Food packaging in the circular economy: Overview of chemical safety aspects for commonly used materials
Food packaging facilitates storage, handling, transport, and preservation of food and is essential for preventing food waste. Besides these beneficial properties, food packaging causes rising concern for the environment due to its high production volume, often short usage time, and problems related to waste management and littering. Reduction, reuse, and recycling, but also redesign support the aims of the circular economy. These tools also have the potential to decrease the environmental impact of food packaging. In this article, we focus on chemical safety aspects of recycled food packaging, as recycling is currently seen as an important measure to manage packaging waste. However, recycling may increase the levels of potentially hazardous chemicals in the packaging and -after migration- in the food. Since exposure to certain chemicals migrating from food packaging has been associated with chronic diseases, it is of high importance to assess the safety of recycled packaging. Therefore, we describe recycling processes of commonly used food packaging materials, including plastics, paper and board, aluminum, steel, and multimaterial multilayers (e.g., beverage cartons). Further, we give an overview of typical migrants from all types of recycled food packaging materials, and summarize approaches to reduce chemical contamination. We discuss the role of food packaging in the circular economy, where recycling is only one of many complementary tools for providing environmentally-friendly and safe food packaging.
Based on the observation that today’s take-make-dispose economy is one driver of global environmental change and ecosystems deterioration, the concept of a circular economy has been developed as a tool to further prevent and reduce those detrimental human activities (Geissdoerfer et al., 2017; Ghisellini et al., 2016; Kirchherr et al., 2017; Loiseau et al., 2016; Winans et al., 2017). The circular economy promotes closing loops in industrial systems, minimizing waste, and reducing raw material and energy inputs (European Environment Agency, 2016; Stahel, 2016). Over the past years, the concept has gained importance in policy making (EC, 2017; The Standing Committee of the National People’s Congress China, 2008) and has been increasingly implemented in production, consumption and waste sectors all over the world (Ghisellini et al., 2016). Practical solutions aiming at a circular economy include eco-design, waste prevention programs, and extending the lifetime of products (European Environment Agency, 2016). “Reduce, reuse and recycle” are three important waste management options. The reduction principle targets the minimization of raw material use, energy input, and waste production whereas the reuse principle refers to the repeated use of products or components for their intended purpose (Ghisellini et al., 2016). Recycling is mostly used to save energy, resources, and emissions and decrease the environmental impacts of a material’s use. Although
reduction and reuse are “greener” options (Allwood, 2014), the use of recycled instead of virgin material is generally also perceived as a beneficial solution (Grosso et al., 2017). In the context of packaging waste, reuse and recycling are political means to initiate a change, which is expected to deliver both economic and environmental benefits (EC, 2015). However, only some types of material can be repeatedly recycled and/or reused (e.g., metals, glass). Accordingly, a material meeting these requirements was defined as:
“[…] permanent if its inherent properties do not change during use and through solid-liquid transformation, it can revert to its initial state. This is the case when the material consists of basic components, which are either chemical elements or robust chemical compounds, making repeated use and recycling possible without change of inherent material properties” (Conte et al., 2014).
In contrast to permanent materials, non-permanent materials either undergo gradual chemical changes during the use-phase and/or recycling leading to limited recyclability (e.g., thermoplastics, paper and board), or they are hardly recyclable (e.g., thermoset plastics). Nevertheless, non-permanent materials may be beneficially used in the circular economy, e.g., when using renewable material resources (Conte et al., 2014; Grosso et al., 2017).
In 2014, packaging waste generated in European households and all sectors of the producing industries was estimated at 82.5 million metric tons per year (Eurostat, 2017), and 69.6 million metric tons of packaging waste was collected as part of the municipal solid waste in the US (US EPA, 2016). 65.5% and 51.5% of the packaging waste was recycled in the EU and the US, respectively, but the share of food packaging in these waste streams has not been reported (Eurostat, 2017; US EPA, 2016). However, the markets for food and beverage packaging are large, with an estimated market share of 69% of all consumer packaging used in both categories in total (Rexam, 2012).
Recycling of food packaging waste into new food packaging presents particular challenges, especially with regard to safety issues. The use of recycled food packaging not only increases the possible sources of contamination, but often also the numbers and levels of chemicals that can migrate from the packaging into foods, thereby potentially affecting human health (BMELV, 2012; Muncke et al., 2017; Pivnenko et al., 2016a; V apenka et al., 2016). It is especially important to monitor recycled materials for the presence of non-intentionally added substances (NIAS), including (often unknown) impurities, reaction and break-down products. NIAS can reach higher levels in recycled food packaging, because (i) materials intended for recycling may contain intrinsic contaminants such as dyes, additives and their degradation products, (ii) the material may be degraded during use and/or recycling, (iii) chemicals may accumulate when materials are recycled several times, (iv) previous use and/or misuse of the packaging may contribute to the presence of unwanted and/or unexpected contaminants, and (v) non-food grade materials may enter the recycling stream.