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Plant for producing organic and/or organic-mineral fertilisers for organic and traditional agriculture

Description of a plant for producing organic and/or organic-mineral fertilizers for organic and traditional agriculture, obtained from various materials.
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PLANT FOR PRODUCING ORGANIC AND/OR ORGANIC-MINERAL FERTILISERS FOR ORGANIC AND TRADITIONAL AGRICULTURE

Description of a plant for producing organic and/or organic-mineral fertilizers for organic and traditional agriculture, obtained from various materials, including most humidified manures, collected directly from farms with which we have signed collection agreements.

Composting reproduces in a controlled manner a process that occurs spontaneously in nature.

The process consists of two stages: the thermophilic or active stage and the maturation or humidification stage.

During the thermophilic or active stage, a specific bacterial flora attacks and breaks down the organic molecules that are broken down most easily (sugars, organic acids, amino acids, etc); this consumes a significant amount of oxygen on the one hand and on the other hand, releases carbon dioxide and energy in the form of heat. In this manner, the temperature of the composting mass reaches values of 50-65 °C that persist for long periods; this ensures devitalization of pathogenic agents and of the seeds of any infesting grasses. The duration of this step is correlated to the types of residue treated and to the production technology used.

Subsequently, during the maturation or humidification stage, the decomposition process slows down as more complex and resistant organic molecules are broken down (cellulose, lignin, etc.) assisted by processes that form more complex and stable composts. The maturation period varies according to the type of product desired.

At the end of the humidification cycles, the organic matrices are processed as they are or they are used as a support for the addition of mineral or chemical (iron sulphate, ventilated sulphur, nitrogen products, potassium sulphates, etc.) parts of other organic materials such as feathers, horn-hoof meal, soft natural phosphate, sulphur, etc or materials classified as ‘non-hazardous waste’ by current legislation.

The production method ensures that stabilized products are obtained that have consistent contents to provide the farmer with a host of products that range from completely organic to organic-mineral to organic-chemical products.

The products can be supplied to customers as granular pellets that are all packaged in bags of varying capacity.

Description of the production cycle

Receipt and mixing

The collecting vehicles entering the plant are weighed. Once weighed, the organic refuse is discharged into separate containers. A ‘slow’ blade shredder known as a “mixer-wagon” partially shreds and mixes the waste coming from the containers, thus finishing the pretreatment stage. The resulting material is transferred by a mechanical loader to the accelerated composting section.

Fermentation or accelerated composting

The fermentation department has a markedly rectangular shape. It extends over a surface of about 3,150 and is dedicated exclusively to the fermentation stage.

The mixed organic material is piled in a heap that is about 4 meters high, where it remains for about 60 to 90 days. Composting is an aerobic transformation, i.e. a transformation that occurs in the presence of air. The air, in fact, supplies the decomposing organisms with the oxygen they require to transform the organic materials into humus. In order to ensure that the heap is always traversed by air as well as being ventilated, the heap has to be turned over daily by mechanical loaders equipped with pressurized cabinets and air conditioning. In this manner, the heaps advance along the axis of the shed to the opposite end of the delivery zone.

To summarise, the composting process ensures:

  • the aerobic conditions are maintained that are required for the biological breaking down of organic substances;
  • the necessary minimum temperature is reached;
  • the temperature is maintained below the level at which the decomposing organisms survive.

Eliminating excess heat and part of the humidity of the material during the composting stage.

In order to prevent the spreading of dust and odors, the department is thoroughly insulated by a portcullis that closes automatically and maintains the internal environment in a vacuum with a suction system and ambient air exchange of about 30,000 m3/h that is expelled into the atmosphere through a flue after treatment in a wet scrubber.

Screening

The product coming from the fermentation departments is transferred to the screening line. This department has a surface area of about 8550 m3 with automatic airtight portcullises as well. In order to prevent the spreading of dust and odors, a suction plant maintains the internal environment in a vacuum and a wet scrubber with 70,000 m3/h capacity purifies emissions before release.

Within the same department, the stabilized manure coming from the previously described fermentation department undergoes a purification process consisting of mechanical separation through screening large fragments that have not been completely transformed (e.g. pieces of wood, paper, etc).

The rejected material is completely recycled by being conveyed to the head of the fermentation departments to be again subjected to the biological decomposition process, as they trigger the humidification of the new material introduced.

Maturation

In the maturation zone, organisms that operate at ambient temperature continue the transformation of the organic material until the soil is obtained. The process has two stages: primary and secondary. After accelerated composting, the material is transferred to the primary maturation building (duration of the process: about 30 days). During this stage, the transformation of the organic compounds is completed. The material is turned over continuously to make it soft and aired. Secondary maturing lasts another 30 days, takes place in an area next to the first area, and does not require periodical turning of the heaps.

The maturation department consists of a shed of about 2500, which is also dedicated exclusively to this stage of the productive process. The operating methods are the same as those that take place in department 1. In order to prevent dust and odors spreading, the department has been completely insulated by an automatically closed portcullis and its vacuum is maintained by a suction and ambient-air exchange system with a capacity of about 30,000 m3/h that expels emissions into the air after they have passed through a wet scrubber.

Calibration

Before the product coming from the maturation department is transferred to the cubing line, it is screened to obtain the ideal calibrated size for mixing and for cubing. The screened materials, which now have an insignificant odor impact, are then transferred to the central shed, where the processing lines are located.

Mineral dosing and mixing

When the material is of a suitable size that will constitute the actual composted fertilizer, it is:

mixed and sent directly to pelletization to produce organic fertilizer with no added minerals,

or

added to mineral or organic raw materials that are dosed in a percentage to produce special types of fertilizer known as organic-mineral fertilizers that correspond to formulas containing specific values, especially NPK values (nitrogen, phosphorus and potassium values), that are suited to the crops to be fertilized.

Palletisation

The product prepared for pelletization is loaded by a mechanical loader to the pellet extruding line. The pelletized material is then dried and sifted from the powder to be packaged. The packs used for marketing can be 25 or 50 kg polyethylene bags or big – bags (500 or 1000 kg jute sacks). Delivery in bulk is also an option.