METHOD FOR OBTAINING A FINE-CRUMBLED CULTURAL SUBSTRATE

Description

[0001] The invention relates to a method for obtaining a fine-crumbly culture substrate for the production of flower or plant soil, wherein the extraction takes place from an input material in the form of excavated soil from a landfill or construction pit and the input material comprises mineral and organic components.

[0002] Furthermore, the invention relates to the use of the culture substrate obtained for the production of flower or plant soil or for application on or introduction into a culture soil in horticulture and landscaping or in agriculture, thus to a process for the production of flower or plant soil or an improved culture soil, in which first the fine-crumbly culture substrate is obtained from the input material and this is then used as an additive for the production of the flower or plant soil or the improved culture soil.

[0003] Along with air and water, topsoil is a vital source of life for plants, animals, and humans, and is therefore a valuable, finite resource. However, topsoil is threatened by erosion, sealing, the introduction of pollutants and toxins, and overexploitation.

[0004] Soil materials from construction projects are currently considered waste in Germany and therefore, according to current knowledge, unsuitable for reuse in the economic cycle. As a result, excavated soil from civil engineering, road construction, sewer construction, gardening, and landscaping projects, particularly excavated earth that cannot be directly used to fill excavations elsewhere or to build embankments, e.g., for visual and / or soundproofing of a residential complex, is inevitably disposed of in landfills. As a result, landfill space is scarce in many parts of Germany. However, it has been shown that a large portion of this excavated and / or landfilled soil is suitable for other purposes, at least provided it is uncontaminated, i.e., not contaminated with toxic substances that are dangerous to humans or animals.It should be noted in this context that a landfill is specifically designed for the final disposal of excavated soil (earth excavation) and does not contain any waste, i.e. it is to be distinguished from a landfill.

[0005] For example, soil from a landfill that is rich in mineral and organic components may still be suitable for use in agriculture, particularly arable farming, and in horticulture and landscaping, including hobby gardens, and thus be economically viable again. However, this requires appropriate mechanical processing of the soil, as its composition, particularly the presence of stones, makes it unsuitable for this purpose.

[0006] International application WO 9748503 A1 discloses a screening system for separating a particle stream into two particle sizes. It uses a screen surface inclined in the shape of a staircase with holes arranged at the edges of the steps. In one embodiment (Fig. 19), two such screen surfaces are arranged one above the other, resulting in three particle streams.

[0007] Shafts for a blade separator are known from document DE20205891 U1.

[0008] The German patent DE 41 21 584 C1 describes coaxial ring sieve sections with different hole sizes, which are arranged axially next to each other on the one hand, but also coaxially within each other on the other hand, so that the input material is divided into several particle streams and certain particle streams are sieved twice.

[0009] Furthermore, German utility model DE 202 18 820 U1 discloses a method for extracting material of a specific particle size from waste material. The material is fed to a screening device and then transported therein over a vibrating screening surface directed downwards in the working direction. The screening surface comprises a first screening area with a first mesh size and, located behind it in the working direction, a second screening area with a second mesh size, the meshes of which have a smaller dimension than the meshes of the first mesh size. However, this method does not involve the use of excavated soil.

[0010] It is an object of the present invention to provide a simpler method for obtaining a fine-crumbly culture substrate from excavated soil, which has cultivation properties comparable to topsoil and is suitable for and used for the production of flower or plant soil or for application to a culture soil or incorporation into a culture soil in agriculture, in particular in arable farming, and in horticulture and landscaping.

[0011] This object is achieved by the subject matter of claim 1. Advantageous further developments are specified in the subclaims and are described below.

[0012] The core idea of ​​the invention is to obtain the culture substrate by sieving the input material or excavated soil, so that the fine-crumbly culture substrate has a particle size distribution of 0 to 2 mm. In this respect, "fine-crumbly" in the sense of the invention means that the culture substrate, sieved from the input material, consists physically of crumbs, i.e., small pieces or fragments smaller than 2 mm in size that have crumbled off due to sieving. Furthermore, a property of the culture substrate is that even the slightest force applied to small clumps (1-2 cm) of the crumb formed due to moisture causes these crumbs to disintegrate, making it very loose and easy to process.

[0013] To obtain this fine-crumbly culture substrate, according to a first aspect of the invention, it is proposed that the input material or at least a fraction of the input material is fed to a screening machine which separates the input material or the fraction into a first grain fraction and a second grain fraction forming the culture substrate, having a grain size of substantially less than or equal to 2 mm, by transporting the input material or the fraction in the screening machine over an oscillating screening surface which is directed downwards at least in sections in a working direction and which comprises at least a first screening area with a first perforation or mesh size, and a second screening area lying behind it in the working direction with a second perforation or mesh size, the holes or meshes of which have a smaller dimension in at least one direction than the holes or meshes of the first perforation.The resulting growing substrate is then used as an additive in the production of potting soil or plant soil, or for application to or incorporation into a growing soil. It thus serves as a substitute for topsoil.

[0014] Due to the mineral and organic components of the input material and its fine crumbliness, the growing substrate obtained by the inventive method has cultivable properties comparable to topsoil. However, topsoil is more compact and solid, making the resulting growing substrate easier to process. The crumbly structure of the growing substrate ensures air exchange and is able to retain water. It therefore requires less water. The organic components promote fertility, loosen heavy soils, and counteract soil acidification. The growing substrate is therefore ideally suited for application in arable farming, horticulture, and landscaping, for application to or incorporation into cultivated soils, as well as for the production of potting soil and plant soil.

[0015] Topsoil, also known as topsoil or top soil and among farmers also as topsoil, is the uppermost and most fertile layer of the soil, which, in contrast to the subsoil, contains a high proportion of nutrients (especially nitrogen) and organic components as well as a large number of soil organisms.

[0016] "Mineral components" essentially include fine sand, silt, and clay. "Organic components" also include topsoil, humus, peat, digested sludge, and / or plant remains (roots). Humus refers to the totality of the decomposed organic matter in the soil, which is heavily permeated by microorganisms such as soil bacteria and fungi, and is continuously broken down, transformed, and decomposed by them.

[0017] To produce potting soil or plant soil, the growing medium can be mixed with compost, topsoil, and / or peat, as well as at least one additive such as lime, fertilizer, and / or sand. Compost soil is defined as soil mixed with compost, the end product of composting organic waste. It serves as a natural fertilizer and soil improvement. The high humus content in compost soil gives it a high nutrient content, which makes the soil particularly fertile. The growing medium eliminates the need for additives such as wood fibers and / or bark.

[0018] The potting soil or plant soil produced with the resulting growing medium can then be spread on beds or fields, or more precisely, on the existing growing soil, or incorporated or mixed into it. Alternatively, the resulting growing medium can also be spread directly on the growing soil or incorporated into it.

[0019] Cultivated soil refers to any soil type that is fundamentally suitable for agricultural use for the cultivation or breeding of plants. For example, cultivated soil includes sandy soil, humus-rich sandy soil, loamy sandy soil, sandy loam soil, non-sandy loam soil, clay soil, and peat soil. The term "agricultural use" does not limit cultivated soil in terms of its size, for example, to large-scale arable land. Rather, cultivated soil also applies to beds in hobby gardening. Cultivated soil may be topsoil or contain topsoil, but it may also be free of topsoil and only become fertile, or at least have its fertility improved, through the cultivation substrate.

[0020] With the use according to the invention, the growing substrate is therefore ideally suited for horticulture and landscaping, including hobby gardening, as well as for agricultural use, particularly for incorporation into the soil (topsoil of the field) during field cultivation. This can improve soil quality and increase soil yield.

[0021] When the screening process is referred to as separation, this does not mean the absolute separation of fractions of specific grain sizes from one another. Rather, the second grain size is screened out from the material fed into the screening machine. The first grain fraction therefore has a lower proportion of grains smaller than 2 mm than the input material and, at best, is free of these grains. The screening success is greater the smaller the proportion of grains from the second grain fraction that remains in the first grain fraction. The first grain fraction therefore contains a grain size essentially larger than 2 mm, but also contains portions of the grain fraction smaller than 2 mm.

[0022] The working direction is the direction in which the material primarily moves within the screening machine during operation. It also corresponds to the direction of the inclination of the screening surface.

[0023] Furthermore, a plant for obtaining the fine-crumbly culture substrate from the input material in the form of excavated soil is described below, comprising a bunker for receiving input material, a screening machine for separating the input material or at least a fraction of the input material into a first grain fraction and a second grain fraction forming the culture substrate with a grain size of substantially less than or equal to 2 mm, and a transport device for conveying the input material or the fraction from the bunker to the screening machine, wherein the screening machine has an oscillating screening surface directed downwards at least in sections in a working direction, which comprises at least a first screening area with a first perforation or mesh size, and a second screening area located behind it in the working direction with a second perforation or mesh size, the holes or meshes of which have a smaller dimension in at least one direction than the holes or meshes of the first perforation.

[0024] The method and corresponding system according to the invention make previously unused excavated soil from construction pits and / or material from landfills available for use in horticulture, landscaping, and agriculture. As already explained, the growing substrate obtained from the excavated soil as input material in this way has cultivation properties comparable to topsoil and can therefore serve as a substitute for topsoil, be used in the production of potting soil and plant soil, or be applied or incorporated directly into cultivated soils.

[0025] The process according to the invention enables landfill operators and civil engineering companies to develop their excavated soil as a new source of valuable materials and to make it technically usable for new purposes. This expands the capacity of landfills and / or allows them to operate for longer periods.

[0026] In principle, all stony, sandy and / or loamy soils with mineral components on the one hand, in particular fine sand, silt and clay, and organic components on the other hand, in particular humus, peat, topsoil, digested sludge and / or plant residues (roots) are suitable as input material.

[0027] The input material can be extracted from pits, especially construction pits, or from landfills. Of course, the input material should be free from contamination by substances harmful to humans or animals, especially toxins and heavy metals.

[0028] Depending on the composition of the input material, a specific processing may be useful, whereby the yield of the second grain fraction of 0-2 mm may vary in percentage terms.

[0029] Before using an input material for the process according to the invention, the input material can be subjected to a qualitative optical test, either by measurement and / or visual inspection by a trained person. The color and / or brightness of the input material is used to assess whether the input material is suitable for producing the culture substrate. Black or dark brown input material indicates a high proportion of organic components and thus its suitability for producing the culture substrate, whereas light brown, ochre, or yellowish input material indicates the absence of organic components and a high content of mineral components, particularly sand. Reddish-brown or reddish input material also indicates the absence of organic components.It can therefore be provided that the input material is only used for the process according to the invention if its colour is dark brown to black or if its colour brightness is below a certain limit value.

[0030] Alternatively and / or additionally, input material may be subjected to a qualitative olfactory test, either by measurement and / or as part of an odor test conducted by a trained person, to determine whether the input material is suitable for producing the culture substrate. For example, soil with a high proportion of organic components has a characteristic odor due to their decomposition by microorganisms and fungi, such as that of forest or peat soil. For example, it is known that the bacterium Streptomycetes releases the two odorants 2-methylisoborneol and geosmin when decomposing rotting material such as fallen leaves, needles, or woody debris.It can therefore be provided that the input material is only used for the process according to the invention if at least one specific fragrance is present in the input material, such as 2-methyl-iso-borneol and / or geosmin, or if this at least one fragrance exceeds a specific limit value.

[0031] In order to increase the yield of the second grain fraction, i.e. the growing substrate, one can try to reduce the throughput of the screening machine, i.e. the amount of input material per unit of time that is fed to the screening machine. Studies have shown that if the amount of input material on the screening surface is too large, less of the second grain fraction is screened out because the input material vibrates less on the screening surface and the holes become clogged more or are less easily cleared. It is therefore recommended that, during operation of the system, the amount of total growing substrate obtained is assessed in relation to the amount of input material or to the amount of the first grain fraction. It is sensible to reduce the amount of input material fed to the screening machine per unit of time if the amount of total growing substrate obtained in relation to the amount of input material or to the amount of the first grain fraction is below a certain limit.Depending on the type and quality of the input material, a proportion of up to 75% of the fine-crumbly culture substrate can be obtained from it, although a proportion of 33% is still economically viable.

[0032] Thus, the limit value can be, for example, between 33% and 66%, preferably 50%.

[0033] In order to reduce the amount of input material to be fed to the screening machine per unit of time, the conveying speed of the conveyor device feeding the screening machine can be changed or adjusted at least in one section. This allows the conveying rate of input material per unit of time to be adjusted. The system can include a corresponding system control system for adjusting the conveying speed of the conveyor device.

[0034] The assessment or determination of the quantity of culture substrate, input material or first grain fraction can be carried out based on weight or volume. Furthermore, the assessment or determination can be carried out by a person operating the system or automatically. If the first and second grain fractions are each thrown onto a repository cone, for example using a conveyor belt, the ratio of the first and second grain fractions can be immediately and qualitatively determined by comparing the height or size of the repositories. The person can recognize when the repository cone of the second grain fraction, i.e. the culture substrate, is significantly smaller than the repository cone of the first grain fraction and, in this case, reduce the conveyor speed, i.e. reduce the quantity of input material that is fed to the screening machine.

[0035] A size comparison of the two repose cones can also be carried out automatically. For example, their diameters and / or heights can be recorded with a camera and evaluated, in particular compared, using image processing software. If necessary, a vertical measuring rod with height marks around which the respective repose cone is formed, or a measuring scale on the base of the respective repose cone, e.g. with concentric measuring rings as floor markings, can provide a quantitative statement about the current height or the current diameter of the respective repose cone. A camera in conjunction with image analysis software can record these heights and / or diameters and provide them to an evaluation unit, which determines the heights and / or diameters of the repose cones and compares them.Alternatively, a sensor system, for example one or more light barriers, can be used to signal to an evaluation unit that a certain height or diameter of the corresponding repose cone has been reached at a certain point in time, whereby in this case the time difference between the corresponding points in time indicates the size or quantity ratio of the two repose cones.

[0036] The evaluation unit can then calculate the size or quantity ratio of the repose cones and send a control signal to the system control system, which then reduces the conveying speed of the conveyor if the above-mentioned limit is exceeded—in other words, if the repose cone of the second grain fraction is significantly smaller than the repose cone of the first grain fraction. This evaluation can be performed at a specific time after the system is switched on, repeatedly at specific times, or even continuously as part of a control system.

[0037] As an alternative to a visual assessment of the cones of material, i.e. the volume of the first and second grain fractions, the mass or weight of the total culture substrate obtained can be used and compared with the weight of the input material or the total first grain fraction produced. This can be done using scales. For example, the weight of the bunker can be continuously measured. Likewise, the first and / or second grain fractions can be collected in appropriate containers, the weight of which is then continuously determined using appropriate scales. While the weight of these containers can then be directly compared with one another, for the bunker the difference in weight must first be determined in order to quantify the amount of input material already removed from the bunker. This difference in weight can then be related to the weight of the second grain fraction, i.e. the culture substrate.

[0038] Preferably, the transport device conveying the input material or its fraction from the bunker to the screening machine has a scale that weighs the material on the transport device at any given time. By integrating the measured values ​​over a period of time, the weight of the total input material conveyed can then be determined. A similar scale can be part of another transport device that transports the second grain fraction or the culture substrate away from the screening machine. By integrating the measured values ​​over the period of time, the weight of the total culture substrate conveyed or obtained can then also be determined.

[0039] The evaluation unit can calculate the weight ratios and send a control signal to the system control system, which then reduces the conveying speed of the conveyor if the above-mentioned limit is exceeded, in other words, if the mass of the second grain fraction is significantly smaller than the mass of the first grain fraction or the input material. This evaluation can be performed at a specific time after the system is switched on, repeatedly at specific times, or even continuously as part of a control system.

[0040] In particular, the amount of input material to be fed to the screening process per unit of time can also be increased if the amount of culture substrate obtained relative to the amount of input material exceeds the limit value or another limit value that is lower than the first-mentioned limit value. This is particularly useful within the framework of the aforementioned regulation in order to increase the throughput (amount of input material per unit of time) of the plant and thus its economic efficiency.

[0041] A high yield of growing substrate is achieved when the system's throughput is set to a value between 50 kg and 200 kg per minute per square meter of screening area, preferably around 100 kg per minute per square meter of screening area. For example, if the screening machine's screening area is 20 m², the throughput is 2 tons per minute or 120 t per hour.

[0042] It is advisable to screen the input material in several stages. In particular, it can be provided that, before the input material is fed to the screening machine, an oversize grain is separated in one of these upstream screening stages. Oversize grain is defined as the fraction of the input material whose grain size exceeds an upper limit, for example, larger than 45 mm. This prevents oversize grain from entering the screening machine and damaging its screening elements. Due to the vibration of the screening surface, the oversize grain can absorb such great kinetic energy and be accelerated that it penetrates the screening elements upon impact or tears open the screening holes.

[0043] The oversize material can be separated by a coarse separator, which forms the first screening stage. The screening machine then forms the downstream second screening stage. The input material is then separated by the first screening stage into an oversize fraction and a fraction with oversize removed. The latter is then separated into the first and second size fractions at the screening machine. However, if the input material has already been removed from oversize, it can be fed directly to the screening machine.

[0044] In a preferred embodiment, the screening surface is formed by screening elements in the form of rectangular, elongated individual screens that abut one another along their longitudinal sides, with the working direction of the screening machine being transverse to the longitudinal extent of the individual screens, i.e., in the direction of their width. Elongated individual screens have the advantage that the screening surface can easily be curved convexly or concavely. For example, the length of the individual screens can be at least five times, preferably ten times, their width. With a width of approximately 30 cm, the individual screens can preferably have a length of 3 m. The screening machine can have a single or double width of the individual screens.

[0045] It is advantageous if the individual screens are formed by elastic screen mats, for example made of elastomeric polyurethane. These have the advantage of absorbing the kinetic energy of the larger grains of the input material sent to the screening machine, or of the oversize fraction thereof, upon impact, thereby dampening the overall grain movement. The kinetic energy is transferred to the material on the screen surface by the vibration of the screen surface. The impact causes smaller grains of the second grain fraction adhering to the larger grains of the input material to be thrown off and can thus fall through the screen holes. This dampening prevents the kinetic energy of the grains from becoming too great and from breaking through the individual screens.

[0046] Furthermore, the elasticity of the sieve mats has the advantage that the sieve holes are not rigid in shape and size. Rather, their deformability allows a grain slightly larger than a sieve hole to be pushed through it, especially if another grain of the same size collides with it. This minimizes the risk of clogging the sieve holes due to grains that could become stuck in them. Furthermore, clogging of the sieve openings by very fine grains (less than 0.5 mm), which increasingly accumulate at the edge of the sieve holes and, in the worst case, close the entire sieve hole, is prevented due to the possible deformation of the sieve hole edge due to the movement of the larger grains. The elastic sieve mats thus achieve a self-cleaning effect.

[0047] A particularly high yield of growing substrate is achieved when the individual sieves have elongated sieve holes oriented parallel to the working direction. The sieve holes are preferably elongated, meaning they have no internal corners. This has the advantage that they are less likely to become clogged with fines and are easier to clean, especially within the framework of the aforementioned self-cleaning effect.

[0048] Furthermore, it is ideal for a good screening result if the vibration of the screen surface is achieved through a vertical up-and-down movement. Generally speaking, this causes the input material to bounce on the screen surface. More precisely, this is achieved by the coarser grains in the input material repeatedly hitting the screen surface, which causes 1. the second grain fraction is shaken off the coarser grains, which increases the yield of growing substrate, 2. the coarser grains push grains that clog the sieve holes through them and remove deposits of very fine grains from the sieve holes, and 3. the grains of the second grain fraction collide with the coarser grains and are thrown by them in the direction of the sieve holes, where they then fall through accordingly.

[0049] It is also advantageous if the vertical up-and-down movement occurs along an elliptical path. This simultaneously imparts a component of movement to the input material on the screen surface in the working direction, thus transporting it forward along the screen surface.

[0050] Depending on the desired screening area, the screening machine can have more or fewer individual screens, in particular between 15 and 25 individual screens. The number of individual screens depends on the size of the screening machine. If, purely as an example, 21 individual screens are used, for example with a length of 3m and a width of approximately 30cm, the resulting area is 18.9m². Of course, it is also possible to use only half the number of individual screens with twice the width to achieve the same screening area. However, using a comparatively narrow width, e.g. 30cm, is advantageous in order to be able to equip the screening area as varied as possible with individual screens of different perforations.

[0051] According to the invention, the screening surface comprises at least a first screening area with a first perforation or mesh size and a second screening area located behind it in the working direction with a second perforation or mesh size. Within a screening area, there is thus a uniform perforation or screening holes of uniform size. In one embodiment, three or more such screening areas can also be arranged one behind the other.

[0052] To form the aforementioned screening areas, the individual screens can each have a uniform perforation and each belong to a group, of which at least a first group has a first perforation and a second group has a second perforation, wherein the second perforation is smaller than the first perforation in at least one direction of extension of the screen holes. The individual screens of the first group can then form the first screening area, and the individual screens of the second group can form the second screening area. The screens of a group are always the same.

[0053] In a preferred embodiment, the individual screens belong to one of three groups, each having a first, second, and third perforation, wherein the second perforation is smaller than the first perforation in at least one direction of extension of the screen holes, and the third perforation is smaller than the second perforation in at least one direction of extension of the screen holes. The individual screens of the first group can then form the first screen area, the individual screens of the second group can form the second screen area, and the individual screens of the third group can form a third screen area, which follows the second screen area in the working direction.

[0054] Empirical studies on a screening machine with three screening areas have shown that a particularly high screening success is achieved when the first perforation has sieve holes with a hole dimension of 5x25mm, the second perforation has sieve holes with a hole dimension of 3x20mm, and the third perforation has sieve holes with a hole dimension of 3x10mm.

[0055] However, perforations with other hole dimensions are also possible. If the screening machine has only two screening areas, these can be formed by individual screens of the first and second perforation.

[0056] In the aforementioned case, for example, the screening surface could consist of four individual sieves with the first perforation, fifteen individual sieves with the second perforation, and two individual sieves with the third perforation. However, the number of individual sieves can also be different.

[0057] It was further recognized that the selection of the perforation or perforation sequence for the individual sieve sections should be dependent on the moisture content of the input material in order to achieve a high yield of culture substrate. Thus, the above-mentioned sequence of perforations or individual sieves is particularly suitable for screening the second grain fraction when the input material is relatively dry. However, a different perforation sequence can be used for moister input material. In particular, larger perforations should be used with increasing moisture content of the input material, and smaller perforations should be used for drier input material.

[0058] Soils with a relative humidity (adherent moisture content) or water content below 8% can be considered comparatively dry input material, whereas comparatively moist input material has a moisture content higher than 8%. For example, the relative humidity of comparatively dry soils, which form the input material in summer, is between 6% and 7%, particularly around 6.6%. In contrast, the relative humidity of soils that form the input material in winter is predominantly between 10% and 15%, for example, 13.8% water content. Of course, the input material must not be wet, which is why it should be stored under cover.

[0059] It can therefore be provided that the moisture content of the input material or a parameter dependent on it, such as electrical conductivity, is determined, and the perforations or individual sieves are selected and used depending on the moisture content or the parameter dependent on it. At higher moisture levels, a substantially larger perforation or individual sieves with a substantially larger perforation are used, and at lower moisture levels, a substantially smaller perforation or individual sieves with a substantially smaller perforation are used. In this context, the terms "smaller perforation" and "larger perforation" refer to the cross-sectional area of ​​the sieve holes.The insight gained from using a smaller screen hole cross-sectional area for drier input material than for wetter input material is based on the fact that the second grain fraction reduces the effective cross-sectional area of ​​the perforation in wetter input material. This phenomenon is counteracted by screen holes with a larger cross-sectional area.

[0060] If the input material is moister, a different sequence of holes can be used, especially holes with substantially larger hole dimensions or cross-sectional areas. For example, in this case The first perforation has sieve holes measuring 7x25mm, the second perforation has sieve holes measuring 5x25mm, and the third perforation has sieve holes measuring 2x20mm. However, perforations with other dimensions are also possible.

[0061] For the aforementioned case of moister input material, the screening surface could, for example, consist of ten individual sieves with the first perforation, five individual sieves with the second perforation, and six individual sieves with the third perforation. However, the number of individual sieves can also vary here.

[0062] In one embodiment, the system can be provided with a first screening machine and a second screening machine to which the input material can be selectively fed, with the first screening machine being responsible for drier input material and the second screening machine for moister input material. In this way, the moisture content or a parameter dependent thereon can be determined and the first or second screening machine can be fed depending on the determined moisture content or parameter. The first and second screening machines can each have a screening surface with at least one first and second perforation, with the screening holes of the first and second perforations in the screening surface of the first screening machine having a substantially larger cross-sectional area than the screening holes of the first and second perforations in the screening surface of the second screening machine.By way of example only, the first screening machine can have the first-mentioned perforation sequence (5x25, 3x20, 3x10), and the second screening machine can have the last-mentioned perforation sequence (7x25, 5x25, 2x20).

[0063] The input material can be fed to the respective screening machine via a shared conveyor system, which can be pivoted, for example, between the first and second screening machines and is aligned depending on the input material or its moisture content. Alternatively, the input material can be fed to the respective screening machine via a conveyor system assigned to each screening machine, which supplies either only the first or only the second screening machine and is optionally fed from the bunker depending on the input material or its moisture content.

[0064] As previously explained, it is possible that the input material has too high a moisture content to be processed. This can be the case, for example, with soils that form the input material in winter. Adequate screening success is then not guaranteed. In this case, lime, particularly unhydrated lime (calcium oxide CaO), can be added to the input material to bind the moisture. It can therefore be provided that the moisture content of the input material is determined and lime, particularly fine white lime, is added to it depending on the moisture content. In one embodiment, this can be done by adding a defined weight proportion of lime, e.g. 1%, above a certain moisture limit, which can be between 8% and 12%, for example. For an input material with a relative humidity of 13.8%, the relative humidity can be reduced to 11.24% by adding 1% lime.2% (by weight) lime would further reduce moisture. Alternatively, the amount of lime added can vary gradually or linearly depending on the moisture content, for example, between 1% lime at 8% moisture content and 5% at 20% moisture content.

[0065] In the simplest case, the addition of lime can be achieved by emptying a so-called "big bag" filled with lime over a heap of input material, and then mixing the lime in using a screening bucket, a bucket separator, or an excavator's screening bucket. It is also possible to equip the bunker with an agitator, such as a rotating bucket, which mixes the input material with the lime.

[0066] Preferably, the addition of lime should not exceed 5% (by weight) of the mass of input material. It is therefore preferable to initially work with a small addition of lime, for example, 1%. If the growth substrate gain is too low, the screening process can be repeated by adding another 1% of lime, for example, to the first grain fraction, mixing it thoroughly, and feeding it to the screening machine.

[0067] When the input material mixed with lime is mixed, it is aerated at the same time. The input material should then be allowed to rest, preferably for at least 4 hours. Aeration and rest are particularly important so that the lime (CaO) can bind the moisture (H2O) in the input material and react to form calcium hydroxide (Ca(OH)2) and with the carbon dioxide (CO2) in the air to form calcium carbonate (CaCO3). This inhibits the pozzolanic reaction, which would cause the culture substrate to harden over time and thus limit its area of ​​application. Hardening is disadvantageous, for example, if the culture substrate is used to embed electrical cables because in this case it is less able to absorb the cable's waste heat. In other words, it thermally insulates the cable, which could lead to local overheating of the cable.

[0068] For example, lime can be added in the form of a binder, but the proportion of fine white lime should be at least 70%. Dorosol ®< can be used as a binder.

[0069] In one embodiment, the moisture content of the second grain fraction or the culture substrate can be determined, and the amount of input material fed to the screening machine per unit of time can be adjusted depending on the moisture content. In particular, the amount of input material to be fed per unit of time can be reduced for processing moister input material and increased for processing drier input material.

[0070] To determine the moisture content, one design variant can measure the electrical conductivity or electrical resistance of the input material, which can then be used to determine the moisture content. For example, electrodes can be installed in the bunker that measure the electrical conductivity or electrical resistance of the input material at the beginning of the process and / or continuously and report the readings to the system control system. This can then increase or decrease the amount of input material fed to the screening machine depending on the electrical conductivity or electrical resistance, for example, by adjusting the conveyor speed accordingly.

[0071] It is also advantageous if the culture substrate obtained or the screened second grain fraction is thrown onto a receptacle and observed to see whether a ring of coarser grains, i.e. grains with a grain size larger than 2 mm, increasingly forms around the base of the receptacle. This impairs the homogeneity of the culture substrate obtained and is the result of an excessive amount of input material on the first screening area of ​​the screening machine, whereby many coarser grains fall through or are pushed through the holes or meshes of the first screening area instead of the desired fine grains of the second grain fraction. This can be prevented by reducing the amount of input material fed to the screening machine per unit time if a ring of coarser grains increasingly forms at the base of the receptacle.

[0072] Furthermore, according to a third aspect of the invention, the use of the culture substrate obtained by the process according to the invention for producing flower or plant soil or for application on or introduction into a culture soil in horticulture and landscaping or in agriculture is proposed.

[0073] Further features, advantages, and effects of the invention are explained in more detail below with reference to exemplary embodiments and the accompanying figures. In the figures, identical or functionally equivalent elements retain the same reference numerals from figure to figure.

[0074] It should be noted that, in the context of this description, the terms "have," "comprise," or "include" in no way exclude the presence of other features. Furthermore, the use of the indefinite article for an object does not preclude its plural.

[0075] They show: Figure 1: Schematic diagram of a screening system for obtaining the fine-crumbly culture substrate Figure 2: Schematic diagram of a screening machine Figure 3: Table with information on screening sequences Figure 4: Diagram showing the addition of lime as a function of moisture Figure 5: Diagram showing the belt speed as a function of moisture

[0076] Figure 1 shows a screening plant 1 for obtaining a fine-crumbly culture substrate 3 from an input material 2 in the form of excavated soil. The plant 1 essentially comprises a bunker 4 for receiving input material 2, a first screening stage 8 in the form of a coarse separator 8, and a second screening stage 9 in the form of a screening machine 9, which is located behind the coarse separator 8 in the transport direction of the input material 2.

[0077] The coarse separator 8 serves to separate oversize grain 13, particularly with a grain size larger than 45 mm, before the input material 2 is fed to the screening machine 9. The coarse separator 8 thus removes an oversized grain fraction from the input material 2, which could lead to damage to the screening elements within the screening machine 9. The oversize grain 13 is piled up on a cone, e.g., via a transport device not shown here, and the remainder of the input material 2, which has been cleaned of oversize grain 13 and is subsequently referred to as fraction 14, is fed to the screening machine. The oversize grain 13 can be used for other purposes.

[0078] The screening machine 9 serves to separate the aforementioned fraction 14 into a first grain fraction 12 and a second grain fraction 3. The latter is the culture substrate 3 to be obtained, which has a grain size of essentially 0 to 2 mm and can therefore also be described as fine-crumbly or fine-grained. The first grain fraction 12, on the other hand, ideally has a grain size between 2 and 45 mm. In practice, however, it is not possible to screen 100% of the first grain fraction 12 from the fraction 14 of the input material 2, so that the first grain fraction 12 always contains a more or less large proportion of the second grain fraction 3. The smaller this proportion, the higher the yield of the screening system or the screening success. The first grain fraction 12 and the second grain fraction 3 are each piled up on a cone.

[0079] The conveyance of the input material 2 from the bunker 4 to the coarse separator 8 takes place continuously via a first transport device 5.1, 5.2, which in the embodiment according to Figure 1 consists of a first section 5.1 and a second section 5.2. The transport equipment of Annex 1 can, in principle, be designed in any way. In the design variant according to Figure 1 They are implemented as a moving conveyor belt. Alternatively, they can also be formed by a rotating conveyor screw. Furthermore, a combination of conveyor belt and conveyor screw is also possible.

[0080] The conveying speed of the first section 5.1 of the first transport device is adjustable, particularly in order to adjust the quantity of input material 2 that is processed per unit time or transported to the screening machine 9. For this purpose, a motor M is assigned to the first section 5.1, which is controlled by a system controller 15 in order to adjust its rotational speed, thus the conveying speed of the first transport device 5.1, 5.2. The second section 5.2 of the first transport device, in contrast, is operated at a fixed speed. It is possible for all or only some of the transport devices of the screening system 1 to be adjustable in speed.

[0081] A second transport device 6, or second conveyor belt, continuously conveys the residual fraction 14 of the input material 2, which is freed from oversize grain 13 and which is discharged by the coarse separator 8, to the screening machine 9. And a third transport device 7, or a third conveyor belt, continuously conveys the second grain fraction 3, which is screened from the residual fraction 14 and which is discharged by the screening machine 9, to a material cone.

[0082] The first section 5.1 of the first transport device and the third transport device 7 are each assigned a scale 10, 11 to determine the weight of the respective bulk material being conveyed. This can be done during operation, with the weight values ​​available at any time and integrated or summed to determine the total amount of material conveyed after a certain period of time. The measured values ​​from the carts 10, 11 are fed to the system control system 15, which can evaluate them, in particular, compare them.

[0083] How Figure 2As shown in more detail, the screening machine 9 has a screening surface 19 which is directed at least partially downwards in a working direction 18 and which oscillates during operation. In this embodiment, the screening surface 19 consists of a first screening area 19a with a first perforation, a second screening area 19b with a second perforation located behind it in the working direction 18, and a third screening area 19c with a third perforation, again located behind it in the working direction 18. Each of the perforations is formed by an arrangement of a plurality of screen holes with specific dimensions. The perforation of the second screening area 19b consists of screen holes 17b which have a smaller dimension in at least one direction than the screen holes 17a of the first perforation. Furthermore, the perforation of the third screening area 19c consists of screen holes 17c which have a smaller dimension in at least one direction than the screen holes 17b of the second perforation.In other words, the perforation gradually becomes smaller from sieve area to sieve area.

[0084] The sieve holes 17a, 17b, 17c are in the form of elongated holes whose longitudinal axis is oriented parallel to the working direction 18. The dimensions of these elongated holes refer to the length of their longitudinal axis and their width. Figure 2 The sieve holes are shown only as examples in terms of their shape, size, and arrangement and only in the left part of the sieve surface 19. Corresponding sieve holes 17a, 17b, 17c are of course also located in the right part of the sieve surface 19, thus on the entire sieve surface 19. The arrangement of the sieve holes 17a, 17b, 17c is symmetrical in rows.

[0085] The screening surface 19 is slightly concave overall. It is mounted on a swinging support and consists of, for example, 21 individual, elongated, narrow screening elements, hereinafter referred to as individual screens 16a, 16b, 16c. The individual screens 16a, 16b, 16c are approximately 3m long and approximately 25-30cm wide. Their long sides are positioned directly adjacent to one another, so that their transverse direction, i.e., the direction of their width, corresponds to the working direction 18. The individual screens 16a, 16b, 16c are elastic screening mats made of elastomeric polyurethane.

[0086] The perforation of the individual screens 16a, 16b, 16c forms the perforation of the corresponding screen area 19a, 19b, 19c. The individual screens 16a, 16b, 16c thus belong to one of three groups, each having a first, second, and third perforation, the second perforation being smaller than the first perforation in at least one direction of extension of the screen holes 17b, and the third perforation being smaller than the second perforation in at least one direction of extension of the screen holes 17c. The individual screens 16a of the first group form the first screen area 19a, the individual screens 16b of the second group form the second screen area 19b, and the individual screens 19c of the third group form the third screen area 19c, which follows the second screen area 19b in the working direction 18, which in turn lies behind the first screen area 19a.In other words, the first sieve area 19a consists of a number of individual sieves 16a with the first perforation, the second sieve area 19b consists of a number of individual sieves 16b with the second perforation and the third sieve area 19c consists of a number of individual sieves 16c with the third perforation.

[0087] In the version according to Figure 2 Not all individual sieves 16a, 16b, and 16c are shown. Purely as an example, ten individual sieves 16a with the first perforation, five individual sieves 16b with the second perforation, and six individual sieves 16c with the third perforation form the sieve surface 19. The first perforation has sieve holes 17a with a hole dimension of 5x25mm, the second perforation has sieve holes 17b with a hole dimension of 3x20mm, and the third perforation has sieve holes 17c with a hole dimension of 3x10mm. The perforation and number of individual sieves 16a, 16b, and 16c thus define a specific sieve sequence.

[0088] Another screening sequence of screening machine 9 is, for example: four individual sieves 16a with the first perforation, whose sieve holes 17a have a hole dimension of 7x25mm; fifteen individual sieves 16b with the second perforation, whose sieve holes 17b have a hole dimension of 5x25mm; two individual sieves 16c with the third perforation, whose sieve holes 17c have a hole dimension of 2x20mm.

[0089] The perforations are therefore always larger than the nominal grain size of 0-2 mm. This is because deposits form at the edge of the perforation, resulting in a smaller effective perforation. Due to the fact that material with a larger grain size, i.e., 2-45 mm, also lies on the screen surface 19, these deposits are removed, so that the screen holes 16a, 16b, 16b do not become clogged but remain open.

[0090] The two screening sequences mentioned are shown in the table according to Figure 3specified. Investigations have shown that the first screening sequence mentioned therein is suitable for moister input material 2 and the other screening sequence for comparatively dry input material, in order to obtain a comparatively high yield of culture substrate 3 from the input material 2. The conductivity of the input material 2 can be easily measured and allows a statement to be made about the moisture content and salt concentration of the material, since water dissolves the ions present in the soil and enables their transport under the influence of an electric field.

[0091] As from Figure 2As can also be seen, the 0-2 mm grains of the second grain fraction 3 forming the culture substrate 3 in the fraction 14 of the input material 2 fall through the sieve holes 17a, 17b, 17c and are carried away from the screening machine 9 by a third transport device 7 in the form of a conveyor belt and thrown onto a reclaimed material cone. The larger grains with grain sizes between 2 and 45 mm that do not fit through the sieve holes 17a, 17b, 17c, as well as the 0 to 2 mm grains that have not been screened out, are transported in the working direction 18 and fall off the end of the screening surface 19. They form the first grain fraction 12 and are also carried away from the screening machine 9 by a fourth transport device 7a in the form of a conveyor belt and thrown onto a reclaimed material cone. The first grain fraction 12 can also be used separately.It is advisable to store the first grain fraction 12 and the second grain fraction 3 in a covered place to protect them from rain and moisture.

[0092] If the screening result is not satisfactory, i.e. the percentage of the obtained second grain fraction 3 (0-2 mm) in relation to the input material 2 or the first grain fraction 12 is too low, for example less than 30%, the screening process can be repeated by returning the first grain fraction 12 to the hopper 4 and feeding it again to the screening machine 9. The throughput of the screening machine 9, or the amount of input material 2 fed to the screening machine 9 per unit time, can also be reduced by reducing the speed V of the belt of the first section of the first transport device 5.1. Figure 1As illustrated, the said ratio (grain ratio) can be fed to the system control 15, which then makes the corresponding speed adjustment.

[0093] The screening machine 9 can be, for example, a flip-flow screening machine, as described in international application WO 2007 / 060155 A1. With a width of 6 m, in such a model, two of the previously described individual screens 16a, 16b, 16c can be placed together in pairs at their head ends to form the screening surface 19. This screening machine 9 consists of a single screen deck and can have a 10°-18° downwardly inclined screening surface 19 that is banana-shaped (concave). The oscillation of the screening surface 19 is preferably vertical along an elliptical path with a frequency of, for example, 800 min -1. This frequency can be excited by a shaft drive with a single imbalance. Thus, the screening surface 19 forms a cantilever with a circular amplitude and a superimposed elliptical amplitude excited by resonance.

[0094] Input material 2 is stony, sandy, or clayey excavated soil from construction pits or landfills, containing mineral components such as fine sand, silt, and clay, as well as organic components, particularly humus. It can be piled up into a cone before feeding bunker 4, from which bunker 4 is then fed.

[0095] Since the screening success, i.e., the recoverable amount of 0-2 mm particle size fraction 3 from the input material 2, depends significantly on the moisture content of the input material 2 and the air humidity, the input material 2 can be subjected to preprocessing. Such preprocessing is also advisable if the yield of culture substrate 3, i.e., the percentage of the second particle size fraction 3 (0-2 mm) relative to the amount of input material 2 or relative to the first particle size fraction 12, is too low.

[0096] This is done by adding unhydrated lime, especially fine white lime, or a mixed lime-cement binder such as DOROSOL ®< C, with the amount of lime being between 0.5% and 5% of the amount of input material and not exceeding the upper limit of 5%. This illustrates Figure 4 Lime is added depending on the moisture content. DOROSOL ®< C consists of white fine lime (EN 459), Portland cement clinker (EN 197), and fillers. The proportion of white fine lime in the binder should be approximately 70%.

[0097] The lime can be added in the form of so-called big bags, which are emptied onto the cone and mixed in using a wheel loader. However, it is also possible to equip bunker 4 with a controllable device for the metered addition of lime, as well as with a mixing device, e.g., a rotating bucket.

[0098] To evaluate the long-term behavior of Input Material 2, a pH test can be performed after the addition of lime. A pH value below 11 ensures that no unbound or reactive calcium hydroxide remains in Input Material 2. This prevents a pozzolanic reaction, and Input Material 2 remains excavable and spreadable.

[0099] As a result of the addition of lime, small amounts of calcium hydroxide are formed in input material 2. To neutralize this, it is advisable to aerate the input material thoroughly before or after the addition of lime. This causes the calcium hydroxide to react with the carbon dioxide (CO 2 ) in the air, cationizing the calcium hydroxide and thus becoming inactive. The reaction time is at least 4 hours. Hydrated lime + water + carbon dioxide > calcium carbonate + water Ca(OH) 2 + H 2 O + CO 2 > CaCO 3 + H 2 O

[0100] To achieve this aeration, the input material can be processed in the simplest case using a so-called bucket separator, which is available as special equipment for hydraulic excavators or bucket wheel loaders, or with similar special equipment, which achieves a high degree of disruption of the input material 2 during mixing. This effect can also be achieved using stationary, mobile or semi-mobile devices that are designed accordingly, such as so-called disc separators based on the disc-in-disc principle or similar mechanical devices. The interlocking of the discs and chisels breaks down the input material 2 as best as possible, which can then be mixed with the lime, which can then be homogenised in the input material. In addition, the spaces between the discs can also be used for very moist, cohesive orThis never clogs up soggy soils because they are constantly being cut free by the opposing discs. It is also possible to allow air to flow from below through bunker 4. If the mixing unit is also in operation, the input material 2 is also well aerated.

[0101] Carbonation (the conversion of hydrated lime to calcium carbonate) effectively stops the pozzolanic reaction. This always occurs when the proportion of unbound lime is so low that no more hydrate phases can be formed and the pozzolanic reaction cannot continue.

[0102] As already mentioned, one measure of the quality of the input material preparation through lime addition and aeration is the pH value, which decreases as a result of carbonation. This evidence of the success of the input material improvement can easily be obtained on a construction site or at the plant's installation site using a soil sample dissolved in water and litmus paper.

[0103] In addition, the blade separator also has a screening function, allowing the required grain sizes for further use to be achieved in conjunction with the mixing process. These grain sizes are achieved depending on the individual disc spacing of the separator shafts.

[0104] If the yield of culture substrate 3, ie the percentage of the second grain fraction 3 (0-2 mm) in relation to the amount of input material 2 or in relation to the first grain fraction 12, is too low after the pre-processing of the input material 2 or is still too low, the addition of lime can be repeated, followed by aeration and resting of the input material 2.

[0105] Furthermore, it must be ensured that no ring of coarser grains forms on the cone of the second grain fraction 3. If this is the case, the amount of input material supplied must be reduced, i.e., the speed V of the belt of the first section 5.1 of the first conveyor 5 must be reduced. Whether such a ring is present can be communicated to the plant control system 15, see Figure 1, which then adjusts the speed accordingly. In addition, a proportion of 1-2% fine grain, ie, the second grain fraction 3 (0-2 mm), should always remain in the medium grain, ie, the first grain fraction 12.

[0106] Another parameter for controlling plant 1 is the moisture content of the input material 2. This can be determined, for example, in the bunker 4 based on the electrical conductivity of the input material 2 and fed to the plant control 15. The moister the input material, the slower the plant 1 must run, which can be adjusted accordingly by the plant control 15. Otherwise, too little culture substrate 3 will be obtained. The actual input quantity per time or belt speed V belt is therefore a function of its moisture content (in %) and the proportion of fine grain in the medium grain. Schematically shown Figure 5This relationship. Curve A describes the case where too little fine grain remains in the middle grain, and curve C describes the case where too much fine grain remains in the middle grain. Curve B describes the optimal case between these two limiting cases.

[0107] The culture substrate 3 obtained according to the invention can be stored and subsequently used for the production of flower or plant soil.

[0108] It should be noted that the foregoing description is given merely by way of example for illustrative purposes and in no way limits the scope of the invention. Features of the invention stated as "may," "exemplary," "preferred," "optional," "ideal," "advantageous," "optionally," or "suitable" are to be considered purely optional and do not limit the scope of protection, which is determined exclusively by the claims.

[0109] Although the above description of the invention mentions a multitude of physical, non-physical, or method-related features in relation to one or more specific embodiments, these features can also be used in isolation from the specific embodiment, at least as long as they do not require the mandatory presence of further features. Conversely, these features mentioned in relation to one or more specific embodiments can be combined with each other as desired, as well as with other disclosed or undisclosed features of shown or not shown embodiments, at least as long as the features do not exclude each other or lead to technical incompatibilities. List of reference symbols

[0110] 1. Plant 2. Input material 3. Growing substrate, second grain fraction, fine grain 4. Bunker, hopper 5. First transport device, conveyor belt 5.1 First section of a first transport device, conveyor belt 5.2 Second section of the first transport device, conveyor belt 6 Second transport device, conveyor belt 7 Third transport device, conveyor belt 7a Fourth transport device, conveyor belt 8 First screening stage, coarse separator 9 Screening machine 10 Scales for input material 11 Scales for growing substrate 12 First grain fraction 13 Oversize grain 14 Fraction of input material 15 Plant control 16a Single screen with first perforation 16b Single screen with second perforation 16c Single screen with third perforation 17a Screen hole of the first perforation 17b Screen hole of the second perforation 17c Screen hole of the third perforation 18 Working direction 19 Screen surface 19a First screening area 19b Second screening area 19c third screening area

Claims

1. Method for the preparation of a finely crumbled growing medium (3) for the production of flower soil or potting soil, or for spreading onto or working into topsoil in horticulture and landscaping or in agriculture, in which preparation is realised using an input material (2) in the form of excavated soil from a soil deposit or excavation pit and the input material contains mineral and organic constituents, and in which the input material (2) or at least a fraction (14) of the input material (2) is supplied to a screening machine (9) that separates the input material (2) or the fraction (14) into a first grain fraction (12) and a second grain fraction (3) forming the finely crumbled growing medium (3) with a grain size that is largely smaller than 2 mm, by means of transporting the input material (2) or the fraction (14) in the screening machine (9) over a vibrating screen surface (19) that, at least in sections, is tilted downward in a working direction (18) and comprises at least a first screening section (19a) with a first perforation or mesh size and a second screening section (19b) located downstream in the working direction (18) with a second perforation or mesh size, the holes (17b) or mesh of which, in at least one direction, have a smaller size than the holes (17a) or mesh of the first perforation, and in which the prepared growing medium (3) is subsequently used as an additive for the production of flower soil or potting soil, or for spreading onto or working into topsoil.

2. Method according to claim 1, characterised by performing a visual inspection of the input material (2), in which the colour and / or brightness of the input material (2) is examined and the input material (2) is only used if its colour is dark brown to black or its colour brightness is below a certain limit value.

3. Method according to claim 1 or 2, characterised by performing olfactory testing of the input material (2), in which the odour of the input material (2) is examined and the input material (2) is only used for the method according to the present invention if at least one certain scent is present in the input material (2), for example, 2-methylisoborneol and / or geosmin, or exceeds a certain limit value.

4. Method according to one of the preceding claims, characterised by the amount of input material (2) supplied to the screening machine (9) per unit of time being reduced if the total quantity of growing medium (3) obtained in proportion to the quantity of the input material (2) or the quantity of the first grain fraction (12) lies below a limit value, for example, 50%.

5. Method according to one of the preceding claims, characterised by the amount of input material (2) supplied to the screening machine (9) per unit of time being reduced by reducing the transport speed of at least one section of a transport device (5) that supplies the screening machine (9).

6. Method according to one of the preceding claims, characterised by the separation of an oversized grain fraction (13), notably with a grain size larger than 45 mm, prior to the supply of the input material (2) to the screening machine (9).

7. Method according to one of the preceding claims, characterised by the vibration of the screen surface being achieved by means of a vertical up and down movement, notably along an elliptical path.

8. Method according to one of the preceding claims, characterised by the moisture content of the input material (2) or a parameter depending on the same being determined and the perforations of the at least first and second screening sections (19a, 19b, 19c) being selected and used depending on the moisture content or a parameter depending on the same, in which a fundamentally larger perforation is used in case of a higher moisture content and a fundamentally smaller perforation is used in case of a lower moisture content.

9. Method according to one of the preceding claims, characterised by the moisture content of the input material (2) being determined and lime, notably quicklime, being added depending on the moisture content.

10. Method according to claim 9, characterised by the addition of lime at a maximum of 5 percent by weight of the input material (2).

11. Method according to one of the preceding claims, characterised by the moisture content of the second grain fraction (3) being determined and the amount of input material (2) supplied to the screening machine (9) per unit of time being adjusted depending on the moisture content.

12. Method according to one of the preceding claims, characterised by the electrical conductivity of the input material (2) being measured and used to determine the moisture content.

13. Method according to one of the preceding claims, characterised by the second grain fraction (3) being thrown onto a material cone and the amount of input material (2) supplied to the screening machine (9) per unit of time being reduced if a ring of coarser grains increasingly forms at the base of the material cone.

14. Method according to one of the preceding claims, characterised by the growing medium (3) being mixed with compost, topsoil and / or peat as well as at least one additive, for example, lime, fertiliser, and / or sand for the production of the flower soil or potting soil.