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Final draft post-refereeing. Waste Management (2014) 34, 468-474.

DOI:10.1016/j.wasman.2013.10.031. Elsevier is acknowledged.

Environmental burdens in the management of end-of-life CRTs

Laura Rocchetti, Francesca Beolchini*

Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Via Brecce Bianche,

60131 Ancona, Italy

* Francesca Beolchini. Phone: +39 071 2204225; fax: +39 071 2204650; Dipartimento di Scienze della Vita e dell’Ambiente,

Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy; e- mail: f.beolchini@univpm.it

Abstract

We compared the environmental burdens in the management of end-of life cathode ray tubes (CRTs)

within two frameworks according to the different technologies of the production of televisions/monitors.

In the first case, CRT recycling is addressed to the recovery of the panel and funnel glass for the

manufacturing of new CRT screens. In the second case, where flat screen technology has replaced that of

CRT, the recycling is addressed to the recovery of the glass cullet and lead for other applications. The

impacts were evaluated according to the problem-oriented methodology of the Institute of Environmental

Sciences, Leiden University, Leiden, The Netherlands. Our data confirm that in both cases, the recycling

treatment allows benefits to be gained for the environment through the recovery of the secondary raw

materials. These benefits are higher for the “CRT technology” framework (1 kg CO2 saved per CRT)

than for the “flat screen technology” (0.9 kg CO2 saved, per CRT, as the highest possible), mainly due to

the high energy consumption for lead separation from the funnel glass. Furthermore, the recovery of

yttrium from the fluorescent powders that are a residue of the recycling treatment would further improve

the CO2 credit for both the frameworks considered, which would provide a further saving of about 0.75

kg CO2 per CRT, net of the energy and raw materials needed for the recovery.

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Overall, this study confirms that, even with a change in the destination of the recovered materials, the

recycling processes provide a benefit for the environment: indeed the higher loads for the environment are

balanced by avoiding the primary production of the recovered materials.

Keywords. End-of-life CRT, recycling, life cycle assessment, environmental impacts, yttrium.

1. Introduction

In the world of today, and at least in the industrialised areas rather than in the developing countries, the

habit of the repair, re-use and recycling of goods is disappearing, often because the repair of a component

that does not work has a cost that is comparable to the purchase of the new item. This is especially true

for electrical and electronic equipment (EEE). In addition to this reason, another important aspect that

enhances this phenomenon is the rate of evolution of new technologies that become available on the

market. This pushes the consumer to buy the latest version of an EEE, and the old one is discarded,

although it might sometimes still be working. In Europe, contrary to the consumerist habits of the people,

the WEEE Directive (Directive 2012/19/EU of the European Parliament and of the Council of 4 July 2012

on waste electrical and electronic equipment, WEEE) supports the “re-use, recycling and other forms of

recovery of such wastes so as to reduce the disposal of waste and to contribute to the efficient use of

resources and the retrieval of valuable secondary raw materials”. Furthermore, the WEEE Directive sets

minimum recovery targets for the various WEEE categories. For example, according to the Directive,

75% of computers and television sets should be recovered, and 65% should be recycled by 14 August

2015.

The WEEE Directive also establishes that from the WEEE collected separately, at a minimum, the

cathode ray tubes (CRTs) must be removed, as well as the fluorescent powders inside these. Fluorescent

powders contain metals of concern, such as yttrium, which can be recycled as a secondary raw material

(Beolchini et al., 2012). Indeed yttrium used for the red phosphors of monitors is mainly mined in China,

where the biggest reserves are located, and it has been estimated that in 20 to 30 years, these reserves

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might run out of this rare earth metal (OECD, 2010; USGS, 2013). Therefore its recycling is of great

importance.

At present, CRT technology for televisions and computers is obsolete, and it is being replaced mainly

by plasma display panel (PDP), liquid crystal displays (LCD) and light-emitting diodes (LED) flat panel

screens (Hischier and Baudin, 2010). In the developed nations, at least, it is now impossible to find a CRT

computer monitor or television in electronic shops. However, they are still present in the houses of many

people, and they are gradually being replaced by new flat screens. Based on WEEE collection and pre-

treatment market, about 50,000-150,000 tons/year of end of life CRTs are currently collected within

Europe and this flux is not expected to decrease in the next years. In Europe, the end-of-life of CRTs

occurs according to the WEEE Directive. Until about 10 years ago, when CRTs were still produced,

glass-to-glass recycling was a feasible option (Kang and Schoenung, 2005). This consisted of the use of

parts of waste CRTs (i.e., glass, metals, plastic) for the manufacturing of new CRTs, in a closed-loop

process. In particular, the parts that were mostly recycled were the funnel and panel glass. The panel

glass, which is the front part of the display, is essentially barium-strontium glass, with a low percentage

of lead (Andreola et al., 2007a). The funnel glass is the back conical part of the CRT, which is mostly

made of glass and lead, as it was used to shield against the X-rays produced inside the CRT. Lead is

present at high concentrations in the funnel glass (lead oxide can be up to ca. 20%; Andreola et al.,

2007b), and it is a hazardous compound that can pose risks for the environment if it is not correctly

handled. In this regard, previous studies have been carried out to determine the leachability of lead from

CRTs in landfill sites, and to have an idea of its potential risks as a hazard (Jang and Townsend, 2003;

Nnorom et al., 2011).

To minimize the amount of waste destined for landfill sites, efforts need to be directed towards the

recycling options. Now that the previous glass-to-glass recycling is no longer a feasible option, glass-to-

lead recycling represents an alternative strategy. Processes for the removal of lead from funnel glass have

been developed and are currently being applied in the UK by the SWEEEP Kuusakoski Facility

(http://www.sweeep.co.uk/glassrecycling/). In this facility, a furnace that works at 1200°C recovers lead

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from glass, with a capacity of 10 tonnes of funnel glass per day. Consequently, through smelting at high

temperatures, the lead is separated from glass, and the glass can be recycled for different uses in the glass

and ceramic industries (Karamanova et al., 2008; Andreola et al. 2008, 2009, 2010). The fluorescent

powders are another part of CRTs that requires particular attention for handling and disposal. These form

a layer inside the panel glass, which can be removed easily. At present, their recycling is not carried out

by recycling companies, and once they are removed they are disposed of in landfill sites for hazardous

materials (Lee and Hsi, 2002; Nnorom et al., 2011). Our research group has developed a cost-effective

recycling process for the recovery of rare earth elements, carried out within the European HydroWEEE

231962 research projects (Innovative Hydrometallurgical Process to Recover Metals from WEEE,

Including Lamps and Batteries), and its follow-up, HydroWEEE Demo 308549 (Toro et al., 2010;

Rocchetti et al., 2013).

The present study was aimed at the assessment of the environmental impact of different options for end-

of-life CRTs through a simplified life-cycle assessment (LCA). Some estimates of the environmental

loads/ benefits of WEEE recycling have already been given in the literature (Hischier et al., 2005;

Gamberini et al., 2010; Wäger et al., 2011) also dealing specifically with the end of life CRTs

management (Andreola et al., 2007a; Song et al., 2012). This study is addressed at the comparison of

several scenarios for CRT recycling, from the more conservative ones, to the most innovative ones, with

all in accordance with the principles of the WEEE Directive. Two main frameworks for the management

of end-of-life CRT have been taken into consideration: (i) conventional recycling for the production of

new CRT monitors; (ii) recycling of the CRT components for other purposes that are feasible in the flat

screen era. The disposal in landfill sites for hazardous waste has also been taken into consideration, as the

present baseline. Indeed, the study did not exclude that in the change in the destination of the recovered

materials - and consequently in the processes applied - the recycling itself might have too high a load for

the environment.

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2. Material and methods

2.1 Goal and scope

2.1.1 Objective of the study

The main goal of the present study is a comparison of the environmental impacts of two different

frameworks for the management of end-of-life CRTs. In particular, the impacts of conventional recycling

(when CRTs were produced on a large scale) and more recent recycling (when CRTs are considered

obsolete and are being replaced by the flat screen technology) of CRTs are considered. These scenarios

are also compared to the disposal in landfill sites of end-of-life CRTs. Deeper consideration is addressed

to the recycling of yttrium from the fluorescent powders, which exploits a process developed by the

authors and coworkers (Rocchetti et al., 2013), as compared with the disposal of the powders in a landfill

site for hazardous materials.

2.1.2 System boundary

Two main frameworks for the end-of-life CRT were taken into consideration:( i) conventional recycling

of the steel, funnel and panel glass for the production of new CRT monitors, and disposal of the other

parts (the “CRT technology”; scenario 1); (ii) recycling of the CRT components for purposes different

from new CRT monitors (“flat screen technology”), on the one hand , with the recycling of the steel and

panel glass (scenario 2), and on the other hand, taking the recycling also to the treatment of the funnel

glass for the recovery of the lead and glass (scenario 3).

In scenario 2, glass cullet is produced from the panel glass, which is usable in the ceramics and glass

industries (Andreola et al., 2007b). In scenario 3, the lead is recovered from the funnel glass through the

use of a relatively new technology available on the market. The impacts determined by these two

frameworks are compared with disposal in a landfill site for hazardous materials of the end-of-life CRTs

(scenario 0). The “CRT technology” framework represents the old way of CRT recycling, when CRT

monitors were routinely produced and when the steel, panel glass and funnel glass were recycled for new

CRT production, as glass-to-glass recycling. The “flat screen technology” framework is an up-to-date

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recycling strategy, where CRTs are dismantled and most of the materials are recycled for purposes

different from inclusion in new CRTs, in compliance with the WEEE Directive, as glass-to-lead

recycling. In particular for the present study we refer to a smelting process carried out by the SWEEEP

Kuusakoski Facility, that is assumed to be equivalent to a furnace at 1200°C.

In the last part of the present study, attention is focused on the recycling of the fluorescent powders only.

We have compared the impacts in terms of CO2 emissions of a treatment addressed to yttrium extraction

from fluorescent powders, with the impacts of the disposal of the fluorescent powders themselves in a

landfill site for hazardous materials. The process for the yttrium recovery is based on sulfuric acid

leaching and selective precipitation of yttrium as an oxalate salts. All of the details of the process are

reported elsewhere (Rocchetti et al., 2013, Innocenzi et al., 2013a,b).

Manual dismantling (assumed to be without impact) of the several components, together with the cutting

of the CRT itself using diamond cutting technology are included as treatments prior to the recycling

phase. In the recycling scenarios, the treatments themselves and the production of the secondary raw

materials and waste are included inside the system boundary. To compare the impacts of the recycling

options, the disposal in a landfill site of the whole end-of-life CRTs is considered inside the system

boundary. Figure 1 provides a schematic representation of the management options for an end-of-life

CRT. All the phases represented are also those considered for the evaluation of the impacts and the

credits. Scenario 1 includes the recycling of the panel and funnel glass and steel for the manufacturing of

new CRT screens. Scenario 2 refers to the recycling of the panel glass and steel, while scenario 3 includes

also the funnel glass recycling, in the “flat screen technology” framework. Scenario 0 represents the

disposal in a landfill site for hazardous waste of the whole end-of-life CRT.

With the intention being to focus the attention just on the impacts of recycling compared to disposal in a

landfill site, we have avoided the inclusion of the impacts of transport of the CRT to the recycling

facilities and the landfill site. Indeed, according to the local situation considered, different estimations of

transportation distances should be made.

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END-OF-LIFE CRT

RECYCLING

FRAMEWORK

OF MONITOR

PRODUCTION

LANDFILL

(SCENARIO 0)

CRT TECHNOLOGY FLAT SCREEN TECHNOLOGY

NO YES

RECYCLING

(SCENARIO 1)

RECYCLING

(SCENARIO 2)

RECYCLING

(SCENARIO 3)

STEEL

PANEL GLASS CULLET

FUNNEL GLASS CULLET

STEEL

GLASS CULLET

STEEL

GLASS CULLET

LEAD

Fig. 1. Flow diagram of the management options for an end-of-life CRT.

2.1.3 Functional units

The functional unit is one end-of-life CRT, as a 14-inches colour monitor. The weight of the CRT is taken

as about half of the total mass of the monitor (Lee and Hsi, 2002). The composition of a CRT unit is as

follows: panel glass, 3.33 kg; funnel glass, 1.72 kg; steel, 0.45 kg; mixed material, 0.10 kg (steel, copper,

glass, plastic); and fluorescent powders, 0.04 kg. The fluorescent powders contain several compounds,

and among these about 15% to20% is yttrium, an element that is worth recycling (Rocchetti et al., 2013).

The composition of a CRT is not constant, as it changes according to the brand of the CRT monitors and

televisions, and so compositions different from that defined in the present study can be found (Menad,

1999; Lee and Hsi, 2002; Andeola, 2007b; Dodbiba, 2008).

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2.2 Inventory data

The production processes of the chemicals and energy used in the recycling scenarios and the data dealing

with the disposal in a landfill site were obtained from the databases of the GaBi 4.4 software (PE

International), which is integrated with the EcoInvent 2.2 database. The consumption of energy due to the

CRT separator, based on the diamond cutting technology, was estimated from data in the literature (MRT

System International, Sweden). The secondary raw materials (glass cullet, steel, lead) arising from the

recycling were considered as credits for the assessment of the impacts.

2.3 Impact assessment and interpretation

The impacts were evaluated according to the problem-oriented methodology of the Institute of

Environmental Sciences, Leiden University, Leiden, The Netherlands (previously the Centrum voor

Milieukunde Leiden; hence CML), as integrated into the GaBi software that is used for LCA. This

methodology includes the following categories: abiotic depletion, acidification potential, eutrophication

potential, global warming potential (excluded biogenic carbon), ozone layer depletion potential and

photochemical ozone creation potential. The methodology chosen for the evaluation of the impact here

was CML2001 - Nov. 09. Normalization was carried out according to CML2001 – Dec. 07, EU25+3, and

weighting was evaluated following CML2001 – Dec. 07, according to the experts of the Institute for

Polymer Testing and Polymer Science (IKP), University of Stuttgart, Germany, and referred to southern

Europe. Normalization and weighting were referred to the numbers of CRTs collected in Italy, where this

study was carried out. The data were retrieved from annual reports of the Italian Rifiuti da

Apparecchiature Elettriche ed Elettroniche (RAEE; Waste Electrical and Electronic Equipment)

Coordination Centre (Centro di Coordinamento RAEE). According to these reports, the collection in Italy

of CRTs, LCDs and plasma televisions (R3 category) has been in the range 70,000 to 84,000 tons per year

in the period from 2011 to 2013. No information was available dealing with the percentage of CRT within

this flow; nevertheless, we assumed that most of these televisions/monitor (90%) were based on a CRT

technology, considering that flat screen are rather new with respect to cathode ray tubes. In conclusion,

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normalization and weighting was based on 66,000 t/year of waste CRT televisions/monitors, and

therefore on 33,000 t/year of CRTs.

3. Results and Discussion

3.1 Impact of different scenarios for the management of end-of-life CRTs

Figure 2 shows the CO2 emissions in the scenarios considered within the two frameworks with the

different technologies of monitor production: either CRT or flat screen displays. The first framework

refers to glass-to-glass recycling of parts of the end-of-life CRTs, for the manufacturing of new CRT

screens (“CRT technology”; scenario 1). The second framework refers to the recycling of components of

CRTs for other uses, as a result of the change in the technology of screen production and law restrictions

(“flat screen technology”; scenarios 2 and 3).

In scenario 1, a net credit of 1.0 kg CO2-equivalents (eq.) is obtained for glass-to-glass recycling, when

compared with disposal in a landfill site for hazardous materials, which is associated with an impact of

0.8 kg CO2-eq. (scenario 0). Carbon dioxide emissions mainly arise from the energy used to separate the

panel glass from the funnel glass through the laser cutting technology, and the impact due to the disposal

in landfill sites of some parts of the end-of-life CRTs (plastic, glass, copper, steel and fluorescent

powders). Most of the credits are attributed to the recycling of steel and cullet glass, from both the panel

and the funnel glass, for the manufacturing of new CRT screens. Scenario 1, on the one hand, allows the

recycling of many components of the CRTs, and on the other hand, it allows the reduction of the

environmental burden for global warming. For the attribution of credits, we hypothesise that the

secondary raw materials are comparable for quality and function to the primary raw materials, and that

the benefits derived from the secondary raw material production are from the avoidance of primary

material production (Noon et al., 2001). Consequently, we have 1.46, 0.04, 2.13 kg CO2-eq. as a credit

per kg of recovered steel, glass and lead, respectively (EcoInvent Database 2.2).

Turning our attention to the current framework of “flat screen technology”, here, two scenarios were

taken into consideration. Scenario 2 addresses the recycling of the steel and panel glass, while scenario 3

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includes a further step directed towards the recycling of the funnel glass. In scenario 2, there is a net

credit towards the environment equal to 0.7 kg CO2-eq. The credit is derived from the recycling of the

steel and panel glass in the form of cullet, while the debit is from the electricity required and the impact

due to the disposal in landfill sites of the waste materials, included the funnel glass. Although scenario 3

is highly energy consuming, there is a net credit of 0.9 kg CO2-eq., mainly due to the recovery of lead,

together with steel. With this last typology of recycling, less waste is conferred in landfill sites and more

secondary raw materials can be recovered. As seen also in other studies that have considered the whole

life cycle of a CRT, the end-of-life represents the phase that produces benefits for the environment,

through the recovery of the secondary raw materials and the consequent avoiding of primary production

(Andreola et al., 2007a, Duan et al., 2009; Song et al., 2012).

Fig. 2. Carbon dioxide emissions for the different options in the management of an end-of-life CRT (see

Figure 1 for details on the considered scenarios).

Figure 3 shows the impacts of the chosen management options on the other endpoint categories. The

option of scenario 0, which represents the disposal of an end-of-life CRT in a landfill site for hazardous

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materials, has the worst performance, as expected. Indeed, there are only burdens for the environment in

the impact categories of abiotic depletion, acidification, eutrophication, ozone layer depletion,

photochemical ozone creation, and human toxicity. Taking into account the other scenarios in the

framework of the “CRT technology” and “flat screen technology”, we observed that the greatest benefits

for the environment in the impact categories of eutrophication and ozone layer depletion are seen for

scenario 1, in which the glass of the panel and funnel of the CRT are recycled for new devices. In this

scenario, the impacts associated with energy consumption and disposal of some of the parts of the end-of-

life CRT in landfill sites are relatively low, and they are largely exceeded by the benefits due to the

recycling of the materials. In scenario 2, in the framework of the “flat screen technology”, we assisted

with a situation where the impacts determined by the disposal in a landfill site increase compared to

scenario 1, while there are no credits, because the recycling of funnel glass is not possible. Finally, in

scenario 3, again in the framework of the “flat screen technology”, where the greatest efforts towards the

recycling of the end-of-life CRTs are made, the lowest impacts in the categories of abiotic depletion,

acidification, photochemical ozone creation, and human toxicity are achieved. Although in this scenario

the impacts are determined by the energy required to separate the lead from the funnel glass, these are

highly counterbalanced by the benefits derived from avoiding the production of lead.

The data were then normalised and weighted, using the factors that are correct for southern Europe, as the

area where the present study was carried out. The greatest impacts are again for scenario 0, and

conversely the lowest benefits compared to the other 3 scenarios, and these are generally observed for the

categories of global warming, photochemical ozone creation and abiotic depletion (Fig. 4).

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Fig. 3. Impacts in the categories of abiotic depletion (a), acidification (b), eutrophication (c), ozone layer

depletion (d), photochemical ozone creation (e) and human toxicity (f) of the management options

considered for an end-of-life CRT (see Figure 1 for details on the considered scenarios).

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Fig. 4. Data normalised (CML2001 – Dec. 07, EU25+3) and weighted (for southern Europe) for scenarios

0 (a), 1 (b), 2 (c) and 3 (d) for the management of 33,000 t of end-of-life CRTs, average value of the

annual collection in Italy, in the period 2011-2013 (see Figure 1 for details on the considered scenarios).

To have a global view of the different scenarios, the impacts determined in the chosen impact categories

were then summed into a single index. As for the results presented above, the disposal in landfill sites of

the whole end-of-life CRTs causes a burden to the environment. On the other hand, all of the other

recycling scenarios considered from this wider view point provide benefits. These data show that as

expected, scenario 3, provides the best performance , despite the highest requirements in terms of energy,

(Fig. 5). Therefore these achievements indicate that the efforts made for finding and applying

technologies that can be used to address the virtual complete recycling of end-of-life CRTs is rewarded

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both from the prospective of the production of secondary raw materials, and from an environmental point

of view. Bearing in mind the legislative acts and the importance of increasing the good habit of reuse and

recycle, management options that are aimed at the maximisation of the recycling of end-of-life CRTs (as

well as other waste) are undoubtedly the best options to choose. This objective should be pursued also in

future years when flat screen televisions start to be disposed of in greater numbers (Chancerel et al.,

2012), even if lower impacts are generally associated with LCD than with CRT disposal (Noon et al.,

2011).

Fig. 5. Global environmental impact of the different scenarios for the management 33,000 t of end-of-life

CRTs (see text for details).

3.2 Impact of the treatment of fluorescent powders

This final section is dedicated to the maximisation of the recycling of end-of-life CRTs. As stated in the

Introduction, fluorescent powders are a small component of CRTs that have to be removed, according to

the WEEE Directive. In the wake of the results of a previous study carried out by Rocchetti et al. (2013),

we report here the impact in terms of CO2 emissions of a hydrometallurgical treatment that is aimed at the

recovery of yttrium from fluorescent powders from end-of-life CRTs (Fig. 6). This treatment includes a

leaching operation with sulfuric acid for yttrium extraction, followed by selective precipitation of yttrium

oxalate from the leach liquor (Innocenzi et al., 2013a, 2013b; Rocchetti et al., 2012). For the sake of

15

comparison, Fig. 6 also shows CO2 emissions associated with the disposal of fluorescent powders in a

landfill site for hazardous waste, that is the current management practice. It can be observed that the

treatment of the fluorescent powders provides a credit of ca. 0.75 kg CO2 per CRT, net of the energy and

raw materials needed for this recovery, due to avoiding the production of yttrium (Koltun and

Tharumarajah, 2010). As the impact of the primary production of yttrium is high, and considering the

relevance of yttrium in technological applications, the data presented here provide further incentive to

encourage and improve treatments aimed at the recycling of the components of end-of-life WEEEs.

Fig. 6. Carbon dioxide emissions of the two options for the management of the fluorescent powders of an

end-of-life CRT.

4. Conclusions

In the present study, we have presented different options for the management of end-of-life CRTs, and we

have considered the environmental impacts and the benefits resulting from the avoidance of primary

production of some of the materials. This analysis has included the change in the destination of the

recovered materials, associated with a change in the technology for television/monitor manufacturing,

from cathode ray tube to flat screen. The achieved results evidenced the highest credit for the

environment (1 kg CO2 per CRT) in the case of a closed loop approach, where the recovered CRT glasses

are used for new CRTs. Relevant credits are also provided by the recycling process in the flat screen era,

with 0.70 and 0.90 kg saved CO2 per CRT, in the two scenarios without and with lead recovery from the

16

funnel glass, respectively. Indeed, in this last case, the high load for the environment due to the lead

recovery process was balanced by avoiding the primary production of lead. Last, but not least, the

yttrium recovery process from fluorescent powders, residue of the CRT recycling process, gave a further

saving of 0.75 kg CO2 per CRT, due to the avoided impact of primary production of yttrium.

As a whole, this analysis confirms the environmental advantage of all the considered scenarios for CRT

recycling, included those without a closed loop approach that are now being considered due to a progress

in the manufacturing technology.

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