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Sustainable Food Packaging

Ana C. Mendes1, Gitte Alsing Pedersen2

1Nano-BioScience Research Group, DTU-Food, Technical University of Denmark, Kemitorvet

202, 2800 Kgs. Lyngby, Denmark

2Division of Risk Assessment and Nutrition, DTU Food, Technical University of Denmark,

Kemitorvet 202, 2800 Kgs. Lyngby, Denmark

Abstract

This article presents the outcome of a literature review that gives a general overview of plastic

materials (petroleum and bio-based) used in food packaging. The functional properties, chemical

safety concerns and environmental impact of plastic materials are presented in a combined and

holistic perspective. Furthermore, the most relevant indicators for sustainability of food packaging

are introduced, aiming at increasing the awareness of food producers about the relevant factors

throughout the life cycle of the combined system of food and packaging to create more sustainable

food packaging.

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Table of Contents 1. Introduction .................................................................................................................................. 3

2. Materials used in food packaging ............................................................................................ 5

2.1. Considerations to select a food packaging material ........................................................ 7

2.2. Materials used in food packaging: properties and applications .................................. 10

2.2.1. Petroleum based materials ........................................................................................... 10

2.2.2. Bio-based materials ....................................................................................................... 11

2.2.3. Alternative materials for food packaging .................................................................. 21

3. Sustainability of food packaging ........................................................................................... 23

3.1 Production of plastic packaging ......................................................................................... 26

3.2. End of life of plastic packaging .......................................................................................... 28

3.2.1. Degradation and composting of plastics .................................................................. 29

3.3. Recycling of plastic .............................................................................................................. 32

4. Summary and perspectives ........................................................................................................ 36

5. Concluding remarks ................................................................................................................. 40

Acknowledgments ............................................................................................................................ 41

References ......................................................................................................................................... 41

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1. Introduction

Packaging materials are part of our daily life. When it concerns foodstuffs, they plays a pivotal

role to ensure that food products are preserved with a desired lifetime and subsequent

optimization of space during handling, shipping, and storage for a minimum of wastage (1)(2).

For many years petroleum-based polymer materials for plastics packaging, such as polypropylene

(PP), polyester (PET), polyethylene (PE) and polystyrene (PS) have been used (3). The

production of plastic has increased twentyfold since 1964 and plastic packaging represents the

largest application with 26 % of the total volume of polymers. Due to its many good characteristics

(e.g. lightweight and good barrier properties) plastics have increasingly replaced other packaging

materials, and the production is expected to continue growing to the double volume within the

next 20 years (4).

Although plastic packagings have been performing successfully in terms of their functionality, the

production of petroleum-based plastics releases greenhouse gases (in particular CO2 and CH4),

and in their disposal they tend to produce significant waste and pollution in freshwater systems

and global habitats (5). Overall, due to the lack of collection or proper handling of plastics waste

in part of the world, the single use food packaging plastic items, tend to end up in landfills or

become trash on land and water streams and ultimately contaminate the oceans (3)(5).

Consequently, the societal concern about climate and environmental impacts has brought a new

focus on the production and use of plastic materials with a special emphasis on plastics for food

packaging. The main concerns behind this focus are: 1) plastic waste in the environment,

including the oceans and its potential to become a source of microplastic in the environment and

in the food chain, 2) the fact that plastics are produced from fossil resources (oil and gas) which

are not renewable and cause emissions of greenhouse gases and 3) a general agenda aiming to

promote a circular economy. Industry is struggling to find a more environmentally friendly way of

producing and using plastic. The overall question is how can plastic become (more) sustainable?

In this context, bio-based plastics(6), have been looked at as a potential alternative solution that

can afford the reduction of carbon footprint compared to conventional petroleum plastic materials

(3). Furthermore, bio-based plastics aim to replicate the life cycle of biomass with the potential to

preserve petroleum resources and reduce CO2 emissions (3). There is a considerable interest in

bio-based plastics from industry and consumers, and it is estimated that the eco-friendly food

packaging market will increase, with a shift in consumer preference towards materials that are

recyclable and “eco-friendly”. However, there is still great uncertainty about the potential and

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possible advantages of bio-based plastics compared to conventional plastics and several

misconceptions exist.

To reduce the use of resources and to reduce generation of plastic waste the EU Commission

launched in 2016 an action plan for circular economy and this was followed up in 2018 with a

European Strategy for Plastics in a Circular Economy claiming that more plastic should be

recycled. The Commission has set an ambitious goal of 55 % of plastic packaging recirculation in

2025 and that in 2030 all plastic are recyclable (or reusable). This puts a pressure on increased

reuse of plastic packaging also for food, as this represents the largest fraction of all plastic

packaging in Europe with two thirds of all packaging used within food and beverages (Plastics

Europe, 2016).

In Denmark, the National Plastic Action Plan from December 2018 has consolidated a Danish

action plan for plastics. The action plan describes several initiatives to develop Denmark in the

direction of a more circular economy within the plastic area.

The rising environmental concerns and the awareness of the consequences for the planet, has

been demanding the adoption of more sustainable solutions within packaging. Consequently,

food-packaging industries have been working towards the use of abundant, low cost, renewable,

and biodegradable alternatives to the traditional, nonrenewable petroleum-based resources (7).

However, sustainability of food packaging requires a wider perspective comprising several

aspects (1). This should include the use of a materials that: i) have been recycled; ii) reduce water

usage; iii) generate zero landfill waste; iv) have the potential to be reused iv) are made by using

renewable energy; v) do not produce air pollution; vi) create no greenhouse gas emissions; vii)

protect human health, among many other considerations.

Although progress has been made towards the creation of alternative packaging systems, there

is not yet a perfect a solution that can meet the many criteria for sustainability and ultimately fulfill

the functionality of the food packaging: preserve and deliver the packed foods in good condition

(1).

The review will give a presentation of plastic packaging materials including petroleum and bio-

based materials, and evaluate and discuss their functional properties and environmental impact

in a combined and holistic perspective. The most relevant indicators for a sustainability of food

packaging are identified and discussed aiming at increasing the awareness of food packaging

producers on the relevant factors throughout the life cycle of a packaging material (Figure 1) to

create more sustainable food packaging systems.

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Figure 1 Life cycle of food packaging material

2. Materials used in food packaging

The market share of food packaging materials in 2020 consists of 34% paper and board (cartons)

worldwide, and about 37 % rigid and flexible plastics (Figure 2). The remaining packaging

materials used for foods consist of metals (e.g. aluminum, steel), glass and others.

Figure 2 Market share of packaging materials used for food (8).

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Common plastics used in food packaging include synthetic polymers such as polyethylene

terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), and

polyethylene (PE) (9)(10). Those plastics are mostly obtained from feedstocks derived from

petroleum and natural gas (10). However, they can also be produced from biomass. Overall,

petroleum based materials are known for their easy processability, low cost, good mechanical

and barrier properties, lightness, transparency, tensile strength and lack of degradability in the

nature (9)(10). Their production causes emissions of greenhouse gases like CO2 and methane

which contribute to imbalance the climate in the planet with consequent environmental damages

(10).

Therefore, bio-based plastic materials, have been investigated in food packaging as potential

sustainable substitutes for the conventional petroleum based plastics. Bio-based plastics are

claimed to be more environmentally friendly, as hazardous substances like chemical residues or

toxins are generally not produced as byproducts during their processing (10).

Bio-based plastics include natural biopolymers (often biodegradable such as starches) and

polymers synthesized/polymerized from natural feedstock (e.g. polylactic acid, bio-PET, bio-PE).

The natural biopolymers are already existing polymers in the nature, and can be defined as a

polymeric compounds occurring in living organisms. They are mostly extracted from plants and

include materials such as polysaccharides (e.g. starch, cellulose) and proteins (e.g. zein). Natural

biopolymers can also be produced from animal origin (e.g. milk proteins) or microbial origin (e.g.

polysaccharides). The use of natural biopolymers for food packaging has mainly been in the

production of plastic films and paper. Furthermore, bio-based plastics can be categorized into

biodegradable and non-biodegradable plastics. The fact that a material is designated as bio-

based does not mean that it is also biodegradable. Natural biopolymers (e.g. polysaccharides and

proteins) are often biodegradable in the environment whereas only a few bio-based plastics made

of bio-based monomers are actually biodegradable or compostable (e.g. PHAs, PLA, polyester

amides) (11). Those concepts will be further explained in the section 3.2 of this paper. Bio-based

substitutes for petroleum based plastics such as bio-polyethylene, bio-polyamide and bio-

polyethylene terephthalate share the lack of biodegradability with their petroleum-based

counterparts (11). Figure 3 gives an overview of the characterization of plastics according to

feedstock and biodegradability.

Figure 3 shows the distribution of food packaging plastics between biodegradable and non-

biodegradable plastic. As seen Bio-PET (26 %) is the most prevalent bio-based non-

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biodegradable plastic on the market and starch (18%) blends the most prevalent biodegradable

biopolymers.

Figure 3 Characterization of common plastic materials used in packaging according to their

feedstock origin and biodegradability properties, market shares in brackets for bio-based plastics (adapted from (12)).

The market for bio-based plastics started in the early 1990s (6)(13), due to the awareness of the

need of creating more sustainable societies and circular economies considering resource

conversion, efficient after-use utilization, and environmental protection (6). Currently the

production of bio-based plastics accounts for about 1 percent of the total amount of plastics

produced annually (14). Although the production of bio-based plastics is still low, the search for

more sustainable packaging materials is expected to increase the bio-based plastic production of

the coming years from 2.11 million tons in 2019 up to 2.43 million tons in 2024 (11).

2.1. Considerations to select a food packaging material

The starting point of a packaging is the design of the packaging. The packaging designer should

emphasize the different purposes of the packaging and take into account a simultaneous design

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of food product and package thereby creating a design that at the same time minimizes food loss

and minimizes environmental impacts of the packaging in a holistic approach (15).

When selecting and designing packaging for food three main properties need to be in focus: i)

Packaging functionality; ii) Packaging chemical safety and iii) Environmental impact of the

packaging.

i) Packaging functionality. First of all the reason to use packaging is to protect the food and

therefor the functionality of the packaging and in particular its barrier properties (light, moisture,

water vapor, and gas barriers) and its mechanical strength should match the needs of the given

food. Moreover, the optical and thermal properties should also be considered. Thus, the food

packaging system must be able to obstruct either moisture gain or loss (depending on the type of

food), avoid or minimize the permeation of water vapor, oxygen, carbon dioxide and other volatile

compounds and prevent microbial contamination(3). Functionality of the packaging is the most

important characteristic in relation to avoiding food loss and the environmental impact associated

with the extra food production that is induced by the food loss. The different conventional plastics

packagings are developed through many years with the aim to achieve the functional properties

that are needed to protect different kinds of food under different circumstances.

ii) Chemical food safety of packaging. When packaging is used to protect food from

contamination, degradation and spoilage and thereby increasing its shelf life, it should also not

contribute to chemical contamination of the food from the packaging itself. In order to ensure that

plastic packaging is safe to use, all plastics intended for contact with food are regulated by EU

regulation 10/2011 (16). The regulation holds a positive list of starting substances, and only

substances on this list may intentionally be used in production of plastic intended for food contact.

When plastic packaging is brought into contact with food, chemical substances in the packaging

can potentially migrate into the food. The migration from plastic into food is a process governed

by diffusion (in the material) and sorption (from packaging to food). The migration rate is strongly

influenced by the nature of the polymer and the temperature of contact. When temperature is

increased, the diffusion rate in the polymer and thereby the level of migration per time into food

increases. Moreover, the level of migration depends on the concentration of the substances in

the plastic, the type of food in the packaging and the time of contact between packaging and food.

According to the regulation, EU 10/2011, migration of specific substances must not exceed the

specific migration limits (SML) given in the regulation. It is the responsibility of industry to ensure

that the material complies with the regulation and document this for the whole production chain.

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Also, non-authorized substances such as degradation- and/or reaction products of the starting

substances and/or impurities added from the materials or processes may become present in the

plastic material. These are so called non-intentionally added substances (NIAS) (17). Even

though these NIAS are not authorized, it is the obligation of the FCM manufacturer to ensure the

safety in accordance with Article 3 of the EU Framework Regulation (EC) No 1935/2004 (18) for

materials and articles in contact with food.

Regarding bio-based plastics, potential NIAS related to the biomass need also be considered

together with potential process contaminants. These substances may potentially include

pesticides and natural toxins in the plants used as biomass feedstock. According to a recent report

on bio-based food contact materials, no data was found regarding migration of pesticides or

natural toxins from bio-based plastics into food (19). If nanoparticles are used in the packaging

material, as for instance with the bio-based materials to improve barrier properties, the potential

risk needs to be assessed on a case-by-case basis as stated by the European Food Safety

Authority EFSA and given in the EU Regulation 10/2011.

iii) Environmental impact of the packaging. The environmental impact of the packaging arises in

particular in the sourcing of feedstock, production of polymers and packaging and end of life

treatment of the packaging. In all these stages, emissions to the environment may contribute to

negative environmental impacts including climate change, air pollution (acidification, particle

pollution and human toxicity) or water pollution (eutrophication or environmental toxicity). The

impacts from the packaging life cycle shall be as low as possible without compromising the first

two properties mentioned previously (i) and ii)) as food waste is of increasing concern. Around

one third of all food intended for human consumption globally is lost or wasted from industry and

households (20). The food manufacturers generate a significant amount of organic waste but

succeed to recover most of it (almost 90%) into e.g. animal feed or compost. According to

Verghese et al, 2013 (21) the largest opportunities to further reduce food waste lie within other

parts of the supply chain covering in particular the distribution and retail system, food services

and households (21). In relation to this, packaging decisions and designs can directly influence

the amount of food waste (22). Evaluation of performance of the quality preservation addresses

microbiological, sensoric, physical and chemical properties of the given food. Studies on

cucumbers have proven that a plastic wrap prolongs shelf life from 3 up to 14 days because it

prevents evaporation and hence increases the likelihood of sale and consumption the food. For

broccoli, active packaging film was found to increase the shelf life by up to 20 days (23).

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Packaging that fails to protect its content, thereby causing food and packaging waste, is a waste

of invested resources and an unnecessary environmental burden.

High fill rate in packaging (i.e. the product packaging volume ratio) has a positive environmental

influence through increased efficiency during storage and transport. Also facilities of the

packaging that e.g. make it easier to open, pour and re-seal can influence how much of the

packaged food product will be consumed and not wasted in households and thus also affect the

environmental impact (23).

2.2. Materials used in food packaging: properties and applications

2.2.1. Petroleum based materials

The most used types of conventional plastics for food are PET, PE and PP with different physical

properties regarding e.g. mechanical-, barrier- and temperature properties. In the Table 1

characteristics of some of the fossil based plastics for food packaging are given (24).

Table 1 Functional properties of some most used polymers for food packaging (24)

Plastic type Barrierproperties Maximum temperature application

(°C)

Mechanical

Low density polyethylene (LD-PE)

Low gas barrier (O2 and CO2, odour and flavors) and good

water vapour barrier properties.

80-90 Good strength Easy to seal

High density polyethylene (HD-PE)

Low gas barrier properties (O2 and

CO2) and good water vapour barrier

properties.

120 - 180 Stiffer and harder than LDPE.

Polypropylene (PP) Low gas barrier properties (O2 and

CO2) and good water vapour barrier

properties.

120 - 140 NMa

Polyester (PET) Good gas barrier properties (O2 and

CO2) and good barrier

APET: 70 CPET: 220

Excellent properties. Used with injection moulding, thermoforming and films

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properties to water vapour, odours and

flavours.

Polyamide (nylon) Medium gas barrier properties and low

water vapour barrier properties.

140 High strength

Polystyrene (PS) Low gas and water vapour barrier

properties. Useful when a “breathable

packaging is required

80 – 90 Hard, stiff and fragile. Very much used for injection

moulding.

Ethylene Vinyl Alcohol (EVOH)

Excellent barrier to gases (especially O2), odours and flavors. Is moisture sensitive to

water vapour.

NMa Used as high barrier material in mulitilayer plastic

aNM= Not Mentioned

In some cases the mono plastics listed above cannot deliver the needed barrier properties. In

such cases multilayer plastics consisting of several layers of different plastics and/or other

materials which gives better barrier and optimum functionality to protect the food and reduce food

waste are used. Moreover, other different technologies such as active packaging, modified

atmosphere packaging (MAP) and aceptic packaging can be used. From a food waste and cost

perspective it is particularly important to protect food products with high environmental impact,

like fish, meat and dairy products.

2.2.2. Bio-based materials

The Bio-based materials consist of two main classes: Polymers synthesized from bio derived

monomers and from natural biopolymers. Both are described below.

A) Polymers synthesized from bio derived monomers (natural feedstock)

Some of the bio-based plastics have identical chemical structure and physical/functional

properties as the petroleum-based plastics, they only differ by using biomass feedstock for the

production of bio-monomers by fermentation of a carbohydrate rich feedstock. This includes bio-

PET, bio-PP and bio-PE. Bio-PET is so far only partly bio-based as only one of its monomers,

ethylene glycol, is produced from biomass; most often from sugar cane (12). Bio-PET is globally

the most common bio-based plastic and is the largest among the non-biodegradable bioplastics.

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A fully bio-based PET, where also the monomer terephthalic acid is produced from biological

feedstock, may come into the market from 2020 (25).

Other types of bio-based plastics are novel kinds of polymers with new chemical structures and

with other functional properties, which can include Polylactic acid (PLA) and

Polyhydroxyalkanoates (PHA’s). PLA is polymerized from lactic acid monomers that are produced

by fermenting of carbohydrates (starch) from maize and wheat (26). PLA plastic is seen as a

promising substitute to conventional petroleum based plastics such as LD-PE, HD-PE, PS and

PET in different applications (27)(28). It has been used for yoghurt and pasta packaging (27) and

for lining of paper cups and plates (e.g. as substitute for PE coating of paper and board). PLA

plastic is transparent and has a high permeability for oxygen which makes it suitable for food

products that require oxygen, e.g. salad leaves (12)or other kinds of vegetables and fruit (27). It

is also available in a foam form that makes it suitable as a potential alternative to expanded

polystyrene (PS) foam packaging(12). However, its characteristics also include brittleness,

thermal instability, low melt strength and difficult heat sealability which together with the high

oxygen and water permeability restrict the use of PLA for many food packaging applications

(29)(30)(31).

Modified atmosphere packaging (MAP) is frequently used for different kinds of food to delay their

deterioration. The MAP is often used with a mixture of O2 and N2 atmosphere which requires good

gas barrier properties of the packaging. Whereas monolayer bio-based materials of PLA do not

have sufficient gas properties for MAP packaging this was obtained when multilayer PLA

materials were used for short and medium shelf life food products (27). PLA belongs to the group

of biodegradable plastisc and represents about 47 % of the total amount of biodegradable

biopolymers (32). PLA is today together with the starch-based polymers the most commercially

used biodegradable polymer.

Polyhydroxyalkanoates (PHA’s) are produced by microorganisms from the fermentation of sugar

and lipids (26). More than 100 PHA composites are known and the properties of the different

PHAs depend on their monomer composition which is dependent on the nature of the carbon

source and microorganism used (33)(26)(27). The most common kind of PHA is

polyhydroybutyrate (PHB). Of relevance to food packaging applications the PHAs have low water

vapour permeability which is close to that of LDPE (26) and it is assumed that PHAs have a

potential to substitute many conventional polymers since they possess similar chemical and

physical properties (27). It is reported that PHB can replace PP for packaging of fat rich products

as mayonnaise, margarine and cream cheese (34) and that PHB and PLA can substitute PE and

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PP packaging of sous vide pasteurized meat salad (35). However, as PHAs and PHB are also

characterized by characteristics like brittleness, stiffness, poor impact resistance and thermal

instability they also have limitations in their packaging applications (36).

Like conventional petroleum based plastics, multilayer bio-based materials can provide much

better barrier properties towards gas and water compared to single layer materials and thus

reduce food spoilage. A multi-layer of PHA and termoplastic starch (TPS) is suggested as a

potential unique bio-based material with improved oxygen and water barrier properties and a

potential to biodegrade in sea-water (37).

B) Natural biopolymers

Natural biopolymers, are polymers produced in a biological system (e.g. plants, animals). Those

biopolymers are often categorized into polysaccharides and proteins, and due to their abundance,

properties and ultimate functionalities, they have been used in a broad range of applications

including food packaging(7,38).

Polysaccharides

Polysaccharides are a natural class of biopolymers consisting of repeating monomeric units of

monosaccharides. Overall, polysaccharides are known for their non-toxic, biodegradable and

biocompatible properties (39). Polysaccharides are abundant resources as they can be found in

many natural organisms (plants, seaweeds, animals, bacteria,) which also makes them low cost.

Polysaccharides have been widely used in food, mainly as ingredients, but also in the production

of bio-based packaging systems. Polysaccharides are often classified according to their charge

into negative (anionic), neutral and positive (cationic), but also according to their origin (bacterial,

plants, sea weeds). Common examples of anionic biopolymers used in food applications include

xanthan, gellan, arabic gums and also alginates, carrageenans and pectins. The most popular

neutral polysaccharides are pullulan, guar gum and dextran. Positively charged polysaccharides

are very limited and so far, only chitosan has been used as cationic biopolymer in some food

applications.

Since polysaccharides can also be food ingredients, they have frequently been applied in edible

coatings used to retard the moisture loss of some foods during short-term storage (40). Herein,

the coating acts as sacrificial moisture barrier to the atmosphere, ensuring that the moisture

content of the coated food can be maintained (41)(40). Depending on the polysaccharide type,

permeability to O2 can be lowered, which can help to preserve certain foods. However, for more

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hydrophilic types of polysaccharides, the physical moisture barrier function may be limited and

the crystallinity of some polysaccharides can cause processing problems, although they can

exhibit excellent gas barrier properties (40).

Much research has been done to implement polysaccharides as alternative packaging materials.

Cellulose and cellulose derivatives, chitin and chitin derivatives (e.g. chitosan´s), and starch are

among the most abundant, least expensive biopolymers used in many industries (7) and they will

be discussed in the following sections.

Cellulose. Cellulose is one of the most abundant natural biopolymers in the world, and therefore

also one of the cheapest (13). Chemically, cellulose consists of (1,4)-linked β-d-glucose units

(42). As cellulose is almost insoluble in several solvents (43), it is also challenging to process it.

As regards packaging, cellulose from woods is heat processed in an aqueous slurry into fibrous

pulp for making paper and cardboard. Paper is commonly used in rigid packaging, due to its

relatively high tensile strength to produce corrugated cardboard boxes to ship delicate items such

as eggs or fruits. However, due to its relatively low elongation to break, paper has not been used

much in flexible film packaging systems, where plastics with a very high elongation to break and

tear resistance such as polyethylene, are preferred (13). Paper is highly permeable to water and

highly permeable to gases, and therefore for applications requiring resistance to moisture and

gas (e.g. meat, fish of other wet foods wrapping), papers are commonly coated with a layer of

polyethylene or wax (13). In contrast to petroleum-based polymers, cellulose is also

biodegradable in soils, waste water treatment plants, compost and marine ecosystems (13). While

the degradation of cellulose based materials into sugars through the action of bacterial and fungal

enzymes might take weeks to months, petroleum based materials might take hundreds or

thousands of years to fully degrade.

Due to the very tight packing of polymer chains of anhydroglucose, cellulose can exhibit a highly

crystalline structure, which might limit its solubility in aqueous media. However, water solubility of

cellulose can increase by treatment with alkali (to swell the structure), followed by reaction with

chloroacetic acid, methyl chloride, or propylene oxide to yield what is commonly designated as

cellulose derivatives, which includes carboxymethyl cellulose (CMC), methyl cellulose (MC),

hydroxypropyl methyl cellulose (HPMC), or hydroxylpropyl cellulose (HPC) (40). Films made of

those cellulose derivatives are generally flexible, transparent, resistant to oil and fats, and

permeable to moisture and oxygen (40). However, those barrier and mechanical properties of

cellulose-based films can be manipulated and improved by the molecular weight of cellulose: the

higher is the molecular weight, better are those mechanical and barrier properties (40). Methyl

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cellulose is less hydrophilic than other cellulose derivatives and consequently more water

resistant (41)(40). Other cellulose derivatives, like cellulose acetate have relatively low barrier to

gas and moisture, and consequently it has to be plasticized for film production. Although many

cellulose derivatives possess excellent film-forming properties, they can simply be expensive for

bulk use (40).

Starch. Starches are the second most abundant type of polysaccharides, as it is a major storage

carbohydrate in plant tubers and seed endosperm, and thus it can be extracted from several crops

including corn, potato, cassava and cereal grains (7). Due to its abundance, starch is inexpensive

(13). Chemically starch is a macromolecule made of combinations of amylose (linear

polysaccharides) and amylopectin (branched polysaccharide), which through their different

proportions confer different properties. For instance, a starch with higher content of amylose

relative to amylopectin is less water soluble than a starch with higher content of amylopectin. The

fact that native starches have poor solubility in cold water, are hygroscopic and are prone to

retrogradation reactions under specific conditions (rearrangement of starch structure into more

crystalline structure), starch derivatives have been synthesized (44). Those starch derivatives are

often aiming at limiting their recrystallization, increase water binding and improve emulsifying

properties(13).

Among other applications, starch is often used as a binder and adhesive in paper, and cardboard.

Furthermore, due to its abundance, low cost and biodegradability the use of starch and starch

based materials have been in demand to replace petroleum packaging based materials(13).

Starch is often used after heat processing (thermoplastic starch (TPS)) or in in granular form.

Granular starch, due to higher degree of crystallinity, comes with higher elastic modulus and thus

is often used as a reinforcing filler in plastics (13). The increase in starch crystallinity can be

accomplished by partial acid or amylase digestion to remove some of the amorphous domains of

the granular native starch.

On the other hand, thermoplastic starch (TPS), also known as destructurized starch, is produced

from the disruption of starch granular state, resulting in a starch with lower molecular order and

crystallinity (45). Usually TPS is processed with low water content (10-30 %) under thermal and

mechanical forces in combination with plasticizers (e.g. sorbitol, glycerol, propylene glycol).

Besides biodegradability and renewability, TPS comes also with the advantage of flexibility to be

used in a several manufacturing industrial equipment’s like injection molding, injection

compression molding, extrusion and extrusion blow molding (45). However, TPS can undergo

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retrogradation and often offers limited mechanical properties (45). TPS are known for their low

strength (below 6 MPa (13)), moisture sensitivity and tendency to become brittle (45). These

properties, can be improved by increasing the amylose content (13), by stimulating molecular

orientation of starch molecules (46), and/or by blending TPS with polymers with superior

mechanical properties such as polyesters (47). Furthermore, due the TPS hydrophilicity,

properties such as water vapor transmission of starch based films are very high (13) and

permeability to non-polar molecules such as oxygen and to hydrophobic compounds is very low

(13). Thus, laminated films containing TPS coated by and outer hydrophobic polymer (protecting

from the moisture) are good candidates for use in food packaging (48)(13).

Due to their biodegradability and composability, TPS-based plastics have been widely used by

the food industry in a broad range of applications including peanuts packaging, packaging film,

and disposable food contact materials such as plates, cups, bowls, food containers and other

utensils (13).

Chitin and Chitosan´s. Chitin, obtained mostly from shells of the crab, shrimp, insects, squids,

fungi and yeasts, etc, is another highly abundant natural biopolymer. Due to its water insolubility,

chitin can be de-acetylated to produce chitosan´s, a type of cationic polysaccharides displaying

biodegradable, nontoxic, biocompatible, intrinsically antimicrobial, antifungal, antioxidant and

adhesive properties (49)(50)(51). Furthermore, chitosan can be used as emulsifier in film-forming

solutions, and because it displays excellent film-forming properties, good oxygen and carbon

dioxide barrier properties, low cost, and has the ability to inhibit microorganism activities (49), it

has been identified as a good alternative material for food packaging.

Furthermore, physical and functional properties of chitosan films and coatings can be enhanced

by changes in the molecular weight and degree of deacetylation (DD), and the type and

concentration of acid solutions and plasticizers, and factors such as pH and temperature related

to film preparation (52)(51)(49).

Although chitosan films, display many relevant properties for their use in food packaging systems

such as their excellent gas barrier properties (both to O2 and CO2), mechanical and antimicrobial

properties, unlike the other conventional petroleum thermoplastic materials, chitosan´s cannot be

process by extrusion or molding (53)(54), which limits their commercialization. To overcome this

disadvantage, chitosan is often blended with thermoplastic polymers such as poly(butylene

terephthalate adipate), poly(butylene succinate), and poly(butylene succinate adipate) (55), which

improve its thermal properties.

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As chitosan based films tend to be brittle and rigid, plasticizers are often added to reduce frictional

forces between polymer chains and enhance their mechanical performance (56). However, if

using hydrophilic plasticizers (e.g. glycerol), water vapor permeability of chitosans films might

increase too (57).

Chitosan film properties can be improved by crosslinking it with proteins, starch, and plant extracts

(polyphenols and aldehyde compounds (e.g. cinnamaldehyde)) (49).

Furthermore, physical and mechanical properties of chitosan based films could be improved also

by the incorporation of reinforcing cellulose nanofillers such as cellulose nanofibers,

nanowhiskers and nanocrystals (CNCs) chitin nanoparticles, lignin and polylactide nanoparticles,

graphene oxide (GO) nanosheets, or montmorillonite (MMT) (53).

Proteins

Proteins are a class of natural polymers with unique properties/functionalities made of

combinations of different types of aminoacids containing different functional chemical groups.

Consequently, protein properties can be manipulated by changes in the pH, salts, temperature,

the addition of plasticizers and/or crosslinkers, and by the interactions with a broad range of

hydrophobic and hydrophilic compounds (42). The chemical reactivity and responsiveness of

proteins can be a limiting factor to their use as packaging materials compared to petroleum-based

plastics (58) or even polysaccharide based plastics.

However, their abundancy, biodegradability, non or low toxicity and facility to make films or

coatings, still makes them potential alternatives to replace petroleum-based materials (58) as

sustainable food packaging systems.

Common proteins used in food industry are classified in globular (e.g. Lactoglobulin, whey

proteins, soy proteins, ovalbumin, lactoferrin), Prolamins (e.g. Zein and gliadin) and

Phosphoproteins (e.g. caseins) (42). However, food-packaging applications based on proteins

have been developed mostly from milk, soy bean, fish gelatin, corn zein and wheat gluten proteins

(58).

Wheat Gluten. Wheat gluten proteins are very appealing packaging materials, as they can form

films with excellent barrier properties against oxygen, carbon dioxide, and aroma compounds

(58). Furthermore, their viscoelastic properties also facilitates the heat sealing with translucent

color (58). On the other hand, gluten based films often have weak physical properties and strong

18

moisture absorption when exposed to humidity, which can be a challenge in some food packaging

applications. To overcome, this issue, clay nanoparticles, cellulose nanocrystals and TiO2 and

other fillers have been added to gluten based films to form composite films (58).

Gelatin. Gelatin is a protein obtained from the hydrolysis of the existing collagen in bones and

skin from mammalians (mainly porcine and bovine) (38). Gelatin like most of the natural

biopolymers is abundant available, has good film forming ability and easy manufacturing (58).

Gelatin based films processed by casting methods are usually transparent, have good flexibility

with excellent water and oxygen barrier properties (58).

However, as packaging material, gelatin by itself offers poor mechanical properties and therefore

has to be combined with fillers such clays ZnO nanoparticles to create composite gelatin based

materials with enhanced mechanical properties (58).

Soy proteins. Soy proteins can be found as soy flour (SF containing about 54% protein), soy

protein concentrate (SPC, about 65-72% protein) and soy protein isolate (SPI, >90% protein)

(38)(58).

Due to the large number of reactive polar amino acids (e.g. cystine, arginine, lysine and histidine)

in soy protein’s structure, mechanical and thermal properties of soy protein based materials can

be improved by crosslinking it with different additives (58). Furthermore, brittleness and poor

water vapour barrier properties of soy protein based materials can be improved by adding

plasticizers such as propylene glycol, glycerol, thiodiglycol, ethylene glycol and 1,3-propanediol

(58). Like the other protein based films, mechanical properties can also be improved by the

addition of fillers such as clays and microfibrillated cellulose (MFC) (38)(58).

Zein. Zein is the main storage protein of corn and has been used to formulate various types of

thermoplastic products (38). Due to the high content of hydrophobic aminoacids, zein is not a

water soluble protein (but soluble in solvents like ethanol) offering excellent barrier to moisture

and oxygen. However, zein based films are easily breakable, difficult to process, display low

percent elongation at break, and have weak thermal properties (58). To decrease brittleness and

increase flexibility of zein films, the addition of plasticizers such as glycerol, oleic acid, linoleic

acid, palmitic acid, poly (ethylene glycol) (PEG), poly (propylene glycol) (PPG), and poly

(tetramethylene glycol) (PTMG) have been used (59). Furthermore, the processing of composite

zein films with clays has been also used to improve mechanical properties of zein based films(58).

19

Milk proteins. Milk proteins consist mostly of whey and caseins (58). While casein based films

are less resistant to moisture uptake and water vapor permeability (like wheat gluten and soy

protein isolates based films (58)), whey based films offer suitable elasticicity with good oxygen

barrier and moderate moisture permeability (38).

As for the other proteins, glycerol has been added as plasticizer during film processing to control

moisture transfer, respiration rate, oxidation, and shelf-life (58). To improve mechanical and

barrier properties of whey based films, clay nanoparticles,cellulose nanofibers (60) or titanium

dioxide (TiO2) (61) can be included.

Table 2 Properties of the films made of natural biopolymers (adapted from (38))

Material Product

Moisture

barriera

Oxygen

barrierb

Mechanical

properties (TS)c

Mechanical

propertiesc (E)

Starch Film

(Prepared in Aqueous)

Poor Moderate Moderate Poor

Chitosan Film

(Prepared in Aqueous)

Poor Good Moderate Moderate

Gluten Film

(Prepared in Aqueous-

Ethanol)

Moderate Good Moderate Moderate

Soy protein Film

(Prepared in Aqueous)

Poor Good Poor Moderate

Zein Film

(Prepared in Ethanol)

Moderate Moderate Moderate Moderate

Whey

Protein

Film

(Prepared in Aqueous)

Poor Good Poor Poor

aTest Condition: 38°C, 90/0%RH, Poor = 10-100 g.mm/m2.d.kPa; Moderate = 0.1-10 g.mm/m2.d.kPa;

Good = 0.01-0.1 g.mm/m2.d.kPa, (LDPE:0.08 g.mm/ m2.d.kPa);

bTest conditions: 25°C, 0-50%RH, Poor = 100-1000 cm3.mm/m2.d.kPa, Moderate = 10-100

cm3.mm/m2.d.kPa, Good = 1-10 cm3.mm/m2.d.kPa;

cTest conditions: 25°C, 50%RH, Moderate TS = 10-100 MPa, Moderate E = 10-50%, (LDPE: TS = 13

Mpa, E = 500%);

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TS: Tensile Strength (MPa), N/A: not applicable, E: Elongation at break (%), EtOH: Ethanol

Table 3 Examples of food packaging and disposable food contact articles made of plastics

Packaging material

type

Material Applications References

Bio-based plastic

materials

Starch-based

polymers

Disposable tableware and

cutlery,

coffee machine capsules,

bottles

(11)

Cellulose-based

polymer

Coated cellulose films are

used for

bread, fruit, meat, and dried

product

packaging, paper straw

(11),(13)

Other natural

materials (e.g.

compressed

sugarcane bagasse,

bamboo, wheat

straw)

Food containers: bowls,

clamshells, boxes, trays,

plates

(13)

PLA (polyester) Cups, bowls, bottles, bags,

jars, and

films

(11),(13)

PHA (polyester) As composite can be tuned

into different applications

e.g. bags for snacks

(11),(13)

PP and PE (vinyl

polymers)

Similar to fossil-based PP and

PE

(11)

21

PET (aromatic

polyester)

Bottles (13)

PEF (aromatic

polyester)

Bottles, fibers, and films (bio-

based

alternative to PET)

(11)

PA High-performance polymer

sourced from resin-rich wood

or vegetable oils

(11)

Petroleum based

plastic materials

PVOH (vinyl

polymer)

Coatings, a component of

adhesives,

paper and board

(11)

PCL (polyester) Medical applications, food

contact

material as blends

(11)

PBS, PES, and

PBSA [aliphatic

(co)polyesters]

Disposable cutlery (11)

PBAT, PBST

[aliphatic-aromatic

(co)polymers]

Fast food disposable

packaging, films

(11)

2.2.3. Alternative materials for food packaging

Despite the use of bio-based polymers as alternatives to petroleum-based material, other

possibilities are being considered and claimed as the future materials of more sustainable

packaging.

When it comes to disposable take-away food packaging materials, such as bowls, plates, cutlery,

bags, containers, many innovative products made of different bio-based materials have been

attempted as alternative to petroleum based plastics.

Examples include 3D-printed straws made of sugars and agar (a polysaccharides type of material

derived from seaweed) (62). Furthermore, since in Japan, agar has been extensively used as

food ingredient, to make traditional Japanese sweets and desserts by melting it in hot water, using

22

similar concept agar based packaging has been initiated by AMAM (63). The company has been

designing box-like packages, with a cushioning structure for delicate objects.

Moreover, plastics made of thread-like roots mushrooms (mycelium), can be grown and recycled,

instead of being processed pre-refinery and discarded. This is why companies like Ecovative

design (64) have been investing in developing mushroom packaging systems made of 2

ingredients: hemp hurds and mycelium. They claim this can offer a competitive high-performing

packaging solution with cost competitiveness and demanding packaging properties such as

thermal insulation, and water resistance. Furthermore, after adding it to the soil, it is expected to

decompose in 45 days (65)(66).

Bamboo packaging has also been considered as an alternative that reduces environmental

impacts (67). Bamboo is a type of fast growing plant that promotes healthy soil and does not

require replanting after harvesting. Furthermore bamboo based packaging provides strength and

flexibility, as it can endure situations that demand high level of stress resistance while being

stretched or pulled (67), in addition to its biodegradability and capacity to be composted (68)(69).

Inspired from ancient packaging models in some Asiatic cultures (e.g. Indian, Chinese, Thai, etc)

some types of leaves such as Areca, Banana, Lotus, Pandan leaves, among others have been

considered as alternative sustainable food packaging systems.

Areca palm trees are abundant in regions like India and have a large leaf and the leaf stalk also

called areca sheath that has been used to make tableware (e.g. plates, bowls, cups and food

containers (70). The areca sheat has a semi-transparent shiny layer on the inner side (looking as

laminated) and can be heat molded too. In addition, it is biodegradable, and causes no

environmental hazard. Consequently, it has been considered as an popular eco-friendly solution

to use in food packaging (71).

Lotus leafs are also considered very interesting materials to be used in food packaging. Due to

their organized nano-structure, they have super hydrophobic properties, which means they can

provide extreme water repellency. Consequently, they have high moisture resistance and self -

cleaning capability (72) in addition to some other bioactive properties, including anti-microbial.

These type of leaves have been used to pack meat and sweets but also as wrappers for the

cooked food, as it can also provide a distinctive flavor, earthy aroma, and taste (73)(74).

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Due to these excellent properties, many food packaging materials have been developed to mimic

the lotus-effect of non-stick properties. Examples include lids for yogurts (75) and waterproof and

grease-resistant paper (76).

Bananas are one of the abundant crops in the world, which makes it easily available. Because

banana leaves can hold water and moisture inside and can biodegrade once they are discarded,

they can be used as a sustainable food packaging material (77).

Furthermore, their production requires very low cost investment; they are water/moisture proof,

which makes them also easy to clean and re-utilize, without additional need for chemical

treatment to enhance any of those properties. Ultimately, banana leaves can degrade and

become a natural compost material (78).

Due to these interesting properties, Bananaleaftechnology, a company based in India (79), has

been investing in cellular enhancement of banana leaves to improve some of the banana leaves

properties. Those improved properties include durability, stretchability, crushability, resistance to

extreme temperatures and maintenance of their properties, with natural green colour for a period

of up to one year and an extended shelf lifespan of three years without losing its natural colour.

Packaging products made of cellular enhanced banana leaves are still chemical-free, animal

fodder, cost-effective and 100 % biodegradable when discarded in the nature. Those

banana leaves packaging materials might take 28 days to fully degrade, while

conventional plastic materials might take hundreds or thousands of years to be degraded

(80).

Most of the plant leaves considered for packaging are renewable and biodegradable materials

and in addition, some of them have bioactive properties e.g. anti-microbial, anti-oxidant and

others. Using leaves as packaging is not a new concept, as it has been practiced in tribal/ancient

civilizations. Due to the abundance of some of the plant leaves mentioned (particularly in specific

countries), and the demand for less invasive environmental food packaging systems, plant leaves

based packaging may have a potential to be marketed as an alternative to single use plastics.

3. Sustainability of food packaging

Overall, sustainability is defined as meeting the needs of the present generations without

compromising the ability of future generations to meet their needs (81), and claims of

sustainability of products or packagings should relate to this definition. The concept

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of sustainability is moreover composed of three pillars: economic, environmental, and social. In

this report we will focus on only the environmental aspect of sustainability of packaging.

When evaluating the environmental impact and sustainability of a food packaging one needs to

consider both the packaging and the food in a product-packaging combination by a holistic

methodology that takes into account the different requirements of a packaging (22)(82).

Production of food uses energy, water, fertilizers and often pesticides, and it causes emissions of

pollutants, including greenhouse gases, in high amounts that are much higher than the production

of the packaging material. In a Danish context agriculture contributed in 2017 with 22.4 % of the

total emission of greenhouse gases in CO2-equivalents (83). In a study, the carbon footprint of

the production of different packages (PP, PE and laminates of plastic or paper/plastic) it was

estimated to be 1-3 % of the packed food (rye bread and ham) whereas for soy based yoghurt

(soygurt) the polypropylene package had about 10% of the total carbon footprint of the package-

product system (84). This applies in general to all kinds of packaging although there can be a

great divergence between different kinds of packaging and different kinds of food. The production

of meat and dairy products hence have a higher environmental impact (use of energy and

emission of greenhouse gasses) compared to vegetables and fruit. The aim of the packaging to

protect most effectively the food to avoid food loss is in particular important for these types of

food.

Methods and indicators of sustainability of the packaging

To evaluate environmental sustainability of packaging a method is needed that can calculate and

quantify the environmental impact of different combinations of packaging and food to compare

different alternative packaging’s. To perform such calculations and evaluations in a structured

way the different stages in the product value chain and the relevant parameters in every step

need to be defined together with the admission to qualified quantitative data on the relevant

parameters.

Life cycle assessment (LCA) is a tool used to evaluate the environmental impact of a packaging

(including the product-package combination) in its entire life cycle. The principle is to quantify the

material and energy used, the waste and emissions produced and to assess the environmental

impacts in the different stages of the entire life cycle of the product (28). The principle and general

methodological framework of performing LCA is given by the ISO 14040 series. In support of the

framework, different internationally accepted models and guidelines are available which can be

used to perform the environmental impact assessment of the different life cycle stages of a

25

packaging material and a food-package combination. One of these models are the European

Commissions guideline: The ILCD Handbook (85).

The output of an LCA should make it possible to (86):

Identify the most relevant impacts (e.g. climate change, acidification etc.) of the product

Identify the processes that generate the highest environmental impact (e.g. manufacturing

of the packaging material, food packaging processes or packaging transport)

Propose guidance for improvement of the system/product.

A full life cycle of the product value chain of a food-package includes the following 4 main stages:

1. Source of material and production of the packaging

2. Packaging of the food product

3. Distribution (transportation and storage) of the food-package product: Protection of food

by the packaging material (functional properties of the packaging in use in relation to shelf

life of the food and chemical food safety of the packaging)

4. End of packaging life

When performing LCA on the food-package system it is important to include the indirect

environmental impact of the packaging caused by its influence on the food products life cycle and

in particular influence on the generation of food waste (87). If the focus is only on the direct

environmental impact of the packaging itself, it may lead to recommendations for packaging with

increased environmental impact of the food-package combination because a low impact

packaging may have poorer properties and therefore lead to a larger loss of the packaged food.

In addition to the protection of the food, a need has been identified for more packaging research

that could provide data on the effects that packaging characteristics (such as size, shape, and

type of material) have on consumer behavior and food waste in households (87). This includes

the importance of completely emptying a package and to purchase the right size for various

customers.

LCA on the packaging itself will always indicate that a larger packaging is advantageous

compared with a small packaging due to the requirement of less packaging material per food unit.

But this could have exactly the opposite effect, if the food is over-consumed, or if the food

deteriorates before eating leading to food waste (87) (84).

According to Wikstrøm et al. smaller packaging size and better information about food safety and

storage may all help to reduce food waste, but also product-specific considerations are necessary

26

(88). Findings indicate that more attention should be directed to the function “protection of food

quality—in opened packaging”. A large share of the food waste emanates from food that has been

partly but not completely used before the “best before date” is passed or the quality has

deteriorated. This waste can be addressed in several ways, such as by reducing the amount of

food, by adding protective functions of the packaging for after opening, information regarding how

to store properly and adding information about how to judge the food safety of the product (88).

When for a given food-package product the packaging properties are determined and evaluated

to achieve an optimal protection and optimal shelf life of the food, the next step should evaluate

if the same properties could be achieved from other kinds of packaging and if so which packaging

solution will have the lowest environmental impact.

In the following section we will evaluate the life cycle stages of “production” and “end of life” for

bio-based plastic packaging and petroleum based plastic as these are the stages where they

differ, provided that they offer the same packaging properties and protect the food equally well.

3.1 Production of plastic packaging

Petroleum based plastic of different kinds as given in section 2.2.1. are produced from oil and

with the input of energy. The energy demand of converting oil or natural gas into plastic means

that two-three kilogram is used for one kilogram of new plastic produced for many plastic types

(89). As oil is moreover not a renewable resource, its production leads to net-emission of CO2

which contributes to global warming. There is an ongoing and increasing interest in bio-based

plastic as a potential solution to make plastic packaging more sustainable. As mentioned earlier,

currently still only about 1 % of all plastic globally is bioplastic (14) and there is a great need for

more knowledge to answer when or if bioplastic is a solution to a have more sustainable plastic

packaging for food.

Life cycle assessment (LCA) studies of PLA show clear advantages in climate protection and

conservation of fossil resources in comparison to petroleum based plastics. In a meta-analysis of

bio-based materials, LCA of 44 different studies were evaluated by (90). The evaluation

concluded that bio-based materials generally exert lower environmental impacts than

conventional materials in the category of climate change (if greenhouse gas emissions from

indirect land use change are neglected.

However, greenhouse gases and global warming is not the only relevant factor when considering

environmental impact of the production of the plastic. As production of bio-based materials

27

requires biomass as feedstock it is typically heavily associated with other environmental effects

from the biomass production. The most relevant environmental impact categories, that are

internationally accepted for evaluation of environmental impact of food packaging include the

following: natural resource depletion, acidification, photochemical ozone creation, eutrophication,

human toxicity and aquatic toxicity (12)(86)(90)(91)(92)(93).

In the evaluation by Weiss et al. 2012 (90) it was concluded that bio-based materials may exert

higher environmental impacts than their petroleum based counterparts in the categories of

eutrophication and stratospheric ozone depletion. In addition, most bio-based materials have

environmental impacts caused by the application of pesticides during the cultivation of biomass.

With regard to acidification (savings of 2 ± 20 kg sulfur dioxide equivalents/t) and photochemical

ozone formation (savings of 0.3 ± 2.4 kg ethene equivalents/t) the studies found high variability

as seen from the given data and were inconclusive.

A comparison of bio-based PE to petroleum based PE showed that the impact categories climate

change, consumption of fossil resources and summer smog were lower for bio-based PE

compared to petroleum based PE. However the reverse situation was found for acidification

potential, terrestrial eutrophication, aquatic eutrophication, human toxicity, water consumption,

total primary energy demand and land use, where environmental impact of bio-based PE was

higher than conventional PE (28).

The choice of feedstock for production of bio-based plastic is important as it matters greatly

whether the feedstock is considered to be a primary crop or a by-product or waste of another

process (28). Indirect land use change given as the unintended expansion of farmland elsewhere

due to the rededication of existing farmland to produce biomass feedstock for plastics production,

may add substantially to the overall environmental impacts of bio-based materials. This includes

greenhouse gas emissions from indirect land use change as well as the potential loss of

biodiversity, soil carbon depletion, soil erosion and deforestation. According to (90) these impacts

should all be considered when evaluating the environmental performance of bio-based materials.

If feedstock is produced from first generation biomass (defined as biomass that is generally

edible) such as e.g. maize or starch the growing of this biomass will compete with the production

of crops for human consumption. This will cause an increased need for cultivated land, and if this

gives rise to clearing of forest, it will add significantly to the release of CO2 from the harvested

trees and from the degradation of organic matter in the soil humus due to the ploughing of the

soil. With a future high growth rate of bio-based plastic, a conflict of interest in land use between

food and bio-based plastics (and also biofuels) is foreseeable, and more clearing of forest and

28

grass land will be needed to have sufficient land for all productions. In this case the increased

CO2 emission from indirect land use of biomass production of bio-based plastics should be taken

into account (91). If bio-based plastic is made from waste feedstocks (second generation

feedstock) and the input material is a waste and hence considered burden free, it will perform

better in a LCA.

It is the overriding trend that for bio-based plastics, the feedstock production affects the resulting

environmental impact categories more than any other lifecycle stage of these materials according

to the Danish EPA (28). According to Weiss et al., 2012 (90) more comprehensive quantitative

analyses should address, in particular, land use-related impacts (such as effects on biodiversity

and soil organic matter (soil erosion)) as well as risks in case of use of genetically modified crops

and microorganisms.

In summary the overriding trends show some advantages to bio-based plastics compared to

petroleum based plastics such as likely reduced climate impact and reduced consumption of fossil

resources but also disadvantages primarily from feedstock production causing environmental

impacts such as increased acidification, eutrophication and human toxicity(12).

3.2. End of life of plastic packaging

The increased use of packaging generates an increased waste problem that needs to be

considered how to solve in the best way. Different pathways for end of life of packaging are

possible and in general include the following routes: littering, landfilling, industrial composting,

anaerobic digestion, thermal treatment in a waste incineration plant, treatment and use as refuse

derived fuel e.g. in cement kilns as well as mechanical or chemical recycling. Globally, landfilling

is still the most used disposal route for many different materials including packaging. According

to Ellen MacArthur (4), 72 % of plastic packaging is not recovered and 40 % of this is landfilled

(the most used way of disposal of plastic packaging) whereas 32 % is not collected or illegally

dumped or mismanaged (4).

LCA-based studies demonstrate that both production and end of life of bio-based and petroleum

based plastics must be taken into account when evaluating and comparing the environmental

impact of the different plastics (25) (94) (92).

29

3.2.1. Degradation and composting of plastics

Degradation of plastic is often considered as an environmentally attractive and sustainable way

to reduce the municipal waste problem. As the degradation of petroleum based plastic materials

is generally very low assuming a rate of 1% over 100 years if such plastic waste is disposed by

landfilling, degradation is not a possible way to dispose of petroleum based plastic. This also

applies for the bio-based counterparts bio-PET, bio-PE and bio-PP, and indeed, as mentioned in

section 2.2, not all bio-based plastics are bio-degradable. Furthermore, there are petroleum based

plastics that are biodegradable. The biodegradable plastics constitute 43 % of the bio-based

polymers with starch blend polymers and PLA as the most common(12).

Biodegradable plastics refer to the properties of the plastic as being degradable as a result of

biological activity by microorganism by aerobic or anaerobic biodegradation(12). The aerobic

degradation requires oxygen to degrade the organically bound carbon in the polymer to CO2 and

water while the anaerobic degradation takes place without oxygen and produces methane (CH4)

rather than CO2. Methane is a much stronger greenhouse gas compared to CO2 with 28 times

higher contribution to global warming than CO2) (95).

Biodegradable or compostable plastics are by many considered to be environmentally preferable

compared to petroleum based plastics and are mentioned to offer a potential solution to plastic

pollution in the environment. However, degradation of biodegradable plastics can result in

significant emission of greenhouse gases (CO2 and CH4) into the environment when disposed in

landfills. This is in contrast to the petroleum based plastics which are inert and do not degrade

and hence do not produce CO2 or CH4 from landfilling of waste.

The ability to biodegrade can moreover vary a lot between different kinds of

biodegradable/compostable plastics and depending on the given circumstances. Many

biodegradable plastics are not biodegradable in the natural environment but have specific

temperature and time requirements that need controlled industrial composting to become

effectively degraded (96) (97) It is therefore important to specify under which conditions and within

which timeframe a given kind of plastic is able to degrade.

For PLA landfilling results in only negligible emission of CO2 and very little environmental impacts

since PLA degradation is only one percent over a life span of 100 years (98). Also, the amount of

carbon converted into methane is less than 0.1 % for this polymer and does not add significant to

greenhouse gas emissions (92). On the other hand, when thermoplastic starch plastic is disposed

by landfilling, a more intense degradation of the polymer takes place resulting in significant

30

methane emission and global warming (98). Landfill emissions are one of the reasons why the

European Parliament calls for a phase-out of biodegradable materials in landfills.

Also composting of bio-based plastic adds to emission of CO2 originally accumulated in the

biomass which is released into the environment. Whether this CO2 release contributes to a net

increase in CO2 depends on the kind of feedstock biomass (first or second generation) used for

the production of the packaging. In Figure 4 the life cycle of compostable bio-based plastic is

shown including different kinds of potential scenarios for end of life of the used packaging.

Figure 4 Life cycle of bio-based compostable plastic produced from maize. When first generation

biomass is used for production of the packaging, land competition with increased CO2 emission occurs

due to indirect land use changes (ILUC). This induces climate changes and environmental impacts (from

e.g. fertilizers, pesticides and use of water).

Comparison of different end of life options of PLA and thermoplastic starch (TPS) packaging for

dry food including landfill, mechanical recycling, direct fuel substitution, anaerobic digestion and

municipal incineration by using LCA showed that industrial composting generates the highest

environmental impacts for the most categories (98). In addition, the study showed that composting

of the given materials does not improve the quality of the compost as the very low N-P-K content

of the compost means that it cannot replace fertilizers. Plastics generally contain neither N, P or

K and hence don’t contribute positively to this aspect of the compost. The lowest environmental

31

impact in most categories was seen for mechanical recycling followed by direct fuel substitution.

Mechanical recycling is the most commonly used method for plastic recycling. By this method the

plastic waste is sorted mechanically using a scanner (e.g., NIR, MIR), a float-sink equipment or

other equipment (e.g., ballistic separator, film separation, electrostatic separation). The sorted

plastic is then washed and remelted (99).

In summary, the hypothesis that composting is environmentally preferable (also compared to

energy recovery), and because composting is a sort of recycling was not confirmed in the given

studies. Instead, the results demonstrate that the recycling of PLA can contribute to improve the

environmental performance of PLA. The authors point out that the conclusion may differ if the

packaging is heavily contaminated with food and therefore requires cleaning steps that would

make recycling less attractive from an environmental point of view (98). Recyclability of the

different bio-based materials, especially of bio-blends and biocomposites, need to be studied

further to have a better understanding of the different factors affecting their performance,

economy and sustainability (100).

The EU Commission recently performed a study comparing PLA and PET for production of

drinking bottles (101). From this study it was concluded that when proper waste collection of the

bottles can be achieved, the use of compostable materials for bottle production does not

represent, per se, a solution to achieve an improved environmental performance compared to

conventional (petroleum-based) materials, especially if these come from recycled feedstock. It

was mentioned that the given evaluation does not include potential impact from the share of

product that may end up as littering into the environment. However, this was also not expected to

be substantial in regions with a well developed waste management infrastructure like most EU

countries, and no dramatic changes in the overall picture may take place (101). It is the priority of

the EU Commission’s waste policy to reduce the amount of waste generated and to maximise

recycling and re-use of materials (102).

A special type of biodegradable plastic is the oxo-plastics or oxo-degradable plastics. These are

petroleum based plastics which include additives to accelerate the fragmentation of the material

into very small pieces, triggered by UV radiation or heat exposure. Due to these additives, the

plastic is over time fragmented into plastic particles, and finally potentially into microplastics, with

similar properties to microplastics originating from the fragmentation of conventional plastics (EU

Commission, 2018 b). According to the Commission a process to restrict the use of oxo-plastics

in the EU was intended to start (103) and on March 2019 the EU Parliament put a ban on

oxodegradable plastic. However, recently this process seems to be interrupted due to

32

disagreement with the European Chemicals Agency ECHA on evidence on the formation of

microplastics from oxodegradable plastic.

3.3. Recycling of plastic

Several studies conclude that recycling is a key for improving environmental sustainability due to

the generally lower impacts of recycling processes, compared with extracting raw materials and

produce virgin materials (104) (105). Recycling of plastic packaging results in significant life cycle

impact reductions by replacing virgin plastic with recyclates. However, only 14 % of all plastic is

collected and recycled, and the plastics that are recycled are mostly downcycled into lower value

applications from which they cannot enter another round of recycling (4).

To reduce energy consumption CO2 emissions and other environmental impacts, the plastic

should be recycled as many times as possible. The European Commission’s action plan prepare

the move towards a circular economy to reduce waste and to reuse more efficiently the value of

products and resources (106) (107). Increased recycling of packaging materials is part of this

plan, and the Commission already in 2015 set an ambitious goal of 55 % of plastic packaging

recirculation in 2025 and that all plastic packaging is recyclable by 2030.

According to the EU Commission, the potential for recycling plastic waste remains largely

unexploited in EU. Reuse and recycling of end-of-life plastics is very low, particularly in

comparison with other materials such as paper, glass or metals (104). Many factors can limit

recycling’s potential to meet materials demand, including: dissipative material losses during the

use stage of a product; loss of material through improper collection, material quality becoming

degraded during collection and processing (downcycling), build-up of stocks, product designs that

impede recycling, lack of suitable recycling infrastructure; contamination with hazardous

substances; and economic factors resulting, for example, from the need for decontamination and

price competition with virgin materials. Additionally, transportation may significantly contribute to

a number of impacts in multiple life cycle stages(108) depending on the distance of the

transportation.

In Denmark 18 % of plastic packaging from Danish households are recycled today according to

the estimate from 2019, which is far from the goal of 55 % in 2025 set by EU Commission.

Mechanical recycling is the kind of recycling so far most used with packaging plastic. The

possibility of mechanical recycling of conventional plastic is however different for the different

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types of polymers as it depends of the composition, mechanical features and chemical safety of

the polymer. The most common types of polymers (PET, PP and PE) used for food contact have

different properties in relation to mechanical recycling as given in the table below (99).

Table 2 Properties of different petroleum based plastics in relation to mechanical recycling (99).

PET PP PE

Homogeneity of polymer

One kind of PET in all kinds of PET for food and non-food.

Wide range of different kinds of PP with different properties.

Different kinds of PE with different properties

Regeneration of polymer after mechanical recycling

Polymer decomposition is reversible Able to recycle several times.

Decomposition of polymer with mechanical recycling.

Decomposition of polymer with mechanical recycling.

Food safety properties of mechanically recycled polymer

Low level of NIAS Low migration rate Evaluation af rPET by EFSA with strict requirement to the recycled material.

NIAS formation in the recycling process rPP for food contact is uncertain and not yet evaluated by EFSA.

NIAS formation in the recycling process. rPE for food contact is uncertain and not yet evaluated by EFSA.

With increasing effort towards developing a circular economy for plastic packagings, chemicals

used in the materials are becoming a central issue if the materials are intended to be reused for

food packaging. The risks associated with the use of recycled plastic materials and articles in

contact with food arise from the possible migration into the packaged food of contaminants

present in the recycled plastics. The following contaminants are considered as potential

contaminants of recycled plastics (109): a) Non-authorised monomers and additives. The

Regulation EC 282/2008 requires that only plastic materials manufactured in accordance with

Community legislation EU 10/2011 on plastic food contact materials and articles are used as input

in recycling processes. However, if the materials originate from third countries there is no

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adequate information and the use of not authorised substances cannot be excluded. b)

Contaminants from possible misuse of the packaging. c) Contaminants from non-food consumer

products (e.g. cosmetic, personal hygiene products, household cleaning) or from the food packed

in the material. d) Chemicals from other materials of the packaging e.g. printing inks, glues,

sleeves or labels. Their presence can result from incomplete sorting and separation. e)

Chemicals used in the recycling process. f) Degradation products and/or reaction products of the

plastic. During the various steps of the recycling process, e.g. high temperature treatments, the

polymeric chain may break down to smaller molecules and any additives or sorbed compounds

may react and be converted into new compounds.

The quality of the input, the efficiency of the recycling process to remove contaminants, and the

intended use of the recycled plastic, are all crucial points for the risk assessment. Taking into

account all the above mentioned potential sources of contamination of the input, it has to be

demonstrated that the recycling process is able to reduce contamination to levels not posing a

risk to human health for the intended use of the final product. A guidance document on how to

demonstrate end evaluate this is given by EFSA (110).

PET is a plastic material which is well suited for mechanical recycling. First of all, there is just one

kind of PET (a de facto standard) for all types of applications (99). Moreover, PET is fairly inert, it

contains a limited range of additives and the polymer is characterized by a low diffusion rate in

and out the material. All together, this means a low risk of chemical migration from recycled PET

(rPET) into food. rPET is so far the only plastic that after mechanical recycling is approved by

EFSA to be used in contact with food after a safety evaluation and testing in accordance with

EFSA’s opinion on mechanical recycling of PET ((109) and EFSA’s guidance document on

recycling (110).

For PP and PE there is currently no EFSA opinion on mechanical recycling of these materials

intended for contact with food. Due to mechanical and chemical properties of PP and PE (as given

in the Table 2) it is so far questionable if it will be possible to obtain such an opinion. Alternative

ways as e.g. chemical recycling may in such cases be considered. By chemical recycling the

plastic is decomposed by thermochemical processes, solvents or other means into basic chemical

building blocks, which can then be used as base materials for new products. This kind of recycling

is able to manage higher level of impurities in the input plastic however, there is a higher energy

consumption compared mechanical recycling.

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Bio-based PET with the same chemical structure as petroleum-based PET is equally suited for

mechanical recycling of food packaging and can fit into existing sorting and recycling systems as

for conventional PET. This is in contrast to the novel kinds of bio-based plastics with another

chemical composition. PLA is technically also recyclable, but at present, the waste infrastructure

is not in place to handle this widely and volumes for PLA are to grow to a certain level to make it

economically viable (111). The benefits of recycling in relation to greenhouse gases and

environmental impact categories could extend to biopolymers if they can be recycled together

with existing waste streams (25). This will need separate sorting and recycling streams which

make circular economy difficult (or maybe impossible) for bio-based materials as these is so far

only produced in lower amount.

Maga et al. performed an LCA and evaluation of recycling of PLA by three different ways:

Mechanical recycling, solvent recycling and chemical recycling of post consumer waste as well

as mechanical recycling of also post industrial waste (112). The different recycling routes for PLA

waste were compared to thermal treatment (with energy recovery). The life cycle impact results

showed that all the recycling technologies lead to higher savings of greenhouse gas emission

and reduction of environmental impacts (regarding photochemical ozone formation, terrestrial and

aquatic eutrophication, acidification and particulate matter) due to avoided biomass cultivation,

harvesting and transportation by replacing virgin PLA with PLA recyclates (112).

The above studies show that end of life is important to take into account also for biodegradable

plastics. As mentioned above, production of more biomass, if not recycled, will in addition to the

climate impact from the increasing of land use also cause an increase in the use of fertilizer and

pesticides and the environmental impacts from this.

Compostable bio-based plastics like PLA may be difficult for end-users to distinguish from some

petroleum based plastics. This can be a problem for recycling of PET as rigid PLA looks and feels

very much as PET, and contamination with PLA can reduce the mechanical and aesthetic

properties of the recycled PET. The effect is most pronounced in high quality streams of food

grade PET and less so for mixed plastic films(28). If compostable PLA is becoming more

widespread it may be possible to identify the waste PLA by Near Infra Red (NIR) scanners for

sorting and recycling if the market creates a demand for recycled PLA (28).

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4. Summary and perspectives

Sustainability is becoming one of the main priorities in food industry (in particular in developed