This study got the producers of the raw materials and semi-finished products as well as the producers of the packs in their final form (printed laminates) involved for the first time in order to provide data and review the results.Footnote 5 The films and laminates that are considered in this study were selected in collaboration with a multinational food producer and its film suppliers and converters. Criteria for selection were 1) that films and laminates consisted at least in part of bio-based materials and 2) that they were proven or expected to have comparable barrier properties as the currently used materials. In total, 32 alternatives were studied; of these 32 options, 17 represent ‘Inner Packs’ and 15 are ‘Outer Packs’. Inner Packs are in direct contact with the food and need to provide water and oxygen barriers. The targets are <0.3 g m-2 day-1 moisture vapour transmission rate (MVTR) and <30 cm3 m-2 day-1 oxygen transmission rate (OTR) respectively.Footnote 6 Outer Packs serve as containers (bags) for the Inner Packs, therefore have no direct food contact and require no barrier function. The options studied are shown in Table 2 and the distribution of weight across the different types of materials in Fig. 1. The majority of the films and laminates are at various stages of development, from conceptual development to small-scale test production and are compared with the currently used reference material. Throughout the text we distinguish between films, which consist of one material (e.g. only PP), and laminates, which consist of multiple layers of materials (e.g. PP and paper). In order to make best use of the properties of the various materials, most of the packaging films are multi-material laminates. We consider laminates consisting practically only of bio-based materials, only of petrochemical materials or hybrid films consisting of both petrochemical and bio-based materials. As a consequence, only some of the novel material composites studied are biodegradable (marked with an asterisk in Table 2). The influence of the metallised layer (aluminium, aluminium oxide or silicium oxide) is minimal in composting: the weight of such a layer is usually much less than 1%, thereby fulfilling requirements of composting certification (EN 13432) and there are several metallised biodegradable films on the market that are certified compostable.
The companies involved were supplied with surveys on the inputs and outputs regarding that part of the production process which takes place at their respective production sites. The data they provided was on the level of process inputs (materials and energy) and outputs (materials, waste and emissions). We then went on to perform a plausibility check and to benchmark the received data against other company data as well as database data (where available). When large discrepancies were found, feedback was provided to the company. In some instances this led to a correction of the material inputs or outputs, but in other cases there was a technical explanation for certain differences. This resulted in a consistent data-set which was then incorporated in our calculations. At the end of the project and before submitting the final results, all contributors to the data-sets received a copy of the preliminary report and an opportunity to give feedback.
It is important to note that despite all these efforts, there can still be substantial differences between individual production sites, which are caused by differences in the qualtity of data or the level of technology. In the first case, data quality varied because only some of the suppliers had individual meters installed to measure energy consumption by individual process steps of the entire production process. Most suppliers broke down data from an entire production site or from the average yearly use of an installation to individual films or laminates. In the second case, the level of technology can lead to higher energy use for novel materials compared with ‘conventional’ films for the following reasons: 1) old production lines may be used for small scale production of these films and, in general, these production lines are less energy-efficient than state-of-the-art production lines as used for current conventional materials, and 2) production processes for conventional materials have been fine-tuned over decades, leading to higher throughput, yields and/or energy efficiency of production. Both cases apply especially to novel materials that have not yet been converted into films on a large scale and where, as a consequence, fine-tuning has not yet occurred. We took this inherent bias in the data into account in a sensitivity analysis (see Section 5.1).
Location of production
We distinguished two levels of specificity, i.e. producer-specificFootnote 7 data and regional (supranational) data. Producer-specific data was collected from production sites and can be grouped into information on materials production and processing. Producer-specific data was used for some polymers in primary form (e.g. PLA) and regional data for others (e.g. PP) and similarly for polymer processing such as the production of films from these materials. For example, regional data was used for OPP film but producer-specific data for PLA film because worldwide, there is only one large-scale plant to produce PLA. Similarly, also cellulose films for food packaging (using a novel technology) and a specific bio-based polyester (BBP) represent very specific products that are currently being produced at one or very few locations only. All these materials are novel and unique, the technology is not widely available and considerable progress can be made from one year to another. For paper we also used producer-specific data because of the multitude of different types of paper and their related LCA profiles, which make it difficult to decide which of the existing data sets are representative. On the other hand, bulk materials such as PP granulate are generally purchased from a wide range of sources, nationally and internationally, and therefore no close link exists to a specific producer or production site.
Producer-specific data were used for:
production of polylactic acid (PLA, Vink et al. 2007) and bio-based polyesters (BBP; these are complete life cycle inventories and therefore include producer-specific data on process inputs and outputs, including electricity)Footnote 8
generation of electricity and heat for the production of PLA and bio-based polyesters, for which there is only one producer each and therefore the respective local electricity profile was used (e.g. producer-specific power production in the USA was assumed for PLA)
process inputs and outputs for the production of paper (includes producer-specific consumption of energy but draws on regional data for the electricity mix, see below)
process inputs and outputs for the production of silicium oxide (SiOx) from silica sand
process inputs and outputs for the metallisation of films (with Al, AlOx or SiOx)
process inputs and outputs for the polymer processing to produce films and adhesive layers from polymer granules
process inputs and outputs for the lamination and printing processes.
Regional data were used for
generation of electricity for which we assumed the average European mixFootnote 9 of power generation for fuel types as well as efficiency (SimaPro 2007)
production of process heat for which we assumed an estimated average efficiency and fuel mix for Europe (with the exceptions just explained for power; SimaPro 2007)
production of standard petrochemical polymers, namely polypropylene (PP, as granulate and oriented film)Footnote 10, polyethylene (PE), polyethylene terephthalate (PET), polyvinylidene chloride (PVdC) and polyurethane (PUR, used as adhesive) as well as ethyl vinyl acetate (EVA) for all of which we made use of data-sets that represent a European average (Boustead 1999–2005)
production of inorganic compounds, in particular aluminium (Al), and aluminium oxide (AlOx) for which we used European averages (SimaPro 2007)
transportation by road, rail and ship for which we assumed European averages (SimaPro 2007); for rail additionally also a US average for the transportation of PLA to the harbour was included.
waste management by composting, digestion, landfilling, and incineration (see Section 3.5)
All regional data (such as electricity, heat, plastic granulate production) were assumed for a European setting, with the exception of PLA raw material produced in the USA and transported to Europe. Technical specifications such as tie layer thickness in extrusion lamination also vary among regions. Results were therefore only calculated for packs used and produced in Europe and may not be identical, nor lead to the same conclusions for the USA, Asia or other regions.
Transport of materials
Transportation was considered during all stages of production, i.e. from the transportation of raw materials (such as wood for paper) to the delivery of laminates to the food producers. All manufacturing activities (production of materials, films and laminates) were assumed to occur within Europe, with the exception of PLA granulate production, for which the only large-scale industrial process is located in the U.S. As a consequence, the transportation distances and therefore also the environmental impacts from transportation are much larger for PLA than for the other materials.Footnote 11 Generic, regional data-sets were used for transport by lorry, rail and ship. Lorries were assumed to have a total maximum weight of 40 tonnes and a conservative load factor of approximately 50%. Ships were also considered to transport loads in large quantities and over long distances. Trains were assumed to run predominantly (70%) on electricity in Europe. A separate data-set was used for the transportation of PLA by train in the USA with higher primary energy use to account for lower energy efficiency.
Post-consumer waste collection and treatment
Compared to the impacts of material production, transportation generally causes comparatively small environmental impacts. Due to the short collection distances this is particularly the case for collection & transportation of mixed household waste (including Inner and/or Outer Packs) in municipalities and their surroundings. We therefore excluded post-consumer waste collection from the LCA calculations. For all post-consumer waste treatment options, readily available data from databases and publications were compiled per type of material embodied in the waste. Based on this available information and additional input by experts from the field, we estimated the water and carbon released (as carbon dioxide or methane) from the material during the waste phase for all materials (Hermann and Patel 2007). For landfilling, composting and digestion, values in literature diverge significantly with respect to the carbon released over time (see e.g. 0–100% for PLA in landfill in Bohlmann 2004, 55% for composting of PLA in Iovino et al. 2008, 80% for composting of PLA in Kale et al. 2007). We take this uncertainty into account through uncertainty ranges for the degradation levels of these materials, i.e. high and low carbon storage (resp. low and high level of degradation, see Figs. 4 and 7).