What are the phases of the FORSU treatment – part 2

The next phase of the FORSU treatment is maturation or humification. It occurs immediately after the bio-oxidation and allows for the production of mature compost, with a high content of humic, nutritious and amending substances.

In fact, it is during this maturation phase that the synthesis of molecules capable of conferring humic characteristics to the compost occurs. 

Maturation lasts about 45 days, during which degradative reactions slow down considerably, there is a decrease in temperature, and a decrease in oxygen consumption. There is also a decrease in pH values related to synthesis phenomena. During this phase of FORSU treatment, biological processes slow down. However, microorganisms that are active on organic fractions that are not easily biodegradable come into action. The oxidative polymerization of phenolic acids and phenols, tannins, and polyphenols give rise to humic substances, and the metabolic activity of aerobic microorganisms induces the production of:

  • A gaseous fraction composed mainly of carbon dioxide, water, and volatile organic compounds
  • A solid fraction consisting of a mixture of humified substances called compost

Compost, a high-quality organic amendment, can fertilize the soil in an entirely ecological way, bringing great benefits in terms of agriculture.

This process can be considered rather innovative in many areas of our territory. In fact, until a few years ago, in the plants, the FORSU fraction underwent an exclusively aerobic process by which the waste and by-products were transformed into an organic amender. Over time, this type of plant has highlighted some critical issues, such as odor, energy consumption, and poor quality of the produced compost.

More recently, anaerobic digestion has marked the real turning point in the phases of FORSU treatment, becoming fundamental in the organic waste and by-products management chain. The best currently available technologies, therefore, invite a management of matrices through an anaerobic digestion process followed by an aerobic post-treatment of the stabilized and digested fraction (digestate) in order to obtain an organic amender suitable for use in the agricultural field.


Towards the end of the FORSU treatment process is the refinement phase, which involves anaerobic digestion to refine the compost before it is marketed as a natural amendment.

Refinement consists of sieving the material to remove coarse parts such as pieces of wood and other materials that are not easily decomposable, such as glass and plastic. At this point, a product similar to soil is obtained, with a dark brown color and almost odorless.

The compost obtained has all the characteristics required by the regulations on fertilizers and can be used for agricultural, floricultural, and nursery purposes.

The use of high-quality fertilizers is a guarantee from an ecological point of view. Therefore, compost is considered a noble product destined for commercialization.

Every treatment of the organic fraction is carried out according to national regulations that require compliance with certain conditions:

  • Health and safety regulations;
  • Environmental regulations;
  • Agronomic regulations;
  • Supply chain regulations.

this ensures that the final product is perfectly in line with the needs of a circular economy.

In regions where the treatment has been in place for some time, local farms benefit from a healthy and useful natural fertilizer for productivity.


The final phase of FORSU treatment is the storage phase. At this point, the obtained product is ready to be put on the market, with all the environmental benefits that its use entails.

It is indeed appropriate to focus on the numerous advantages that FORSU treatment brings:

  • reduction of waste;
  • improved soil fertilization;
  • less synthetic fertilizers;
  • less pesticides;
  • reduced CO2 emissions;
  • increased soil water retention.

Thanks to FORSU treatment, the disposal of waste in landfills is greatly reduced, while the use of compost improves the physicochemical characteristics of the soil. Microorganisms and plant roots benefit greatly, requiring less mechanical soil preparation operations. Thanks to the accumulation of slow-release organic nutrients in the soil, the use of synthetic fertilizers, nitrogen fertilizers, and pesticides is reduced. Compost has a phytorepressive power that inhibits the growth of weeds and scrub, favoring energy savings with less production of chemical fertilizers.

Its use also results in a reduction in CO2 from the atmosphere, with beneficial effects on the containment of emissions of harmful gases to the environment. The richness of organic matter in the soil also has other environmental benefits, such as greater water retention capacity with significant savings in waterconsumption for irrigation and greater resistance to soil erosion due to atmospheric agents.

In the last decade, FORSU treatment has undergone constant growth, making the results and compliance with the European Community Waste Directive increasingly satisfying.

By maintaining this growth trend, the ecological and economic expectations for the country and the community objectives seem increasingly tangible and concrete.