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LCA of thermoplastics recycling

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Thermoplastics make up roughly 80% of the plastics produced today. There are hundreds of types of them and new variations are being developed. But not all thermoplastics are recyclable. The most commonly recycled thermoplastics are PE, PP, PS and PVC. In this study, real data from the industry is used in the analysis of the environmental impact of plastics recycling by means of the application of the LCA methodology to the products and processes involved in mechanical plastic recycling of black HDPE for extrusion or blow moulding coming from industrial scrap. The results obtained were compared with assessments made by other authors and with the impact associated with the manufacturing of virgin thermoplastic according to databases. The interpretation of these comparisons leads us to conclude that the recycling process has been optimised over the past years, thus reducing its environmental impact. Furthermore, the clear advantages from the eco-efficiency viewpoint of plastic recycling against direct manufacturing from petroleum are highlighted.
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LCA of thermoplastics recycling
Daniel Garraín1, Pilar Martínez2, Rosario Vidal1, María J. Bellés1
1GID, Engineering Design Group, Dpt. MEC, Universitat Jaume I Castellón
Av. Sos Baynat s/n, 12071 Castellón (Spain)
2AIMPLAS, Technological Institute of Plastics
València Parc Tecnològic, C/ Gustave Eiffel, 4, 46980 Paterna-Valencia (Spain)
garrain@uji.es
Keywords: LCA, thermoplastics, recycling, HDPE, LCI
ABSTRACT
Thermoplastics make up roughly 80% of the plastics produced today. There are hundreds of types of them and
new variations are being developed. But not all thermoplastics are recyclable. The most commonly recycled
thermoplastics are PE, PP, PS and PVC.
In this study, real data from the industry is used in the analysis of the environmental impact of plastics recycling
by means of the application of the LCA methodology to the products and processes involved in mechanical
plastic recycling of black HDPE for extrusion or blow moulding coming from industrial scrap. The results
obtained were compared with assessments made by other authors and with the impact associated with the
manufacturing of virgin thermoplastic according to databases. The interpretation of these comparisons leads us
to conclude that the recycling process has been optimised over the past years, thus reducing its environmental
impact. Furthermore, the clear advantages from the eco-efficiency viewpoint of plastic recycling against direct
manufacturing from petroleum are highlighted.
Introduction
In the past 30 years, global plastic consumption has multiplied by 10, reaching an estimated value of 100 M
tonnes per year. However, this technological development has not foreseen the implications of product recycling.
The recycling of these materials is a must given their limited or no biodegradability and the fact that they cause
the depletion of a non-renewable resource like petroleum (they account for 4% of Europe’s total petroleum
consumption), in addition to their visual impact on landfills.
Thermoplastics make up roughly 80% of the plastics produced today. There are hundreds of types of them and
new variations are being developed. But not all thermoplastics are recyclable. The most commonly recycled
thermoplastics are PE, PP, PS and PVC.
The most widespread recycling process is mechanical recycling, by which plastics are recovered from the waste
stream. Plastics undergo sorting, shredding and washing processes to yield plastic flakes, pellets or powder. The
material hence obtained is ready for its subsequent transformation into new products. This type of recycling is
the best option from the environmental perspective when compared to chemical, physicochemical or energy
recovery recycling, although it is not optimised from the economic viewpoint [1].
Goal and scope
The goal of this study is to perform the life cycle assessment of the products and processes involved in the
mechanical recycling of thermoplastic materials coming from industrial waste. The results are then compared to
data provided by recycling machinery manufacturers and bibliographical data from other authors. Furthermore,
the impacts of recycling are compared to those associated with the production of virgin plastics.
Life Cycle Inventory (LCI)
1. Recycling industry
Real data from the industry were used in the analysis of the environmental impact of plastics recycling through
the application of the LCA methodology to the products and processes involved in mechanical plastic recycling
from industrial scrap for extrusion or blow moulding of black HDPE.
Figure 1 shows the flux diagram of black HDPE along with the amounts of materials and energy used. A mass
and energy balance was performed for system inputs and outputs. In this case, transport of HDPE from plastic
processing plants to recycling plants has been taken into account as well.
Figure 1: Flow diagram of black HDPE recycling
2. Bibliographical data
i) White et al.[2] carried out a LCI on the integrated management of solid waste –including plastics-, analysing
the inputs and outputs of recycling processes in order to assess their environmental impact. The data available
come from an internal report [3] of a recycling plant, which provides detailed information on mass and energy
flows in the process of recycling rigid HDPE bottles.
ii) Perugini et al. [4] published a life cycle assessment of mechanical recycling of plastic waste as a follow-up to
a previous study [5]. Their assessment encompassed a comprehensive set of Italian firms dedicated to the
mechanical recycling of plastic, which they compared from the environmental point of view to other alternatives
such as incineration or mere landfilling. They also analysed the impact caused by other innovative post-recycling
processes such as low-temperature pyrolysis or high-pressure hydrogenation, confirming these processes are
more environmentally friendly than conventional ones.
The inventory data collected by the authors corresponding to material and energy flows are related to the
production of recycled PET and polyethylene from plastic waste. For this study, only the data related to the
production of 1 kg of mechanically recycled polyethylene were taken into account.
3. Manufacturers of recycling machinery
The recycling process comprises fragmenting or shredding plastic waste, heating above melting point, extruding
and finally pelletizing plastic. In our case, solely energy consumption figures of machinery –extracted from
technical data provided by machinery manufacturers- were considered, dismissing additives, transport, lubricants,
etc. Specific consumption figures were obtained from production rates and required power inputs.
The firm Schulz & Partner (Heilbronn, Germany) possesses a PE or PP washing and drying line model TC 500
by Italian manufacturer TECNOFER, which they use to process plastic waste prior to extrusion and pelletizing.
Plastic waste enters the line as film or bales, and comes out as clean, dry bits ready for extrusion. Considering its
processing capacity and total power of all elements in the line, a specific consumption figure was obtained per
weight unit of PP or PE.
Sorting of raw
materials
Pelletizing and
washing
Water treatment
Extrusion
Industrial
Waste
(packaging)
Valorizable waste (PP,
paper, wood, Al)
Plastic bulk, filters and injection samples
Laminated HDPE,
other waste
Black HDPE pellets Evaporated water
Crushed HDPE
Anionic surface
-
active agents
NaOH
Fresh water
(agricultural grade)
Mud
(65%
humidity)
Black HDPE concentrate
Zinc stearate
Fresh water
(washing)
Fresh water (extrusion)
AlCl3
Lime
Contaminated
water
Purified water
Metallic filters
Valorizable metallic filter waste
Total valorizable waste
Recirculated purified water (washing)
Technical data for extrusion and subsequent pelletizing were obtained from Austrian manufacturer Artec. A
mean value from several extruding machines was considered.
These data were used to estimate total energy consumption of the process of plastic recycling.
4. Production of virgin HDPE
The data regarding the manufacturing of HDPE come from the following databases, found in Simapro 7.0 impact
assessment software:
o Buwal 250 [6].
o Ecoinvent [7].
o PlasticsEurope (Association of Plastics Manufacturers in Europe) [8].
Impact assessment
The following table shows the environmental impact of each of the processes analysed after inventory data
collection. The impact assessment methodology followed was CML 2 baseline 2000, as developed by the
Institute of Environmental Sciences in Leiden (The Netherlands). The normalisation factor set employed
corresponds to Western Europe in 1995 [9].
Table 1: Normalised eco-profile of 1 kg of HDPE (recycling or manufacturing)
Abiotic resource
depletion
Global warming
GWP100 Acidification Eutrophication
Recycling industry 1,15E-14 5,82E-14 6,13E-14 8,06E-15
White et al. [2] 3,63E-14 3,25E-13 4,10E-13 4,80E-14
Perugini et al. [4] 1,38E-14 9,43E-14 1,15E-13 1,12E-14
Machinery industry 1,45E-14 9,89E-14 1,21E-13 1,18E-14
Buwal 250 [6] 2,04E-13 4,47E-13 4,47E-13 1,05E-13
Ecoinvent [7] 2,08E-13 3,94E-13 7,83E-13 1,09E-13
PlasticsEurope [8] 2,15E-13 3,91E-13 7,82E-13 1,04E-13
Figures 2 and 3 illustrate the comparison between the environmental impact caused by the recycling process
studied and the impact caused by recycling HDPE derived from petroleum.
The differences between the data from the recycling firm and those from machinery firms are attributed to the
fact that the latter offer machinery capable of recycling plastics with higher melting points than those of HDPE,
whereas the recycling firm possessed one line exclusively dedicated to the recycling of HDPE, with highly
optimised shredding and washing processes.
The inventory compiled by Perugini et al. [4] comes from Italian polyethylene recycling firms, just like the one
considered. The similarities of the impacts in both cases can be appreciated.
When comparing results with White et al. [2], it must be noted that their data dates back to the 1990s, when
plastic recycling was not as optimised and profitable as it is today. This leads to high environmental impact
results, as observed in figure 2.
Figure 2: Eco-profile of recycling 1 kg of HDPE, by data source
The recycling of HDPE is compared to the production of virgin HDPE in figure 3. Recycled HDPE is clearly
more eco-efficient.
Figure 3: Eco-profile of 1 kg of recycled HDPE vs. virgin HDPE
0,00E+00
1,00E-13
2,00E-13
3,00E-13
4,00E-13
5,00E-13
6,00E-13
7,00E-13
8,00E-13
9,00E-13
Abiotic resource depletion Global warming GWP100 Acidification Eutrophication
Recycling industry
Buwal 250
Ecoinvent
PlasticsEurope
0,00E+00
5,00E-14
1,00E-13
1,50E-13
2,00E-13
2,50E-13
3,00E-13
3,50E-13
4,00E-13
4,50E-13
Abiotic resource depletion Global warming GWP100 Acidification Eutrophication
Recycling industry
Machinery industry
White et al. [2]
Perugini et al. [4]
Discussion and conclusions
There are noteworthy similarities between the eco-profiles using data from HDPE recycling firms. When
comparing these results to those from the 1990s, we can appreciate how recycling processes have been optimised,
especially in terms of electricity consumption.
The difference between the eco-profiles of recycled and virgin plastic is also considerable. These results come to
support the development of new recycled products for a sustainable development.
Acknowledgements
This work has been developed as a part of the project of the National Environmental Science and Technology
Programme of the R&D National Programme 2004-2007 (Ministry of the Environment of Spain): Reference
566/2006/1-2.4. “Análisis del ciclo de vida de residuos de materiales biodegradables y biocompuestos, como
alternativa a los polímeros convencionales (Life cycle assessment of the waste of biodegradable materials and
biocomposites, as an alternative to conventional polymers)”.
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Life cycle assessment (LCA) methodology is generally considered one of the best environmental management tools that can be used to compare alternative eco-performances of recycling or disposal systems. It considers the environment as a whole, including indirect releases, energy and material consumption, emissions in the environment, and waste disposal and follows each activity from the extraction of raw materials to the return of wastes to the ground (cradle-to-grave approach). The study refers to the whole Italian system for recycling of household plastic packaging wastes. The aim was to quantify the overall environmental performances of mechanical recycling of plastic containers in Italy and to compare them with those of conventional options of landfilling or incineration and of a couple of innovative processes of feedstock recycling, low-temperature fluidized bed pyrolysis, and high-pressure hydrogenation. The results confirm that recycling scenarios are always preferable to those of nonrecycling. They also highlight the good environmental performance of new plastic waste management schemes that couple feedstock and mechanical recycling processes. © 2005 American Institute of Chemical Engineers Environ Prog, 2005
Article
Goal, Scope and Background. The object of the study is the Italian system of plastic packaging waste recycling, active until 2001, that collected and mechanically recycled the post-consumer PE and PET liquid containers. The phases of collection, compaction, sorting, reprocessing and refuse disposal were individually analysed and quantified in terms of energy and material consumptions as well as of emissions in the environment. The work is the result of a joint research project with the Italian Consortium for Packaging (CONAI), carried out in co-operation with the main Italian companies active in the field. The main aim was the quantification of the real advantage of plastic container recycling and the definition of criteria, at the same time environmentally compatible and economically sustainable, for their management. Main Features For each of the unit processes, and in order to increase the data quality, all the data of interest were collected during technical visits to several selected plants active in Italy or deduced by official documents and certificate declarations of the same companies. To allow comparison of resource consumption and environmental pollution from different management scenarios producing different products, thebasket of products method was applied. Results The results indicates that the production of 1 kg of flakes of recycled PET requires a total amount of gross energy that is in the range of between 42 and 55 MJ, depending on whether the process wastes (mainly coming from sorting and reprocessing activities) were sent or not to the energy recovery. The same quantity of virgin PET requires more than 77 MJ. The energetic (and then environmental) saving is so remarkable, even for PE, being 40–49 MJ for the recycled polymer and about 80 MJ that for the virgin polyolefin. The calculations were made with the reasonable assumption that the final utilisation can use the virgin or the recycled polymer without any difference. Conclusions and Outlook The analysis defined and verified a suitable tool in the field, based on objective data, for comparing different coherent scenarios of waste management politics. This allows one to propose the extension of the tool under different collection schemes, as well as for different systems of packaging recycling. As an immediate consequence of the success of the present study, the joint-research programme with CONAI has been extended for another three years. The focus will be the Italian system for paper and paperboard recycling and that for all plastic packagings. In parallel, a different study has been scheduled with reference to the integrated solid waste management of the Regione Campania, the largest and most populated area in the South of Italy.
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