Discover the Acea Group online 2019 Sustainability Report

Waste management: composting, waste-toenergy and related services


The company Acea Ambiente manages a major plant for the treatment, recovery and disposal of waste in Umbria, 3 km from the town of Orvieto, in particular the treatment of the integrated cycle of solid urban and assimilated waste produced in the area that includes all the municipalities of the province of Terni. The landfill is also authorized to receive special waste.

The main plant sections are mechanical biological treatment of solid urban waste, composting and refining of the organic fraction of the separated waste and disposal in landfills. The activities carried out enable the recovery of material (production of quality compost) and energy (use of the biogas produced).

Management is carried out in compliance with certified management systems (see Management systems in Corporate identity) with the aim of achieving maximum recovery from the materials and encouraging both the production of energy from renewable sources and the reduction of waste to be sent to landfills.

In 2019 the total waste entering the plant was 99,910 tonnes.

57% (about 56,700 tonnes) was disposed of in landfills and the remainder almost entirely sent to the anaerobic digestion and composting section of the treatment plant. For more details see Environmental Accounts.

At the Orvieto site there are two energy production plants powered respectively by the biogas produced by the anaerobic section of the treatment plant and by the biogas produced by the landfill. The electricity generated is broken down as follows:

  • about 3.3 Mm3 of biogas and 6.7 GWh of energy were produced at the treatment plant in 2019;
  • about 7.9 Mm3 of biogas and 13.1 GWh of energy were produced at the landfill.

Overall, about 18.6 GWh of electricity was fed into the grid.

The Orvieto hub is also equipped with a photovoltaic plant owned by Acea Produzione, which generated about 390 MWh in 2019, used to cover part of the plant’s consumption of electricity.


In addition to the Orvieto site, Acea Ambiente has three other composting plants in Aprilia, Monterotondo Marittimo and Sabaudia.

The Aprilia plant, still under seizure, was the subject of an expansion which, once completed, will enable the recovery of 120,000 tonnes of organic fraction per year, while the Monterotondo Marittimo plant, which has undergone expansion and revamping in recent years, has a recovery capacity of 70,000 tonnes/year for organic waste fraction, green fraction and sludge. Both sites have also implemented a new anaerobic digestion section, which will allow the recovery of electrical and thermal energy from 2020110.

At the Sabaudia plant, which has been undergoing revamping/ maintenance since 2016, operations were resumed in August 2018 and again suspended on 31.10.2019 to allow further revamping111.

The liquid waste treatment section is currently inactive.

The plant has a treatment capacity of 20,000 tonnes of compostable waste per year and 30,000 tonnes of liquid waste per year.


In 2019, Aquaser, which loads, transports, recovers and disposes of waste produced by purification plants, managed a total of 580,000 tonnes (570,000 tonnes in 2018).

With regard to intermediation, during the year Aquaser took charge of approximately 207,000 tonnes of waste, of which 184,000 tonnes are attributable to the Group’s water companies112, and in particular approximately 130,000 tonnes to Acea Ato 2 and Acea Ato 5.

The dried out and dehydrated sludge coming from these companies was sent to the following end destinations:

  • 49.3% to material recovery operations (pretreatments aimed at agricultural use – conditioning, composting);
  • 1.6% to recovery of energy (waste-to-energy).

The remaining 49.1% was disposed of. Also this year, due to regulatory constraints direct spreading was not used in agriculture.

Aquaser in particular used its own means to transport about 61,000 tonnes of non-hazardous waste.


Energy recovery from waste is an important part of the Circular Economy113 and, in addition to providing energy and economic advantages, it leads to a notable volumetric reduction and the biological stabilisation of waste, avoiding as far as possible the disposal of this waste in landfills as such.

In addition to the activities already described of waste treatment and anaerobic digestion, Acea Ambiente also manages the waste-to-energy process through two plants, one in San Vittore del Lazio and the other in Terni. The plants operate according to certified environmental management systems: UNI EN ISO 14001:2015 certification and EMAS III European registration, extended to 2021. For additional information on these aspects see also the section on Management systems in Corporate identity.


Working with Assocarta and Comieco, Acea Ambiente organized the conference “Closing the Circle: Recovering waste to improve Recycling and the Circular Economy in the Paper sector”, held in Terni for the Paper and Cardboard Recycling Month. Designed to take stock of the circular economy in the paper sector, thanks to the large number of players involved in the supply chain the initiative provided an important opportunity for reflection to offer significant insights into the recovery of waste and the improvement of recycling. For example, Acea Ambiente’s waste-to-energy plant in Terni uses pulper as its fuel, a waste of paper processing that is not recyclable and would therefore end up in a landfill. Treating almost 100,000 tonnes of waste per year, the plant is one of the top industrial entities on a national scale for the amount of pulper converted into electricity, on average 75,000-80,000 MWh/year, and the recovery chain is planned to be further extended through the use of fly ash, a volatile by-product generated by the combustion. The conference, which included presentations by the President of Acea’s Industrial Environment Segment, the Head of the Research and Development Unit and the Operations Director of Acea Ambiente, highlighted the sustainability aspects inherent in the sector.

The Plant of San Vittore del Lazio is composed of three independent lines of waste-to-energy designed to be fed with refuse- derived fuel (RDF), now called Solid Refuse Fuel (SRF), with these characteristics:

  • 52 MWt of thermal power for line 1 and 56.7 MWt of thermal power installed for each of the other two lines;
  • 13.9 MWt of electric power for line 1 and 15.1 MWt of each of the other two lines;
  • Approximately 400,000 t/year of SRF, sludge and other waste at full capacity.

2019 was a year of normal operation. The plant’s actual available electric power was about 44 MW and about 276 GWh of electric power was produced. In 2019 energy from waste has been generated from about 340,500 tonnes of waste.

In its current configuration, the San Vittore del Lazio plant is the largest in the Lazio Region and plays an important role in the management of urban waste, both for the advanced technologies used for its construction and for its considerable treatment potential114.


 m.u.2017 20182019
incinerated fuelt345,639357,174340,531
gross electric power producedGWh301.15306.731276.270
conversion efficiency (*)kWh/kg CSS0.870.860.81

(*) Relationship between gross electricity produced (GWh) and quantity of SRF converted from waste to energy (t).

The Terni plant is composed of a waste-to-energy line and has the following characteristics:

  • 52 MWt of thermal power installed;
  • 12.33 MWe of electrical power installed;
  • 120,000 t/year of pulper waste (paper mill waste resulting from the pulping of waste paper), as the maximum potential for incoming waste.


 m. u.201720182019
pulp incineratedt99,97099,97194,092
gross energy producedGWh83.1082.4180.93
conversion efficiency (*)kWh/kg pulper0.830.820.86

(*) Relationship between gross electricity produced and quantity of pulper waste converted to energy.

The plant of Terni is also equipped with a photovoltaic plant, which in 2019 has generated about 453 MWh of electricity, about 56% consumed on site and the rest injected into the grid.

For data on the emissions of both waste to energy plants see the chapter Air emissions in addition to the data in the Environmental accounts.

110 The anaerobic digestion plants were started in early 2020.
111 During 2020, it is hoped that the pending authorisation procedures will be concluded so that the tender procedure for the executive design and construction of the new composting plant can be published. The upgrading project will increase the treatment capacity to 60,000 t/year of incoming waste.
112 The data detailed here for the sake of completeness concerns sludge for which Aquaser has managed the entire supply chain, from loading to transport and final disposal, originating from the following Group Companies: Acea Ato 2, Acea Ato 5, AdF, Umbra Acque, Publiacqua, Acque, Crea Gestioni, Umbria2SII.
113 The European Union’s circular economy package has been in force since 04.07.2018.