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Compostable Polymer Materials This Page Intentionally Left Blank Compostable Polymer Materials Compostable Polymer Materials This page intentionally left blank Compostable Polymer Materials Ewa Rudnik Amsterdam • Boston • Heidelberg • London • New York • Oxford Paris • San Diego • San Francisco • Singapore • Sydney • Tokyo Elsevier The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK Radarweg 29, PO Box 211, 1000 AE Amsterdam, The Netherlands First edition 2008 Copyright © 2008 Elsevier Ltd. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (ϩ44) (0) 1865 843830; fax (ϩ44) (0) 1865 853333; email: [email protected]. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-08-045371-2 For information on all elsevier publications visit our website at www.books.elsevier.com Typeset by Charon Tec Ltd (A Macmillan Company), Chennai, India www.charontec.com Printed and bound in Hungary 08 09 10 10 9 8 7 6 5 4 3 2 1 Contents Preface vii Symbols and abbreviations xi CHAPTER 1 Introduction 3 1.1 Situation in Europe 4 1.2 Situation in the United States 6 1.3 Situation in other regions of the world 6 References 7 CHAPTER 2 Compostable polymer materials – definitions, structures and methods of preparation 11 2.1 Biodegradable polymers from renewable resources 14 2.2 Other compostable polymers from renewable resources 25 2.3 Biodegradable polymers from petrochemical sources 28 References 35 CHAPTER 3 Properties and applications 39 3.1 Biodegradable polymers from renewable resources 39 3.2 Biodegradable polymers from petrochemical sources 52 3.3 Blends 60 3.4 Summary 63 References 64 CHAPTER 4 Thermal and thermooxidative degradation 73 4.1 Biodegradable polymers from renewable resources 73 4.2 Biodegradable polymers from petrochemical sources 77 4.3 Blends 79 4.4 Summary of thermal stability of compostable polymer materials 80 References 83 CHAPTER 5 Composting methods and legislation 89 5.1 Composting definitions 89 5.2 Composting process and methods 89 5.3 Composting of biodegradable polymers 98 5.4 Labelling systems in different regions 103 5.5 Cooperation between certification and labelling systems 108 References 109 vi Contents CHAPTER 6 Biodegradability testing of compostable polymer materials 113 6.1 Definitions related to biodegradation testing 113 6.2 International standards related to composting 115 6.3 Principles of main standards related to composting and biodegradability testing 117 6.4 Composting at laboratory scale 123 6.5 Biodegradability testing methods 127 6.6 Biodegradation of biodegradable polymers from renewable resources 130 6.7 Biodegradation of biodegradable polymers from petrochemical sources 142 6.8 Biodegradation of blends 153 6.9 Summary of composting 159 References 159 CHAPTER 7 Ecotoxicological assessment 169 7.1 Introduction 169 7.2 Definitions 170 7.3 Methods 170 7.4 Compostable polymers ecotoxicity testing 176 7.5 Conclusions 177 References 180 CHAPTER 8 Environmental impact of compostable polymer materials 183 8.1 Introduction 183 8.2 Life cycle assessment methodology 183 8.3 Life cycle assessment of poly(lactic acid) 186 8.4 Polyhydroxyalkanoates 187 8.5 Starch-based polymers 191 8.6 Blends 192 8.7 Overview 194 8.8 Conclusions 197 References 198 CHAPTER 9 Perspectives 203 9.1 Price evolution 203 9.2 Capacity 204 9.3 Legislation initiatives 204 9.4 Demand estimation 206 9.5 Conclusions 207 References 208 Index 209 Preface Let us permit nature to have her way. She understands her business better than we do. Michel do Montaigne If one way be better than another, that you may be sure is Nature’s way. Aristotle Composting is Nature’s way of recycling. When a plant dies, the stem, flowers and leaves are broken down by microbes in the soil and the nutrients they contain will feed the seed to grow into a seedling and then into a mature plant. The cycle is complete. The natural decay proc- esses that occur in soil include raw organic materials like manure, leaves, grass clippings, food wastes and municipal biosolids. During composting organic residues are converted to stable soil-like humic substances, called compost. This final product is a valuable soil resource for agricultural, horticultural and silvicultural purposes. Composting is probably the oldest recycling technique in the world. The art of composting dates back to the early Greeks and Romans. There are also biblical references to composting. The Chinese are thought to be the first people to develop larger composting sites for use in farming. George Washington, the first president of the USA, was the first recognized com- poster in America. The knowledge and practices of composting were passed from country to country, down through generations until today where modern composting facilities have been developed. The composting process used in municipal or industrial composting facilities is only mim- icking and speeding up what nature is doing every day. The difference is that the degradative rates in composting are higher because of the higher temperatures. The composting industry has expanded significantly in recent years and this trend seems set to continue in different regions in the world, e.g. in Europe, America and in Asian countries like China. Environmental awareness has led to a growing interest in developing an environ- mentally friendly manner of disposal of municipal and industrial wastes. It is known that plastics waste contribute to a large volume of municipal waste. In general, waste management strategy puts a growing emphasis on the three Rs: Reduce, Reuse, and Recycle. Composting, recognized as organic recycling, provides a means of accomplishing these objectives. It is noteworthy that composting as a technology is adaptable and suitable for treating wastes in a variety of socioeconomic and geographical locations. The aim of the book is to describe in a coherent manner the special class of polymers espe- cially designed to be disposed of after their useful life in composting facilities. Compostable plastics are polymers that undergo degradation by biological processes during composting to yield CO2, water, inorganic compounds and biomass at a rate consistent with known composta- ble materials (e.g. cellulose). The book is concerned with the hot topic of dealing with a family of polymers that are designed to be degraded in industrial and municipal compost facilities. Recently, compostable packaging materials were introduced into the market to reduce the amounts of conventional packaging materials and at the same time be recovered by the munici- pal organic waste collection system. An example of commercial implementation of composta- ble polymers includes Cargill Dow Nature Works polylactic acid (PLA), which is produced at a rate of 140 000 tonnes/year at Blair, Nebraska (USA), via carbohydrate fermentation. Other vii viii Preface global companies are also producing compostable polymer materials. NEC is using a PLA composite with kenaf fibres for laptop computer cases. Polyhydroxyalkanoates produced by microbial “biofactories” are suitable for films, fibres, adhesives, coatings, moulded goods and a variety of other applications. The largest and most successful effort to date to recycle organic waste and use composta- ble cutlery and food serviceware was at the 2000 Olympic Games held in Sydney (Australia) where the collection and composting of the wastes generated by the nine million visitors to the Games resulted in the recovery of 76% of the solid wastes generated. I hope that this book may be useful in developing ideas about composting and provides information for researchers and students interested in materials science as well as ecologi- cal issues. The book covers the entire spectrum of preparation, properties, degradation, and environmental issues of this kind of polymer. Emphasis is given to the recent studies concern- ing compostability and ecotoxicological assessment of polymer materials – important issues from an ecological point of view. Moreover, thermal behaviour of compostable polymers is described. Future perspectives, including price evolution during last decade and market esti- mation, are presented. Chapter 1 introduces the problem, explaining the role of compostable polymer materials in a sustainable development and the reasons for the growing interest. Chapter 2 gives an overview of compostable polymer materials starting with definitions, and explaining differences in comparison with biodegradable polymers. It discusses origin (syn- thetic and natural), structures and methods of preparation of compostable polymers. The pro- ducers 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 behaviour of compostable polymer materials during degradation in different environments (inert and oxidative
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