The FORSU treatment has acquired a prominent role in waste management for some years now. Here are its various stages.

What are the phases of FORSU treatment

In this article, we would like to discuss the various stages of FORSU treatment (Organic Fraction of Urban Solid Waste), which has gained a significant role in waste management and plays a strategic role in integrated management of urban waste.

The European Commission aims to create measures to guide Europe’s transition towards a unique economic model and has proposed a circular economy package, including the goal of recycling 65% of urban waste and disposing of no more than 10% in landfills by 2030.

To achieve this, new technologies applied to FORSU treatment are a valuable resource that allows for the recovery of organic fractions from clippings, prunings, and food waste, including both household and industrial food waste.

PemoPumps’ experience in the field of organic waste treatment has led to the creation of a highly customizable, high-quality product – the anti-abrasive pump. These pumps are used to pump material resulting from grinding in accumulation tanks, decantation, feeding of anaerobic digesters, and recirculation of digestate. The pump designed by PemoPumps to support the various phases of the FORSU process is designed to meet the many needs that may arise during treatment and promptly resolve any issues.

Pemo’s technologies for FORSU treatment are a decisive factor in exploiting their recycling potential, minimizing the environmental impact and risks to humans and the environment during disposal.

They ensure:

  • Long-lasting components that are anti-wear.
  • A clog-free system thanks to the structure of bodies and impellers.
  • Flow rates of up to 1500 m3/h.
  • Head up to 160 m.c.l.
  • Now let’s take a closer look at the various phases.

Firstly, we need to distinguish treatments based on the type of product that is desired through recycling:

  • Compost
  • Biogas

The first two phases share different processes, while the subsequent phases differ based on the product desired from the treatment.

1. Materials Reception

The first phase of FORSU treatment involves the reception of materials and is useful for the production of both compost and biogas.

This first phase is particularly challenging but represents a great opportunity for our planet. It is estimated to make up the dominant part of our waste, accounting for 46% to 64% globally, with an upward trend in favor of more developed countries. It represents only 28% in high-income nations.

Inappropriate treatment of urban organic waste pollutes the environment and poses a risk to human health, as well as forcing collection companies to occupy more and more space for disposal.

Instead, their recycling allows for the obtainment of precious resources whether it is transformed into compostthrough aerobic digestion or into biogas through anaerobic digestion. The residual product is used as an amendment.

Once the vehicles carrying organic waste enter the plant area, they are inspected and weighed, and then directed into a closed building where the waste is unloaded into a storage area. This building is usually a double-locked structure, located in a depression to prevent the emission of unpleasant odors.

2.Pre-treatment and mixing

The second phase of FORSU treatment, which involves pre-treatment and mixing, is also functional for obtaining both compost and biogas, two valuable resources for a planet that urgently needs natural and non-aggressive fuel and nutrient elements for the environment.

The pre-treatment and mixing phase begins with the opening, through specific mills, of the bags containing the waste, the removal of any parts of non-treatable materials, such as plastics or metals erroneously disposed of, which require other transformation treatments or cannot be transformed at all.

This is followed by mixing with other substances intended to facilitate the transformation of the material.

This pre-treatment and mixing phase is useful for eliminating any foreign materials susceptible to sedimentation that could create blockages in the plants. Additionally, by crushing, diluting, or adding structural matrices, a substrate is prepared consisting of a dry substance compatible with the final product and the adopted technology. For example, if compost is to be produced, crushed wood and cellulose waste must be added.

Further phases follow, differentiated based on the desired result, either biogas or compost.


Bio-oxidation is a phase during which biological decomposition processes are triggered.

Bio-oxidation, which constitutes the first phase of the composting process, is characterized by the degradation of organic substances that occurs through the intervention of thermophilic aerobic microorganisms that consume oxygen and generate heat until reaching a temperature of 60-65°C, a temperature that cancels the activation of pathogens. At this point, the temperature begins to decrease and stabilize.

The second phase is characterized by a decrease in temperature (40-45°C) and the completion of the decomposition phase. The activity of this phase lasts several months with a reduction in the volume of the initial product, until obtaining compost. This loss of product is caused by water evaporation and CO2 loss. Despite the losses of ammoniacal nitrogen, the nutritional characteristics remain unchanged, resulting in an excellent soil amendment.

In contrast to compost, which is obtained from an aerobic treatment process of the organic fraction of urban solid waste, biogas is obtained from an industrial process in plants called anaerobic digesters.

Biogas is used for the production of electricity and heat.