Compostable Polymer Materials
By Ewa Rudnik
()
About this ebook
- Provides a comprehensive study of the composting process
- Details methods of compostable polymers preparation, including properties, processing and applications
- Presents the state-of-the-art knowledge on ecotoxicity testing and biodegradation under real composting conditions of compostable polymers, as well as biodegradation in various environments, such as marine environments and anaerobic conditions
- Discusses the evolution of waste management in Europe and the United States, as well as the status of MSW disposal and treatment methods in countries such as China and Brazil
- Overviews biodegradation studies under real composting conditions of products made of compostable polymers, e.g. bags, bottles, cutletry
- Analyzes evolution of market development, including price of compostable polymers during the last decade
Ewa Rudnik
Professor Ewa Rudnik works at the Faculty of Fire Engineering, The Main School of Fire Service, Warsaw, Poland. Professor Rudnik is actively engaged in the dissemination of new knowledge concerning the biodegradation behavior and mechanisms of specific polymers in soil and under composting conditions. In 2002, she carried out the study as a research guest at GSF- National Research Center for Environment and Health in Neuherberg/Munich (Germany). Additionally, Professor Rudnik was a Marie Curie Fellow at the Agricultural University of Athens in the research group of Professor Demetres Briassoulis. Professor Rudnik’s publications address important issues related to environmental safety, including 1 monography, 3 book chapters, publications, seminars, and lectures aimed at scientists and students, as well as people interested in the fields of ecology and environmental science.
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Compostable Polymer Materials - Ewa Rudnik
Compostable Polymer Materials
Second Edition
Ewa Rudnik
Table of Contents
Cover image
Title page
Copyright
Preface
Chapter 1. Introduction
1.1. Situation in Europe
1.2. Situation in the United States
1.3. Situation in other regions of the world
Chapter 2. Compostable polymer materials – definitions, structures and methods of preparation
2.1. Biodegradable polymers from renewable resources
2.2. Other compostable polymers from renewable resources
2.3. Biodegradable polymers from petrochemical sources
Chapter 3. Properties and applications
3.1. Biodegradable polymers from renewable resources
3.2. Biodegradable polymers from petrochemical sources
3.3. Blends
3.4. Summary
Chapter 4. Thermal and thermooxidative degradation
4.1. Biodegradable polymers from renewable resources
4.2. Biodegradable polymers from petrochemical sources
4.3. Blends
4.4. Summary of thermal stability of compostable polymer materials
4.5. Flammability and fire testing of compostable polymers
Chapter 5. Composting methods and legislation
5.1. Composting definitions
5.2. Composting process and methods
5.3. Composting standards
5.4. Labelling systems in different regions
5.5. Cooperation between certification and labeling systems
Chapter 6. Biodegradability testing of compostable polymer materials under laboratory conditions
6.1. Definitions related to biodegradation testing
6.2. International standards related to composting
6.3. Principles of main standards related to composting and biodegradability testing
6.4. Composting at laboratory scale
6.5. Biodegradability testing methods
6.6. Biodegradation of biodegradable polymers from renewable resources
6.7. Biodegradation of biodegradable polymers from petrochemical sources
6.8. Biodegradation of blends
Chapter 7. Biodegradation of compostable polymer materials under real conditions
Chapter 8. Biodegradation of compostable polymers in various environments
8.1. Introduction
8.2. Compostable polymers-degrading microorganisms
8.3. Biodegradation in soil environment
8.4. Biodegradation in anaerobic environment
8.5. Biodegradation in marine environment
Chapter 9. Ecotoxicological assessment of compostable polymer materials
9.1. Introduction
9.2. Definitions
9.3. Methods
9.4. Compostable polymers ecotoxicity testing
9.5. Conclusions
Chapter 10. Environmental impact of compostable polymer materials
10.1. Introduction
10.2. Life cycle assessment methodology
10.3. Life cycle assessment of poly(lactic acid)
10.4. Life cycle assessment of polyhydroxyalkanoates
10.5. Life cycle assessment of polysaccharides and gluten-based polymers
10.6. Life cycle assessment of blends
10.7. Overview
10.8. Conclusions
Chapter 11. Waste treatment of bio-based compostable polymers
11.1. Introduction
11.2. Mechanical recyling
11.3. Chemical recycling
11.4. Comparison of compostable polymer waste treatment methods
Chapter 12. Perspectives
12.1. Introduction
12.2. Price evolution
12.3. Capacity
12.4. Legislation inititatives
12.5. Demand estimation
12.6. Conclusions
Index
Copyright
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Notices
Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.
Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.
To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein.
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ISBN: 978-0-08-099438-3
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Preface
The increasing environmental awareness of the society has become an important factor in recent decades affecting legislation, commerce and industry as well as research and development to a great extent. In the near future the role of polymers especially designed to be disposed after their useful life in industrial and municipal composting facilities, as well as the role of both renewable-based materials and biodegradability is expected to grow in the polymer industry, thus scientific research and development has been paying more attention to those areas.
The second edition of Compostable Polymer Materials represents an extensive revision of the chapters in the first edition and a substantial enlargement through the addition of three new chapters. It covers the entire spectrum of preparation, properties, degradation, and environmental issues of this kind of polymers. The emphasis is given on the recent studies concerning biodegradation under real composting conditions of products made of compostable polymers, as well as biodegradation in various environments (soil and marine environments, anaerobic conditions). Moreover, thermal behaviour of compostable polymers, including flammability properties is described. Possible routes of compostable polymers waste disposal and ecotoxicological assessment of polymer materials – important issues from ecological point of view were presented. Evolution of market development, including price of compostable polymers during last decades was outlined.
Chapter 1 introduces to problem, explaining the role of compostable polymer materials in a sustainable development and reasons for growing interest.
Chapter 2 gives the overview of compostable polymer materials starting from definitions, explaining differences in comparison with biodegradable polymers. It discusses origin (synthetic and natural), structures and methods of preparation of compostable polymers. The producers of compostable polymer materials and their websites are given.
Chapter 3 summarizes the main properties of compostable polymers, i.e. physico-chemical, mechanical, and thermal properties. It also contains data about their processing and current applications.
Chapter 4 describes the thermal behaviour and flammability properties of compostable polymer materials. The overview about thermal stability and apparent activation energy of degradation in different environments (inert and oxidative atmosphere) is presented.
Chapter 5 gives the overview of composting process and methods, including up-to-date standardized guidelines for evaluating compostability of polymer materials. It also contains the information about compost quality standards as well as the description of certification systems for compostability used in different regions in the world (Europe, USA, Japan).
Chapter 6 summarizes current testing methods used for biodegradability testing of compostable polymer materials under laboratory conditions, standardized as well as non-standardised reported in the literature. The focus is given on studies under composting conditions.
Chapter 7 gives the overview of composting studies of compostable polymers under real conditions. The effective decomposition of compostable polymers on real scale composting plant under outdoor conditions is reviewed. Special emphasis is given on biodegradation studies under real composting conditions of products made of compostable polymers, e.g. bags, bottles, cutlery.
Chapter 8 reviews biodegradation behaviour of compostable polymers at different environment, i.e. in soil, marine and anaerobic environments. Specificity of various environments in relation to biodegradation of polymers is discussed.
International and regional standards related to biodegradation for polymers in soil, marine and anaerobic environments are presented.
Chapter 9 gives the definitions related to ecotoxicity testing, describes the currently used method as well as gives overview of ecotoxicological assessment of compostable polymer materials.
Chapter 10 describes environmental performance of compostable polymer materials, including Life Cycle Analysis (LCA).
Chapter 11 discusses possible routes of compostable polymer waste disposal. Studies on mechanical and chemical recycling of compostable polymers are presented. The best waste treatment option for compostable polymer materials is assessed.
Chapter 12 addresses main issues related to compostable polymers development. Price evolution and production capacity of compostable polymers since 1998 are discussed, and legislative framework and demand is presented.
I hope that this book may be useful in developing ideas of environmentally friendly materials and provides the information for researchers and students interested in chemistry and materials science as well as in ecology and environmental science.
I would like to thank most warmly to my family and friends for their support and love.
Ewa Rudnik
Chapter 1
Introduction
Abstract
The rise in the rate of plastics production over the last decades has aroused environmental concerns. The trends in management of municipal solid waste (MSW) generation in different regions of the world were summarized. The status of MSW disposal/treatment methods, including composting was reviewed in different countries. Data on the generation and disposal of waste in Europe (in the reference period 1995–2016) and United States (in the reference period 1960–2012) were reported. The Waste Management Hierarchy, most preferably approach taken, includes waste prevention, re-use, recycling and other recovery (e.g. energy recovery). Landfilling is regarded as the least desirable option. Composting as organic recycling is attractive alternative for reducing plastics waste, especially suitable for those segments of conventional plastics in which recycling is difficult or economically non feasible.
Keywords
Municipal solid waste; Recycling; Composting; Statistics; Compostable polymers
1.1 Situation in Europe
1.2 Situation in the United States
1.3 Situation in other regions of the world
1.3.1 Asian countries
1.3.2 Africa
1.3.3 Brasil
References
Polymer materials with a range of excellent properties like mechanical properties, low density, durability and low cost, have been widely used in the daily needs of contemporary society from simple packaging to heavy construction, playing important role in the improvement and quality of life. However, due to their persistence in the environment, polymer materials present the danger to our ecosystems.
With continuous growth for more than 50 years, global production of plastics in 2016 rose to 335 million tonnes – a 4% increase compared to 2015 [1]. However, this increased use of plastics is accompanied by a rapid accumulation of solid waste and plastics litter, which, due to their resistance to biodegradation, have a deleterious effect on the environment as an obvious contributor to pollution.
The world-wide increase in plastics waste has involved, within the global vision of environmental protection and sustainability, a great deal of actions and strategies aimed at minimizing the negative impact of the increasing production and consumption of polymer materials.
In general, waste strategies taken in different regions in the world are similar and are based on the prevention and recycling of waste. For example, Japan has extensive legislation related to waste and other sustainable production and consumption policies under the ‘3R-reducing, re-using and recycling’ umbrella.
The strategy of the EU to cope with waste is to:
• prevent waste in the first place;
• recycle waste;
• optimize the final disposal of waste.
In response to the growing challenges of waste production and management, the European Parliament and the Council have adopted a certain number of Directives to ensure that waste is recovered or disposed of without impairing the environment and human health.
According to European Directive on packaging and packaging waste [2] the management of packaging and packaging waste should include at first priority, prevention of packaging waste and, as additional fundamental principles, reuse of packaging, recycling and others forms of recovering packaging waste and, hence, reduction of the final disposal of such waste (Fig. 1.1).
Prevention means the reduction of the quantity and of the harmfulness for the environment of:
• materials and substances contained in packaging and packaging waste,
• packaging and packaging waste at production process level and at marketing, distribution, utilization and elimination stages, in particular by developing ‘clean’ productions and technology.
Reuse is defined as any operation by which packaging, which has been conceived and designed to accomplish within its life cycle a minimum number of trips or rotations, is refilled or used for the same purpose for which it was conceived, with or without the support of the auxiliary products present on the market enabling the packaging to be refilled.
Recovery includes operations provided for in Annex II. B to Directive 75/442/EEC on waste [3], e.g. use as a fuel or other means to generate energy, recycling/reclamation of organic substances which are not used as solvents (including composting and other biological transformation processes).
Energy recovery means the use of combustible packaging waste as a means to generate energy through direct incineration with or without other waste but with recovery of the heat.
Recycling is defined as the reprocessing in a production process of the waste materials for the original purpose or for other purposes including organic recycling but excluding energy recovery.
Disposal operations include deposit into or onto land (e.g. landfilling), incineration etc.
Fig. 1.1 Plastics waste treatment strategy.
The use of compostable plastics is one of valuable recovery option (biological or organic recycling). According to EU Directive on Packaging and Packaging waste [2] organic recycling means the aerobic (composting) or anaerobic (biomethanization) treatment, under controlled conditions and using micro-organisms, of the biodegradable parts of packaging waste, which produces stabilized organic residues or methane. Landfill is not considered as a form of organic recycling.
The Waste Management Hierarchy, i.e. minimization, recovery and transformation, and land disposal have been adopted by most developed countries with strategies used depending on such factors like population density, transportation infrastructure, socioeconomic and environmental regulations.
1.1. Situation in Europe
Current EU waste policy is based on a concept known as the waste hierarchy. This means that, ideally, waste should be prevented and what cannot be prevented should be re-used, recycled and recovered as much as feasible, with landfill being used as little as possible. The long-term goal is for the EU to become a recycling society.
Despite the intensive efforts of some countries to reduce the amounts of waste, the quantity of solid waste is significantly increasing within the European Union.
In Europe (EU-27), nearly 300 million tonnes of municipal solid waste are generated yearly, which corresponds to over 500 kg per capita per year (2012 data) [4]. On average, in 2012, almost 40% of MSW was landfilled, while material recycling (including composting) and incineration with energy recovery counted for about 40% and 20%, respectively.
From 1995 to 2003 municipal waste generation in the European Union (EU 25) has constantly grown by about 2% per year from 204 million tonnes (457 kg/person) in 1995 to 243 million tonnes (534 kg/person) in 2003 [5].
Between 2000 and 2009 municipal waste treatment in the EU changed significantly. By 2009, 38.2% of municipal waste was placed in landfills, compared with 57.6% in 2000 [6]. This 4.5% annual reduction from 2000 to 2009 supports the objectives of the EU directive on the landfill of waste. During the same period, the amount of municipal waste incinerated, recycled or composted increased substantially. Incineration rose from 16% in 2000 to over 20% in 2009, representing an average annual growth of 2.8%. Similarly, recycling rose by an average of 4.7% per year from about 16% in 2000 to over 23% in 2009. Composting showed the biggest average increase of 5.5% per year from 11% in 2000 to almost 18% in 2009. Recycling and composting together accounted for about 41% of municipal waste treatment in 2009.
In spite of the increase in waste generation in the EU-27, the amounts of municipal waste landfilled have been reduced. In the reference period (1995–2009), the landfilled total in the EU-27 declined by 45.6 million tonnes, or 32%, from 141.3 million tonnes (296 kg per capita) in 1995 to 95.7 million tonnes (191 kg per capita) in 2009, corresponding to an annual decline of 2.7% [6]. Since 2002, the landfilled amounts have fallen by as much as 4.4% per year. As a result, the share of landfilling in the EU-28 dropped from 68% in 1995 to 38% in 2008. The highest rates for recycling were reported by Germany (48%, 274 kg per capita), Sweden (36%, 171 kg per capita) and Belgium (36%, 175 kg per capita), whereas Austria (40%, 235 kg per capita) and the Netherlands (28%, 144 kg per capita) reported the largest shares of composting [6]. Italy’s reported share of composting is the second highest (32%), but national data for 2007 suggest that the Italian figure for composting contains more than 70% amounts treated by mechanical-biological operations. Belgium was among the countries with the largest shares for both recycling (36%) and composting (24%).
Fig. 1.2 shows the amounts of municipal waste generated and treated in the European Union (EU-28) for the period 1995 to 2016 by treatment method in million tonnes.
For 2016, municipal waste generation totals vary considerably, ranging from 261 kg per capita in Romania to 777 kg per capita in Denmark with average in Europe: 483 kg per capita [6].
Even though more waste is being generated in the EU-28, the total amount of municipal waste landfilled has diminished. In the reference period (1995–2016), the total municipal waste landfilled in the EU-28 fell by 85 million tonnes, or 59%, from 145 million tonnes (302 kg per capita) in 1995 to 60 million tonnes (118 kg per capita) in 2016. This corresponds to an average annual decline of 4.1%. For the shorter period 2005–16 landfilling has fallen by as much as 5.4% per year on average. As a result, the landfilling rate (landfilled waste as share of generated waste) compared with municipal waste generation in the EU-28 dropped from 64% in 1995 to 24% in 2016.
Fig. 1.2 Municipal waste generated and treated by EU countries (28) from 1995 to 2016.
The recovery of organic material by composting has grown with an average annual rate of 5.1% from 1995 to 2016. Recycling and composting together accounted for 45% in 2016 relative to waste generation. Waste incineration has also grown steadily in the reference period, though not as much as recycling and composting. Since 1995, the amount of municipal waste incinerated in the EU-28 has risen by 34 million tonnes or 112% and accounted for 68 million tonnes in 2016.
1.2. Situation in the United States
The U.S. Environmental Protection Agency (EPA) supports the policy transition from focusing on waste management to focusing on Sustainable Materials Management (SMM), which refers to the use and reuse of materials across their entire life cycle [7]. SMM conserves resources, reduces waste and minimizes the environmental impacts of materials.
EPA’s integrated waste management hierarchy includes the following pathways:
• Source reduction (or waste prevention), including the reuse of products and the on-site (or backyard) composting of yard trimmings;
• Recycling;
• Composting, including off-site (or community) composting;
• Combustion with energy recovery; and
• Disposal through landfilling.
The total generation of municipal solid waste in USA was 262.4 million tons of MSW in 2015, approximately 3.5 million tons more than the amount generated in 2014. MSW generated in 2015 increased to 4.48 pounds per person per day.
In 2015, plastic products generation was 34.5 million tons, or 13.1% of generation. This was an increase of 3.1 million tons from 2010 to 2015, and it came from durable goods and the containers and packaging categories. Plastics generation has grown from 8.2% of generation in 1990 to 13.1% in 2015. Plastics generation as a percent of total generation has grown slightly over the past five years.
Over the last few decades, the generation, recycling, composting, and disposal of MSW have changed substantially. The recycling rate has increased–from less than 10% of MSW generated in 1980 to over 34% in 2012. Disposal of waste to a landfill has decreased from 89% of the amount generated in 1980 to under 54% of MSW in 2012.
Organic materials are the largest components of MSW in USA. Paper and paperboard products account for over 27% of the waste stream and yard trimmings and food waste account for another 28%. Plastics comprise about 13%; metals make up 9%; and rubber, leather, and textiles account for almost 8%.
In 2012, over 65 million tons of MSW was recovered through recycling and over 21 million tons through composting. About 29 million tons of MSW was combusted for energy recovery (about 12%) (Fig. 1.3).
Fig. 1.3 Municipal waste generated, recovered for recycling and composting in the USA from 1960 to 2012.
1.3. Situation in other regions of the world
The significant increase in plastics consumption is also observed in other regions of the world. For example, rapid industrialization and economic development in Singapore have caused a tremendous increase in solid waste generation. The yearly disposed solid waste increased from 0.74 million tonnes in 1972 to 2.80 million tonnes in 2000 (5) [8]. It is estimated that solid waste generation in Singapore has amounted to about 4.5–4.8 million tonnes per year. Plastics accounts for 5.8% of the total solid waste, positioning himself at the third position after food waste (38.3%) and paper/cardboard (20.60%). Taking into account that plastic bags and bottles have become one of the major solid waste stream, using waste plastics to manufacture polymer concrete and developing biodegradable plastics have received much attention in recent years.
In Australia, the annual plastics consumption has increased from 1,336,386 in 1997 to 1,476,690 tonnes in 2011–2, whereas the total recycling rate of plastics has increased from 7.0% to 20.5% [9]. A total of 302,635 tonnes of plastics were sent for recycling, either locally or via export in 2011–12.
In China, along with urbanization, population growth and industrialization, the quantity of municipal solid waste generation has been increasing rapidly. MSW generation in China has increased rapidly in the past 30 years, from 31,320 thousand tons in 1980 to 178,602 thousand tons in 2014, with an annual average growth rate (AAGR) of 5.5% [10]. As well as MSW generation in 2014 is 5.7 times than that in 1980. A slight decline is observed during the five consecutive years of 2006–10, which could be attributed to the revision of the ‘Law on Solid Waste’ in 2004. MSW generation per capita increased rapidly until the early 1990s. After that, the MSW generation per capita showed an unsteadily decline from 913.0 to 653.2 g/per/day during between 1994 and to 2014 [10]. It was explained that the rate of urban population is increasing faster than the rate of MSW generation.
1.3.1. Asian countries
Collection and management of MSW in Asian countries are part of the problems whose solution has always rallied around sustainability based on the implementation of the 3Rs (reduction, reuse and recycling) technologies. Solid waste generated in Asian countries has risen to almost an equal amount to those generated in the developed countries at 0.7–0.8 kg/person/day [11].
Municipal solid waste management constitutes one of the most crucial health and environmental problems facing countries in the Arabian Gulf. It is estimated that 120 million tons of waste is produced per year in Gulf Cooperation Council states, of which little is recycled or even managed; 60% is from Saudi Arabia, 20% from the United Arab Emirates.
(UAE) and the rest is from Kuwait, Qatar, Oman and Bahrain. According to Qatar MSW organization, Qatar reached 1,000,000 tons of solid municipal waste annually corresponding to a daily solid waste of about 3,000 tons/day [12]. About 60% of MSW is organic material. Polymers account for about 14% of the total waste volume (5% by weight) produced by the municipal sector. Only 1–2% of this is being recycled, while the amount of polymers waste is expected to increase to 50% by the year 2020 from 2009 waste tonnage figure of 1,900 tons [12].
Environmental problems including disposal of municipal solid waste are recognized in Korea due to its limited carrying capacity. The population in Korea is 481 people per km², ranking the third-highest in the world. In Korea, the total MSW per person per day changed from 2.3 kg per day per person in 1991 to 1.04 kg per day per person in 2008 [13]. In 1995, the Korean government implemented a volume-based waste fee system (unit pricing system) that required every household to purchase certified plastic bags for waste disposal.
In Japan a detailed analysis of the composition of household waste was carried out for more than 30 years in Kyoto city [14]. It was reported that packaging waste accounted for 60% more than other household waste in volume ratio, and this pointed out that measures to deal with packaging waste were vital to reduce household waste. On average, each person in Japan uses 1.1 plastic shopping bags and 2.2. plastic packages daily.
1.3.2. Africa
The average urban MSW waste production in Africa is around 230 kg/head/year of which the organic content is around 56% [15]. A sustainability assessment for practical waste treatment and disposal scenarios for Africa was reported [15]. It was recommended that waste recycling and composting was beneficial over controlled landfilling.
1.3.3. Brasil
The urban solid waste generated in Brasil reaches 190,000 Mg/day, in which São Paulo Municipality solely is responsible for about 7.5% of that total. Almost 64% of urban solid waste (USW) collected in Brasil (2008) is disposed in sanitary landfills, 16% in controlled landfills, 18% in open sky dumps, 2% is recycled and a negligible fraction is incinerated [16]. In São Paulo Municipality, the Sorting and Composting Waste Treatment Plant (SCWTP) is suggested as an appropriate way to manage the 14,000 Mg of USW generated daily by 11 million habitants in 2010. The majority amount (84.5% in wet weight) of USW in São Paulo Municipality is taking to sanitary landfills, only 13.5% is sent to SCWTP, and the remaining 2% is incinerated. In 2015, Brazil’s generation of MSW was around 79.9 million t, corresponding to 1.071 kg MSW person-1 day-1 [17].
Recently, a zero-waste strategy is growing in popularity as one of the most visionary concepts for solving waste concepts. Zero waste means designing and managing products and processes systemically to avoid and eliminate waste, and to recover all resources from the waste stream [18]. It not only focuses on recycling of products but also aims to restructure their design, production and distribution to prevent waste emerging in the first place. Three high consuming cities (Adelaide, San Francisco and Stockholm) have declared their zero waste vision [18]. The average person generated around 681 kg of MSW in Adelaide in 2008–9. Around 46% of all MSW was recycled, 8% was composted and the remaining 46% was disposed to landfill [18]. In San Francisco 609 kg per person per year of MSW was generated in 2008. MSW was managed by recycling (52%), composting (20%) and landfill (28%). The average person in Stockholm generated around 480 kg of MSW per year, which 59% was incinerated, 31% was recycled, 1% was composted and 9% was landfilled.
Plastics, especially from packaging, have gained increasing attention in waste management, driving many policy initiatives to improve the circularity of these materials in the economy to increase resource efficiency. In this context, the EU has proposed the circular economy concept, which foresees a production and consumption system where materials are circulated as wastes are re-used, recycled and recovered [19]. Plastics are considered as one of the five priority areas in the EU action plan for the circular economy.
However, despite the efforts which have been made, overall waste volumes are growing. Management of plastics waste remains a problem. The observed increased plastics consumption throughout the world makes it necessary the development of more recyclable and/or biodegradable plastics to reduce the amount of plastic to landfill. According to amendment to European Directive on packaging and packaging waste [20] recovery and recycling of packaging waste should be further increased to reduce its environmental impact.
Compostable polymers which have been designed to be disposed after their useful life by means of organic recycling, i.e. composting are one of the strategic options available for the management of plastic waste. Composting is an attractive alternative for reducing solid waste and is especially suitable for those segments of conventional plastics in which recycling is difficult or economically non feasible.
The growing environmental awareness and new rules and regulations, as well as new trends in solid waste management have led scientists to increase activities on the design of compostable polymer materials that easily degrade under well-defined environmental conditions.
References
[1] Plastics – the facts . PlasticsEurope; 2017.
[2] European Parliament and Council Directive 94/62/EC of 20 December 1994 on packaging and packaging waste.
[3] Council Directive 75/442/EEC on waste, as amended by Council Directive 91/156/EEC.
[4] Manfredi S, Goralczyk M. Life cycle indicators for monitoring the environmental performance of European waste management. Resour Conserv Recycl . 2013;81:8.
[5] Waste generated and treated in Europe. Data 1995-2003 . Luxembourg: European Commission, Eurostat; 2005.
[6] Waste generated and treated in Europe. Data extracted in July 2018, European Commission, Eurostat.
[7] Municipal solid waste generation, recycling, and disposal in the United States: facts and figures for 2012. United States Environmental Protection Agency. https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/national-overview-facts-and-figures-materials.
[8] Bai R, Sutanto M. The practice and challenges of solid waste management in Singapore. Waste Manag . 2002;22:557.
[9] 2011–2012 national plastics recycling survey, final report . PACIA; May 2013.
[10] Gu B, Jiang S, Wang H, Wang Z, Jia R, Yang J, He S, Cheng R. Characterization, quantification and management of China’s municipal solid waste in spatiotemporal distributions: a review. Waste Manag . 2017;61:67.
[11] Othman S.N, Noor Z.Z, Abba A.H, Yusuf R.O, Abu Hassan M.A. Review on life cycle assessment of integrated solid waste management in some Asian countries. J Clean Prod . 2013;41:251.
[12] Al- Maaded M, Madi N.K, Kahraman R, Hodzic A, Ozerkan N.G. An overview of solid waste management and plastic recycling in Qatar. J Polym Environ . 2012;20:186–194.
[13] Lee S, Paik H.S. Korean household waste management and recycling behavior. Build Environ . 2011;46:1159.
[14] Takatsuki H. Waste problems and our lifestyle. Waste Manag . 2013;33:2145.
[15] Couth R, Trois C. Sustainable waste management in Africa through CDM projects. Waste Manag . 2012;32:2115.
[16] Agostinho F, Almeida C.M.B, Bonilla S.H, Sacomano J.B, Giannetti B.F. Urban solid waste plant treatment in Brazil: is there a net energy yield on the recovered materials? Resour Conserv Recycl . 2013;73:143.
[17] de Souza Marotta Alfaia R.G, Moraes Costa A, Carbonelli Campos J. Municipal solid waste in Brazil: a review. Waste Manag Res . 2017;35:1195.
[18] Zaman A.U, Lehmann S. The zero waste index: a performance measurement tool for waste management systems in a zero waste city
. J Clean Prod . 2017;50:123.
[19] Communication from the Commission to the European Parliament, the Council, The European Economic and Social Committee and the Committee of the Regions. Closing the loop – an EU action plan for the circular economy, Brussels; 2015.
[20] Directive 2004/12/EC of the European Parliament and Council of 11 February 2004 amending directive 94/62/EC of 20 December 1994 on packaging and packaging waste.
Chapter 2
Compostable polymer materials – definitions, structures and methods of preparation
Abstract
Compostable polymers which have been designed to be disposed after their useful life by means of organic recycling, i.e. composting, are one of the strategic options available for the management of plastic waste. This review gives the overview of compostable polymer materials starting from definitions, explaining differences in comparison with biodegradable polymers. It discusses origin (synthetic and natural), structures and methods of preparation of compostable polymers. Examples of commercially available compostable polymers are given.
Keywords
Compostable polymers; Biodegradable polymers; Synthesis; Methods of preparation; Polylactic acid; Polyhydoxyalkanoates; Thermoplastic starch; Cellulose; Proteins; Chitosan; Aliphatic polyesters; Aromatic polyesters; Polycaprolactone; Polyesteramide; Polyvinyl alcohol
2.1 Biodegradable polymers from renewable resources
2.1.1 Poly(lactic acid) – PLA
2.1.2 Polyhydroxyalkanoates – PHA
2.1.3 Thermoplastic starch – TPS
2.2 Other compostable polymers from renewable resources
2.2.1 Cellulose
2.2.2 Chitosan
2.2.3 Proteins
2.3 Biodegradable polymers from petrochemical sources
2.3.1 Aliphatic polyesters and copolyesters
2.3.2 Aromatic polyesters and copolyesters
2.3.3 Poly(caprolactone) – PCL
2.3.4 Poly(esteramide) – PEA
2.3.5 Poly(vinyl alcohol) – PVA
2.3.6 Blends
References
‘Biodegradable polymers’ or ‘compostable polymers’ were first commercially introduced in the 1980s. These first-generation biodegradable products were made from a conventional polymer, usually polyolefin (e.g. polyethylene) mixed together with starch or some other organic substance. When starch was eaten by microorganisms, the products were broken down, leaving small fragments of polyolefins.
In 1994 Narayan et al. wrote: ‘The U.S. biodegradables industry fumbled at the beginning by introducing starch filled (6–15%) polyolefins as true biodegradable materials. These at best were only biodisintegradable and not completely biodegradable. Data showed that only the surface starch biodegraded, leaving behind a recalcitrant polyethylene material’ [1].
The situation confused consumers and government regulators, and put into question the biodegradable plastics market for some years. Since then the confusion or misunderstanding appeared about what was and what was not biodegradable and/or compostable. Additionally, no scientifically based test methods or standards existed to support claims made by plastics manufacturers for the ‘biodegradability’ or ‘compostability’ of their products.
More recently, international and national standards bodies, i.e. International Organization for Standardization (ISO), American Society for Testing and Materials (ASTM), Japanese Standards Association (JIS) and European Organization for Standardization (EN), have developed definitions related to the degradation of plastics. Nowadays, ISO and ASTM standards exist describing in detail the purposes of ‘biodegradable’ and ‘compostable’.
The ASTM D6400 standard establishes the requirements for the labelling of materials and products, including packaging made from plastics, as ‘compostable in municipal and industrial composting facilities’ (Table 2.1).
ISO 17088 specifies test methods and requirements to determine and label plastic products and products made from plastics that are designed to be recovered through aerobic composting. It particularly establishes the requirements for labelling of materials and products, including packaging made from plastics, as ‘compostable’, ‘compostable in municipal and industrial composting facilities’ and ‘biodegradable during composting’ (Table 2.2).
The definition of ‘compostable plastic’ proposed in ISO 17088 is identical to that given in the ASTM D6400 standard.
In spite of its very large use (and abuse) term ‘biodegradable’ is not helpful because it is not informative. The term does not convey any information about the specific environment where the biodegradation is supposed to take place, the rate that will regulate the process (fast, slow), and the extent of biodegradation (partial or total conversion into CO2).
Table 2.1
Table 2.2
The definition of ‘biodegradable’ has been assessed during the past decade. Some examples of definitions of ‘biodegradable plastic’ are given below.
ASTM definition [2] : ‘a degradable plastic in which the degradation results from the action of naturally occurring microorganisms such as bacteria, fungi, and algae’.
ISO and CEN definition [4] : ‘degradable plastic in which degradation results in lower molecular weight fragments produced by the action of naturally occurring microorganisms such as bacteria, fungi and algae’.
According to ISO definition [4] degradable plastic means ‘A plastic designed to undergo a significant change in its chemical structure under specific environmental conditions resulting in a loss of some properties that may vary as measured by standard test methods appropriate to the plastic and the application in a period of time that determines its classification. ‘
Japanese Biodegradable Polymers Society (BPS) defines biodegradable plastics (called GreenPla) as plastics which can be used as conventional plastics, while on disposal they decompose to water and carbon dioxide by the action of microorganisms commonly existing in the natural environment [5].
Most of the definitions of biodegradation are based on the same concept: the action of microorganisms on the material and its conversion into carbon dioxide or methane and water.
A plastic can be degradable without being biodegradable, i.e. it might disintegrate into pieces or even an invisible powder, but not be assimilated by microorganisms. A plastic can be degradable and even biodegradable without being compostable, i.e. it might biodegrade at a rate that is too slow to be called compostable [6].
The difference between biodegradable and compostable polymers lies in additional requirements related to the latter. Besides biodegradation into carbon dioxide, water, inorganic compounds, and biomass compostable polymers must fulfil other criteria such as compatibility with the composting process, no negative effect on quality of compost and a degradation rate consistent with other known composting materials.
Simplified relationships between degradable, biodegradable and compostable polymers is given in Fig. 2.1.
It is noteworthy that compostable plastics are a priori designed for a given method of safe disposal, i.e. composting. This means that after their useful life they will biodegrade in a composting process. The idea of compostable polymers is in agreement with life cycle thinking.
To summarize, the requirements a material must satisfy to be termed ‘compostable’ include mineralization (i.e. biodegradation to carbon dioxide, water and biomass), disintegration into a composting system, and completion of its biodegradation during the end-use of the compost, which, moreover, must meet relevant quality criteria, e.g. no ecotoxicity. The satisfaction of requirements should be proved by standardized test methods. These requirements and test methods are described in detail in Chapters 5 and 6.
Compostable polymers can be divided according to source of origin or method of their preparation (Fig. 2.2).
Fig. 2.1 Simplified relationships between degradable, biodegradable and compostable polymers.
Fig. 2.2 Classification of compostable polymers.
On the basis of origin, compostable polymers are derived from renewable and petrochemical resources.
Biodegradable polymers from renewable resources include:
1. Polylactide (PLA).
2. Polyhydroxyalkanoates: poly(3-hydroxybutyrate) (PHB).
3. Thermoplastic starch (TPS).
4. Cellulose.
5. Chitosan.
6. Proteins.
Biodegradable polymers from petroleum sources comprise:
1. Aliphatic polyesters and copolyesters (e.g. poly(butylene succinate) – PBS; poly(butylene succinate adipate) – PBSA).
2. Aromatic copolyesters (e.g. poly(butylene adipate terephthalate) – PBAT).
3. Poly(ε-caprolactone) – PCL.
4. Polyesteramides – PEA.
5. Poly(vinyl alcohol) – PVA.
There are three principal ways to produce polymers from renewable resources, i.e. bio-based polymers, i.e.:
1. to make use of natural polymers which may be modified but remain intact to a large extent (e.g. starch polymers);
2. to produce bio-based monomers by fermentation which are then polymerized (e.g. polylactic acid);
3.