Elettrocompostaggio agricultural biomass

Elettrocompostaggio

Following work experience and technical cooperations in the early nineties with the academic world of the then Soviet Union, the engineering of COIND became aware of electrochemical processes used for the stabilization of animal wastes. The vertevano studies on intensive production technology humus, made from organic raw materials, such as discharges of pig farms, poultry and urban sewage waste.
The process adopted consisted in obtaining electrochemical simple molecular structures derived from the lysis of long-chain organic compounds (natural polymers, such as lignin, albumin, polysaccharides, etc.) and subsequent recombination in ranked compounds of iron, calcium and other metals in the form ionic. It should be borne in mind that in the USSR there was no specific rules about the spreading of slurry on the ground that impose purification or stabilization of the same; the COIND has developed the use of electrochemical technology adapted to the local climatic conditions, which inhibited from spreading on the ground for a period of seven / eight months a year, when the ground was frozen.
The process of electro-composting takes place in two phases:

  1. Saturation of the organic components of the sludge with active hydroxides, produced by the passage of electric current and low voltage continues through the mass of the slurry. Water molecules, subjected to electrolysis, is split into OH- groups strongly active against the CC bonds and C = C of biopolymers molecules present in the wastewater (polysaccharides, egg whites, etc.). It was also detected the formation of oxides, carbossidi and amino groups. It has thus the saturation of the slurry by means of strongly polarized organic molecules. The reaction takes place in a first tank equipped with permanent titanium electrodes.
  2. Formation of organo-metallic compounds of colloidal matrix. In the second reaction tank you will have sacrificial electrodes consist of a trivalent metal (generally iron or aluminum). The current applied to the plates causes the oxidation of iron anodes and the consequent dissolution of Fe2 + and Fe3 + ions, trivalent ions tend to return rapidly in bivalent form due to a reducing environment in which they are generated. The polar organic molecules, formed in the first tank, then enter into contact with the ions Fe2 + and form complexes colloidal very dithered. The result of the processes described above, for a period of 15 – 20 minutes, is the stabilization of sludge and transformation of organic molecules in humic compounds in typical weight ratios of a compost, which does not happen in a conventional sewage treatment plant. The sterilization of the influential bacterial load is carried out either by direct electrocution of higher organisms, both for breaking of the cell membranes due to the passage of current. The output dall’elettrocompostatore material must pass through a thickener which separates the large amount of material sedimenting present. The polluted water of result can be treated with biologically performance to be evaluated case by case. The elettrocompostaggio also need spaces much smaller than the natural composting and a fraction of the overall investment.

The plant
In 2006 COIND in partnership with RIVOIRA, has developed a pilot plant fully renovated with regard to the reactor, and some electromechanical components, then tested the droppings of a poultry farm. The purpose was to investigate the elettrocompostaggio process of various animal faeces and in general on all those waste or organic sludge, which currently have no other target, if the storage in landfills or the spreading of the field with the stringent restrictions imposed by legislation for vulnerable zones.
In order to be able to conduct an experiment that encompassed both electrocoagulation, both the waters of result, the pilot plant was equipped with a biological purification section which allows to evaluate the processes of reduction of the polluting load so as to fall within the parameters discharge of the effluent into surface waters. The collaboration with RIVOIRA has made it possible to employ oxygen in the various sections of the plant so as to evaluate the reaction kinetics accelerated by the use of an energetic oxidant instead of air.

schema-elettrocompostaggio

Considerations
In the light of the latest experiments carried out, COIND believes that the pilot plant constitutes an extremely useful tool for testing the behavior of different effluents or sludges from biological digestion / purification processes.
The results obtained open several routes for the management of waste resulting from the production processes agronomic and renewable energy such as:

  • the solid part: as fertilizer in the soil or covering the ground in landfills;
  • for the liquid fraction: ferti-irrigation, redeployment within the company or to be allocated to the classic biological treatment.

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