COVID-19 Induced Changes in Residual Municipal Waste Management in Provincial Territories of the Marche Region (Italy): Flow Analysis and Environmental Assessment

Abstract

The COVID-19 pandemic posed challenges to pre-crisis waste management systems. In this study, two sequential scenarios were identified and compared to investigate the quantitative and environmental impacts of COVID-19 induced changes in the generation and management of residual municipal waste (RMW) in two provincial territories (PT_PU, PT_MC) of the Marche region (Central Italy, Adriatic Sea side). The pandemic implied, in 2020 (COVID-19 scenario), quantitative reductions in RMW compared to the preceding year, 2019 (Pre-COVID-19 scenario), which were limited to −3.9 and −1.9% in PT_PU and PT_MC, respectively. Life cycle assessment (LCA) results showed that adapted RMW management practices in 2020 (COVID-19 scenario) improved all the considered environmental indicators in PT_MC, compared to the preceding year, 2019 (Pre-COVID-19 scenario), and most of them in PT_PU, with the exception of climate change (CC), human toxicity, non-cancer (HTnc), and eutrophication, marine (Em). The hypothetical option of waste-to-energy (WtE) for the RMW, originally destined for direct landfilling in 2020 (COVID-19 scenario), would have represented a safe and environmentally sound option in terms of health protection and CC indicator.

1. Introduction

Following the initial occurrence in Wuhan (Hubei Province, China) in December 2019, the corona virus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [1], rapidly spread worldwide, and consequently, it was characterised as a pandemic by the World Health Organisation (WHO) [2,3]. The transmission behaviour of SARS-CoV-2 was expected to occur through the respiratory system (via airborne droplets) and indirect contact with surfaces contaminated by infectious droplets [4,5], particularly in colder temperatures [6]. The survival time of SARS-CoV-2 in the environment on a range of different surfaces was expected to vary from several hours up to several days [7,8]. Thus, human-to-human transmission and the persistence of this virus on several surfaces caused the rapid spread of COVID-19 [4]. Since 2020, the COVID-19 pandemic posed enormous health, social, economic, and environmental challenges to the human population [1]. Particularly, the temporally implemented efforts to limit the transmission of SARS-CoV-2, based on lockdown or restriction measures of human activities, were expected to induce positive and negative impacts on the global environment inclusive of resource, material, and energy flows [1,9,10,11,12].

Referring to the overall waste management sector, industrial waste [13] generation was expected to decrease, during the COVID-19 pandemic, due to the forced non-functioning or reduction in various types of industrial activities [1,10]. Differently, food losses and consequential waste [14] from farming were expected to increase due to the restriction of harvesting activities caused by the impact of lockdown measures on the related workers [7,10]. Concerning municipal waste (MW) [14], the influence of the COVID-19 pandemic was expected to differ depending on geographical, sociological, behavioural, and operational factors and situations [4,9]. Certainly, the COVID-19 pandemic posed challenges to the pre-crisis MW management systems, particularly in terms of operational procedures for the stream of residual or mixed MW (RMW) generated from households and quarantine facilities with infected or suspected patients and possible modifications to specific treatment steps or practices as health and safety protection measures for employees involved in the waste sector in order to reduce the risk for a spread of the virus [4,7]. Consequently, there is the technical–scientific need for detailed research studies that evaluate different MW management situations occurred during the COVID-19 pandemic in diversified regions or areas worldwide, with the aim of facilitating the development of a comprehensive understanding and decision making to overcome waste management challenges in similar disease outbreaks or public health emergencies in the future [7,9]. Particularly, evaluation approaches, such as material flow analysis and life cycle assessment (LCA), could be properly implemented to comprehend the occurred environmental impacts of COVID-19 induced temporal changes in MW generation and management [10]. Several works (for instance [15,16,17]) applied LCA in relation to the waste management of single-use masks and gloves that represent less than 1% of the RMW [10]. Few studies focused on LCA of medical waste, providing recommendations on their management and disposal for future similar emergencies [18,19], and infectious waste in emerging and underdeveloped nations [20]. However, only a few researchers applied LCA for evaluating the environmental impact of changes in MW management during COVID-19, providing recommendations for future cases, in diversified areas around the globe (for instance, in Teheran, Iran [21], and in Goiânia, Brazil [22]), while Aldaco et al. [23] evaluated the impact in terms of greenhouse gas (GHG) emissions from modifications in food waste generation and management in Spain during COVID-19.

Among the Western countries, Italy was one of the first nations that faced the COVID-19 pandemic, starting from the day (i.e., 21 February 2020) the first patient was diagnosed with COVID-19 within the national territory [11]. In particular, the provincial territory of Pesaro-Urbino, which is located in the Marche region (Central Italy, Adriatic Sea side), was directly included in the inter-regional area of the national territory interested by the first emergency limitation measures issued on 1 March 2020 by a specific decree of the Italian President of the Council of Ministers [24]. Indeed, Italy also has a long tradition in the separate collection (SC) and recycling of MW fractions, with the associated management of the remaining RMW [11,25].

Given the above considerations, this study aimed at comparing the environmental impacts of the RMW management practices that were implemented regularly before (reference year 2019 as the corresponding scenario) and extraordinarily during the COVID-19 pandemic (reference year 2020 as the subsequent scenario) in two selected provincial territories of the Marche region. The environmental impact assessment was performed by LCA, and it was preceded by a waste flow analysis to quantify and compare the resulting streams of the main separately collected MW fractions and remaining RMW before and during the COVID-19 pandemic (according to the respective reference years) in the selected provincial territories.

2. Materials and Methods

2.1. Provincial Territories and Scenarios

The provincial territories of the Marche region selected in this study are (Figure 1) (1) the mentioned provincial territory of Pesaro-Urbino (hereinafter identified as PT_PU), which is located in the northern part of the region with an extension of about 2570 km² [26] and an average population of about 358,000 inhabitants in the biennial period 2019–2020 [27,28], and (2) the provincial territory of Macerata (hereinafter identified as PT_MC), which is located in the south-central part of the region with an extension of about 2800 km² [26] and an average population of about 325,000 inhabitants (including a neighbouring municipality also operated by the provincial waste management company) in the same biennial period [27,28].

In the first scenario, temporally referred to as 2019 and called “Pre-COVID-19”, the regularly implemented SC of MW, in the provincial territories PT_PU and PT_MC, regarded the following material fractions (and related European Waste Codes—EWCs) [27,29]: paper and cardboard (identified by the aggregation of EWCs 15 01 01 and 20 01 01); glass (identified by the aggregation of EWCs 15 01 07 and 20 01 02); biodegradable kitchen and canteen waste (identified by EWC 20 01 08); green waste (identified by EWC 20 02 01); plastic (identified by the aggregation of EWCs 15 01 02 and 20 01 39); metal (identified by the aggregation of EWCs 15 01 04 and 20 01 40); mixed plastic and metal packaging (identified by EWC 15 01 06); wood (identified by the aggregation of EWCs 15 01 03 and 20 01 38); and other (including textile, waste electrical and electronic equipment, medicines, batteries and accumulators, and bulky waste). In the Pre-COVID-19 scenario, the remaining RMW (identified by EWC 20 03 01 [29]) was regularly addressed, for both the provincial territories PT_PU and PT_MC, to the aerobic biostabilisation variation of the mechanical biological treatment (MBT) [30], generating the following material outputs [31]: magnetically separated metal (identified by EWC 19 12 02 [29]), destined for material recovery [14]; mechanically separated, oversize fraction of RMW (os-RMW, identified by EWC 19 12 12 [29]); and aerobically biostabilised organic fraction of RMW (bios-OFRMW, identified by EWC 19 05 03 [29]). Both the bios-OFRMW and os-RMW were disposed of at pertaining controlled landfills (Figure 1). Concerning provincial territory PT_PU, the implemented complementary aerobic biostabilisation MBT system comprised two mechanical (selection) treatment (MT) steps, located in the upper and lower coastal districts, whose generated streams of undersize organic fraction of RMW (us-OFRMW, identified by EWC 19 05 01 [29]) were addressed to the aerobic biological treatment phase of the complete MBT plant located in the inland district (Figure 1).

In the subsequent scenario, temporally referred to as 2020 and called “COVID-19”, in line with the European Commission recommendation on waste management in the context of COVID-19 pandemic [32], both the provincial territories PT_PU and PT_MC were intended to safeguard the overall continuity of the implemented SC of MW. However, the COVID-19 pandemic induced changes in the previously implemented management practices of RMW due to the consequential generation of two diversified streams following the start of emergency. At first, according to the specific guidelines issued by the Italian National Institute of Health (ISS) [5,11,33] and technical report issued by the European Centre for Disease Prevention and Control (ECDC) [34], the RMW generated (without any preceding sorting) by suspected or confirmed COVID-19 subjects self-isolating or treated at home, hereinafter identified as RWM_COVID-19, was directly addressed to the thermal treatment of incineration, which was made possible—for both the provincial territories PT_PU and PT_MC—at the waste-to-energy (WtE) plant operating in the Province of Rimini of the adjacent Emilia-Romagna region (Figure 1). However, the remaining, main stream of RMW, hereinafter identified as RMW_NO-COVID-19, was subjected to the following temporal and territorial management variations: after a first emergency decree by the President of the Marche region, issued on 21 March 2020 and aimed at ensuring health and hygienic protection in all phases of MW management [35], the RMW_NO-COVID-19 was directly addressed (without treatment) to landfilling in both provincial territories PT_PU and PT_MC, by skipping the aerobic biostabilisation MBT as an initial precautionary measure; then, in provincial territory PT_PU, the RMW_NO-COVID-19 continued to be destined directly to landfilling until the end of 2020, as a confirmed safety measure, particularly considering the disaggregated location of the available MT and MBT facilities (in provincial coastal and internal districts, Figure 1); instead, following a further emergency decree by the President of the Marche region, issued on 24 April 2020 and offering the alternative to reactivate the conventional MBT approach under the conditions of confinement of treatment operations and avoidance of any direct contact of workers with waste [36], the provincial territory PT_MC reactivated the confined aerobic biostabilisation MBT [37] for the RMW_NO-COVID-19, prior to landfilling, from the end of May until the end of 2020.

The changes in RMW management in 2020, described above, are expected to bring non-negligible modifications on the environmental impacts of the overall waste management systems, with respect to the preceding 2019 situation. In particular, the direct landfilling of non-pretreated RMW_NO-COVID-19 is expected to increase the environmental impacts, since higher biodegradable and non-stabilised fractions are contained in the deposited waste [38]. On the other hand, the direct energy recovery in WtE of the RWM_COVID-19 is expected to provide beneficial avoided effects [39,40,41], depending on the incidence of waste amounts effectively addressed to the thermal treatment of incineration.

The schematisation in Figure 2 summarises the temporal and provincial evolutions of the RMW management practices in the considered scenarios.

2.2. Data Collection and Elaboration for Waste Flow Analysis

For the Pre-COVID-19 scenario, the basic data to perform the waste flow analysis in the year 2019 were represented by a complete database in Microsoft Excel format containing the resulting amounts of separately collected MW fractions and RMW disaggregated in terms of individual EWCs [29], months of the year, and municipal territories of generation within the respective provincial territories (PT_PU, PT_MC). This database was defined by the Waste Register Section at the Environmental Protection Agency of the Marche Region (ARPAM) through the institutional web-based application called “ORSo, Supra-Regional Waste Observatory” [42].

For the COVID-19 scenario, the resulting amounts of separately collected MW fractions and RMW disaggregated in terms of individual EWCs [29], months of the year 2020, and municipal territories of generation, particularly with the RMW distinguished between RMW_NO-COVID-19 and RMW_COVID-19, were provided (as Microsoft Excel databases) by the respective waste management companies operating in the upper coastal and internal districts of provincial territory PT_PU, the lower coastal district of provincial territory PT_PU, and provincial territory PT_MC (Figure 1).

The adoption of the pivot tool in Microsoft Excel format allowed the aggregation of resulting amounts of separately collected MW fractions and RMW (or RMW_NO-COVID-19 and RMW_COVID-19) for the overall provincial territories PT_PU and PT_MC, respectively, in the reference years 2019 (Pre-COVID-19 scenario) and 2020 (COVID-19 scenario).

2.3. LCA

The LCA was carried out according to the procedural phases defined by the ISO (International Organisation for Standardisation) standards 14040 [43] and 14044 [44].

2.3.1. Goal and Scope Definition

The LCA was applied to assess and compare the environmental impacts of the implemented RMW management practices in provincial territories PT_PU and PT_MC in the sequential Pre-COVID-19 and COVID-19 scenarios (Figure 2). The LCA application considered the consumption and/or production of energy and materials, as well as the pollutant emissions generated over the entire life cycle of each treatment approach. The waste collection step was not included. The functional unit (FU) was assumed as 1 tonne of RMW.

2.3.2. Inventory Analysis

In this LCA phase, the studied systems on RMW were described according to the material and energy flows across the system boundaries in the considered scenarios.

Pre-COVID-19 Scenario

Figure 3 shows the process units included in the RMW management in provincial territories PT_PU and PT_MC during the ordinary Pre-COVID-19 scenario. These units consisted of: the MT of the incoming RMW; the aerobic biological treatment of the us-OFRMW, which included—in provincial territory PT_PU—the preliminary transportation of the pertaining us-OFRMW from the upper and lower coastal MT steps to the inland MBT (at distances of about 41 and 61 km, respectively) and the consequential transportation of the obtained bios-OFRMW back to the upper and lower coastal controlled landfills (Figure 1); the os-RMW and bios-OFRMW landfilling, which included—in provincial territory PT_MC—their preliminary transportation from the MBT to the pertaining controlled landfill at a distance of about 27 km (Figure 1); and the treatment and combustion of the extracted landfill gas (LFG). Material recovery from the separated metal in the MBT and energy recovery from the extracted LFG were considered by expanding the overall system boundary to include avoided primary productions (Figure 3). The transportation of separated metal from provincial territories PT_PU and PT_MC to dedicated installations for material recovery in Northern Italy, at average distances of about 350 and 500 km, respectively, was included in the system boundary. However, the building of plants and assembly of equipment were not considered.

The mass balances of the aerobic biostabilisation MBTs in provincial territories PT_PU and PT_MC (Table S1 of the Supplementary Materials) were derived in a previous study [31]. The specific electric energy (EE) consumption for the MT steps (Table S2 of the Supplementary Materials) was derived from the permit on Integration Pollution Prevention and Control of the MBT in provincial territory PT_MC [37]. Instead, the specific EE and material (water, diesel) consumptions (per tonne of us-OFRMW) for the aerobic biological treatment steps (Table S3 of the Supplementary Materials) were retrieved from Ardolino et al. [45], while the specific air emissions (per tonne of us-OFRMW) after biofiltration from the aerobic biological treatment steps (Table S4 of the Supplementary Materials) were retrieved from Avadí et al. [46] and the mentioned study [45]. The separated metal was assumed to be reprocessed with an efficiency of 88%, while the substitution by secondary raw metal was considered with a ratio of 100% to the virgin one [41]. Consequently, the overall inventory data for the aerobic biostabilisation MBTs in provincial territories PT_PU and PT_MC, in the ordinary Pre-COVID-19 scenario, are summarised in

Table 1. Pre-COVID-19 scenario: overall inventory data for the aerobic biostabilisation MBTs in provincial territories PT_PU and PT_MC (units expressed per tonne of RMW).

		PTPU	PTMC	Unit
MT	EE consumption	2.38E+01	2.38E+01	kWh t−1
	os-RMW	7.81E-01	6.91E-01	t t−1
	us-OFRMW	2.19E-01	3.09E-01	t t−1
	Metal	0.00E+00	2.94E-04	t t−1
Metal recovery	Recovered metal	0.00E+00	2.94E-01	kg t−1
	Secondary raw metal	0.00E+00	2.59E-01	kg t−1
Aerobic biological treatment	EE consumption	4.07E+00	5.74E+00	kWh t−1
	Water consumption	8.28E+00	1.17E+01	kg t−1
	Diesel consumption	1.78E-01	2.51E-01	kg t−1
	bios-OFRMW	1.33E-01	2.54E-01	t t−1
	Leachate	0.00E+00	2.78E-02	m3 t−1
	Losses	8.60E-02	2.45E-02	m3 t−1
	Aqueous waste	0.00E+00	2.45E-03	m3 t−1
Air emissions	CO2	1.84E-01	2.59E-01	kg t−1
	CH4	2.52E-01	3.55E-01	kg t−1
	N2O	2.85E-02	4.01E-02	kg t−1
	NH3	1.22E-03	1.72E-03	kg t−1
	VOCs	4.60E-02	6.48E-02	kg t−1
	H2S	1.35E-04	1.90E-04	kg t−1

.

Regarding the bios-OFRMW and os-RMW landfilling, the specific landfill EE and water consumptions (both per tonne of deposited waste, Table S5 of the Supplementary Materials) were derived from the annual environmental statement on the controlled landfill in provincial territory PT_MC [47] and assumed the same for the controlled landfills in provincial territory PT_PU. The specific leachate productions (per tonne of deposited waste, Table S6 of the Supplementary Materials) were derived from the mentioned environmental statement [47] for the controlled landfill in provincial territory PT_MC and from the annual reports [48,49,50] for the controlled landfills in provincial territory PT_PU [51].

The estimation of methane and related landfill gas (LFG) generations, expected from the deposited bios-OFRMW and os-RMW, was based on the following assumptions: the values of biochemical methane potential (BMP) and related physico-chemical characteristics derived in previous studies [30,31], as representative for the bios-OFRMW in provincial territories PT_PU and PT_MC (Table S7 of the Supplementary Materials); the values of BMP and related physico-chemical characteristics derived in a further previous study [52], as representative for the residual organic fraction still contained (with the related compositional percentage level) in the os-RMW in provincial territory PT_PU, along with an identical assumption for provincial territory PT_MC (Table S7 of the Supplementary Materials); and the compositional percentage levels (by vol) of methane in LFG, as derived from the annual reports [48,49,50] for the controlled landfills in provincial territory PT_PU, along with the assumed mean of compositional percentage level (from these landfills) for the controlled landfill in provincial territory PT_MC. For the provincial controlled landfills, a volumetric LFG collection proportion of 76% and a complementary volumetric LFG diffuse emission incidence of 24% were assumed, as derived from a multiyear LFG diffuse emission monitoring study performed at the lower coastal controlled landfill in provincial territory PT_PU [53,54]. The disaggregation of LFG diffuse emissions as gaseous components was based on available LFG compositions for the controlled landfills in provincial territory PT_PU from the respective annual reports [48,49,50], while compositional means derivable from these landfills were assumed for the controlled landfill in provincial territory PT_MC (Table S8 of the Supplementary Materials). The specific EE consumption for the cooling treatment of the collected LFG (0.0267 kWh Nm⁻³) was determined from the permit on Integration Pollution Prevention and Control of the lower coastal controlled landfill in provincial territory PT_PU [55], with the same assumption for the remaining controlled landfills in provincial territories PT_PU and PT_MC. To derive the EE productions from on-site conversion of the collected LFG through internal combustion engine (ICE) technology, the following assumptions were made: an EE efficiency of 37% [31], a methane lower heating value (LHV) equal to 35.8 MJ m⁻³ [56], and a self-consumption of 3% [57]. Finally, the compositions of exhaust gases from ICEs were retrieved from the annual reports [48,50] for the lower coastal and inland controlled landfills in provincial territory PT_PU; however, the resulting mean conditions from the previous sites were assumed for the remaining controlled landfills (i.e., the upper coastal one in provincial territory PT_PU and the pertaining one in provincial territory PT_MC, Table S9 of the Supplementary Materials). Consequently, the overall inventory data for the bios-OFRMW and os-RMW landfilling in provincial territories PT_PU and PT_MC, in the ordinary Pre-COVID-19 scenario, are summarised in

Table 2. Pre-COVID-19 scenario: overall inventory data for the landfilling of bios-OFRMW and os-RMW in provincial territories PT_PU and PT_MC (units expressed per tonne of RMW).

		PTPU			PTMC	Unit
		Upper Coastal Landfill	Lower Coastal Landfill	Inland Landfill
Transport us-OFRMW		5.40E+00	4.38E+00	-	-	t km t−1
Transport bios-OFRMW		3.28E+00	2.66E+00	-	-	t km t−1
Transport os-RMW + bios-OFRMW		-	-	-	2.55E+01	t km t−1
Landfilling	EE consumption	9.36E-01	5.10E-01	1.11E-01	1.61E+00	kWh t−1
	Water consumption	5.30E+00	2.89E+00	6.31E-01	9.12E+00	kg t−1
	Leachate	8.38E-02	1.01E-01	3.95E-01	5.27E-02	t t−1
	LFG production	3.72E+01	2.70E+01	4.94E+00	7.85E+01	m3 t−1
	LFG collection	2.83E+01	2.05E+01	3.76E+00	5.96E+01	m3 t−1
	LFG diffuse emissions	8.93E+00	6.47E+00	1.19E+00	1.88E+01	m3 t−1
	CH4 production	1.36E+01	7.41E+00	1.62E+00	2.53E+01	kg t−1
	CH4 collection	1.03E+01	5.63E+00	1.23E+00	1.92E+01	kg t−1
	CH4 diffuse emissions	3.26E+00	1.78E+00	3.89E-01	6.08E+00	kg t−1
LFG cooling	EE consumption	7.54E-01	5.46E-01	1.00E-01	1.59E+00	kWh t−1
LFG energy recovery	EE consumption	1.27E+00	6.95E-01	1.52E-01	2.37E+00	kWh t−1
	Gross EE production	4.25E+01	2.32E+01	5.06E+00	7.91E+01	kWh t−1
	Net EE production	4.12E+01	2.25E+01	4.91E+00	7.68E+01	kWh t−1
	Exhaust gas	4.84E+02	6.96E+02	2.72E+02	6.03E+02	m3 t−1
Components in LFG diffuse emissions	CH4	3.26E+00	1.78E+00	3.89E-01	6.08E+00	kg t−1
	CO2	5.82E+00	3.49E+00	7.85E-01	1.16E+01	kg t−1
	H2S	4.91E-05	9.82E-04	1.80E-04	1.91E-03	kg t−1
	HCl	-	4.92E-06	8.01E-08	7.91E-06	kg t−1
	HF	-	2.07E-06	2.75E-07	5.27E-06	kg t−1
	SO2	-	3.69E-04	1.03E-03	8.68E-03	kg t−1
	CO	8.48E-05	-	-	1.79E-04	kg t−1
	NH3	1.35E-04	2.47E-04	1.15E-06	3.41E-04	kg t−1
Components in ICE exhaust gas	PM	3.75E-05	7.31E-05	1.36E-05	4.68E-05	kg t−1
	NO2	1.78E-01	2.67E-01	9.58E-02	2.22E-01	kg t−1
	CO	7.97E-02	1.64E-01	2.53E-02	9.92E-02	kg t−1
	TOC	4.31E-02	8.57E-02	1.50E-02	5.37E-02	kg t−1
	SO2	3.03E-02	5.57E-02	1.23E-02	3.77E-02	kg t−1
	HCl	3.74E-04	8.11E-04	1.03E-04	4.66E-04	kg t−1
	HF	1.39E-04	2.96E-04	4.08E-05	1.73E-04	kg t−1

.

COVID-19 Scenario

Regarding the thermal treatment of incineration for the RMW_COVID-19, Figure 4 shows the included process units that consisted of: the RMW_COVID-19 transportation to the WtE plant in the Province of Rimini, at the considered distances of about 29, 50, 64, and 159 km from the assumed collection centres at MT locations in upper and lower coastal districts of provincial territory PT_PU and MBT locations in the inland coastal district of provincial territory PT_PU and in provincial territory PT_MC, respectively (Figure 1); the combustion process with energy recovery; the manufacturing processes of chemicals required for flue gas cleaning (FGC); the treatment and final disposal of bottom ash (BA); and the disposal of fly ash (FA) and air pollution control residues (APCR). Material and energy recoveries through the treatment of BA were considered by expanding the overall system boundary to include the avoided primary productions. However, plant building and equipment assembly were not considered.

The basic consumption data (Table S10 of the Supplementary Materials) for the adopted WtE plant (with a moving grade combustion technology and a double filtration dry acid removal FGC) were derived from the annual operating report [58]. For consistency with the considered WtE plant in the Province of Rimini, alternatives for the thermal treatment of the RWM_COVID-19, for instance the advanced waste gasification [59], were not evaluated. The LHVs for the RMW in provincial territories PT_PU and PT_MC were estimated using the modified Dulong expression [60]. In this respect, the compositions (in terms of needed C, H, O, S, and moisture contents) of the RMW in the considered provincial territories were determined based on the assumed typical elemental compositions for relevant waste material fractions (organic as kitchen and fines, green, glass, metal, paper/cardboard, plastic, textile, and wood) and the compositional characteristics (expressly in terms of the mentioned material fractions) for the RMW in provincial territories PT_PU and PT_MC, as derivable from a previous study [31] (Tables S11–S13 of the Supplementary Materials). The resulting LHVs, along with the specific gross EE productions based on the assumption of a typical electric net efficiency of 24% for a conventional WtE plant [61], are reported in Table S14 of the Supplementary Materials. The basic data on outputs (such as flue gas and residues) from the considered WtE plant (Table S15 of the Supplementary Materials) were derived from the annual operating report [58]. The specific inert recovery from BA was assumed equal to 751 kg t BA⁻¹, according to a previous study [62]. Consequently, the recovered inert was considered for use in concrete preparation with substitution levels of gravel and sand equal to 40 and 60%, respectively [62]. For the separated metal from BA, the assumptions on the reprocessing and substitution efficiencies were identical as for the inventory analysis of the biostabilisation MBT. The basic data on chemical consumptions (for FGC) and air emissions for the considered WtE plant (Table S16 of the Supplementary Materials) were retrieved from the annual report [58]. Regarding CO₂ emissions, only those originated from non-renewable RMW material fractions were considered [62], in accordance with the assumptions and resulting values in Table S17 of the Supplementary Materials. Consequently, the overall inventory data for the thermal treatment of RMW_COVID-19 in provincial territories PT_PU and PT_MC, in the COVID-19 scenario, are summarised in

Table 3. COVID-19 scenario: overall inventory data for the thermal treatment (WtE) of RMW_COVID-19 in provincial territories PT_PU and PT_MC (units expressed per tonne of RMW).

	PTPU	PTMC	Unit
Transport RMWCOVID-19	2.33E-01	4.28E+00	t km t−1
Diesel consumption for energy	1.12E-03	5.58E-03	kWh t−1
Diesel consumption for handling	4.64E-05	2.31E-04	kg t−1
Methane consumption for energy	2.12E-01	1.06E+00	kWh t−1
Water consumption	2.30E+00	1.15E+01	kg t−1
EE consumption from grid	4.51E-02	2.24E-01	kWh t−1
EE self-consumption	6.00E-01	2.99E+00	kWh t−1
Gross EE production	5.50E+00	2.73E+01	kWh t−1
NaOH consumption	1.58E-05	7.85E-05	kg t−1
NaClO consumption	1.18E-05	5.89E-05	kg t−1
NaHCO3 consumption	3.75E-02	1.86E-01	kg t−1
Ca(OH)2 consumption	4.62E-02	2.30E-01	kg t−1
High efficiency Ca(OH)2 consumption	8.95E-03	4.45E-02	kg t−1
Activated carbon consumption	2.36E-03	1.18E-02	kg t−1
NH3 consumption	1.40E-02	6.96E-02	kg t−1
Flue gas	2.87E+01	1.43E+02	m3 t−1
BA to disposal	1.17E-03	5.83E-03	kg t−1
EE consumption for BA treatment	4.21E-03	2.09E-02	kWh t−1
Inert from BA to recovery	7.90E-01	3.93E+00	kg t−1
Gravel substitution	3.16E-01	1.57E+00	kg t−1
Sand substitution	4.74E-01	1.94E-01	kg t−1
Inert from BA to disposal	2.45E-01	1.22E+00	kg t−1
Secondary raw metal	1.50E-02	7.49E-02	kg t−1
FA + APCR	2.60E-01	1.30E+00	kg t−1
Aqueous liquid waste	2.42E-05	1.21E-04	m3 t−1
CO air emission	2.72E-04	1.35E-03	kg t−1
NOx air emission	1.63E-03	8.13E-03	kg t−1
N2O air emission	6.43E-05	3.20E-04	kg t−1
SOx air emission	4.68E-05	2.33E-04	kg t−1
PM air emission	1.29E-05	6.44E-05	kg t−1
HCl air emission	6.55E-05	3.26E-04	kg t−1
HF air emission	1.44E-06	7.15E-06	kg t−1
TOC air emission	2.61E-05	1.30E-04	kg t−1
NH3 air emission	1.09E-05	5.43E-05	kg t−1
Hg air emission	3.45E-09	1.72E-08	kg t−1
Cd+TI air emission	7.18E-09	3.58E-08	kg t−1
Metals air emission	4.60E-08	2.29E-07	kg t−1
PAH air emission	8.04E-10	4.00E-09	kg t−1
PCDD/F air emission	2.87E-14	1.43E-13	kg t−1
PCB-DL air emission	6.32E-15	3.15E-14	kg t−1
Non-renewable CO2 air emission	3.56E+00	1.69E+01	kg t−1

.

Regarding the RMW_NO-COVID-19 management in provincial territories PT_PU and PT_MC during the COVID-19 scenario, Figure 5 shows the involved process units that were the same as for the Pre-COVID-19 scenario (Figure 3), while addressing diversified temporal evolutions and waste flows (Figure 2). In addition to assumptions and data in Tables S1–S6, S8, and S9 of the Supplementary Materials, the estimation of methane and related LFG generations, from the direct landfilling of RMW_NO-COVID-19, considered the following (Table S7 of the Supplementary Materials): a BMP value for the organic fraction in RMW derived in a previous study [30], as representative for the us-OFRMW in provincial territory PT_PU, along with the same assumption for provincial territory PT_MC; the values of related physico-chemical characteristics for the us-OFRMW in provincial territories PT_PU and PT_MC, as derived in a further previous study [31]; and the resulting compositional levels of the organic fraction in RMW, as obtained in the mentioned study [31], based on detailed compositional analyses on RMW samples in provincial territories PT_PU and PT_MC (including the material fractions diaper, glass, metal, organic, paper/cardboard, plastic, textile, wood, and other). Consequently, the overall inventory data for the aerobic biostabilisation MBTs and the bios-OFRMW + os-RMW and RMW_NO-COVID19 landfilling in provincial territories PT_PU and PT_MC, in the COVID-19 scenario, are summarised in

Table 4. COVID-19 scenario: overall inventory data for the aerobic biostabilisation MBTs in provincial territories PT_PU and PT_MC (units expressed per tonne of RMW).

		PTPU	PTMC	Unit
MT	EE consumption	4.39E+00	1.94E+01	kWh t−1
	os-RMW	1.44E-01	5.64E-01	t t−1
	us-OFRMW	4.04E-02	2.52E-01	t t−1
	Metal	0.00E+00	2.40E-04	t t−1
Metal recovery	Recovered metal	0.00E+00	2.40E-04	kg t−1
	Secondary raw metal	0.00E+00	2.12E-01	kg t−1
Aerobic biological treatment	EE consumption	7.52E-01	4.69E+00	kWh t−1
	Water consumption	1.53E+00	9.53E+00	kg t−1
	Diesel consumption	3.28E-02	2.05E-01	kg t−1
	bios-OFRMW	2.45E-02	2.07E-01	t t−1
	Leachate	0.00E+00	2.27E-02	m3 t−1
	Losses	1.59E-02	2.00E-02	m3 t−1
	Aqueous waste	0.00E+00	2.00E-03	m3 t−1
Air emissions	CO2	3.39E-02	2.12E-01	kg t−1
	CH4	4.65E-02	2.90E-01	kg t−1
	N2O	5.25E-03	3.28E-02	kg t−1
	NH3	2.25E-04	1.41E-03	kg t−1
	VOCs	8.49E-03	5.29E-02	kg t−1
	H2S	2.48E-05	1.55E-04	kg t−1

and

Table 5. COVID-19 scenario: overall inventory data for the landfilling of bios-OFRMW + os-RMW and RMW_NO-COVID-19 in provincial territories PT_PU and PT_MC (units expressed per tonne of RMW).

			PTPU		PTMC	Unit
		Upper Coastal Landfill	Lower Coastal Landfill	Inland Landfill
Transport us-OFRMW		8.06E-01	7.70E-01	-	-	t km t−1
Transport bios-OFRMW		4.90E-01	4.68E-01	-	-	t km t−1
Transport os-RMW + bios-OFRMW		-	-	-	2.08E+01	t km t−1
Landfilling	EE consumption	7.68E-01	5.75E-01	3.25E-01	1.58E+00	kWh t−1
	Water consumption	4.35E+00	3.26E+00	1.84E+00	8.96E+00	kg t−1
	Leachate	6.87E-02	1.14E-01	1.15E+00	5.18E-02	t t−1
	LFG production	3.65E+01	3.65E+01	1.72E+01	7.79E+01	m3 t−1
	LFG collection	2.77E+01	2.78E+01	1.31E+01	5.92E+01	m3 t−1
	LFG diffuse emissions	8.76E+00	8.76E+00	4.14E+00	1.87E+01	m3 t−1
	CH4 production	1.33E+01	1.00E+01	5.65E+00	2.51E+01	kg t−1
	CH4 collection	1.01E+01	7.63E+00	4.29E+00	1.91E+01	kg t−1
	CH4 diffuse emissions	3.20E+00	2.41E+00	1.35E+00	6.03E+00	kg t−1
LFG cooling	EE consumption	7.40E-01	7.40E-01	3.49E-01	1.58E+00	kWh t−1
LFG energy recovery	EE consumption	1.25E+00	9.41E-01	5.29E-01	2.36E+00	kWh t−1
	Gross EE production	4.17E+01	3.14E+01	1.76E+01	7.86E+01	kWh t−1
	Net EE production	4.04E+01	3.04E+01	1.71E+01	7.62E+01	kWh t−1
	Exhaust gas	5.04E+02	7.25E+02	2.83E+02	6.15E+02	m3 t−1
Components in LFG diffuse emissions	CH4	3.20E+00	2.41E+00	1.35E+00	6.03E+00	kg t−1
	CO2	5.71E+00	4.73E+00	2.74E+00	1.15E+01	kg t−1
	H2S	4.82E-05	1.33E-03	6.27E-04	1.89E-03	kg t−1
	HCl	-	6.66E-06	2.79E-07	7.85E-06	kg t−1
	HF	-	2.80E-06	9.57E-07	5.24E-06	kg t−1
	SO2	-	5.00E-04	3.58E-03	8.62E-03	kg t−1
	CO	8.32E-05	-	-	1.78E-04	kg t−1
	NH3	1.33E-04	3.34E-04	4.01E-06	3.38E-04	kg t−1
Components in ICE exhaust gas	PM	3.91E-05	7.61E-05	1.42E-05	4.76E-05	kg t−1
	NO2	1.85E-01	2.78E-01	9.97E-02	2.26E-01	kg t−1
	CO	8.29E-02	1.71E-01	2.63E-02	1.01E-01	kg t−1
	TOC	4.49E-02	8.91E-02	1.56E-02	5.47E-02	kg t−1
	SO2	3.15E-02	5.80E-02	1.27E-02	3.84E-02	kg t−1
	HCl	3.89E-04	8.44E-04	1.08E-04	4.75E-04	kg t−1
	HF	1.45E-04	3.08E-04	4.25E-05	1.77E-04	kg t−1

, respectively.

2.3.3. Impact Assessment Method

The Environmental Footprint (EF) 3.0 method [63], developed by the Joint Research Centre (JRC) of the European Commission [64], was used to perform the Life Cycle Impact Assessment (LCIA), comprising the following EF impact categories: climate change (CC) in kg CO₂ eq; ozone depletion (OD) in kg CFC-11 eq; ionising radiation (IR) in kBq U²³⁵ eq; photochemical ozone formation (POF) in kg NMVOC eq; particulate matter (PM) in disease incidence; human toxicity, non-cancer (HTnc) in CTUh (comparative toxic unit for humans); human toxicity, cancer (HTc) in CTUh; acidification (A) in mol H⁺ eq; eutrophication, freshwater (Ef) in kg P eq; eutrophication, marine (Em) in kg N eq; eutrophication, terrestrial (Et) in mol N eq; ecotoxicity, freshwater (ETf) in CTUe (comparative toxic unit for ecosystems); land use (LU) in Pt (soil quality index); water use (WU) in m³ deprived; resource use, fossils (RUf) in MJ; and resource use, minerals and metals (RUmm) in kg Sb eq. In the classification step, all the material and energy flows of the inventory phase were identified according to their contribution to each EF impact category [41].

The calculation of EF indicators was performed using SimaPro software (version 9.2) [65] with its database Ecoinvent 3.7.1 [66], which is updated to the year 2020, granting the representativeness of data for the reference years 2019 (Pre-COVID-19 scenario) and 2020 (COVID-19 scenario). In this LCA study, normalization and weighting steps were not performed.

3. Results and Discussion

3.1. Comparison of Waste Flows in the Considered Scenarios

The generation of MW (as the sum of separately collected material fractions, RMW, street cleaning residues to disposal, and bulky waste to disposal) in provincial territory PT_PU amounted to 209,098 and 192,815 tonnes in 2019 (Pre-COVID-19 scenario) and 2020 (COVID-19 scenario), respectively, with a resulting relative reduction (calculated as [(MW₂₀₂₀ − MW₂₀₁₉)/(MW₂₀₁₉)] × 100) equal to −7.8%. In provincial territory PT_MC, 165,509 and 160,427 tonnes of MW were generated in 2019 and 2020, respectively, with a resulting relative reduction equal to −3.1%. Indeed, the temporally implemented and repeated lockdown measures might have affected the generations of MW due to urban activities forced to stop and possible material accumulations by citizens at home; although, the yearly decreasing effects were likely counterbalanced partially by occurred seasonal mitigations of restriction measures [11,67].

3.1.1. Main Separately Collected MW Fractions

Figure 6 and Figure 7 display the resulting amounts of main separately collected MW fractions in 2019 (Pre-COVID-19 scenario) and 2020 (COVID-19 scenario) in provincial territories PT_PU and PT_MC, respectively. The amounts of biodegradable kitchen and canteen waste (Figure 6a and Figure 7a) showed relative decreases, calculated comparing 2020 to 2019 as [(kitchen-canteen waste₂₀₂₀ − kitchen-canteen waste₂₀₁₉)/(kitchen-canteen waste₂₀₁₉)] × 100, equal to −4.6 and −1.6% in provincial territories PT_PU and PT_MC, respectively (Figure 6f and Figure 7f). Indeed, the temporally implemented and repeated lockdown measures might have caused reductions in the generation (and collection) of food waste due to the closing of restaurants and bars and a possible attitude of citizens to buy more frozen and packed and less fresh foods [68]; probably, these reductions were partially counterbalanced by a possible different attitude of citizens to make provision of food in inadequate large amounts [6].

The amounts of green waste (Figure 6b and Figure 7b) presented relative decreases, calculated comparing 2020 to 2019 as [(green waste₂₀₂₀ − green waste₂₀₁₉)/(green waste₂₀₁₉)] × 100, equal to −8.2 and −20.7% in provincial territories PT_PU and PT_MC, respectively (Figure 6f and Figure 7f). Indeed, the temporally implemented and repeated lockdown measures might have affected the regular management of gardens and parks [11]. The amounts of paper and cardboard (Figure 6c and Figure 7c) also presented relative decreases that, calculated comparing 2020 to 2019 as [(paper-cardboard₂₀₂₀ − paper-cardboard₂₀₁₉)/(paper-cardboard₂₀₁₉)] × 100, were equal to −3.5 and −3.0% in provincial territories PT_PU and PT_MC, respectively (Figure 6f and Figure 7f). Effectively, the physical closing of offices and institutional and educational activities, which mostly shifted to smart working and telematic procedures during the temporally implemented and repeated lockdown measures, might have caused reduced usages of clean paper and cardboard materials; although, partly counterbalancing effects were likely given by expected increases in packaging waste (including cellulosic-based materials) due to online shopping for home delivery [4,6,11].

However, the amounts of glass (Figure 6d and Figure 7d) showed relative increases, calculated comparing 2020 to 2019 as [(glass₂₀₂₀ − glass₂₀₁₉)/(glass₂₀₁₉)] × 100, equal to 2.4 and 1.3% in provincial territories PT_PU and PT_MC, respectively (Figure 6f and Figure 7f). Indeed, people’s preference in buying long shelf life products (expected to be also in glass jars), during the temporally implemented and repeated lockdown measures, might have caused increases in glass fractional waste generation (and collection); although, partly counterbalancing effects were likely given by the forced closing of bars and restaurants with reduced beverage consumptions [6]. Finally, the aggregated amounts of plastic and metal (Figure 6e and Figure 7e) remained almost unchanged due to resulting relative differences, calculated comparing 2020 to 2019 as [(plastic-metal₂₀₂₀ − plastic-metal₂₀₁₉)/(plastic-metal₂₀₁₉)] × 100, limited to 0.1 and 0.2% in provincial territories PT_PU and PT_MC, respectively (Figure 6f and Figure 7f). In this respect, the opposing effects of the expected increase in light packaging (from online shopping for home delivery) and decrease in waste (including plastic and metal fractions) assimilable to MW might have concurrently occurred during the temporally implemented and repeated lockdown measures [9,11,69].

3.1.2. RMW

Figure 8 displays the resulting amounts of overall RMW in 2019 (Pre-COVID-19 scenario) and 2020 (COVID-19 scenario) in provincial territories PT_PU and PT_MC. The overall RMW presented relative decreases, calculated comparing 2020 to 2019 in provincial territories PT_PU (Figure 8a) and PT_MC (Figure 8b) as [(RMW₂₀₂₀ − RMW₂₀₁₉)/(RMW₂₀₁₉)] × 100, equal to −3.9 and −1.9%, respectively (Figure 8c). The comparative sequence of these relative decreases qualitatively agreed with the mentioned provincial relative reductions on MW generation due to resulting similar values for the respective MW_{relative reduction}/RMW_{relative reduction} ratios (equal to 2 for provincial territory PT_PU and 1.6 for provincial territory PT_MC). The quantitative impact on overall RMW in 2020 of the large utilisation of single-use masks and gloves by provincial populations was expected to be of minor concern due to the light individual weights of these personal protective equipment products [11,33].

In the COVID-19 scenario (2020), the yearly quantitative incidences of RMW_COVID-19 to overall RMW in provincial territories PT_PU (Figure 9a) and PT_MC (Figure 9b) were limited to 0.54 and 2.7%, respectively (Figure 9c). Indeed, the resulting higher incidence of RMW_COVID-19 in provincial territory PT_MC, compared to provincial territory PT_PU (Figure 9c), was likely related to the precautionary attitude by the waste management company in provincial territory PT_MC to include also RMW from provincial nursing homes into the collected RMW_COVID-19 stream [36].

Interestingly, both the temporal evolutions of monthly amounts of RMW_COVID-19 and percentage ratios of RMW_COVID-19 to overall RMW, during 2020 (COVID-19 scenario) in provincial territory PT_PU (Figure S1 of the Supplementary Materials), qualitatively paralleled the temporal evolution of the occurred COVID-19 crisis, with comparatively higher monthly RMW_COVID-19 amounts and RMW_COVID-19/RMW ratios revealed from April to June and in November–December in agreement with the initial and second waves of emergency (with related lockdown measures) and the start (from end of March, see Section 2.1 and Figure 2) of operational RMW differentiation in RMW_COVID-19 and RMW_NO-COVID-19 streams; however, comparatively lower monthly RMW amounts and RMW_COVID-19/RMW ratios were revealed in summer and initial autumn seasons (i.e., from July to October) in qualitative combination with the occurred seasonal mitigations of restriction measures [24,35,67]. In provincial territory PT_MC, the comparative differences in monthly RMW_COVID-19 amounts and RMW_COVID-19/RMW ratios during 2020 became less pronounced, while still indicating higher values in April extended to July and November–December (Figure S2 of the Supplementary Materials); in this respect, it should be considered the mentioned precautionary attitude to include also RMW from provincial nursing homes into the RMW_COVID-19 stream.

Finally, the quantitative partitions of RMW_NO-COVID-19 management practices during 2020 (COVID-19 scenario) resulted higher (at 81.4% of the yearly stream) to direct landfilling and lower (at 18.6% of the yearly stream) to combined aerobic biostabilisation MBT + landfilling in provincial territory PT_PU, while the opposite occurred in provincial territory PT_MC (i.e., lower at 16.1% and higher at 83.9% of the yearly stream to direct landfilling and combined aerobic biostabilisation MBT + landfilling, respectively) (Figure S3 of the Supplementary Materials). This comparative difference in provincial percentage partitions reflected the diversified monthly durations of RMW_NO-COVID-19 management practices that occurred in the considered provincial territories (see Section 2.1 and Figure 2).

3.2. Comparison of LCIA in the Considered Scenarios

Table 6. Resulting values of the indicators calculated for the EF impact assessment categories of RMW management in provincial territories PT_PU and PT_MC in the sequential Pre-COVID-19 (2019) and COVID-19 (2020) scenarios (FU = 1 tonne of RMW).

Category	Indicator Unit	PTPU			PTMC
		Pre-COVID-19 (2019)	COVID-19 (2020)	∆% 1	Pre-COVID-19 (2019)	COVID-19 (2020)	∆% 1
Climate change	(kg CO2 eq t−1)	1.87E+02	2.08E+02	11.2%	2.14E+02	2.12E+02	−0.9%
Ozone depletion	(kg CFC-11 eq t−1)	−2.03E-06	−5.54E-06	−172.9%	−2.19E-06	−4.29E-06	−95.9%
Ionising radiation	(kBq U235 eq t−1)	−2.03E+00	−4.89E+00	−140.9%	−2.36E+00	−4.23E+00	−79.2%
Photochemical ozone formation	(kg NMVOC eq t−1)	5.87E-01	5.69E-01	−3.1%	2.70E-01	2.49E-01	−7.8%
Particulate matter	(disease inc. t−1)	1.57E-06	1.22E-06	−22.3%	6.07E-07	3.55E-07	−41.5%
Human toxicity, non-cancer	(CTUh t−1)	2.69E-07	2.88E-07	7.1%	2.48E-07	1.93E-07	−22.2%
Human toxicity, cancer	(CTUh t−1)	−2.15E-09	−5.34E-09	−148.4%	−5.36E-09	−5.83E-09	−8.8%
Acidification	(mol H+ eq t−1)	−1.92E-02	−1.09E-01	−467.7%	−5.87E-02	−1.18E-01	−101%
Eutrophication, freshwater	(kg P eq t−1)	−3.85E-03	−8.74E-03	−127%	−5.26E-03	−8.64E-03	−64.3%
Eutrophication, marine	(kg N eq t−1)	2.11E-01	2.20E-01	4.3%	7.53E-02	7.01E-02	−6.9%
Eutrophication, terrestrial	(mol N eq t−1)	7.06E-01	5.76E-01	−18.4%	2.13E-01	1.30E-01	−39%
Ecotoxicity, freshwater	(CTUe t−1)	−3.76E+00	−5.12E+01	−1262%	−2.34E+02	−4.38E+02	−87.2%
Land use	(Pt t−1)	−2.34E+02	−5.82E+02	−148.7%	−2.66E+02	−4.85E+02	−82.3%
Water use	(m3 depriv. t−1)	−1.32E+01	−3.07E+01	−132.6%	−1.47E+01	−2.43E+01	−65.3%
Resource use, fossils	(MJ t−1)	−2.18E+02	−5.53E+02	−153.7%	−2.47E+02	−4.52E+02	−83%
Resource use, minerals and metals	(kg Sb eq t−1)	−3.36E-05	−8.02E-05	−138.7%	−4.39E-05	−6.55E-05	−49.2%

¹ Relative difference in indicator comparing 2020 (COVID-19 scenario) to 2019 (Pre-COVID-19 scenario), calculated as [(Indicator₂₀₂₀ − Indicator₂₀₁₉)/(|Indicator₂₀₁₉|)] × 100.

shows the resulting values of the indicators calculated for the EF impact categories of RMW management in provincial territories PT_PU and PT_MC, in the Pre-COVID-19 (2019) and COVID-19 (2020) scenarios, according to the chosen FU. In general, positive values of the indicators mean a burden for the environment, while negative values represent a saving for the environment [41]. Specifically, some impact categories resulted in Table 6 in environmental burdens (positive values), regardless of the RMW management practices implemented in the respective Pre-COVID-19 (2019) and COVID-19 (2020) scenarios for the considered provincial territories (i.e., CC, POF, PM, HTnc, Em, and Et). However, some other impact categories resulted in Table 6 in environmental benefits (negative values) in the Pre-COVID-19 (2019) and COVID-19 (2020) scenarios for both provincial territories (i.e., OD, IR, HTc, A, Ef, Etf, LU, WU, Ruf, and Rumm).

Interestingly, all the calculated indicators resulted in improved (lower) values for the COVID-19 (2020) scenario compared to the ordinary Pre-COVID-19 (2019) scenario in provincial territory PT_MC, as shown by the negative relative differences reported in Table 6. Concerning provincial territory PT_PU, the predominance of calculated indicators confirmed improved (lower) values for the COVID-19 (2020) scenario compared to the ordinary Pre-COVID-19 (2019) scenario, except for three indicators (i.e., CC, HTnc, and Em) showing in Table 6 higher values in the COVID-19 (2020) scenario with resulting positive relative differences. To better understand the behaviour of the calculated indicators, the analysis of contributions from different process units has been detailed in the following section Contribution Analysis. However, it is rather expected that, for CC, the predominant practice of direct landfilling of RMW_NO-COVID-19 in the COVID-19 scenario (2020) for provincial territory PT_PU (see Section 3.1.2 and Figure S3 of the Supplementary Materials) had a detrimental environmental effect, explaining the positive relative increase resulting in Table 6.

Contribution Analysis

The contribution analysis helped in investigating the causes of different behaviours in the considered impact indicators. Particularly, the following key process units were identified to investigate the main contributions that affected the total environmental performances of RMW management practices in provincial territories PT_PU and PT_MC in the sequential Pre-COVID-19 (2019) and COVID-19 (2020) scenarios: MT, aerobic biological treatment, metal recovery, post-MBT landfilling (i.e., for the resulting main MBT outputs of os-RMW and bios-OFRMW), direct landfilling of RMW_NO-COVID-19, LFG treatment (via cooling), LFG energy recovery, transportation, and direct WtE for RMW_COVID-19. For each process unit, the contribution of each involved activity (consumption/production of energy and substances, emissions, treatment of residues/waste) has been accounted for. Avoided impacts due to beneficial effects from the substitution of conventional energy or material (metal) have been expressed as negative values.

Figure 10 reports the contribution analysis for the three impact categories presenting variations in Table 6 from 2019 (Pre-COVID-19 scenario) to 2020 (COVID-19 scenario) that are qualitatively different in the respective provincial territories (i.e., increasing values for PT_PU while decreasing values for PT_MC), i.e., the mentioned CC, HTnc, and Em.

The total CC resulted in environmental burdens (positive values) for the two provincial territories in both considered scenarios (Figure 10a,b). Despite the energy recovery from the collected LFG combustion represented an avoided impact (accounting for −16 and −18% for PT_PU and both −16% for PT_MC in 2019 and 2020, respectively), it was not enough to counterbalance the large positive contribution given mainly by landfilling. In 2019 (Pre-COVID-19 scenario), only the post-MBT landfilling of os-RMW and bios-OFRMW occurred (see Section 2.1 and Figure 2), accounting for 99 and 97% for provincial territories PT_PU and PT_MC, respectively. In 2020 (COVID-19 scenario), two landfilling contributions overall occurred, i.e., for post-MBT outputs (os-RMW and bios-OFRMW) and directly for RMW_NO-COVID-19 (see Section 2.1 and Figure 2). While, for provincial territory PT_MC, the direct landfilling of RMW_NO-COVID-19 took place for only two months with a lower amount (see Figure 2 and Section 3.1.2) contributing to the 2020 indicator for 17% (post-MBT landfilling contributed for 80%), in provincial territory PT_PU, the direct landfilling of RMW_NO-COVID-19 was implemented for the whole yearly time after the start of management of the COVID-19 pandemic and at higher amount (see Figure 2 and Section 3.1.2), thus representing 98% of 2020 impact (post-MBT landfilling only contributed for 17%). It is rather clear from Figure 10a how the predominance of the direct landfilling of RMW in provincial territory PT_PU influenced the indicator worsening in 2020 (COVID-19 scenario), because of the higher methane diffuse emissions from disposal of untreated RMW. At the same time, MT and aerobic biological treatment impacts decreased in 2020 (COVID-19 scenario), especially for provincial territory PT_PU, but their contributions were definitely less relevant in both scenarios (6 and 1% and 10 and 2% for PT_PU, 5 and 4% and 13 and 10% for PT_MC in 2019 and 2020, respectively) than landfilling ones (Figure 10a,b). Overall, WtE impact in 2020 (COVID-19 scenario) was negligible for provincial territory PT_PU, given the very small amount of RMW_COVID-19 directly addressed to thermal treatment (see Figure 9 and Section 3.1.2). For provincial territory PT_MC, the overall WtE impact in 2020 accounted for 2.9%, given the slightly higher quantitative incidence of RMW_COVID-19 (see Figure 9 and Section 3.1.2).

The Increase in the HTnc indicator from 2019 (Pre-COVID-19 scenario) to 2020 (COVID-19 scenario), in provincial territory PT_PU, was referable again to the main contribution of direct landfilling of RWM_NO-COVID-19 during 2020 (Figure 10c). Figure 10c also shows in 2020 the increase in negative contribution from collected LFG energy recovery (because more LFG has been produced) and the very small negative contribution of WtE, but both were in all not enough to compensate for the mentioned positive increase. In provincial territory PT_MC (Figure 10d), the sum of contributions of the direct landfilling of RMW_NO-COVID-19 and the post-MBT landfilling of os-RMW and bios-OFRMW in 2020 (3.02E-07 CTUh t⁻¹) was very similar to the contribution of post-MBT landfilling in 2019 (3.04E-07 CTUh t⁻¹); however, the contributions of MT and aerobic biological treatment slightly decreased from 2019 to 2020; in addition, a visible contribution from WtE in Figure 10d further decreased the total indicator value in 2020 (COVID-19 Scenario), resulting in a lower value with respect to 2019 (Pre-COVID-19 scenario).

The Em indicator (Figure 10e,f) was dominated by the collected LFG combustion emissions, in particular NO₂ emissions (included in LFG energy recovery contribution), generally lower for provincial territory PT_MC than for provincial territory PT_PU because of different assumptions and consequential inventory data on components in ICE exhaust gas resulting in the considered provincial territories (with specific NO₂ emissions per FU, in provincial territory PT_PU, almost 2.4–2.5 times larger than in provincial territory PT_MC, see Table 2 and Table 5). The Em indicator slightly worsened from 2019 (Pre-COVID-19 scenario) to 2020 (COVID-19 scenario) in provincial territory PT_PU (Figure 10e) because of the resulting higher volume of produced and consequently collected LFG sent to energy recovery during 2020. The same contribution also dominated the indicator for provincial territory PT_MC (Figure 10f), but in this case, the volume of produced and, consequently, collected LFG was similar during 2019 and 2020, and so, the impact, while the slight decrease in the indicator from 2019 (Pre-COVID-19 scenario) to 2020 (COVID-19 scenario) was due to the negative contribution of WtE. The contribution from landfilling (of os-RMW and bios-OFRMW or direct RMW_NO-COVID) was more evident in the case of provincial territory PT_PU (Figure 10e) for the predominant sub-contribution of leachate treatment due to leachate specific production values higher in PT_PU than in PT_MC (see Table 2 and Table 5). Similarly, other indicators were dominated by the sub-contribution of the LFG combustion emissions (included in the LFG energy recovery contribution) as OD, POF, HTc, A, RUmm, IR, Ef, ETf, WU, LU, and RUf (Figures S4–S14 of the Supplementary Materials). Also, PM and Et indicators were dominated by the LFG combustion emissions for provincial territory PT_PU, while for provincial territory PT_MC, the contributions were more equally distributed (due to different assumptions and consequential inventory data on components in ICE exhaust gas, see Table 2 and Table 5) (Figures S15 and S16 of the Supplementary Materials).

Finally, given the mentioned impact of direct RMW_NO-COVID-19 landfilling on the distinctive CC indicator in 2020 for provincial territory PT_PU, it has been worth simulating, in a definable “hypothetical 2020” option oriented to a very strict precaution on lowering any potential spreading of the virus from management of RMW [33], what the CC indicator would have been in 2020 if the RMW_NO-COVID-19 amounts, originally destined at diversified provincial partitions (see Section 3.1.2 and Figure S3 of the Supplementary Materials) for direct landfilling, were sent (in addition to RMW_COVID-19) to thermal treatment (WtE). As consequently shown in Figure 11, the potential option to address the RWM_COVID-19 and the RMW_NO-COVID-19, originally destined for direct landfilling, to WtE (hypothetical 2020) would have reduced the value of the CC indicator by −15% with respect to 2020 (COVID-19 scenario) and −5% with respect to 2019 (Pre-COVID-19 scenario), in the case of provincial territory PT_PU, and −4% with respect to 2020 (COVID-19 scenario) and −5% with respect to 2019 (Pre-COVID-19 scenario), in the case of provincial territory PT_MC.

The results of this simulation agreed with several studies in the technical–scientific literature, showing how the introduction of WtE for RMW allows for an improvement in the CC indicator [41,70,71].

4. Conclusions

In 2020 (COVID-19 scenario), the pandemic resulted in limited quantitative reductions in the overall RMW in both provincial territories (PT_PU, PT_MC) compared to the preceding 2019 (ordinary Pre-COVID-19 scenario). These yearly reductions, qualitatively in agreement with concurrent and higher decreases in MW generation, were likely the effect of the closing of urban activities and material accumulations by citizens at home, partially counterbalanced by seasonal mitigations of restrictions. Although the yearly quantitative incidences of collected RMW_COVID-19 to overall RMW (COVID-19 scenario) were limited or minimal, particularly in provincial territory PT_PU, the temporal evolutions of monthly incidences qualitatively paralleled the occurred evolution of the COVID-19 pandemic, with more evidence in provincial territory PT_PU. As RMW is the remaining stream after the SC of MW, the contextual flow analysis on main separately collected MW fractions showed in 2020 (COVID-19 scenario) resulting decreases (for green waste more evidently, kitchen and canteen waste, and paper and carboard), increases (for glass), or almost invariances (for plastic and metal) in both provincial territories compared to the preceding 2019 (ordinary Pre-COVID-19 scenario).

The LCA results showed that adapted and combined management practices in 2020 (COVID-19 scenario) of direct thermal treatment (WtE) for RMW_COVID-19 (at limited amount) and addressing RMW_NO-COVID-19 in a lower amount to direct landfilling and a prevailing amount to maintained and confined aerobic biostabilisation MBT + landfilling, as occurred in provincial territory PT_MC, improved all the environmental indicators compared to the preceding year, 2019 (ordinary Pre-COVID-19 scenario), but with diversified relative performances. However, adapted and combined management practices in 2020 (COVID-19 scenario) of direct thermal treatment (WtE) for RMW_COVID-19 (but at minimal amount) and addressing RMW_NO-COVID-19 in a lower amount to maintained aerobic biostabilisation MBT + landfilling, while sending a higher amount to direct landfilling, as occurred in provincial territory PT_PU, improved the majority of environmental indicators compared to 2019 (ordinary Pre-COVID-19 scenario), again with diversified relative performances, but this worsened three indicators (CC, HTnc, and Em). Particularly, the contribution analysis of the mentioned indicators highlighted that the prolonged direct landfilling of RMW_NO-COVID-19 implied burdens for the environment; the reduced adoption of the aerobic biostabilisation MBT generated limited savings for the environment; and addressing RMW_COVID-19 to direct thermal treatment (WtE), even if at limited amount, was able to generate some beneficial effects on the environment. Indeed, the hypothetical option of using WtE for the treatment (in addition to RMW_COVID-19) of RWM_NO-COVID-19, originally destined—at diversified amounts—for direct landfilling in provincial territories PT_PU and PT_MC, would have implied improvements for the distinctive CC indicator. At the same time, the WTE option would have represented a strict precaution on the safety management of RMW during a pandemic like the COVID-19 one, by avoiding any waste movement expected during placement operations in the case of direct landfilling or any waste movement and transportation during treatment steps in the case of MBT with diversified locations of MT and aerobic biological treatment facilities.