Atmospheric emissions

[GRI - 305-6], [GRI - 103-1], [GRI - 103-3], [GRI - 102-11], [GRI - 305-7], [GRI - 305-1], [GRI - 305-2], [GRI - 308-2], [GRI - 102-48], [GRI - 305-3], [GRI - 305-4], [GRI - 305-5], [GRI - 102-48],

Atmospheric emissions due to Acea plants are subject to scheduled and continuous monitoring. Plants are managed according to the UNI EN ISO 14001 and UNI EN ISO 45001/OHSAS 18001:2007 standards. The waste-to-energy plants and the Orvieto plant are also registered under the European EMAS III scheme, extended until 2024.
The most significant macro-pollutants connected with the main production processes of Acea Ambiente and Acea Produzione plants are presented in Table no. 65. The data, tracked through the Continuous Emissions Monitoring Systems (CEMSs) are in line with the values for previous years, with the exception of SOx emissions. In fact, in 2021 the greater concentration and therefore greater mass of sodium hydroxide (SO2) is attributable to the trend in the chemical constituents of fuel. The values are still very low.

Table no. 65 – Total atmospheric emissions of pollutants from the main Group plants (2019-2021)

emissions (t) 2019 2020 2021
CO2 7,02 8,22 7,68
NOx 188,19 190,67 198,11


0,33 0,9 1,6
particles (particulate matter) 0,6 0,6 0,74

NOTE: the emissions refer to the plants of Acea Ambiente – waste-to-energy and Acea Produzione.

Specifically, monitoring of the waste-to-energy plants is carried out by means of fixed and mobile stations that sample and analyse the fumes coming out of the chimneys, measuring concentrations for numerous parameters that are periodically checked by internal personnel and certified by qualified external laboratories. Again in 2021, the values of the main pollutants were also significantly below the legal limits (see Table no. 66).
At the San Vittore del Lazio plant, during the year surveys were performed on odorous emissions, as well as monitoring of diffuse and fugitive emissions and continuation of a biomonitoring campaign using bees as bioindicator insects (see section Safeguarding of land and biodiversity, in the chapter Environmental sustainability and the primary challenges). Finally, each waste-to-energy line is equipped with systems to monitor emissions from the chimney, enabling continuous tracking for concentrations of pollutants 24/7, with availability of data on the Group website ( Environmental monitoring is performed at all plants, For example, in October and November 2021, there was a campaign of monitoring for chemical and biological risk at the Aprilia plant, including areas of the new anaerobic-digestion section.

Table no. 66 – Concentrations of atmospheric emissions generated by waste-to-energy plants (2019-2021)

  San Vittore del Lazio plant (*) Terni plant (*)
pollutant u. m. scope of
2019 2020 2021 scope of
reference (**)
2019 2020 2021
HCl mg/Nm3 8 0,151 0,145 0,064 8 3,58 3,807 3,701
NOx mg/Nm3 70 29,652 29,925 29,488 180 128,65 125,989 120,644
SO2 mg/Nm3 40 0,003 0,086 0,31 25 0,43 0,969 0,928
HF mg/Nm3 1 0,023 0,02 0,016 1 0,08 0 1,04
CO mg/Nm3 40 0,803 0,604 1,083 25 1,14 1,057 0,049
total particles
mg/Nm3 3 0,007 0,01 0,049 25 0,79 0,763 0,76
PAH (polycyclic aromatic hydrocarbons) mg/Nm3 0,01 0,00001 0 0,000007 0,01 0 0 0,00002
dioxins and furans (PCDD +PCDF) ng/Nm3 0,1 0,0074 0,0094 0,0023 0,1 0,0087 0 0
heavy metals (Sb, As, Pb, Cr, Co, Cu, Mn, Ni, V) mg /Nm3 0,5 0,0387 0,0246 0,0315 0,3 0,033 0,03 0,04

(*) The analysis of PAH, dioxins and furans and heavy metals and their composites are four-monthly and discontinuous. The “<” symbol identifies the concentration values that are equal to or below the thresholds that the devices used by the laboratory are capable of measuring.
(**) Reference parameters, Legislative Decree no. 46/2014, 2000/76/EC and AIA, are separate for each waste-to-energy plant.
NOTE: For San Vittore del Lazio, over the years the recorded concentrations of the parameters HCl, SO2, dust and HF were close to the instrument’s detection limit. Therefore, in these measurement areas deviations are to be considered insignificant for absolute changes in concentrations and masses.

Monitoring carried out on installations at risk159 has shown the absence of emissions in significant quantities of substances responsible for reducing the ozone layer (for consumption see the section Resources used, in the Environmental accounts).


Acea quantifies its CO2 emissions by monitoring and evaluating the carbon footprint of the individual macro production processes according to the guidelines of the GHG protocol160 which requires reporting in the categories of direct (Scope 1) and indirect (Scope 2 and Scope 3).
Direct Scope 1 emissions mainly come from the Group’s two waste-to-energy plants and the thermoelectric power plants. Three plants are subject to the Emission Trading Scheme (ETS) (the waste-to-energy plant in Terni and the thermoelectric plants in Montemartini and Tor di Valle). The allowances assigned under the NAP (National Allocation Plan) are lower every year and in any case small, compared to the actual emissions recorded. Data for the three-year period 2019-2021 is presented Table no. 67.


Table no. 67 – CO2 emission allowances as per the National Allocation Plan (NAP) and actual emissions by plant (2019-2021)

  2019 2020 2021
plant (t) assigned by NAP actual assigned by NAP actual assigned by NAP actual
Tor di Valle (*) (**) 4.775 46.993 3.782 44.227 3.564 49.863 (***)
Montemartini 0 1.513 0 1.546 0 1.704
Terni waste-to-energy plant (**) 0 99.281 0 122.338 0 123.552 (***)

(*) As with previous years, in 2021 the applicable legislative framework allowed the Tor di Valle plant to benefit from free of charge emission allowances (3,564 t) as it serves a district-heating network.
(**) The 2020 figures for actual emissions have been updated with the certified figures.
(***) Estimated emissions, pending certification by the responsible body.

Scope 1 emissions include other components deriving from cer- tain processes of plants in the Environment Segment (composting, treatment and disposal of liquid waste), from drying at treatment plants, from petrol and diesel vehicles in the fleet, from leaks of sulphur hexafluoride (SF6) that may arise at Areti plants, from com- bustion processes for heating of premises and offices, and finally from leaks of freon gases from air-conditioning units.

The figures for CO2 issued emitted by waste-to-energy plants in the two years 2020-2021 was down on 2019 (see Table no. 68). This is due primarily to a decrease in the biodegradable fraction of waste for both the San Vittore del Lazio and Terni plants (from 51% and 47% in 2019 to approximately 42% for both plants in 2020 and 43% in 2021), partly attributable to a change in the composition of waste due to closures of businesses with a higher biodegradable fraction (restaurants and catering) due to the health emergency.

Greenhouse-gas emissions for Scope 2 deriving from electricity consumption decreased further in 2021, primarily due to the var- ious actions taken by Group Companies to increase efficiency, as illustrated in the section Energy savings161.

Scope 3 emissions include those reported deriving from the sale of gas, from the sale of electricity, from consumption of electricity by suppliers from whom we purchase goods, services and labour, from employee commuting and from work travel (see Table no. 68).

In 2021 emissions for commuting and business travel were further reduced due to restrictions triggered by the Covid-19 pandemic as well as extension of remote working for the majority of employees and consequent limitation of travel.

Scope 3 emissions associated with the purchase of goods, services and labour are calculated using monitoring data for energy con- sumption outside the Group, requested from a representative panel of suppliers using a questionnaire (see the section Energy consump- tion outside the Group). In particular, the data requested regards en- ergy (primarily consumption of fuels, electricity and vehicle fuels) and data for refrigerant gases used at supplier premises, which con- tribute to Scope 3 emissions.

To reduce emissions from the sale of electricity (values indicated in table both using location-based and market-based methodologies), Acea Energia has for several years proposed commercial offers to customers for green energy with GO (guarantee of origin) certifi- cation. Since 2021, all new retail customers in the free market will have green energy with GO certification, and this will be progres- sively extended to existing contracts. This sustainable offer also ap- plies for gas, with compensation through purchase of VER (Verified Emission Reduction) certified carbon credits. See also the section Customer care, in the Chapter Customers. Green energy sold to free market customers in 2021 totalled approximately 2,300 GWh162 (1,198 GWh in 2020), corresponding to 38% of total energy sold to free market customers (see also the Environmental Accounts). The sale of electricity with GO certification has therefore led to a saving of approximately 724,000 t of CO2 in the Scope 3 cat- egory. For sales of gas in 2021, there has been compensation of approximately 2.2 MSm3 (1% of the total sold) corresponding to approximately 4,360 t of CO2.


Scope 2 carbon dioxide emissions, deriving from leaks on electric- ity distribution networks, relative to total electricity distributed, is one of the intensity indices for greenhouse gas emissions mon- itored. This index has improved further, changing from 0.0112 t/ MWh in 2019 to 0.0097 t/MWh in 2021, in line with the continu- ous decrease in relative leaks on the network (technical leaks/issued electricity). The index for Scope 1 emissions against energy pro- duced has also improved163, due in particular to improved operating conditions at the waste-to-energy plants (see Table no. 68).

Table no. 68 – Environmental indicators: CO2 emissions, greenhouse gas intensity indices and vehicle emissions (2019-2021)

  u. m. 2019 2020 2021
CO2 emissions from Acea Produzione thermoelectric power stations (*) t 48.506 45.773 51.567
CO2 emissions from the Ecogena plants t 10.925 9.607 7.829
CO2 emissions from Acea Ambiente waste-to-energy plants (*) t 280.504 341.763 320.483
CO2 emissions from waste-management plants (**) t 1.507 1.582 1.895
CO2 emissions from water-plant processes of the IWS (***) t 6.893 6.979 7.486
CO2 emissions from heating (***) t 940 872 881
CO2 emissions from vehicle fleet t 9.550 9.705 10.533
CO2 emissions from Areti plants (from SF6) (****) t 9.400 8.695 6.975
CO2 emissions from refrigerants (HCFCs) (*****) t 0 1 0
TOTAL SCOPE 1 EMISSIONS (******) t 368.225 424.977 407.649
Location-based Scope 2 emissions (market based) (*******) t



380.010 (278.452)



of which CO2 emissions from network leaks t 118.824 100.489 95.414
CO2 emissions deriving from the purchase of goods/services and works (********) t 22.303 11.642 31.701 
CO2 emissions from commuting (*********) t 7.060 1.937 1.651
CO2 emissions from business travel t 288 46 38
CO2 emissions from volumes of gas sold t 214.043 276.284 346.567
CO2 emissions from the sale of electricity, location based (market based) t 2.168.154 (2.382.384) 2.200.491 (2.382.384) 2.447.005 (2.507.585)
intensity indices of the GHG emissions u. m. 2019 2020 2021
CO2 emissions (Scope 1 + Scope 2)/Acea Group added value (t/k€) 626,2 594,3 519,8
Scope 1 CO2 emissions/gross production (**********) (g/kWh) 357,8 423 368,8
Scope 2 CO2 emissions deriving from losses on the electrical energy distribution network/issued GWh (t/MWh) 0,0112 0,0104 0,0097

NOTE: From 2021 the table has been updated for the whole three-year period, adding Scope 1 CO2 emissions for all Ecogena plants and Scope 2 emissions for internal use by Areti, consumption of Ecogena the PV plants of Acea Produzione. In addition, 2019 and 2020 data have been adjusted to include the Bio Ecologia plant, and the plants of the companies Berg and Demap.
(*) The 2020 figures for the Tor di Valle and Terni Plants have been corrected after the ETS certification, while the 2021 figure is estimated pending certification by a third-party body.
(**) The figure includes the emissions of the ancillary services of the waste-to-energy plants, not strictly related to the production of electricity, of Acque Industriali, and non-biogenic emissions from the combustion of biogas produced on site.
(***) Data refers to uses of dryers and generators.
(****) These are the tonnes of equivalent CO2 corresponding to the emissions of insulating SF6 present in Areti’s HV equipment (1 t of SF6 equates to 23,500 t of CO2, GHG Protocol-5th Assessment Report- AR5). The 2019 figure has been adjusted.
(*****) In the last three years, the replenishment of HCFC fluids in the Group’s plants was so small that it did not lead to significant CO2 emissions.
(******) Also including the companies Umbra Acque, AdF, Publiacqua and Acque (outside the NFS scope), only considering the stake owned by Acea, for the three-year period 2019-2021 Scope 1 CO2 emissions are: 369,565 t, 426,304 t and 409,060 t.
(*******) The indirect emissions (Scope 2) include all the Companies within the NFS scope. As an emission factor per unit of electricity consumed (t CO2/MWh), for the location-based calculation the value of 0.315 was used for 2021 (0.336 for 2020 and 0.360 for 2019), as per Terna’s “International Comparisons” document (updated annually). For the calculation of Scope 2 emissions using the market-based method, the residual mix coefficients are the following for 2019, 2020 and 2021, respectively: 0.487 t/MWh, 0.466 t/MWh and 0.459 (Source: AIB document “European Residual Mixes 2020”). Also including the companies Umbra Acque, AdF, Publiacqua and Acque (outside the NFS scope), only considering the stake owned by Acea, for the three-year period 2019-2021, location-based CO2 emissions are 438,882 t, 419,377 t and 387,198 t respectively, whereas market-based emissions are 333,092 t, 332,714 t and 316,233 t. Emissions due to technical network losses in 2020 were calculated on the basis of the corresponding adjusted figure in 2021.
(********) This value, estimated, refers to suppliers of goods, services and works. The 2021 figure is broken down as follows: 26,205 tonnes of CO2 for suppliers of services and works and 5,496 tonnes of CO2 for suppliers of goods. The significant increase compared to 2020 is attributable to a change in the composition of the panel of suppliers included in the calculation (90% of suppliers of services and labour responded compared to only 41% in 2020 and 26% in 2019) as well as due to progressive phase-out of restrictions and shutdowns caused by the pandemic.
(*********) Since 2021, emissions from commuting have been calculated using a new methodology.
(**********) Scope 1 emissions included are those from power generation plants. The figure for this indicator was lower in 2021 due to reduced CO2 emissions both from waste-to-energy plants and due to an increase in energy production, primarily at the Terni plant.

NOTE: Emission factors for Scope 1 emissions are taken from the standard parameters – ISPRA data 2020, DEFRA 2021 and GHG Protocol-5th Assessment Report-AR5.

159This is primarily air conditioning equipment using refrigerant gases subject to the 1987 Montreal protocol, particularly chlorofluorocarbons.
160See for more information.
161The other reason is associated with the energy conversion factor from consumption in MWh to tonnes of CO2 emitted, which decreased in 2021 to 315 g/kWh from the 336 g/kWh in 2020.
162Of which an estimated 1,896 GWh by Acea Energia, including internal consumption of the Group Companies (420 GWh) and an estimated 404 GWh by Acea Energy Management.
163For calculation of the index, energy produced by thermoelectric power plants and waste-to-energy plants is considered.