Innovations to overcome the current waste problem caused by single-use plastics in the pursuit of a circular economy

The paper understands sustainability as described in Elkington’s Triple Bottom Line (1998) with the three dimensions People, Planet, and Profit or dimensions that reflect a company’s responsibility. People stands for social sustainability and appreciation towards human capital in and outside the company. This refers to the contribution to health, equity and prosperity of society as a whole (Elkington 1998). Planet, in this context, stands for ecologically sustainable development, i.e., “development that meets the needs of the present without risking, that future generations will not be able to meet their own needs” (Hauff 1987, p. 46). Profit refers to economic sustainability, that is achieved when a company is engaged in long-term value creation and ensuring solvency and market share. In particular, this systematic literature review focuses on environmental sustainability. Planet, as it addresses the prevention of plastic waste and thus the impact on the environmental side. Profit appears in the discussion as a bridge from the materials to business and the achievement of greater social welfare, while the People dimensions is not specifically mentioned in this review, but exploring this aspect might be relevant for future research. In line with Günther and Schneidewind (2017), the research focus set here is not intended to disregard the importance of the social component or compromise on the social compatibility of innovations.

Innovation can be defined as “the commercial or industrial application of something new—a product, process, or method of production” (Schumpeter 1934, p. 19). Eco-innovation, green innovation or sustainable innovation are some of the terms used, often synonymously, in relation to sustainability and innovation (OECD 2010). Several perspectives and concepts exist, as do various definitions (Maier et al. 2020). Schaltegger and Wagner (2011), for example, use the term sustainable innovation, without a clear definition, and point out different types and characteristics as well as the connection to entrepreneurship, the associated private and societal benefits and the need for interaction of multiple stakeholders. The OECD uses the term eco-innovation and defines it as “the implementation of new, or significantly improved, products (goods and services), processes, marketing methods, organisational structures and institutional arrangements which, with or without intent, lead to environmental improvements compared to relevant alternatives” (see OECD 2010, p.40).

This paper uses the term “innovations for environmental sustainability”. In the authors understanding, this refers to innovations that utilize renewable resources and by-products, such as food wastes, with awareness to end-of-life scenarios and circular economy.

One step towards the sustainable development of plastics production and consumption is the transformation from a linear economy into a circular economy. The basic principles of this are avoidance, reduction, reuse and recycling, so that the utilized materials remain in use for as long as possible (Pinheiro de Souza et al. 2022), recyclable waste is minimised and the amount that can be returned to a cycle is maximised (Hatzfeld et al. 2022). Various studies have already shown the positive effects of this model on the efficient use of resources (Günther 2008), business practices (Koh et al. 2017), infrastructure (Korhonen et al. 2018) and employment (Repp et al. 2021). By considering and preserving resources, the circular economy offers the potential to develop an economic model which takes impacts on biodiversity into account (Junge et al. 2023).

There are various approaches to integrate a product in a further life cycle. For these reasons, the 9R-concept of the circular economy by Potting et al. (2017) is taken as a further basis to justify the framework developed by the authors. It consists of ten strategies in total (R0 = Refuse, R1 = Rethink, R2 = Reduce, R3 = Re-use, R4 = Repair, R5 = Refurbish, R6 = Remanufacture, R7 = Repurpose, R8 = Recycle, R9 = Recover). The lower the sequential number, the higher the circularity of resource consumption. Thus, in R9-Recover, the end-of-life solution is the incineration of the material, from which primarily energy is recovered that does not reflect a direct product cycle. Consequently, one can talk about a linear economy. With R0-Refuse, on the other hand, the product itself is replaced by another product that can take over the task, or the function of the actual product becomes completely redundant. In addition, the higher the circularity, the more socio-cultural change must precede (Potting et al. 2017). The developed framework will combine primarily the R9-Recover and the R8-Recycle strategies with the biodegradability of a certain product, which results in a so-called “circular bioeconomy of natural resources” (Kacprzak et al. 2022). Goswami and O´Haire (2016) describe biodegradability as the decomposition of a certain material after the interaction with biological elements.

Packaging plays a particularly important role in the food industry, as it is necessary to protect food and is also an important carrier of information and part of the marketing strategies of companies. It is therefore not surprising that a large proportion of the packaging waste generated each year comes from this sector (Pinheiro de Souza et al. 2022; Süßbauer et al. 2022; Zhao et al. 2020). Regarding the requirements on food packaging, there are two different point of views: the producer’s and retailer’s as well as the consumer’s perspective. The European Parliament and the European Council (EC Regulation 1935/2004, 2004, Article 3) strictly specify, that the packaging of food has to inherit the following four basic properties:

The used materials shall not:

Breaking these down into two different points of view, the German Consumer Office (2022) says, from the producers´ view, the packaging has to look appealing, should enable transportation without damage, should be stable to be stacked and should be light, to minimize transportation costs. On the contrary, the consumer requires the package to be informative, easy to handle, environmentally friendly and not harmful to the food it is protecting. This means, that in the end all of these characteristics have to be fulfilled by the packaging, to 1) be allowed to be retailed in the first place and 2) to appeal to consumers in the long term.

Food products are to be protected by different packaging stages, which is ensured by primary, secondary and tertiary (transit) packaging levels (Saghir 2004). Primary protection is in direct contact with the product thus the materials must not react with the product to protect it from natural, chemical, and other contaminants (Chasta et al. 2019). The secondary layer is used for additional security and mainly for the neat logistical organization and bundling of individual containers. For long distance transportation and bundling of products, the secondary packs are loaded into tertiary packaging such as drums, crates, cartons, bundling material on pallets, etc. (Saghir 2004).

This review will mainly focus on alternatives as well as different approaches and characteristics of the primary packaging levels. The primary level in particular stands out from conventional packaging materials in the food industry due to its special requirements.

Plastic polymers can be classified as either fossil-based or bio-based. Bio-based polymers have a significantly lower environmental impact compared to those derived from crude oil. Therefore, it is recommended to exclude fossil-based polymers from the product portfolio in the future (Piergiovanni & Limbo 2016). Further common packaging materials are ceramic, metal and cellulose as well as combinations of the named materials to create different barrier properties and characteristics. Ceramic packaging splits up into glass and ceramic earthenware, like stoneware and pottery, whereas metal is categorized as mostly aluminium or (stainless-) steel-coated packaging. With around 40% of all materials, the most used are probably cellulose-based materials, most common in paper or cardboard form (Piergiovanni 2009) (Tables 1, 2).

The main environmental problem is the “inadequate treatment and inefficient management of the increasing volume of plastic waste” (Pinheiro de Souza et al. 2022, p. 2). Commercially available plastics are often not biodegradable due to their chemical composition, so they end up in landfill or are incinerated, releasing many greenhouse gases (GHG) such as CO₂ (Plastics Europe 2021). This is especially important considering the relatively short lifespan of regular plastic packaging in the food sector or a conventional plastic bag compared to cotton, aluminium, or something similar. Furthermore, the production of fossil-based plastics accounts for approximately 8% of the global oil and gas production (Lambert and Wagner 2017). Due to the fact that common Polyethylenterephthalat (PET) plastics and many similar kinds have a half-life starting from 58 years for bottles, up to 1200 years when looking at plastic pipes (Chamas et al. 2020), the plastic will not disappear or biodegrade into compostable materials in a reasonable time. This results in large amounts of waste being disposed of and accumulating in ecosystems and polluting and disrupting them in the long term (Lamberti et al. 2020; Pinheiro de Souza et al. 2022). A prominent example is the Great Pacific Garbage Patch in the Pacific Ocean, which currently contains around 80,000 tonnes of plastic and is estimated to be three times the size of France (The Ocean Cleanup 2022). Apart from wildlife and environmental damage, this marine pollution affects the human food chain due to chemicals absorbed by animals and eventually finding their way to the food which is consumed. Moreover, it also comes with economic aftermaths. A reported 13 billion dollars per year must be spent, just to handle the impacts on tourism, fisheries, aquaculture and clean-ups, not including the impact on human health and marine ecosystem (The Ocean Cleanup 2022).

The data shows that the selected time frame was suitable as the findings steeply go up from 2021. One paper each was published in 2013, 2017, 2019, and 2020. In 2021, 6 of the papers were published. The greatest number of reviewed publications are from 2022 with an absolute number of 8. The steep increase of publications in 2021 and 2022 might be due to work by the EU Commission (2022) on bio-based, biodegradable and compostable plastics, which started with an official consultation in 2021 and a published report in 2022. This overview (Fig. 2) indicates the increasing relevance of the topic and mirrors the current awareness for sustainability. The authors note the limited number of papers, which is linked to the keywords and observed inconsistent use of bio-based plastics-related keywords, e.g. green composites, biopolymers, bioplastics etc. It was further noted that, especially in material science literature, the keywords are usually mainly substance specific e.g. chitin and not all authors include keywords related to bio-based plastic. To avoid further confusion between different terms and properties, such as bioplastics and biodegradable plastics, this paper uses the term bio-based plastics or polymers, as recommended by the European Commission (2022), which refers to the origin of the material, not its biodegradability.

Full size image

The analysis showed that most of the papers dealt with substitutes for conventional fossil-based single-use plastic, i.e. bio-based plastics, as well as additives that change the characteristics of bio-based plastics towards even more practical properties. Only a few papers focused specifically on surrounding innovation challenges and opportunities, such as consumer behaviour and regulations. As the two main topics of bio-based plastic sources and additives are related, they will be presented together in the next section, followed by challenges and opportunities.

Based on the results of this SLR, it is possible to categorizes the materials according to their origin. The classification is shown in Table 2. There are three main categories: industrial by-products, raw material and food wastes. In this paper, industrial by-products are understood to include all substances that occur as waste or unused resources in production processes. Based on the reviewed literature, there is only a separation between the food industry and other industries, e.g., paper and pulp. Here, raw materials are all substances whose extraction and processing are geared towards producing bio-based plastics. This overview can be seen as a supplement to existing classifications such as Pinheiro de Souza et al. (2022), according to which biodegradable plastics can be obtained from biomass, with the aid of microorganisms, from biotechnological processes or petrochemical products.

It is shown that a significant proportion of the materials utilized for biobased plastics originate from the value chain of the food industry. As Scarpi et al. (2021) state, the fibres emerge from all stages of the manufacturing and consumption process, as by-products and as food waste at different sections of the value chain. According to the Food and Agriculture Organization of the United Nations (FAO), a third of the globally produced food is wasted or lost (Gustavsson et al. 2011). Therefore, the use of these resources is crucial to reduce wastage and to create a higher value. This corresponds with the goals of reducing consumption, use of natural resources, and minimization of waste production towards a circular economy by Potting et al. (2017). This transformation of waste is an approach for the development of a circular economy. Even if the value of the food cannot be restored, developing packaging material from the remains is a significant increase in value compared to incineration or rotting for energy. A resource of higher value is reintroduced into the cycle. At this point, Potting et al. (2017) and Scarpi et al. (2021) agree in their thoughts on the handling and value of apparent waste products. This process also addresses the concerns of Heller et al. (2019) who state that the waste of food is a much more serious problem in today’s society than packaging waste. Therefore, instead of using fossil or new natural resources, already existent material should be processed. Further, the value chains of the food and packaging production are connected to each other because food waste from retailers and consumers is not recovered (R9-strategy) by landfilling, composting or incineration, instead it is repurposed (R7-strategy) to new bio-based packaging material (Heller et al. 2019; Potting et al. 2017). Making such a process possible, a whole new supply chain construction is necessary. Scarpi et al. (2021) confirm, that such a strategy needs to combine considerations regarding food waste as feedstock and “the creation of new products, processes and markets [as well as] the technology to support new, sustainable industrial processes” (p. 585).

Despite all these promising thoughts and approaches, this seemingly sustainable solution is built on an unsustainable system. If human society is producing at least one third of nutrition just to throw it away, there is a huge wastage of resources. This starts with land use, labour force, cruelty against animals and ends with emissions of GHG. So, in a short-term perspective, the use of food waste as a raw material for environmentally sustainable plastic alternatives is a better option than recovering (R9-strategy). But, in a long-term perspective, this form of plastic production could worsen the avoidable food wastage as it seems to be a useful application, which justifies such actions. Excluded from this are wastes from food production that arise as by-products, e.g., leaves, peels, feathers, or skins. These are unavoidable in the current food industry and should therefore be utilised as resources for further value creation. Under this condition, an environmentally friendly production system for food-derived bio-based plastics could be established. Incorporating the resource nexus approach, which considers the links between multiple resource and socio-economic components (Bleischwitz & Miedzinski 2018), could provide insightful assessments for this transition process.

Especially for single-use products and packaging, the material’s value chain is really short. Additionally, as mentioned before, the impacts of plastics on the environment are tremendous. Hence, it is not only important to develop plastics from natural and renewable substances, but it is also necessary that the created material is biodegradable, recyclable or repurposable in order to reduce the continuously growing amount of plastic waste.

A material is defined as biodegradable if natural composting with the aid of microorganisms or with abiotic factors (e.g., hydrolytic degradation, environmental temperature) is possible (Eriksen et al. 2014) and organic material rich in nutrients is released as humus (Mahpuz et al. 2022). The biodegradability also depends on the type and nature of the material, the soil and its chemical-physical conditions (Mahpuz et al. 2022; Blinková & Boturová, 2017). Based on the SLR, it is evident that most of the materials, except PLA, fulfil the characteristics of compostability. PLA is only biodegradable in industrial composting facilities and not under real environmental conditions (Mahpuz et al. 2022; Rudnik & Briassoulis 2011; Siakeng et al. 2020; Venkatesh et al. 2021), which is why it does not alleviate the existing waste problem in the environment. This is consistent with the findings of Pinheiro de Souza et al. (2022) that less than 50% of bio-based plastics are biodegradable and further reinforces the recommendation of the European Commission (2022) to differentiate between the terms bio-based and biodegradable. Taken this into account, a framework was developed to emphasise the different end-of-life scenarios that newly established materials may have (Fig. 3).

Full size image

The first aspect of the framework concerns the source material of the bio-based plastic and its origins and characteristics. The next step in the framework distinguishes between biodegradable and non-biodegradable polymers. As mentioned above, more than 50% of bio-based plastics are biodegradable. This is the result of processing the materials into a substance that resembles fossil plastic in its structures and properties are attempted to be achieved (Mahpuz et al. 2022; Mansingh et al. 2022). Thus, there are conflicting objectives regarding the material properties.

The last stage of the framework is the decision on how to treat the packaging after it has been used. To create a circularity, the material should be recycled as much as possible and in a high quality, so that the products remain in the cycle for a longer period of time. This results in a reduction in the use of materials, energy, and land, as well as a decrease in pollution (Evode et al. 2021). Therefore, the recycling is the preferred option as an end-of-life solution. If this is not possible, the biodegradable material can be repurposed as a commodity in agriculture, e.g., as compost fertilizer, animal food, or treatment for water and soil (Chollakup et al. 2020). Due to this downcycling process, the material leaves the circle of packaging production but is still useful for another value chain. The last preferred option is the recovery where the plastics are incinerated und used as a source for energy supply. Even if this creates an opportunity to use renewable energies, the feedstocks are lost.

Of course, there are also some challenges associated with the implementation of a circular plastic economy. The manufacturing effort for plastic from recycled packaging increases significantly compared to the use of raw material (Pinheiro de Souza et al. 2022). Therefore, the design of a value chain as a cycle may very well lead to an increase in resource consumption at another point. As an example, Potting et al. (2017) cite the effort involved in cleaning and dismantling contaminated plastics, which requires a lot of energy, often derived from fossil fuels. Furthermore, the composting of biodegradable waste in landfills releases large amounts of GHG, such as methane and carbon dioxide and water pollution, which in turn has an impact on the climate (Mahpuz et al. 2022; Deckert 2016; Venkatesh et al. 2021). Moreover, according to Deckert (2016) the recyclability of materials is limited due to their nature and the stresses and strains they undergo during the recycling process. That is the reason why a product cannot be returned to the cycle an infinite number of times, which is reflected in a recycling rate of less than 100%. This ultimately results in downcycling, which reduces the value of the product (Deckert 2016). In Potting’s model, this corresponds to stage R9-Recover.

Important players for innovation and implementation of new bio-based plastic substitutes are companies. For producers as well as retailers, it is important that the packaging materials for food provide standards in quality, safety, and efficiency (Mahpuz et al. 2022). In addition to requirements regarding health and damage protection, there are different demands for visual features and shelf life in general. The packaging should be transparent to allow a view of the product inside (Moussaoui et al. 2022; Zeng et al. 2022). Compared to conventional plastics, this seems to be quite complicated because of the properties of the different materials. Also, the condition of transparency can change over time as the components react to environmental influences, which could lead to an unsightly appearance (Mahpuz et al. 2022; Klinmalai et al. 2021; Mansingh et al. 2022). This creates the risk of food being discarded prematurely due to the appearance of the packaging, which has a negative impact on food waste prevention.

The next challenge to a colourless transparency is to achieve a protection against UV-radiation, because this also negatively impacts the shelf life (Ashraf et al. 2021; Etxabide et al. 2022). In this context, different bio-based plastic substitutes possess antioxidant, antibacterial, and antimicrobial characteristics, which help to expand the durability and decrease food loss during transport and storage (Mahpuz et al. 2022; Klinmalai et al. 2021; Varghese et al. 2022; Zeng et al. 2022). There are findings that the use of bio-based plastics could extent the durability of meat and dairy products as well as fruits, vegetables and baked goods (Adhikari et al. 2022; Mahpuz et al. 2022; Moussaoui et al. 2022; Klinmalai et al. 2021).

Moreover, businesses are crucial in communicating and promoting new products to customers. They can influence the consumer awareness towards sustainable products in various ways. It is possible to raise attention for bio-based products for low-aware customers and to increase the awareness of those with an already high environmental conscience (Scarpi et al. 2021). A first step to reach even more customers could be educational campaigns, created and executed by institutions and companies to promote environmentally sustainable materials used in packaging (Rose Amnah 2015; Süßbauer et al. 2022). An additional approach, provided by Scarpi et al. (2021), is to label environmentally friendly and sustainable sourced products to draw customers’ attention to them. This could make it easier for them to recognise and evaluate environmentally sensitive brands and their offers. Following such proposals could mean drawing higher popularity and therefore greater sales of products packaged in sustainable materials.

Due to the current waste problem, manufactures and retailers should be obliged to actively seek and implement solutions for managing the end-of-life of plastic packaging. As mentioned above and in regard of Potting et al. (2017), possibilities of improving the reusability, recyclability, repurposability, and recovery of disposed material should be considered by corporates (Mahpuz et al. 2022; Pinheiro de Souza et al. 2022). Additionally, the high effort of changing the current value chain is compensated in the long term by time, energy and cost savings in production as well as increasing independence from fossil raw materials and suppliers of virgin material (Korhonen et al. 2018). These factors should be an incentive for companies to use their responsible role to support change in the plastics industry.

As it is the same for all innovations and products, there needs to be a customer base who is willing to purchase and use the items. The advantage of bio-based plastic alternatives is the growing awareness and demand for environmentally friendly products by the society. The new materials are beneficial for consumers due to the fact that they are cheaper than fossil materials and at the same time fulfil the ecological-sustainable requirements (Scarpi et al. 2021).

But despite that, there are still obstacles to the adoption and use of the new bio-based materials, especially concerning their application in contact with food. As long as there is a perceived risk that is higher than the perceived value of an item, it is unlikely that it is adopted by the customers (Scarpi et al. 2021; Wang and Hazen 2016). Bio-based plastics could be perceived as products with a poorer quality, shorter durability, and inferior loading capacity compared to fossil products (Brockhaus et al. 2016; Scarpi et al. 2021; Wang and Hazen 2016). Furthermore, from a customer perspective, there could be long-term risks regarding their own health and the safety of the food. This should be considered especially when using recycled materials or substances made from food waste or bio-based degradable materials respectively.

Another obstacle for the application of innovations like bio-based plastics is simply the lack of knowledge about certain options, possibilities, and processes. As Scarpi et al. (2021) stated, not knowing about the existence, the performance, or the quality of a product, will affect the perception of the value of an article and the purchase intention. This should be the starting point of corporate communication towards customers because the perceived value is a relevant factor in switching intentions. Consequently, it is necessary to inform and educate customers about features of new products in order to increase their perceived value.

In addition, there is a connection between the value system and self-identity of customers and their purchases. If both attitudes lead to consciousness for and attraction to environmentally friendly products, it is more probable that a customer will choose bio-based plastics. Especially emotional, conditional, functional as well as social and ecological value concepts influence consumer behaviour and preferences towards environmentally sustainable purchasing decisions (Khan and Mohsin 2017; Lin and Huang 2012).

In the end, there is no distinct forecast for the reaction of the market and customers to the new products, especially if continuously changing markets are considered, as well as rising consciousness and demands by customers towards a sustainable value and supply chain.