinetti a secco

Come utilizzare un GCS
La composizione chimica degli escrementi umani
Compostaggio di escrementi umani
Sistema GCS sul mercato
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"Therefore the Sage says:
Only he who accepts the country's filth,
Can become lord of its sacred soil."

Lao-Tzu, Tao Te Ching 78th Chapter

The text within this page was first published in French on www.eautarcie.com : in 2003

The original text has been adapted and translated by André Leguerrier. First published on this page at www.eautarcie.org: 2009-06-15

Last update : 2016-02-21

Compostaggio di escrementi umani

Correctly done composting is inescapable as a sustainable agricultural practice. In view of growing world population, humanity's survival on the planet will be conditioned by our choices in this matter, between its widespread use, or its exclusion. Agricultural reuse of human dejecta is the way of the future. In light of ongoing farmland degradation, our children and grandchildren will no doubt accuse us of wilful negligence in persistently denying the untenable character of black water purification until it's too late. Flush toilets and their inherent «all to the sewer» reasoning have long overstayed. For sustainable environmental management, we must move on and adopt preventive problem-solving techniques.

Those who have adopted the biolitter toilet (BLT) are at the state-of-the-art in terms of global sustainability. Since present-day society refuses to even consider selective gathering and collective composting of human dejecta, it becomes the responsibility of individuals to take charge of the problem. Those who already compost kitchen or garden wastes will have less problem adapting. In most areas, composting dry toilet effluent adds little extra work in this regard. Others will have to learn composting basics, which, according to some, is almost an art form. We don't intend to contradict other excellent literature available on the subject. We simply purpose to provide more technical data on the specifics of composting human waste.

Elementary Rules of Good Composting

The purpose of composting is to restore animal- and plant-sourced biomass back into the process of humus formation, which is the «brown gold of the earth». Without humus, we are quickly heading towards arable land loss and eventually desertification. This can only lead to additional climate changes and worsening water (and food) shortages. The converse is also fortunately true [2] restoring humus content to soil will regenerate land, modify (i.e. stabilize) climate, and re-establish soil's moisture regime. Water problems then resolve themselves without other intervention. Remember that humus can hold 50 times its weight in water. Humus restoration stabilizes sandy soils, protecting them against wind and water erosion. It makes compact clay soils friable and easier to till. [3].

[2]
...as long as this is corrected in time. When earth has been totally eroded, regenerating the soil becomes quite difficult.
[3]
History has shown that there is an intimate link between humanity and humus. When humus disappears from land, man must ultimately move on. Most human migrations and bloody wars are a result of soil degradation. A civilization's fate is ultimately dependent on farmland's capacity to feed its people, which is tied directly to the soil's humus content.

Humus is organic matter composed of large molecules (humic acid), the elements of which are present in plant and animal biomass [4]. Plant biomass provides the carbon «skeleton» whereas animal biomass provides the «flesh»: nitrogen- and phosphorus-containing protein. The whole is «seasoned» with mineral salts. The soil, with its clay, calcite and sand particles provides the support on which the synthesized humic acid particles fix themselves. This forms a clay-humus complex that is the ultimate phase of what is called stabilized humus. For further reading on this, go to the importance of humus.

[4]
The word «element» used herein does not refer to chemical elements shown on the Mendeleev periodic table, but to macro-molecular sequences having a relatively large carbon-based framework. Plant cellulose (that is found in litter) thus constitutes the structural support for synthesis of humic acids. Without this support, the large nitrogenous molecules contained in dejecta will decompose into carbon dioxide (mainly in an aerobic milieu), methane (in an anaerobic milieu), and water. Their nitrogen components will turn into ammonium ions, nitrites and nitrates. That is why there cannot be humus formation when sewage is discharged into water. On the contrary, nitrogen is mineralized and thus becomes a water pollutant. Wastewater purification, which is none other than the treatment of nitrogen-containing organic compounds seriously undermines the biosphere.

First Golden Rule

Composting must be done in direct contact with the soil [5]. This follows from the above observations. As an extremely complex biological process, composting occurs thanks to the microscopic and macroscopic fauna that naturally thrive in the soil. These organisms' lifecycles include activity in the soil below, but also in the compost above. There is continual movement and exchange between the two zones. Composting on a concrete or wood pad or in a plastic container prevents these essential exchanges within the composting process [6].

[5]
...therefore, not in a floored compost bin or closed compost container.
[6]
Plus, compost must never be done in a hole in the ground, or covered with a plastic sheet. Such practices hinder the essential aerobic exchanges with soil and air fauna. Organic matter placed in such conditions will rot and generate unpleasant odours, instead of being transformed into humus.

Second Golden Rule

You must find the right balance between plant- and animal-sourced components in the compost. From a scientific point of view, the carbon/nitrogen ratio must be about 60, at the start of composting. During composting, this ratio goes down and stabilizes at 14. Most people are not equipped to measure this ratio, but that is not essential. When you have acquired the «art» of composting, you can «feel» what scientists can measure with their instruments.

When compost contains too little animal matter, the composting process is slow. Dead leaves can take up to two years to decompose without addition of dejecta. Plant stems and twigs remain relatively intact and the compost tends to dry out. On the other hand, when there is too much animal manure, the compost will smell bad. When you turn it over after a few months, the smell of ammonia will be omnipresent. The compost tends to be moist and compact. The process is no longer that of composting, but rather of rotting. This is what often happens when you try to compost kitchen wastes in plastic containers.

Third Golden Rule

You must find the right moisture balance. Good compost is not too moist, nor too dry. When building up the compost pile, it is relatively simple to check this. When removing your foot from the compost pile, if you boot makes a suction noise or the compost sticks to your sole, the pile is too moist. It will tend to settle and become compact. It will rot for sure. In contrast, if you detect the presence of too many sowbugs or pillbugs, the pile is too dry.

In too moist compost, you must add straw, plants with stems or even twigs. This will also bring better aeration to the pile. Let's not forget that composting is mainly an aerobic process.

In too dry compost, you must make sure that there is enough animal-sourced matter (usually very moist). Then again, an excess of twigs (from hedge or tree trimming) will make your compost too dry. Generally, the addition of BLT effluent quickly rectifies the situation. This same phenomenon happens when you put too much wood shavings as litter in your dry toilet. Therefore, when building up your compost pile, those few times that it may be too dry can be offset by watering the compost, without however flooding it.

Fourth Golden Rule

Composting needs time. Composting is an inherent part of an annual cycle: that of gardening. It serves no purpose to hurry up the process in this context. To want to make compost in three months with compost activators is questionable [7]. As will be seen further on, proper composting of correctly balanced plant- and animal-sourced biomass that contains dejecta needs 2 years to cure before actually being ready for use (in temperate regions [8]).

[7]
The situation is altogether different when it comes to centralized collective composting, where the duration of the process determines the land area required to support it. In this case, the use of compost activators can be considered, and even glass-enclosed or «greenhouse» composting.
[8]
Comparatively, composting of dejecta takes about 3 months in tropical climates, 2 years in temperate regions like Belgium, and will no doubt take longer in much colder regions. Composting's duration must be adapted to the specific climate conditions in which it is being done. It's obvious that there are ways of going faster, like adding compost activators or composting under glass (greenhouse composting). But why insist on this? The stationary nature of the composting process means that compost made 3 years ago, for example, will still remain available year after year. We should be cautious not to precipitate natural processes, at the risk of provoking some unforeseen natural backlash.

Composting Dejecta

Composting dejecta is a two-stage process, unlike traditional domestic composting practices worldwide. Although composting is not yet fully adopted as a gardening technique, most who practice composting usually limit its application to garden and kitchen wastes: no animal or human manure is added. And the composting is usually a one-stage process.

Stage One: The Compost Bin

To start, set up a compost bin[9] in a corner of the yard not too far from the house, sized on the basis of about 1 m² per person in the household. The sides can be fenced in with a latticed frame and chicken wire or other wire mesh. Provide enough manoeuvring space for wheelbarrow access. Before starting to fill your compost bin, make sure to first till and rake the soil. It is better that the compost area be located in a shady area, under small trees for example.

[9]
The term «bin» herein applies to those compost enclosures that are open to the ground. Worldwide, the term «composting bin» is a carryall term for all types of compost enclosures, including closed containers or floored enclosures that prevent direct contact of the compost with the soil. These are inadequate compost enclosures. Always choose those that are open to the ground.

In the compost bin, you put in everything that must be composted, doing this all year long. This will include garden and kitchen wastes, and dry toilet effluent. If you expect to start off your compost with more BLT effluent than plant waste, place a 20 to 30 cm layer of straw bedding at the bottom of the compost bin.

Every time after emptying the BLT bucket content into the bin, make sure to cover the effluent with additional litter, e.g. straw, grass clippings, culled weeds, dead leaves [10], etc. Then, immediately rinse the bucket and put it back in service, in the BLT.

[10]
At home, we prepare our litter with dead leaves and trimmings from our hedge and fruit trees, after having first shred them with a plant shredder. After grinding or shredding, the plant waste must be left to dry (especially if it was green initially). This recipe better controls odours than do wood shavings for example. The litter can be stored in a greenhouse, a barn or a garden shed.

After about one year, the compost bin should be full. Thereafter, preferably in fall or at the start of winter, it is time to start up your compost heap, which is a second compost set-up, nearby but separate from the primary compost bin.

Stage Two: The Compost Heap

You now empty the compost bin to build up a compost heap. After having tilled and raked the area you wish to use for your compost heap, you transfer the entire compost bin contents to the intended heap, stacking it layer by layer to create a pile with a sloped roof configuration. The pile will measure about 1.3 m wide at its base, and 1 to 1.2 m high. Its length will be determined by the quantity of matter that needs further composting. You can also build up the heap within a wire-screened enclosure.

At the bottom of the heap, it is useful to lay out a bedding of twigs or straw. This will promote better aeration. Than, continue by putting fresher (less decomposed) compost matter at the bottom. Fill in progressively with the older mor e compact matter. As an option, you can spread some basalt mineral fines (also known as basalt dust) and calcareous algae meal (such as lithothamnion, a kind of marine algae used for soil improvement in Europe), between each layer. You can also put in some wood ash (not too much), but no lime. If the compost is used for asparagus crops, a bit of powdered premixed plaster can also be added.

Finally, cover the heap with a 20 cm thickness of straw. Then, lay a few branches on the straw to prevent its dispersal by birds, as it will not take long for these to seek out the exposed worms. (In the mean time, the emptied compost bin is again tilled and raked at its bottom, and a new composting cycle begins.)

The compost heap is then left to itself for one year. Its volume will shrink by more than 50% and its straw topping will have been partly absorbed. Before again emptying the compost bin, the compost within the compost heap will be transferred near the vegetable garden. Ripe compost is friable, brown, and has the sweet smell of earth. It is ready for use in the garden, flowerbeds, etc. It is best to use it before winter. Part of the remaining stored compost should be covered with straw for the winter, to be used for interior seed start-up and spring planting.

For Those Who Can't or Won't Compost

Older persons often find it difficult to empty the compost bin in order to build a separate heap. Handling a pitchfork is not to everyone's liking either.

In such cases, one option is to reserve a few square meters of your garden (or«backyard» in North America) for spreading of BLT effluent directly on top of the soil, to a thickness of 15 to 20 cm. To prevent exhibiting toilet paper and the like, you cover the toilet effluent with some plant matter : dead leaves, grass clippings, culled weeds or straw. Some people use wet cardboard packaging, which is efficient, but not very sightly. Yet, this is the most ecological way of eliminating this type of waste. While the soil is «digesting» the matter, printing inks are fully eradicated in a matter of months. It is however wise to initially remove packaging staples (metal) and tape (plastic).

The effluent that has been spread in this way is a remarkable stimulant for the soil's wildlife. Countless earthworms appear and transform our dejecta into precious humus. This can indeed be the simplest and most efficient way of remediating polluted industrial brownlands, and regenerating degraded and sterile soils (artificial embankments for example). After a few years of such a treatment, a sterile sandy soil becomes a light and humus-rich soil that holds together. A compact clay soil becomes crumbly and fertile. A rocky or gravelly soil is transformed into fertile land.

Thus, thanks to the biolitter toilet, anyone can create a flourishing garden anywhere, without composting.

This method is well adapted to such activities as Boy Scout summer camps or jamborees, for example. Toilet effluent would be spread in a distant corner of the woods or field, and covered with plant matter such as fallen leaves. Obviously, measures would need to be taken to prevent people from accidentally walking on or passing through the designated patch of land.

Preconceived Notions on Agricultural Reuse of Human Dejecta

In my contacts with the public, concerns have been expressed about the health risks of using composted human dejecta in the vegetable garden.

We commonly use stable manure (sheep, cow, etc.) in our gardens and fields, yet they contain the same pathogenic bacteria as human excreta. Let's not also forget the use of sewage or septic tank sludge in agriculture. The larger public often ignores, or does not realize that vegetables we buy on the market can come from farmland that has been fertilized with septic tank sludge, and even sewage sludge. This sludge contains much more reputed pathogenic bacteria than composted dejecta. In addition, sludge contains intestinal parasite eggs not found in compost [12]. Yet, spreading septic tank sludge on land is accepted in most countries and even encouraged by legislation in some. Farmers are often registered as septic tank sewage collectors.

[12]
After 18 months of aerobic composting, the eggs of intestinal parasites disappear. This is far from true in sanitation plants where black water is only held a few hours. The parasites and their eggs are then discharged back in nature as treated water (eventually getting to bathing sites such as sea-side beaches) or as treated sludge spread on farmland. Bathing on the seacoast is a greater risk (if risk there is) than taking a bath in filtered rainwater. Pre-set notions and preconceived ideas about bacterial contamination are pertinacious!

When composting is inadequately done, concerns about health risks are partly justified [13]. Composting time is of the essence: that is why conventional composting must be extended to 2 years. During compost's 2nd stage of curing, intestinal parasite eggs altogether disappear. During this stage, compost becomes reticulated by a mycelium network. These microscopic fungi represent a genuine antibiotic that eliminates pathogenic bacteria, but they only show up near the end of the second year.

[13]
Intestinal parasites represent a greater danger when sewage sludge is spread on agricultural land. For the same reasons, water discharged from treatment plants is a permanent threat for bathing places, including beaches on the seaside, near river outlets or near water treatment plant outlets.

Let us also speak of the Chinese Emperor Syndrome. It is said that Chinese emperors, unlike their subjects, did not consume food harvested from fields that had been fertilized with night soil (human manure). It is also said that grazing animals do not eat grass that grows on their own dejecta. Yet, we mustn't lose sight of the fact that:

- The Chinese did not compost their excreta, but used them directly on the soil;

- Prairie grass fertilized with composted manure is well accepted by animals.

There is no doubt that non-composted dejecta introduce a large number of pathogenic germs in our food production milieu. (This includes liquid pig manure, septic tank sludge and sewage sludge that are commonly spread on farmland, without this fact apparently disturbing people concerned about sanitation). In contrast, the use of composted dry toilet effluent does not present this inconvenient. Its pathogenic bacterial content is much weaker than that of septic tank sludge or industrial pig manure. (People's fear of manipulating human manure lacks objective reasoning; denial and refusal will always find some sort of justification. Ultimately, reluctance to use human manure is profoundly psychological and cultural in nature, as is fear of bacterial contamination.)

Composted human manure increases land's water holding capacity, and in so doing, reduces irrigation needs. Each kilogram of compost that is substituted for chemical fertilizers reduces agricultural pollution, AND it also reduces pesticide needs.

Let us insist on the fact that the composting process starts in the BLT bucket. Therefore, what we put in the BLT is of great importance.

Medicine in Composted Dejecta

What happens to compost's quality when we ingest medicine, particularly antibiotics? Concerns are primarily expressed about potential medicinal residues in vegetables fertilized with such composted manure. There are also concerns about antibiotics' effects on beneficial bacterial fauna during composting. (Remember: antibiotic = antibacterial).

First, it is rare that all members of a family take antibiotics all year round. Antibiotic absorption can only be temporary. Let's not forget that compost is also composed of kitchen and garden wastes. Therefore, an antibiotic's concentration will be quite weak in the overall compost.

In 1998, we proceeded to an interesting composting experiment at one of Belgium's experimental farms (Ferme Modèle de l'Institut Agricole de Ath (CARAH)). Liquid pig manure from a local pig farm that made use of great quantities of antibiotics was used to impregnate a pile of shredded wood waste reclaimed from a nearby housing demolition. After a few days of impregnation, a compost pile was built up. Start-up samples were analyzed by gas-phase chromatography. The analyses highlighted great quantities of organic pollutants: antibiotics, colourings and paint residues, wood preservatives and fungicides, etc.

Contrary to predictions, the antibiotics did not kill any composting bacteria: after a few days, the temperature at the centre of the pile was greater than 60°C. After 3 months of composting, new analyses were performed on the compost. Organic pollutants had almost altogether disappeared: the chromatogram showed only «background noise». The concentrations of the various pollutants were practically undetectable by this method (which is sensitive enough). Albeit, we noticed that heavy metals that were present at the start of composting remained in the compost.

Our project – which's financing was refused by the state, but also by the European Community – intended to develop a composting technique that would make heavy metals biologically unavailable, therefore, non-absorbable by plants. This was of particularly interest for brownfield (contaminated industrial land) soil reclamation and dredging of gravely polluted river/canal sludge. It was intended as an elegant approach to cleaning these sites, relatively easy to implement and not too expensive. As they considered composting to be insufficiently innovative, the regional and European decision-makers preferred financing other projects, such as removal of polluted soil, its trucked transport to a centre for lixiviation with concentrated sulphuric acid, neutralization of the acid, washing the lixiviated earth and putting it back in place, all this at an extremely high cost. As to what they intended to do with the pollutant-containing sulphuric acid, we were answered that «some other company would take charge of it» (i.e. to dump it in a controlled toxic substances landfill site)!

To conclude, the two-year period prescribed above for composting of dejecta is quite sufficient to eliminate antibiotics and any other medicinal residues from compost before its use in the vegetable garden.

Composting in Winter

Although we don't have specific experience on winter composting [14], information available on the web tends to confirm that you can compost year-round in most temperate zones, even those having harsh winters.

In the northern USA where winters are generally milder than in Canada, Joseph Jenkins keeps adding his kitchen waste and toilet effluent to the compost bin throughout winter, taking care to add litter to the heap, frozen or not, in expectancy of the spring thaw. Nevertheless, the composting process is more active between spring and first autumn frosts.

According to Canadian sources in Quebec, the composting process continues on into early winter, but slows down and even stops during extreme cold spells, especially in smaller-sized domestic composting bins (measuring less than 1 m3). For such a volume, bacterial activity diminishes substantially as outside temperatures drop below –10°C. Remember that the compost pile stays generally warmer than ambient temperatures due to bacterial activity at its core.

Winters in continental Europe, like in Hungary, can also be pretty harsh. Experiences in Hungary have shown that when the compost heap's volume exceeds 2 m³, the core of the heap does not freeze, even when outside temperatures hit -20°C for weeks on end. Moreover, compost heaps in large-scale or industrial set-ups maintain a constant temperature due to their large size, whatever the outside temperatures.

For small-sized composting bins, winter is mostly a season for storage of organic matter than for actual composting. In spring, compost that has frozen will begin composting with renewed vigour upon thawing. It will quickly decompose as the cells will have been broken down by ice crystals, giving the compost heap a jump-start on decomposition.

Winter composting involves additional tasks inherent to snowy regions, such as snow removal to maintain access to the compost heap, and snow removal from the heap itself. Since the compost heap must be covered up with litter after each use (for example with hay or straw), the litter should be stored in a shelter close by to keep it dry and manageable.

Based on Joseph Jenkins' experience, a compost curing time of 2 years appears to be satisfactory in his region (Pennsylvania). In regions with much colder winter climates, composting time will most likely need to extend beyond 2 years for compost to properly and safely cure.

[14]
This text has been written by André Leguerrier for Canadian readers and other residents from cold climate regions.

Preparing Litter for the BLT

To start, there's the question of quantity. One recurrent criticism of the BLT is to say that «if ever the BLT becomes a universal standard, there will never be enough plant matter to supply the required toilet litter». In reality, the dead leaves of one single large tree are sufficient to cover the needs of one person for a whole year. The leaf production from a few hectares of forest or tree plantations is sufficient for an average city.

Plus, need I repeat: any cellulose matter (of plant origin) is adequate for litter preparation. One of the best litters available comes from one's backyard and garden: dead leaves, dried grass clippings, hedge and tree trimmings, culled weeds, etc. To make these more easily useable, it is better to use a plant shredder.

About plant shredders, without denying their usefulness, I personally feel uncomfortable about them because they consume expensive electric power or liquid fuels. I have noticed that dead leaves, culled weeds or other torn out plants easily break up into smaller pieces after having been left to dry for a few months (sheltered from rain). As such, they supply an excellent litter, without electricity (coal or nuclear produced) or fossil fuel consumption.

You can also get your litter material at woodwork shops. Wood shavings and sawdust are often given out, although an inconvenient with this litter is its dust content. To avoid dust, many people use shredded paper as litter, processed with a commercially-sold paper shredders. This makes an excellent litter material, although it could better be recycled into paper. You can also purchase plant litter that is sold for animals. Others use corrugated cardboard which, when moisturized, easily shreds into small pieces. In spite of ever-present printing inks, cardboard makes an excellent litter. The inks entirely decompose during composting, without leaving any toxic residue. However, you must first remove any plastic (stickers, wrapping) and metal (staples). Shredded paper towels of all sorts (kitchen towels, napkins, nasal tissue) also go into litter.

What Does Not Go into the BLT

Earth

Our dejecta's carbon/nitrogen ratio is too weak for humus formation. Thus, when mixed with earth, which contains practically no carbon, a good part of our dejecta's organic nitrogen is quickly lost by spontaneous mineralization (transformed into nitrates, nitrites and ammonium). Un-composted manure's fertilizing capacity comes specifically from this mineralization, but its impact is similar to that of chemical fertilizers [15].

[15]
That is exactly the same situation as when spreading dried faeces that are produced by most dry toilets on the market. It is most disturbing to read that what is none other than dried faeces is presented as «compost» in the publicity for these toilets.

Peat moss

Even though the carbon/nitrogen ratio can easily be adjusted with peat, let's not forget that it is a non-renewable product. In addition, it has been observed that due to peat's acidity, odours are less well controlled than dried plant matter [16].

[16]
Those who understand Rudolph Steiner's work will quickly understand the fundamental reasons peat is inadequate to adjust our dejecta's C/N ratio. Instead of rejecting his work outright, scientists would be surprised by the findings they would find there for further useful research.

Ashes or lime

Being highly alkaline, these materials inhibit the bacterial activity that needs to take place to transform organic matter into humus. At best, you can add a bit of ash in the compost heap, but not in the BLT. Old-timers say, «Lime makes the father rich, but makes the son poor». Lime and potash (an ash component) accelerate the spontaneous decomposition of soil's humus, by quickly freeing organic nitrogen and phosphorus. As a result, agricultural yields will surge at the same time that the soil's humic reserves decline. The addition of lime to compost, as recommended by some agricultural specialists, actually interrupts the process of soil regeneration.

To continue, go to BLT's on the market

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