Packaging solutions in this category include the Triple Bottom Line (TBL) approach based on economic, social, and environmental impacts (Jain and Hudnurkar, 2022) and their integration into the life cycle of the packaging material—from cradle to grave—throughout each stage of the supply chain. Terms like environmentally friendly and green packaging are often used as synonyms for sustainable packaging, therefore those were also put in this category; however, these are not necessarily synonyms. When describing sustainable packaging, authors either used their own definitions or the definitions by the Sustainable Packaging Coalition (2005, 2009) or the Sustainable Packaging Alliance (2004). These definitions offer a valuable starting point, but have also been criticized earlier in literature (Grönman et al., 2013). It is also noted that sustainable packaging always comes with an environmental impact, therefore ‘more’ and ‘less’ sustainable packaging would be a more appropriate term (Boz et al., 2020), or the concept of ‘sustainable packaging’ should be deconstructed, because this absolute value is rather utopic. Moreover, these terms do not refer, at least directly, to the potential of reducing food waste, although this may be sometimes the case, and are mostly focused on avoiding unnecessary packaging, overpackaging or single-use plastics, thus reducing the direct environmental consequences of the use of the materials.

Packages in this category are designed according to the principles of the circular economy. Recyclable, recycled, reusable and zero waste are often considered as similar terms, and so grouped together. Circular packaging can be seen as one way toward sustainability due to the reduction in new resources entering the system. It can be regarded as a subcategory of sustainable packaging, however the concept shifts the focus more to the life-cycle (resource cycles) and to the end of life of the material (Testa et al., 2020), in spite of the fact that avoidance should be the highest priority in the decision tree. Re-introducing a material to avoid the use of virgin resources may at times be costly, or very difficult to be proven safe (Nerín et al., 2022; Tsochatzis et al., 2022). Reusing, mechanical or chemical recycling are all within the circular packaging definition, and the origin of the material (e.g.: from renewable sources, fossil fuel) or the amount of resources (energy, raw materials, etc) are not included in the definitions. Their end of life can also be quite varying, for example, in the case of compostable materials, their conditions for compostability may vary from simple household composting to complex industrial composting. Similarly, recycling can be chemical, mechanical, and may result in a downgrade of the material. Furthermore, in this category of terms, there is no reference to the specific functions (i.e., protection) that the packaging material may impart to the food.

This is a diverse and slightly ill-defined category, since packages in this category can also be those labeled “compostable,” “bio-degradable,” “oxo-degradable,” or “bio-based.” These packages are highlighting the origin of the packaging material and/or its ability to degrade. The materials can be made from renewable sources (e.g.: second generation feedstocks), or are in some cases fossil-based. Plastic material made from bio-based material may not necessarily be bio-degradable. This broad group of packaging could be regarded as a subcategory of sustainable packaging, however, one must consider the material’s origin, and especially in the case of displacement of food crops with biomass waste or residues, e.g., unavoidable agricultural or forestry wastes as well as their potential degradability at end of life alternative (Cruz et al., 2022). Moreover, such terms are a big source of confusion not only among consumers, therefore could lead to an environmental risk in the long term.

Packages in this category fulfill certain aspects of sustainability (Lewis et al., 2007, 2010; Santi et al., 2022), which looks at broader solutions for sustainable packaging, leading to effective, efficient, cyclic and safe practices. For example, refills, innovative and lightweight packages indicate solutions which bring significant improvements to current practices, and to some extent also are easily demonstrating to the end user (i.e., consumer) the improved function; for example, they lead to minimizing food waste, decrease plastic littering, or improving waste sorting are indicated in the definitions. These can be also considered as a subcategory of sustainable packaging.

Based on the numerous (38) expressions collected, one can conclude that, unfortunately, literature uses too many terms, of which many are very similar (see synonyms such as ‘Environmentally friendly’, ‘Eco-friendly’, ‘Ecologically responsible’, ‘Ecologically conscious’, ‘Pro-environmental’, ‘Eco-designed). In many cases the definitions are superficial and cannot be used outside of the context they belong to. The definitions treat the three pillars of sustainability (natural, human, and economic capital; Hansmann et al., 2012) unequally, and the environment gets the most focus. Moreover, there is little emphasis on the role (responsibility) that the actors (i.e., consumers, managers) may play, and, more importantly, these terms do not relate the packaging together with the product, which in food is a grave simplification. The use of technical terms also may present communication challenges, as this may hinder the public (mostly consumers, but also journalists and managers) to understand, evaluate and make appropriate practical decisions. Hence, the current definitions of sustainable packaging are too complex and cannot be communicated well because consumers and other stakeholders do not have enough abilities (will) to process this information (Dörnyei et al., 2017). All these factors can lead to the so-called problem of ‘information overload’, or worse, to misleading communication of sustainable packaging (greenwashing).

Packaging exists because of the product. This is especially true for food products, where packaging can be regarded as an added service (Löfgren, 2005; Löfgren et al., 2008). Therefore, the packaging solution needs to ensure, first and foremost, without compromises, the quality and safety of the food it contains (Han et al., 2018). However, this sometimes includes over-packing with the use of unnecessary long shelf life (often forced by retailers) instead of optimal shelf life or ‘just necessary packaging’ (Coffigniez et al., 2021). Food packaging and shelf life extension is a balance between the packaging and waste. Longest shelf life sometimes is not necessary, especially in areas where logistic and technological infrastructure make it possible to consume food in a much shorter time or if products are on average sold much before the expiration date. When long distances are instead critical to provide consumers with healthy and affordable choices (i.e., remote locations) long shelf life is critical to avoiding food waste. This means that the materials have a verifiable means to ensure – among others – no chemical components in amounts that can endanger the health of the consumers should migrate from the environment (and from the packaging material) into the food, or release micro/nanoplastics in the environment. Such a product centered approach of packaging is very unique to the food packaging field and significantly complicates the adoption and validation of universal sustainable packaging solutions.

To evaluate and measure the sustainability of packaged food products, the product and (and not necessarily only the primary) container should be regarded as a unit with a common environmental footprint, and the material should not be evaluated alone itself, nor the food (Meherishi et al., 2021). In particular, for food, it should be emphasized that primary packaging prevents food waste, which is a very important aspect of the environmental footprint (Dilkes-Hoffman et al., 2018; Molina-Besch et al., 2019). Food waste contributes to a significant amount of the total greenhouse gas emissions of the food, and once it is processed, all resources used are part of the final balance. The package is only a portion of the entire footprint (Crippa et al., 2021). Hence, no sustainable solutions can be found where the quality and shelf life of the product are compromised.

Environmental impacts related to food packaging could be the result of direct (refer to the impacts caused during production, consumption, and disposal) or indirect (refer to the impacts generated by the industries that supply the final production point) effects on the environment (Lindh et al., 2016). While the negative direct effects of packages are usually considered in sustainability evaluations, the positive or negative indirect effects that packaging could provide through food product protection, supply chain, or sorting and end of life are not always included. In case of packaged food products, the two environmental effects need to be considered together (de Koeijer et al., 2017) as including indirect effects may show very different overall environmental impact, depending on the food-packaging system (Williams and Wikström, 2011; Wikström et al., 2016).

Packaging is a people-made novel entity (Persson et al., 2022), and it will always have a negative environmental cost; it is not possible to have packaging materials with no impact on the environment. All packaging material has an environmental footprint (Morgan et al., 2022), and there is a cost associated with the resources used, even when recycled or reused. In the case of food products, it is important to quantitatively measure the environmental footprint of the food, from cradle to grave, including the packaging material with its own life-cycle (if circular). Furthermore, the added value the package can offer needs to be taken into consideration, together with any littering or recovering efforts (consumer behavior is very important in the late stages of the life cycle), as well as any reduction in food waste. Food packaging then should be considered as an additional, valuable resource integral part of the food product, and can no longer be considered of low value, ending up in litter or waste.

As with many resources employed in the food system, complete avoidance of the packaging use should be the preferred solution, but only if this does not have a detrimental effect on the safety and quality of the product or on minimizing food waste (Beitzen-Heineke et al., 2017; Williams et al., 2020). In particular, minimizing food waste needs to be the primary goal. On average, packaging is estimated to account for only 10% of the total energy inputs for one person’s weekly consumption of food, while it plays a critical role in ensuring that the other 90% of energy inputs to the supply chain are not wasted (Verghese et al., 2015). Instead, a critical hierarchy needs to be established, and it has to be related to an overall decrease of the footprint, as quantified for example using a life cycle assessment (LCA), which takes into consideration all resources, as well as the end of life and food waste (Nguyen et al., 2020), and a social life cycle assessment (SLCA), which is aimed at evaluating social and socioeconomic aspects of product-packaging units (Jørgensen, 2013).

A well designed package needs to fulfill basic important functions, such as protection, storage, loading and transport, marketing, sale, promotion and communication, and impart trust of the food to the consumer, a ‘guarantee’ of its quality and consistency (Molina-Besch et al., 2019; Ketelsen et al., 2020); all of this while also satisfying any sustainability requirements originating from the entire life of the product-package unit, including, but not limited to, logistics, production, engineering, material sources, end of life functions such as sorting, composting or recycling (Lindh et al., 2016; Wandosell et al., 2021). A sustainable packaging can be achieved by operating on three different levels: (1) at the level of raw materials (through the use of recycled raw materials, renewable resources or deriving from the revaluation of industrial processing waste); (2) at the production level (through more energy efficient processes); and (3) at the level of eco-design (through the reduction of thicknesses and weights; the realization of mono materials, fully recyclable structures in alternative to heterogeneous, multi material packaging, which are harder to sort; the realization of biodegradable and/or compostable packaging, in alternative to fossil fuel-based materials). In order to provide sustainable packaging with satisfying performance suitable for food applications, it is fundamental to implement appropriate innovative functionalization strategies; among these, the use of nanotechnologies, blending and/or filling technologies, the development of active packaging, the realization of high performance active and passive coatings and layers orientation. The combination of multiple requirements and sustainability implementation possibilities makes sustainable packaging development an extremely difficult balancing act which is hard to measure. As a consequence, in practice, sustainability in packaging development is still limited (de Koeijer et al., 2017).

Packaging sustainability is defined and measured differently depending on the discipline (Jiménez-Guerrero et al., 2015; Martinho et al., 2015; Han et al., 2018; Herbes et al., 2020; Zeng and Durif, 2020; Wandosell et al., 2021; Zeng et al., 2021). For example, from the materials engineering perspective packaging sustainability means balancing resource use while optimizing the properties of the packaging source material (e.g.: ease in processability, low energy consumption, or less use of chemicals in production or end of life). In this case sustainability is mostly measured by LCA (Steenis et al., 2018). The process is not easy, especially if data input is poor (Radonjič, 2019), but at least with LCA it is possible to give an exact answer between scenarios. On the other hand, from a marketing perspective, packaging is an essential tool to communicate and influence consumers (Dörnyei and Lunardo, 2021), deliver information, and aid in decision making. In this case the effectiveness of a package is mostly measured by consumers’ willingness to buy, and sustainability is only applied with designs that facilitate sales goals. Companies have clear ambitions with regard to improving food packaging sustainability; but not at the expense of product’s market potential. However, as far apart as the two disciplines are at the current time, they must work together to find optimal sustainable packaging solutions for food products.

When developing innovative sustainable food packaging solutions, challenges of technological nature, concerning materials and processes, can be encountered. For example, in an attempt to replace fossil-fuel-based plastics, the use of renewable materials in bio-plastics is steadily growing (Cruz et al., 2022; Rosenboom et al., 2022; Shlush and Davidovich-Pinhas, 2022). Although the use of bio-plastic is associated with positive consumer perception (Herbes et al., 2018), these materials may not be necessarily compostable, biodegradable, recyclable, or may be a challenge to sort depending on the economies of scale in the various municipalities. In addition, some technological properties of these materials are still not fully satisfactory, hindering their large market uptake. Among these, raw material variability, a too narrow processing window, inherent brittleness, poor barrier properties, scarce impact and thermal resistance. As for the processes, a fundamental requirement for the implementation of innovative sustainable packaging solutions on a large scale is industrial feasibility. In general, non-invasive innovations compared to conventional technologies (e.g., redesigning packaging by reducing thickness and weight) are excellent options for improving current practices and are generally welcomed and accepted by all stakeholders. On the other hand, more invasive innovations (for example the use of new materials or “niche” technological innovations, not compatible with conventional manufacturing processes or machin-ability) often raise a number of additional problems along the value chain, will rarely meet industrial acceptance and may create confusion and slow down acceptance and implementation (Morone and Imbert, 2020).

Determining the sustainability of the food packaging solution by omitting the context in which the solution exists can lead to incorrect evaluations. The context, i.e., country of origin, consumption region and supply chains, specific product features, and user (consumer) habits, plays a major role in determining packaging sustainability (Lindh et al., 2016). For example, an LCA analysis of packaging for olive oil demonstrated that while glass bottles are preferable for local distribution, tinplate cans are more sustainable for long-distance distribution (Guiso et al., 2016). Therefore, including more context-specific factors into sustainable packaging evaluations will lead to more sustainable and transparent solutions, toward true harmonization of sustainable packaging in the marketplace.

Sustainable packaging is not yet properly defined by law, current regulations are not comprehensive and often misleading to some extent, which makes it a challenge to design truly sustainable packaging solutions. Similarly, unnecessary packaging is also an ill-defined concept. Labeling regulations are also limited: uses of claims (symbol, color) which falsely convey that the package is more sustainable than the alternative in the market can be misleading and lead to greenwashing (Boz et al., 2020). It is then clear the need for a shared regulatory framework, which constitutes a guideline for the sustainable design of packaging and is supported by consumer engagement, through a more transparent communication (Dörnyei et al., 2022).

Recent studies highlight that consumers show increasing concern about sustainability issues, and sustainability affected food consumption is becoming a genuine driver of choice (Trivium Packaging, 2022). It is critical therefore that consumers are provided with information on the sustainability of the food package, and that there are clear instructions also on how to dispose of the food package at the post consumer phase. Indeed, the consumer is mindful of the environment but is often poorly informed about specific issues, for example, the degree of sustainability of the various materials and the context in which they are used. Consumers are often not able to distinguish between industrial composting and household (home-) composting, in addition, there is no real control (composition, rest of plastic fragments, etc) on the compost made at home, which may result in more littering. Recent evidence also shows that the sustainability rating of European consumers and scientific LCAs currently are misaligned (Otto et al., 2021). Moreover, complexity in use of terms (as already described above) also hinders consumer understanding of truly sustainable packaging choices. Consumer knowledge about packaging sustainability needs to be improved to prevent and avoid greenwashing at consumer but also at industry level.

As one of the main contacts in the consumer journey, the package itself has increasingly become an effective way to communicate with consumers and other stakeholders about sustainability (Wyrwa and Barska, 2017). Consumers use multiple attributes and cues, such as packaging design (Otto et al., 2021), verbal attributes (e.g., text labels, logos and other cues), symbolic and text-based cues (Dinh et al., 2022) to evaluate the sustainability of the food product (such as product composition or shelf-life) and its packaging (such as showing garbage sorting instructions; Magnier and Crié, 2015). This dual task can sometimes confuse users if not sufficiently explicit.