Waste Management 31 (2011) 1133–1138

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Waste Management

journal homepage: www.elsevier .com/locate /wasman

Influence of RFID tags on recyclability of plastic packaging

César Aliaga a,⇑, Beatriz Ferreira a, Mercedes Hortal a, María Ángeles Pancorbo b, José Manuel López b,Francisco Javier Navas b

a Sustainability Division, Packaging, Transport & Logistics Research Center, Albert Einstein 1, 46980 Paterna, Valencia, Spainb Andaltec, Plastics Technology Center, Avda. Principal s/n, Ampliación polígono cañada de la fuente, 23600 Martos, Jaén, Spain

a r t i c l e i n f o a b s t r a c t

Article history:Received 29 July 2010Accepted 28 December 2010Available online 3 February 2011

0956-053X/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.wasman.2010.12.015

⇑ Corresponding author. Tel.: +34 963905400; fax:E-mail addresses: caliaga@itene.com (C. Aliaga), bfe

mhortal@itene.com (M. Hortal), pancorbo@andaltejmlopez@andaltec.org (J.M. López), navas@andaltec.or

The use of Radio Frequency IDentification Technology (RFID) in the packaging sector is an importantlogistical improvement regarding the advantages offered by this technology in comparison with bar-codes. Nevertheless, the presence of these devices in plastic packaging, and consequently in plastic waste,can cause several problems in the recycling plants due to the materials included in these devices.

In this study, the mentioned recycling constraints have been experimentally identified in a pilot scalerecycling study consisting in three recycling tests with an increasing presence of RFID tags. Differences ineach test were evaluated. Furthermore, the quality of the recycled material of each test was studiedthrough the injection and testing of tests probes.

The results of the pilot scale recycling tests did not show a decrease in the quality of the recycled plasticdue to the presence of RFID tags. Nevertheless, several operational problems during the recycling processwere observed such as the obstruction of the screens, which lessened the process yield and created pro-cess interruptions, as well as the loss of extruded plastic during the process.

These recycling constraints cannot be directly extrapolated to the industrial plants due to the differentworking scales. Nevertheless, technological solutions are proposed in order to avoid these recycling con-straints if they appear.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Radio Frequency IDentification technology (RFID) is being intro-duced in the packaging sector due to the logistic advantages re-lated with the utilization of these electronic devices. Thisintroduction is mainly focused in the pallet level because the utili-zation in the item level (product identification) has been difficult tojustify in economical terms. Specifically, 250–300 million of tagswere used in 2006 in the pallet level (IDTechEx, 2006). Further-more, Thoroe et al. (2009) have predicted that in 2016 there willbe 450 times more RFID tags in use than today. Therefore, a rapidincrease in RFID tags consumption is expected, especially in thepackaging sector, in the coming years.

Due to the advantages offered by this technology in comparisonwith barcodes (registration of the whole product supply chain,theft reduction, possibility to register the consumption tendencies,etc.), a progressive introduction of RFID tags in the item identifica-tion is also expected (Oertel et al., 2005).

RFID tags consist of three parts (chip, antenna and substrate)made of a high variety of materials. Some of these substances are

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+34 963905401.rreira@itene.com (B. Ferreira),c.org (M.Ángeles Pancorbo),g (F.J. Navas).

not commonly present in the packaging waste flows (silicon, cop-per, silver) and therefore the recycling technologies cannot beadapted to its presence especially if the consumption of RFID tagsincreases as predicted (Griese et al., 2004; Hilty et al., 2004; Köhlerand Erdmann, 2004; Lincoln et al, 2005). Furthermore, other sub-stances such as adhesives, plastic, aluminium and paper can alsoproduce recycling constraints depending on the recycling processconsidered as demonstrated by the theoretical studies carried outin recent years.

In the frame of the project Globalog (López et al., 2008) the the-oretical recycling constraints caused by the introduction of RFIDtags in the plastic recycling plants were analysed. The resultsshowed a higher potential for the generation of discontinuities inthe recycled plastic due to the presence of unfused metals thatcan be present in the final recycled product.

Furthermore, other studies have analysed whether the presenceof these electronics devices in traditionally non-electronic wastestreams would be able to affect the recycling processes of alumin-ium, paper and board, glass, poly(ethylene terephthalate) (PET)and tinplate as well as municipal waste incineration (Kräuchiet al., 2005).

According to this study and in the concrete case of PET, severalrecycling problems are expected from antennas as well as from thesolder used to join the chip with the antenna. The metals of the an-tenna might cause material inconsistencies in recycled PET and the

Fig. 1. Recycling tests procedure.

Table 1Composition of the RFID tag used.

Component Materials Percentage (%) Weight (g)

Substrate Paper 39.36 0.2302PET 31.07 0.1818Adhesive 24.20 0.1417

Antenna Aluminium 5.32 0.0310Chip Silicon 0.05 0.0003Total 100 0.5850

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solder could release lead during the smelting process. The resultsof this study were deeply analysed by Wäger et al. (2005) estab-lishing that the presence of this substance can become critical ifthe maximum metal content of 100 ppm admitted by the EU Pack-aging Directive were exceeded in recycled packaging materialsafter several recycling processes.

Apart from the theoretical recycling constraints previously de-fined, the presence of RFID tags can also produce important envi-ronmental impacts in landfilling (Hellweg et al., 2005). Due tothat, some studies have proposed to modify the composition ofthese devices. For instance, Kunnari et al. (2009) studied the envi-ronmental advantages of printed electronics in comparison withtraditional electronic devices. According to this study, packagingrecyclability in presence of RFID tags can be improved throughthe utilization of printed electronics. Nonetheless, applications cre-ated using these devices are not at the same level as that of con-ventional RFID tags (Pekkanen et al., 2007). Specifically, thetechnology of printed electronics uses inks instead of metals likesilicon and consequently the conductivity and mobility of the elec-trons is reduced in comparison with traditional RFID technologies.Therefore, these devices present simpler logic structures, lowermemory capacity as well as lower reading ranges (Myny et al.,2009). Due to that, rapid substitution of conventional RFID devicesfor this new technology it not expected.

In order to eliminate the RFID tags prior to the recycling pro-cess, and consequently avoid the possible recycling constraints,two main strategies can be used. Nevertheless, optimum resultscannot be expected. The first strategy is the manual eliminationof these devices. Nevertheless, this alternative reduces the process-ing capacity of the recycling plants due to the introduction of amanual process. Moreover, trained personnel are needed in orderto carry out the process which causes the processing costs to in-crease. Additionally, RFID tags could be separated by means ofinfrared sorting technologies. Nonetheless, these technologies havethe disadvantage of recognizing only the labels directly visible(Gasparian and Lucht, 2000; Groot et al., 2002). Therefore, lowsorting performances can be expected in the case of the tags lo-cated in the bottom of the packaging materials (in contact withthe sorting conveyor).

As previously mentioned, several recycling constraints causedby the presence of RFID tags in plastic recycling processes havebeen theoretically identified. Nevertheless, these investigationshave not carried out experimental studies in order to verify therecycling constrains theoretically established.

The objective of this study is to identify experimentally theinfluence of RFID tags on the recyclability of plastic packaging.With this aim, an experimental recycling methodology, basedon the industrial parameters, has been developed and appliedto three groups of high-density polyethylene (HDPE) packagingwith different concentrations of RFID tags. The analysis carriedout has been mainly focused on the mechanical and aestheticalproperties of the final recycled materials obtained. Additionally,the recycling constraints produced during the process have beenalso analysed.

1 The weight of the substrate, antenna and chip was measured with the analyticalbalance OHAUS AP250D (readability of 0.01 mg, repeatability of 0.02 mg and linearityof 0.03 mm). Moreover, the results obtained were compared with the manufacturer ofthe RFID tag analysed in order to validate them.

2 The introduction of three RFID tags in order to represent the hypotheticalsituation in which both primary and secondary HDPE containers were provided withRFID tags was decided in collaboration with recyclers and HDPE packagingmanufacturers.

2. Materials and methods

2.1. Plastic box and RFID tag

Samples of representative plastic packaging and RFID tagswere submitted to recycling processes. The selected packaging isHDPE box with dimensions of 400 � 300 � 160 mm and a weightof 830 g. This packaging was provided by LOGIFRUIT. The pas-sive RFID tag used is constituted by an aluminium antenna(93 � 23 mm) and a silicon chip on a substrate composed of paper

and plastic. The composition of the RFID tag is specified inTable 1.1

2.2. RFID tags attachment to plastics boxes

Three groups of 15 plastic boxes were selected. No RFID tagswere attached to the first packaging group. One and three RFID tagswere fixed in every box of the second and the third packaginggroup, respectively. The second group represents the situation thatall the boxes are provided with one RFID tag. The third group sim-ulates that not only secondary packaging (boxes) but also primaryHDPE packaging was provided with these devices.2 These threegroups of boxes were subjected to three recycling tests. The proce-dure carried out in the recycling tests is specified in Fig. 1. Further-more, the weight of the different materials introduced in each one ofthe three recycling tests is specified in Table 2.

2.3. Crushing process

A circular saw GWS 780 C-Bosch-Germany was used to cut thethree groups of plastics boxes into small pieces (150 � 150 mm).Subsequently, plastic pieces were crushed in a shredder 250WSGM-Wen Sui-China with a screen width of 8 mm.

Table 2Material composition in the three recycling tests.

Component First recycling test Second recycling test Third recycling test

Packaging Number 15 HDPE boxes 15 HDPE boxes 15 HDPE boxesWeight of HDPE (g) 12450 12450 12450

RFID tags Number No RFID tags 15 RFID tags (1 tag per box) 45 RFID tags (3 tags per box)Weight of paper (g) 0 3.4530 10.3590Weight of PET (g) 0 2.7270 8.1810Weight of adhesives (g) 0 2.1255 6.3765Weight of aluminium (g) 0 0.4650 1.3950Weight of silicon (g) 0 0.0045 0.0135

Total weight (g) 12450 12458.7750 12476.3250

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2.4. Cleaning process

Plastic flakes were manually cleaned in a 10% NaOH solutionduring 10 min at room temperature (25 �C) in order to reproducethe cleaning process carried out in the plastics recycling plantsand facilitate the partial dissolution and elimination of aluminiumand paper present in RFID tag (López et al., 2008). Subsequently,the plastic flakes derived from the three plastic packaging groupswere drained and dried at 80 �C for 16 h (drier 60 KKT-KockTechnic-Germany) in order to eliminate the humidity present inthe material.

2.5. Extrusion process

The crushed and cleaned material derived from three packaginggroups was subsequently extruded and pelletized in an extruderEV38-Mateu&Solé-Spain. This equipment consists of feeding hop-per, extruder screw, water tank and pelletizer. Plastic flakes wereintroduced constantly in the feeding hopper which conducted thematerial to the extruder screw. This component applied the tem-perature needed to reach the molten state (220 �C) to the plasticflakes and forced the extruded material to go through the extruderhead in order to form three constant plastic strands. Furthermore,the extruder head was provided with a 45 mm diameter screeningsystem in order to retain the contaminants. Wide screens (270 lm)were used in order to faithfully represent screening stage carriedout by the main plastic recycling industries. Finally, plastic strandswere cooled in a water tank and pelletized.

2.6. Injection of standard plastic probes

Two different types of standard plastic probes were injectedfrom the pellets derived from three recycling tests carried out.

– Plastic probes A: length (75 mm), minor width (5 mm), higherwidth (10 mm) and thickness (2 mm).

– Plastic probes B: length (80 mm), width (10 mm) and thickness(4 mm).

Table 3Quality results of the injected plastic probes derived from the different recycling tests.

First recyclin

Maximum strength (MPa) ISO 527-2:1993 24.380 ± 0.33Strength at failure (MPa) ISO 527-2:1993 21.320 ± 0.18Elongation at failure (%) ISO 527-2:1993 452.476 ± 16Vicat softening point (�C) ISO 306:2004 127 ± 0.1Charpy Impact resistance (kJ/m2) ISO 179-1:2000 5.1 ± 0.39Density (g/cm2) 0.959 ± 0.003Angle of incidence (20�) Specular gloss: ISO 2813:1994 1.5Angle of incidence (60�) Specular gloss: ISO 2813:1994 10.1Angle of incidence (85�) Specular gloss: ISO 2813:1994 15.3

2.7. Characterization of the standard plastic probes

Plastic probes were subjected to several quality tests in order toevaluate the effect on the product quality derived from the pres-ence of these devices: tensile properties, Vicat softening tempera-ture, Charpy impact properties, density and specular gloss.

The determination of the tensile properties was conductedthrough the implementation of the ISO 527-2:1993. Five plasticprobes A were used in every test. The test was carried out with astrength precision of ±0.5%, elongation precision of ±0.01 mmand a velocity precision of 0.05%. A strain gauge was used as elon-gation measurement system. The plastic probes were held byeccentric cylinder rugged jaws.

The Vicat softening temperature test was carried out with plas-tic probes B and through the implementation of the standard ISO306:2004 and method A50. This methodology uses strength of10 N and a temperature slope of 50 �C/h. Initial temperature is25 �C, final temperature of 160 �C and security temperature of180 �C. The temperature accuracy and the temperature uniformitywere ±0.1 �C and ±0.5 �C, respectively.

The Charpy impact test was performed through the implemen-tation of the standard ISO 179-1:2001 and method ISO 179-1/1eB.Ten plastic probes B were subjected to 2.90 ms�1 speed and 5 Jenergy impacts.

The density of the material was established through the imple-mentation of the standard ISO 1183-1:2004. Plastic probes B wereused in this test.

The specular gloss of plastic probes B was identified by meansof the implementation of the standard ISO 2813:1994 using reflec-tometer geometry of 20�, 60� or 85�.

3. Results

The determination of tensile properties did not reveal outstand-ing variations in maximum strength, strength at failure and elon-gation at failure of the plastic probes derived from the recyclingtests carried out (Table 3). Furthermore, small variations identifiedare not correlated with the level of RFID tags present in the plastic

g test Second recycling test Third recycling test

8 23.946 ± 0.160 24.013 ± 0.2872 20.780 ± 0.120 21.953 ± 0.263.633 428.417 ± 11.725 545.419 ± 20.997

127 ± 0.1 127 ± 0.14.9 ± 0.22 4.7 ± 0.180.959 ± 0.002 0.960 ± 0.0011.5 1.58.2 10.310.5 15.1

Fig. 3. Components of the RFID tag present in the extruder screen.

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packaging. Thus, the results of the pilot scale recycling tests did notrevealed statistically significant influence of the RFID tags on thetensile properties of the recycled HDPE.

Vicat softening point is identical in all the tests carried out.Hence, the results of the pilot scale recycling tests did not provean influence of the RFID tags in the softening point of the recycledHDPE.

A correlation between Charpy impact results and the presenceof RFID tags in the plastic packaging analysed can be observed.Nonetheless, the range of differences is insufficient to prove theinteraction between presence of these devices in the recycling testsand impact resistance of the recycled plastic material (Table 3).

Although low density differences can be observed from thematerial of the third sample, these variations are not sufficient todemonstrate a correlation between the presence of RFID tags andthe density of the recycled plastic material (Table 3).

Results of the specular gloss analysis did not reveal differencesin the angle of 20 �C (Table 3). Nevertheless, result variations wereidentified in the 60 �C and 85 �C angle analysis. These variationsare not correlated with the level of RFID tags presence in the plasticpackaging. Therefore, the results did not prove that the presence ofRFID tags in the HDPE recycling process has a significant influenceon the specular gloss of recycled plastic.

Fig. 4. Rejected material outflow through the extruder vent conduction observed insecond and third recycling test.

4. Discussion

According to the theoretical studies commented in Section 1,the presence of RFID tags in the plastic recycling process could af-fect the final product quality due to the material migration fromthese devices to the extruded material. Nonetheless, the resultsof the quality tests carried out did not reveal a quality reductionin the recycled HDPE. Thus, a minimal presence of these contami-nants in the extruded plastic is hypothesized. In fact, the presenceof paper, PET, aluminium or silicon was visually imperceptible inplastic probes derived from the second and the third recycling test(Fig. 2). Nevertheless, it has to be noted that a dissolution of theHDPE after extrusion was not carried out in order to prove the ab-sence of these substances in HDPE.

Therefore, most of the substances present in the RFID tags couldhave been eliminated during the previous stages of the pilot scalerecycling process. In fact, silicon chips, aluminium and plastic de-rived form the RFID tag could be observed in the screen surface

Fig. 2. Plastic probes derived from second (A) and third (B) recycling test.

Fig. 5. Constant plastic extrusion observed in the first recycling test (A) and interruption due to plastic strands rupture in the second and third recycling test (B).

C. Aliaga et al. / Waste Management 31 (2011) 1133–1138 1137

(Fig. 3). This is due to the fact that the melting point of these sub-stances (aluminium 660 �C, silicon 1414 �C) is higher that theextrusion temperature (120 �C). Thus, these not fused componentswere not able to pass through the screening system with the ex-truded plastic.

However, the presence of paper derived from the tag was visu-ally imperceptible in the screen surface. As previously mentioned,this material was not detected in the recycled material (Fig. 2).That means that the main part of paper fibers was previously elim-inated during the cleaning process. In case that some of the fiberswere no totally disaggregated in water, this material could havebeen burnt during the extrusion at 220 �C. Nevertheless, the totalabsence of paper in the screen surface cannot be proved since dis-solution trials of HDPE were not carried out.

In conclusion, retention of contaminants in the screening sys-tem is a positive factor because the final recycled product qualityis preserved. Nonetheless, several complications were identifiedduring the pilot scale recycling tests related to the progressiveaccumulation of the substances derived from the RFID tags in thescreens as commented below.

The quantity of plastic flakes introduced in the extrusion pro-cess is constant because the screw system forces the materialdeposited in the hopper inside the extruder camera. Furthermore,at the beginning of the recycling process, when the screening sys-tem is not obstructed, the amount of material getting out of the ex-truder head was also constant. Nevertheless, in the second andespecially in the third recycling test, with higher contaminant con-centrations due to the presence of RFID tags, a progressive decreasein the output material was observed.

In turn, this constant accumulation produced the material out-flow through the extruder vent conduction (Fig. 4). This circum-stance represented an important process yield decrease becausethe rejected material could not be directly reintroduced into theextruder.

In addition, the reduction of the extruded material flowingthrough the head of the extruder implied the constant reductionand even the rupture of the plastic strands during the secondand especially during the third recycling test (Fig. 5).

Screen systems used in recycling industries normally presentsimilar screen width but higher diameters than those one used inthe pilot scale recycling analysis (45 mm). Therefore, the pressuredrop caused by the presence of contaminants could be lower inrecycling plants if the plastic flow was similar. Nonetheless, indus-trial recycling processes normally have also higher plastic flows incomparison with the pilot scale recycling analysis carried out.Therefore, it can be assumed that pressures drops are likely to oc-cur in the industrial recycling scale if the concentration of RFIDtags would increase.

In order to avoid this recycling constraint, the use of a self-cleaner screening system in the head of the industrial extruderswas analysed. This technology, currently used by several plastic

recycling companies, permits the mechanical cleaning of theobstructed screens. Furthermore, the process interruption is notneeded.

This system consists of two screens placed in parallel throughwhich the extruded material is flowing (European Patent 0056214-A1). The first of the screens is mechanically removed and cleanedonce it presents a high obstruction level. In that moment thesecond screen starts to filter the plastic material. Several cleaningmethodologies can be used such as water countercurrent, counter-current air, vibration or ultrasound. Finally, the clean screen is placedagain in the initial position.

5. Conclusions

The objective of this study was to identify experimentally theinfluence of RFID tags in the plastic packaging recycling process.The results did not reveal statistically significant quality differ-ences between the recycled HDPE obtained in the different recy-cling tests because substances derived from the RFID tag weremainly retained in the extruder screen system. Therefore, retentionof contaminants in the screening system permitted to maintain thequality of the recycled HDPE. Nevertheless, the progressive accu-mulation of these substances caused the screening system to beobstructed and consequently decreased the extrusion processyield.

This recycling constraint, which cannot be directly extrapolatedto the industrial process because of the different working scales,can be solved in plastic recycling plants through the introductionof self-cleaner sieving systems able to eliminate automaticallythe substances retained in the screens. Furthermore, methodolo-gies to eliminate RFID tags from the plastic packaging prior to recy-cling process can be also used although they also presentimportant limitations.

Finally, it has also to be considered that the recycling tests car-ried out have only identified the constraints produced in the firstrecycling process. Nonetheless, the substances derived from theRFID tags can be accumulated in the recycled materials producingnew constraints in subsequent recycling processes. Therefore, newstudies will have to be focused on this area.

Acknowledgements

The authors are grateful to LOGIFRUIT for providing the plasticpackaging used during the pilot scale recycling analysis. Specialthanks to Jose Luis Estrada for the technical assistance regardingto the technical data of the packaging provided.

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César Aliaga works as a technical researcher in theSustainability and Management Department of ITENE(Packaging, Transport and Logistics Research Center).His activities in Investigation, Research and Innovationare focused in the reduction of the environmentalimpact of packaging wastes through the development ofnew pretreatment processes and technologies toimprove mechanical and chemical recycling processes.

Beatriz Ferreira works as a technical researcher in theSustainability and Management Department of ITENE(Packaging, Transport and Logistics Research Center).She has an expertise of 5 years in Life Cycle Assessment,Ecodesign, Ecoeficience and packaging sustainability.Her current activities in Investigation, Research andInnovation are focused in the development of newprocesses and technologies for the collection, sortingand valorization of packaging waste.

Mercedes Hortal is the group leader of the Sustain-ability and Waste Management Department of ITENE(Packaging, Transport and Logistics Research Center).Her activities in Investigation, Research and Innovationhas been focused in the reduction of the environmentalimpact of packaging waste through the introduction ofstrategies based on Life Cicle Assessment, ecodesign,ecoeficiency, reverse logistics and waste management.

María Ángeles Pancorbo works as a technicalresearcher in the Research and Development ProjectsDepartment of Andaltec (Plastic Technological Center).Her activities in this department are focused in theinvestigation and research of packaging for fresh foodlike vegetables, meat and fish. Besides, she works as apartner in collaborative project with another researchcenters and companies from plastic sector. She also hasbeen working in automotive industry with differentplastic materials.

José Manuel López is the responsible of the laboratoriesof Fundación Andaltec I+D+i: the Industrial Laboratoryfor process optimizations and developments of newtransformation processes in plastics, the Physics Labo-ratory for plastics characterizations and the Dimen-sional Laboratory for accurate measure of parts andtools. He also has been working in automated sortingsystems for technical plastic recycling in automotiveindustry.

Francisco Javier Navas works as a technical researcherin the Research and Development Projects Departmentof ANDALTEC (Plastic Technological Center). His activi-ties in investigation, research and innovation arefocused in the use of waste and by-products fromindustrial activities in order to obtain new plasticcomposites.