An attributional Life Cycle Assessment application experience to highlight environmental hotspots in the production of foamy polylactic acid trays for fresh-food packaging usage
Introduction
In 2015, the global plastic market reached 322 Mtons, 58 of which have been produced in Europe (PlasticsEurope, 2016). A significant portion of the total European plastic demand (about 40% of 49 Mtons) is employed for packaging purposes, whilst other sectors include building and construction (20%), automotive (9%) and electrical and electronic (6%) (PlasticsEurope, 2016).
The huge employment of polymers in the packaging sector is due to a combination of several favourable factors such as light weight, flexibility, strength, transparency, impermeability and ease of sterilisation (Siracusa et al., 2008).
This massive consumption of polymeric materials is accompanied by a consistent waste generation that causes several environmental pollution problems. Plastics are mainly produced for durable scopes and, therefore, can persist un-degraded for decades in the environment where they are disposed. In particular, the marine litter issue has raised great environmental concern since it is harmful to ocean ecosystems, wildlife, and humans. Besides cigarette residues, food wrappers/containers, plastic bags, beverage plastic bottles and plastic cutlery are the most important sources of debris (Marine Litter Solutions, 2016). A recent study from Jambeck et al. (2015) indicated that, only in 2010, 4.8–12.7 Mtons of plastics ended up in the oceans.
Waste production and management is currently one of the main focuses of the environmental strategies and policies that have been developed thus far at international and European level. To date, the European Union has promoted a number of industry regulations with the aim of both pursuing environmental objectives and preventing possible risks to human health, and introducing numerous innovations in the classification of wastes as well as in the ways adoptable for their recovery and/or disposal. In this regard, it is now widely accepted that waste management policies should not rely only upon the traditional form of landfill disposals, but should also be focussed upon integrated strategies (Messineo et al., 2012) that provide both development and optimisation of separate-municipal-collection systems, and more environmentally sustainable disposal scenarios.
In the field of plastic materials and finished-products, several disposal scenarios could be considered. In this regard, Michaud et al. (2010) reviewed several types of plastic wastes and the environmental performances of their disposal scenarios, namely recycling, incineration (with energy recovery) and landfill, considering the following environmental impact indicators: ‘Climate change potential’, ‘Depletion of natural resources’, ‘Energy demand’, ‘Acidification’, ‘Photochemical oxidation’, ‘Eutrophication’, and ‘Human toxicity’. They documented that, on an average basis, mechanical recycling is the most environmentally sustainable option for plastic waste treatment as it performs best in almost all of those indicators. This should be attributed to the avoided production of virgin plastics generating, in turn, avoided environmental impacts, and could be maximised by collection of good quality material and replacement of virgin plastics on a high ratio (1–1). Additionally, in their review report, Michaud et al. (2010) highlighted that, for all those environmental impact indicators, incineration (with energy recovery) can be considered on an average basis as the intermediary option, whilst landfill is confirmed as having the worst environmental performance. Despite of this, yet above 30% of plastic wastes were land-filled in 2014 (PlasticsEurope, 2016). So, recycling can be considered as the most environmentally favourable scenario (Rossi et al., 2015), though it results as not being always a viable option. This is the instance case of food packaging systems, like the one investigated in this study, that cannot be recycled due to the organic substances contamination. In such cases, composting remains, therefore, the only alternative to landfill (Kale et al., 2007, Ingrao et al., 2015c).
In this framework, the growing environmental awareness imposes also eco-friendly attributes to packaging products and processes. Amongst other possibilities, the use of biopolymers (i.e. bio-based polymers and/or biodegradable polymers) for the realisation of sustainable food packaging offers several advantages.
The development of materials with biodegradability and/or compostability attributes would in fact significantly reduce the municipal solid waste (Peelman et al., 2013). Water and enzymes produced by microorganisms are firstly responsible of the polymer breakdown to low molecular weight intermediates, which are taken up by the microbial cells to be finally converted into water, carbon dioxide and biomass (Grima et al., 2002, Gigli et al., 2013, Genovese et al., 2014). On the other hand, the exploitation of renewable resources for the synthesis of polymeric materials would lower the consumption of and so dependence upon fossil fuels, although it was reported that, at least in Europe, only 4–6% of the oil and gas production is utilised for plastic production (PlasticsEurope, 2016). It is also worth highlighting that consumers and producers have recently become more sensitive towards environmental issues, and it is consolidated that packaging plays an important role in the overall sustainability of food productions (Licciardello et al., 2014).
Amongst other characteristics, food packaging mainly needs to guarantee food conservation and preservation for long periods, reducing at the same time waste and utilisation of preservatives. Therefore, the selection of packaging systems by food producers should consider both effectiveness, i.e. the ability to maintain quality through shelf life, and efficiency, meant as the containment of environmental impact and costs generated by packaging production and disposal (Licciardello et al., 2017).
To date, due to these strict requirements, not many biopolymers have been successfully employed for food packaging, most common being aliphatic polyesters (above all polylactic acid), starch and cellulose (Peelman et al., 2013).
In this context, Polylactic Acid (PLA) is a family of bio-based and biodegradable thermoplastic aliphatic polyesters. Whilst in the past it has been mostly used for biomedical applications because of the high cost and poor availability (Castro-Aguirre et al., 2016), PLA is recently growing as a greener alternative to conventional packaging. PLA has already received the Food and Drug Administration (FDA) approval for food-contact applications (Ahmed and Varshney, 2011), which makes it usable for food-packaging applications. As a matter of fact, it is currently used to realise short shelf-life food packaging such as trays, drinking cups, sundae and salad cups, over-wrap and lamination films, and blister packages (Ahmed and Varshney, 2011).
Large scale productions of PLA started in 2003 under the trade-name Ingeo by NatureWorks LLC (Natureworks, 2016). Today, Ingeo is produced with a capacity of 150 Mtons a year by ROP of lactide (Castro-Aguirre et al., 2016). The lactic acid raw material can be obtained either by chemical synthesis or by bacterial fermentation, this last being the preferred option by the two main PLA industrial producers, i.e. Natureworks LLC and Corbion.
A detailed description of PLA production, properties and processing falls beyond the scope of this paper, and comprehensive reviews on this topic have been recently published and can be found in the literature (Castro-Aguirre et al., 2016, Chen et al., 2016).
The increasing utilisation of PLA in the food packaging field makes it important and useful to develop studies for the assessment of both environmental impacts and improvement potentials in the life-cycle of PLA-based food packaging products. Several tools and methods are currently available for this purpose: Life Cycle Assessment (LCA) is acknowledged globally to be a valid one.
In this context, the study discussed in this paper regards application of LCA of fresh-food packaging trays made out of PLA with the aim of understanding their effective impacts on the environment as the starting base for the greening of their supply chains.
Section snippets
Environmental assessment in the food packaging field: a literature review
This section provides a brief overview of the most recent publications in the field of LCA assessment of food packaging with a particular focus upon bio-polymeric systems.
Indeed, as reported by Verghese et al. (2012) it is of key importance that LCA shifts from a reflective to an action-oriented decision-making tool, in order to aid packaging designers and producers to reduce the environmental impact of their products.
In an interesting study, 12 polymers (7 obtained from fossil fuels, 4 from
Materials and methods
Life Cycle Assessment (LCA) has been significantly improved over the past three decades, so becoming more systematic and robust for both identification and quantification of the potential environmental impacts associated with a product’s life-cycle (Jeswani et al., 2010). Currently, LCA is used for product/process selection, design and optimisation and can be coupled with simulation techniques and design tools to help companies become fully aware of the environmental consequences that their
Life Cycle Impact Assessment
The study highlighted that the total damage is equal to 1.85 mpt and is mainly due to: the production (for almost 49.7%) and transport (for 25.43%) of the PLA granules; the electricity consumption for their processing (for 12.2%); and for 5.94% to the delivery of the produced trays. All the other processes and phases shown in Ingrao’s et al. (2015c) Tables 4 and 5 account for the remaining 6.73%.
In this regard, a flow chart of the materials, energies and processes causing the highest damages
Monte Carlo analysis
This analysis was developed to create the probability distribution and so to determine the uncertainty associated with the life cycle of 1 kg PLA trays for fresh-food packaging.
To perform the analysis, a 95% confidence interval was considered and 1000 runs were made in order to obtain a really good impression of the standard deviation and graphically represent the probability distribution: the obtained results were shown in Fig. 5.
There is evidence that, based upon the standard of mean obtained
Conclusions and future perspectives
Food packaging systems are worldwide acknowledged to have the main function of containing and protecting foods during their shelf-lives. However, to perform this and other related functions a package generates several environmental impacts in its entire life-cycle. Therefore, it should be designed taking into account not only issues like cost, food shelf-life and safety, as well as user-friendliness, but also environmental sustainability. The latter is required to be addressed and improved to
Acknowledgments
• Dr. Carlo Ingrao has set up the whole study and has coordinated its development, in joint discussion with his co-authors, and has fully developed all parts related to application, discussion and conclusion of LCA.
• Dr. Matteo Gigli has worked upon the introduction and literature review sections.
• Prof. Valentina Siracusa has revised the final version of the paper before submission.
In this regard, Dr. Ingrao warmly thanks both co-authors for their multiple contributions in the development of
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