the induced employment generated
by Hera in 2018
million euro
for innovation and digitalisation,
22 projects in smart city, circular
economy and data analytics
reused soil
in projects implemented in 2018

Atmospheric emissions of waste-to-energy plants

All Hera Group waste-to-energy plants are equipped with fume purification and process and emission control systems, designed and built so as to attain:

  • high fume purification performance in all process conditions;
  • high operational versatility;
  • high reliability of emission control systems.

In order to meet these goals, the new plants and those that have been renovated (Modena, Bologna, Ferrara, Forlì, and Rimini) are equipped with the following systems:

  • double reaction and filtration system to lower the concentrations of particulate, hydrochloric acid, hydrofluoric acid, sulphur dioxide, heavy metals, dioxins and furans and aromatic polycyclic hydrocarbons (the Modena plant has a bag filter and an electrostatic precipitator);
  • double reaction system (catalytic and non-catalytic) to reduce concentrations of nitrogen oxides;
  • double fume monitoring system for process control: the two systems measure the concentrations of the main pollutants from the oven and downstream of the first reaction and filtration phase, on the basis of which a calculation is made of the volume of reactants required to ensure purification levels that ensure compliance with for statutory emission thresholds and which are, on average, 80-90% below these;
  • continuous double monitoring system for chimney emissions: one as a reserve for the other in order to ensure the continuity of the analysis of concentrations in atmospheric emissions.

The possibility of using double purification and monitoring systems in series (in parallel as regards chimney monitoring) allows the above objectives to be successfully pursued.

This paragraph also contains data on the Faenza biomass plant (operated by Enomondo, 50% owned by Herambiente and not consolidated using the line-by-line method), equipped with a double reaction system (catalytic and non-catalytic) to reduce concentrations of nitrogen oxides.

The Padua, Pozzilli and Trieste plants have a single reaction and filtration system to lower the concentrations of particulate, hydrochloric acid, hydrofluoric acid, sulphur dioxide, heavy metals, dioxins and furans and aromatic polycyclic hydrocarbons, a single reaction system for reducing nitric oxide concentrations (double for Padua) and a single fume monitoring system.

In addition to the aforementioned activities, the following operations are carried out on an annual basis to monitor emissions and environmental impact:

  • timely controls of the chimneys, at a frequency set by the Integrated Environmental Authorization, for the parameters which cannot be continuously monitored, using certified inspectors;
  • checks on soil fallout of pollutants: through external monitoring programmes in collaboration with University and research agencies, deposition analyses are performed on soil, ground and vegetation, etc., in order to ascertain that the emissions, in addition to being within the regulatory limits, do not have any significant impact on the surrounding environment.
Atmospheric emissions generated by waste-to-energy plants
t 2016 2017 2018
Particulates 6.4 6.2 6.2
Hydrochloric acid 15.6 17.4 16.7
Nitrogen oxides 703.7 705.3 689.9
Sulphur oxides 11.7 14.9 13.1
Carbon monoxide 72.7 83.0 82.2
Hydrofluoric acid 0.7 0.6 0.6
Total Organic Carbon 9.4 10.4 9.7
Waste treated in the plants (thousands of t) 1,439 1,403 1,407
Net electricity generated (MWh) 828,906 802,675 754,043
Thermal energy produced (MWh) 239,282 265,920 245,493

The data are calculated using continuous measurement systems which are subject to the approval of the supervisory bodies at the time of authorization for operation of the plant. The procedures used by individual plant systems to collect and calculate the volume of substances released are not completely standardized. Including the Enomondo waste-to-energy plant.

The mass flow analysis shows an improvement in terms of emissions of hydrochloric acid (-4% compared to 2017), nitrogen oxides (-2% compared to 2017), sulphur oxides (-12% compared to 2017), carbon monoxide (-1% compared to 2017) and total organic carbon (-7% compared to 2017). The values for particulate and fluoridic acid remain stable. Note, furthermore, that for all continuously monitored pollutants, the concentrations at the chimney, in 2018 were once again much lower than the regulatory limits: from a maximum of 97.9% below the regulatory limits for sulphur oxides to a minimum of 63.3% for nitrogen oxides.

Concerning pollutants not continuously monitored, total emissions can be estimated on the basis of the results of the analyses performed during the year. In 2018, 120 kg of metals were emitted (154 in 2017), along with 0.56 kg of aromatic polycyclic hydrocarbons (0.55 in 2017) and 22.7 mg of dioxins (40.9 in 2017). All values are at least 95% below regulations.

The results of the emission measurements at Hera Group’s waste-to-energy plants confirm that, since they are equipped with the best technologies available and run in the most efficient manner possible, these plants emit levels of particulate, dioxins and furans, aromatic polycyclic hydrocarbons and metals that are far below the emission limits. Compared with the other parameters, subject to continuous monitoring, at plants equipped with the double reaction sulphur oxide reduction system (Bologna, Ferrara, Forlì, Modena, and Rimini) the concentrations were not only well below the regulatory limits, but also below the limits set by local authorities, which are much more stringent than national regulations.

Legislative Decree 133/2005 requires continuous monitoring of flue emissions for seven parameters. In addition, in the Ferrara, Forlì, Modena and Rimini plants, mercury is also continuously monitored.

Including the Enomondo waste-to-energy plant.

The plant renovation process has resulted in a significant improvement in the abatement percentages of pollutant emissions:

  • in January 2008, two new lines of the Ferrara waste-to-energy plant became fully operational;
  • the new Forlì plant became fully operational at the beginning of 2009;
  • in April 2010, the new line 4 of the Modena waste-to-energy plant became operational;
  • in October 2010, the new line 4 of the Rimini waste-to-energy plant became operational;

In 2018, the average concentrations of the atmospheric emissions of the waste-to-energy plants were 13.8% of the regulatory limit. This means that in 2018, emissions were 86.2% below the limit, while in 2003 the percentage stood at 59%. The levels of parameters that do not require continuous monitoring (total metals, polycyclic aromatic hydrocarbons, dioxins and furans, cadmium and thallium, mercury) are also below legal limits: from -95% to -99%.

Atmospheric emissions from waste-to-energy treatment plants compared to authorization limits – continuously monitored parameters (optimal values <100%)
% 2016 2017 2018
Bologna (FEA) waste-to-energy plant 27.1% 28.3% 26.7%
Ferrara waste-to-energy plant 10.7% 10.2% 10.8%
Forlì waste-to-energy plant 21.3% 22.2% 23.8%
Modena waste-to-energy plant 17.4% 16.7% 17.7%
Ravenna waste-to-energy plant (special waste) 11.6% 11.4% 13.4%
Faenza (Enomondo) waste-to-energy plant 16.9% 20.7% 20.3%
Average 17.5% 18.2% 18.8%

The Integrated Environmental Authorisations for the plants in Ferrara, Forlì, Modena and Faenza also require continuous mercury monitoring.

The same indicator was calculated for the six plants with authorized limits that are more stringent than the Italian regulations for 2018 (for the eight continuously-monitored parameters on average the limits set by the authorizations are 73% of the limits set by Legislative Decree 133/2005). The data are shown in the table above. The results are excellent also in this case: the concentrations are, on average, 81.2% below the most restrictive limits. Note that since the limits set by the individual authorizations depend on the specific plant, they are not comparable.

Electricity generated in relation to waste disposed of
KWh/t before revamping 2017 2018 2018 delta (before revamping)
Ferrara waste-to-energy plant 251 395 438 75%
Forlì waste-to-energy plant 295 513 574 95%
Modena waste-to-energy plant 282 588 545 93%
Rimini waste-to-energy plant 351 468 447 27%
Weighted average on volumes of waste treated 290 503 504 74%

The performance of some plants is expressed here as the ratio between electricity generated and waste disposed of, highlighting the improvement resulting from their revamping. After revamping the waste-to-energy plants, electricity generation performance improved by 74%.