Material to be added to the soil mainly to preserve or improve its physical or chemical characteristics or biological activity (Legislative Decree no. 75 of April 29, 2010).

Anaerobic digestion

Complex biological process through which the organic fraction of solid waste is transformed, in the absence of oxygen, into simple elements, also obtaining a gaseous by-product, biogas.



Set of chemical processes operated by microorganisms and catalysed by enzymes that transform complex organic compounds into simple and stable, non-polluting molecules.


Exhausted air treatment system that involves contact with porous organic material in order to control odorous emissions and remove volatile organic substances: the air to be treated passes through the layer of filter material and the microorganisms present degrade the polluting compounds.


Combustible gaseous mixture, consisting mainly of methane (50-60%) and carbon dioxide (35-40%), with the presence of pollutants such as hydrogen sulphide and ammonia. It is produced in digesters and landfills from the organic fraction of waste following anaerobic decomposition by microorganisms.


Combustible gas that contains at least 95% methane. It is the product of the process of purification and removal of CO2 from biogas (upgrading). By reaching the quality of natural gas, it thus becomes suitable for injection into the network itself and can also be used as a fuel for transport.



Calorific value

It represents the quantity of internal energy of a certain substance that is transformed into heat by complete oxidation of the oxidizable components. It is therefore a measure of the energy content of a given fuel. For waste this depends on the product composition and the water content.


Simultaneous production of electricity and heat. The heat can be used for the remote heating of buildings and / or for industrial processes.


Chemical reaction of oxygen with organic substances to produce oxidized compounds, accompanied by the emission of light and rapid generation of heat.


Material produced by the biological degradation of the organic fraction present in the waste. Compost is a stable material, in which biological reactions no longer occur and has such properties that it can be used in agriculture as a soil improver.


Treatment process of the organic fraction of the waste which provides for its biological degradation in the presence of oxygen. The resulting product is compost.



Semi-stabilized material generated by the anaerobic digestion process as a residue. It can be used as a fertilizer in agriculture due to its significant content of mineral nutrients and organic matter.


Closed reactor where the anaerobic digestion process takes place.


Elementary composition

Chemical composition of the waste expressed as the content of the individual constituent elements (e.g. carbon, hydrogen, nitrogen, oxygen, etc.).

End of waste

End of Waste means “cessation of the qualification of waste”: a waste ceases to be such when, following recovery operations, it complies with the four general conditions provided for by Directive 2008/98 / EC:

  1. the substance or object is commonly used for specific purposes;
  2. there is a market or demand for that substance or object;
  3. the substance or object meets the technical requirements for specific purposes and complies with existing legislation and standards applicable to products;

the use of the substance or object will not lead to overall negative impacts on the environment or human health.

EWC code

All types of waste are listed in the European Waste Catalogue (EWC), where they are encoded with a specific EWC code: it is a six-digit code, in which the first pair indicates the source from which the waste derives (e.g. the production sector), the second couple the process that generated it and the last two identify the specific waste.



Chemical process that involves the partial oxidation, i.e. in lack of oxygen, of a carbon-rich material such as coal, biomass or waste, generating a gaseous fuel called synthesis gas, rich in carbon monoxide, hydrogen and other compounds.



Liquid produced by the washout of waste deposited in landfills due to precipitation and infiltrations or from their decomposition. It is a biologically active liquid, which must be treated in aerobic or anaerobic reactors, or recirculated.


Mass balance

Once a control volume of a system has been identified, considering its mass (with possible variations over time) and the different flows that cross its boundary, the mass balance is defined as the algebraic sum of these flows, conventionally taking the incoming ones positive and the outgoing ones negative. In terms of flow rates, the algebraic sum between the total incoming mass flow and the total outgoing mass flow is equal to the mass variation in the unit of time with respect to the control volume itself.


Simple molecule with functional groups such as to make it able to recursively combine with other molecules to form macromolecules.



Chemical reaction in which an element combines with oxygen, forming an oxide. The complementary reaction is that of reduction.



Thermal process of chemical decomposition of organic materials conducted in the absence of oxygen, which requires heat from the outside.
Pyrolysis gives rise to the formation of three products: one liquid, one solid and one gaseous, which can be valorised according to their composition and their energy content.


Macro-molecule formed by the combination of different monomers.

Preparation for reuse

This definition includes the control, cleaning and repair operations to which waste is subjected so as to be made suitable for re-use without the need for further treatments.


Paper that has reached the end of its life and is collected and sent for recovery at the paper mills.



Recovery operations are those that allow waste to play a useful role by replacing other materials that would otherwise have been used to perform a certain function. Recovery includes material recovery (recycling) and energy recovery.


Recycling is a form of recovery, with the specific aim of recovering material and not energy. In fact, according to the legislation, recycling consists of operations that involve the treatment of waste in order to obtain products, materials or substances, while excluding operations aimed at recovering energy and the treatment of waste to obtain materials to be used as fuels.

Reducing agent

Chemical agent that tends to yield electrons to another substance.

Refuse Derived Fuel (RDF)

Solid fuel produced from non-hazardous, urban or special waste, through treatments aimed at maximizing its energy content, reducing the content of non-combustible materials (glass, metals, aggregates, etc.) and the organic fraction, and ensuring compliance with standards regulatory. It can be used in waste-to-energy plants or in co-combustion in cement factories or thermoelectric plants.


Operations through which an asset, which has not yet become waste, is reused for the same purpose for which it was conceived.

Residual Solid Waste (RSW)

When separate collection is carried out, a part of the waste does not find its place in the different fractions collected separately; this amount of material goes under the name of Residual Solid Waste (RSW).

Ripening (composting)

In the composting process, the ripening phase is the final one, in which, once the biological degradation reactions of the organic substance have taken place, the compost stabilizes and the temperature drops down to the ambient value.


Secondary Raw Material (MPS)

Materials derived from the recovery and recycling of waste.

Selection residues

Unwanted fractions within the homogeneous waste flows, which are generated as waste from the material selection process.

Slag (or Bottom ash)

Solid residue from the waste-to-energy process consisting of the waste fraction that does not participate in combustion. It is approximately equal to 15-20% by weight of the incinerated waste and consists mainly of inert material and potentially recoverable metals.

Supply chain consortia

These are non-profit organizations whose task is to manage the collection, recycling and recovery of separately collected packaging waste. There are 6 supply chain consortia in Italy, one for each type of material used for the production of packaging: paper, plastic, glass, wood, steel, aluminium. The activities of the 6 Consortia are coordinated by CONAI – National Packaging Consortium.



“Any substance or object that the holder discards or has the intention or obligation to discard” (according to the European Directive no. 2008/98 / EC of November 19, 2008)

Waste composition

Composition of the waste expressed on the basis of the different fractions of materials contained in it, such as paper, plastic, metals, organic, etc.