Compostability of bioplastic packaging materials: an overview

Packaging waste accounted for 78.81 million tons or 31.6% of the total municipal solid waste (MSW) in 2003 in the USA, 56.3 million tons or 25% of the MSW in 2005 in Europe, and 3.3 million tons or 10% of the MSW in 2004 in Australia. Currently, in the USA the dominant method of packaging waste disposal is landfill, followed by recycling, incineration, and composting. Since landfill occupies valuable space and results in the generation of greenhouse gases and contaminants, recovery methods such as reuse, recycling and/or composting are encouraged as a way of reducing packaging waste disposal. Most of the common materials used in packaging (i.e., steel, aluminum, glass, paper, paperboard, plastics, and wood) can be efficiently recovered by recycling; however, if packaging materials are soiled with foods or other biological substances, physical recycling of these materials may be impractical. Therefore, composting some of these packaging materials is a promising way to reduce MSW. As biopolymers are developed and increasingly used in applications such as food, pharmaceutical, and consumer goods packaging, composting could become one of the prevailing methods for disposal of packaging waste provided that industry, governments, and consumers encourage and embrace this alternative. The main objective of this article is to provide an overview of the current situation of packaging compostability, to describe the main mechanisms that make a biopolymer compostable, to delineate the main methods to compost these biomaterials, and to explain the main standards for assessing compostability, and the current status of biopolymer labeling. Biopolymers such as polylactide and poly(hydroxybutyrate) are increasingly becoming available for use in food, medical, and consumer goods packaging applications. The main claims of these new biomaterials are that they are obtained from renewable resources and that they can be biodegraded in biological environments such as soil and compost. Although recycling could be energetically more favorable than composting for these materials, it may not be practical because of excessive sorting and cleaning requirements. Therefore, the main focus is to dispose them by composting. So far, there is no formal agreement between companies, governments and consumers as to how this packaging composting will take place; therefore, the main drivers for their use have been green marketing and pseudo-environmental consciousness related to high fuel prices. Packaging compostability could be an alternative for the disposal of biobased materials as long as society as a whole is willing to formally address the challenge to clearly understand the cradle-to-grave life of a compostable package, and to include these new compostable polymers in food, manure, or yard waste composting facilities.     

Biodegradable polyesters for medical and ecological applications

Numerous biodegradable polymers have been developed in the last two decades. In terms of application, biodegradable polymers are classified into three groups: medical, ecological, and dual application, while in terms of origin they are divided into two groups: natural and synthetic. This review article will outline classification, requirements, applications, physical properties, biodegradability, and degradation mechanisms of representative biodegradable polymers that have already been commercialized or are under investigation. Among the biodegradable polymers, recent developments of aliphatic polyesters, especially polylactides and poly(lactic acid)s, will be mainly described in the last part.     

Degradable polymer blends. I. Screening of miscible polymers

Blends of biodegradable polymers having properties distinct from the individual polymer components, and that are suitable for use as carriers of pharmaceutically active agents, were prepared from two or more polyanhydrides, polyesters, and mixtures of polyanhydrides and low molecular weight polyesters. The blends have different properties than the original polymers, providing a mean for altering the characteristics of the polymeric matrix without altering the chemical structure of the component polymers. Aliphatic, aromatic, and copolymers of polyanhydrides were miscible in each other and formed less crystalline compositions with a single melting point which was lower than the melting point of the starting polymers. The polyesters: poly(lactide-glycolide), poly(caprolactone), and poly(hydroxybutyric acid) presented some miscibility in each other. However, the polyanhydrides were immiscible with the polyesters resulting in a complete phase separation both in solution or in melt mixing. Only low molecular weight polyesters (in the range of 2000) of lactide and glycolide, mandelic acid, propylenefumarate, and caprolactone presented some miscibility with polyanhydrides. Similarly, poly(orthoester) and hydroxybutyric acid polymers formed a uniform mixture with the anhydride polymers which had the two melting points of the original polymers. Drug release from polymer blends composed of poly(hydroxybutyric acid) or low molecular weight poly(lactic acid) with poly(sebacic anhydride) (PSA) showed a constant release of drug for periods from 2 weeks to several months as a function of the PSA content in the blend. Increasing the content of PSA, a fast degrading polymer, increases the release rate from the blend. © 1993 John Wiley & Sons, Inc.     

Correlation between mechanical adhesion and interfacial properties of starch/biodegradable polyester blends

Biopolymers are preferred ingredients for the manufacture of materials because they are based on abundantly available and renewable raw materials that have benign environmental problems associated with their production, fabrication, use, and disposal; however, the wide use of biopolymers in engineering applications has not been achieved, mainly because of the inferior quality of many biopolymer‐based products. To overcome this limitation, studies have been initiated on blends of biopolymers and biodegradable synthetic polymers. We used the contact angle of probe liquids to measure the surface energy of polystyrene, the biodegradable polyesters polycaprolactone, poly(hydroxybutyrate‐co‐hydroxyvalerate), polylactic acid, polybutylene adipate terephthalate, and adipic poly(hydroxy ester ether), and normal starch. The surface energies were used to estimate the starch/polymer interfacial energy and work of adhesion. The calculated starch/polyester work of adhesion showed mixed correlation with published starch/polyester mechanical properties, indicating that factors other than interfacial properties might be dominant in determining the mechanical properties of some starch/polyester blends. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 920–930, 2001     

Synthetic biodegradable functional polymers for tissue engineering: a brief review

Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly (glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix (ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.     

To compost or not to compost: Carbon and energy footprints of biodegradable materials’ waste treatment

Many life cycle assessments of bio-based and biodegradable materials neglect the post-consumer waste treatment phase because of a lack of consistent data, even though this stage of the life cycle may strongly influence the conclusions. The aim of this paper is to approximate carbon and energy footprints of the waste treatment phase and to find out what the best waste treatment option for biodegradable materials is by modelling home and industrial composting, anaerobic digestion and incineration. We have compiled data-sets for the following biodegradable materials: paper, cellulose, starch, polylactic acid (PLA), starch/polycaprolactone (MaterBi), polybutyrate-adipate-terephthalate (PBAT, Ecoflex) and polyhydroxyalkanoates (PHA) on the basis of an extensive literature search, experiments and analogies with materials for which significant experience has been made. During biological waste treatment, the materials are metabolised so a part of their embodied carbon is emitted into air and the remainder is stored as compost or digestate. The compost or digestate can replace soil conditioners supporting humus formation, which is a benefit that cannot be achieved artificially. Experimental data on biodegradable materials shows a range across the amount of carbon stored of these materials, and more trials will be required in the future to reduce these uncertainties. Experimental data has also shown that home and industrial composting differ in their emissions of nitrous oxide and methane, but it should be noted that data availability on home composting is limited. The results show that anaerobic digestion has the lowest footprint for the current level of technology, but incineration may become better in the future if energy efficiency in waste incineration plants improves significantly. Home composting is roughly equal to incineration with energy recovery in terms of carbon and energy footprint when carbon credits are considered. The same applies to industrial composting if carbon credits are assigned for compost to replace straw. Carbon credits can therefore considerably affect the results, but there are significant uncertainties in how they are calculated. Incineration may become better than home composting in the future if the average energy efficiency in waste incineration plants improves significantly. However, biological waste treatment options should be chosen when soil carbon is a limiting factor.     

开环可控聚合制备脂肪族聚酯的最新研究进展

近年来,作为生物降解高分子材料,脂肪族聚酯由于良好的生物降解性及生物相容性受到人们的广泛关注。脂肪族聚酯在环境友好材料和生物医用材料领域都具有极大的应用价值,目前,部分聚酯材料已经商品化。与此同时,脂肪族聚酯的合成方法尤其是活性开环聚合也成为学术界及工业领域的研究热点。采用开环聚合法得到的聚合产物化学组成精确、分子量分...     

Determination of trimethylsilanol in the environment by LT-GC/ICP-OES and GC-MS

The combination of element-specific investigation by low temperature gas chromatography coupled on-line with inductively coupled plasma optical emission spectroscopy (LT-GC/ICP-OES) and gas chromatography using mass spectrometry detection (GC-MS), as an additional analytical technique for molecular identification, was employed for the determination of volatile organosilicon species. Gaseous and liquid samples from waste deposit sites, waste composting tanks and sewage-disposal plants were investigated. It was frequently possible to identify the labile silanol compound trimethylsilanol as a dominant silicon species in waste disposal and waste composting gases. The results presented give rise to the assumption that trimethylsilanol is a volatile product of the degradation of organosilicon materials under special environmental conditions.     

Degradation and recovery in poly(butylene adipate-co-terephthalate)/ thermoplastic starch blends

The economic and social impact of the increasing waste disposal problems of conventional plastic materials are well known and promoted the search for better recyclable and biodegradable polymers, blends and compounds. Fully biodegradable blends of poly(butylene adipate-co-terephthalate) (PBAT), a synthetic copolyester, and thermoplastic starch (TPS), a natural polysaccharide, are of technical and economic interest in the quest for eco-friendly polymeric materials to substitute conventional alternatives. One of less desirable characteristics of many new biodegradable materials is their relative thermal instability (degradation) under processing conditions.In the present work, PBAT/TPS blends with up to 30% TPS were processed at different temperatures in a laboratory internal mixer, with and without the incorporation of a chain extender additive (Joncryl). The rate of change of torque during the melt processing stage, adjusted to eliminate minor temperature variations, is a very sensitive indicator of variation of molar mass due to degradation and recovery. It was found that TPS content promotes thermal degradation in the PBAT/TPS blends at levels above those observed in neat components, in a strongly composition and temperature-dependent process. The addition of 1% of the chain extender additive partially reverts the process, especially during processing at high temperature.     

Determination of trimethylsilanol in the environment by LT-GC/ICP-OES and GC-MS

The combination of element-specific investigation by low temperature gas chromatography coupled on-line with inductively coupled plasma optical emission spectroscopy (LT-GC/ICP-OES) and gas chromatography using mass spectrometry detection (GC-MS), as an additional analytical technique for molecular identification, was employed for the determination of volatile organosilicon species. Gaseous and liquid samples from waste deposit sites, waste composting tanks and sewage-disposal plants were investigated. It was frequently possible to identify the labile silanol compound trimethylsilanol as a dominant silicon species in waste disposal and waste composting gases. The results presented give rise to the assumption that trimethylsilanol is a volatile product of the degradation of organosilicon materials under special environmental conditions. Received: 24 July 1997 / Revised: 8 October 1997 / Accepted: 21 October 1997     

Biodegradable polymer matrix nanocomposites for tissue engineering: A review

Nanocomposites have emerged in the last two decades as an efficient strategy to upgrade the structural and functional properties of synthetic polymers. Aliphatic polyesters as polylactide (PLA), poly(glycolides) (PGA), poly(?-caprolactone) (PCL) have attracted wide attention for their biodegradability and biocompatibility in the human body. A logic consequence has been the introduction of organic and inorganic nanofillers into biodegradable polymers to produce nanocomposites based on hydroxyapatite, metal nanoparticles or carbon nanotructures, in order to prepare new biomaterials with enhanced properties. Consequently, the improvement of interfacial adhesion between the polymer and the nanostructures has become the key technique in the nanocomposite process. In this review, different results on the fabrication of nanocomposites based on biodegradable polymers for specific field of tissue engineering are presented. The combination of bioresorbable polymers and nanostructures open new perspectives in the self-assembly of nanomaterials for biomedical applications with tuneable mechanical, thermal and electrical properties.     

Chemical preparation and characterization of new biodegradable aliphatic polyesters end‐capped with diverse steroidal moieties

Novel metal complexes with a single catalytic site and less transesterification seem to provide alternative efficient synthetic approaches to preparing new biodegradable and biologically responsive materials with well‐defined structures. In this study, we rationally designed a new category of aluminum metal complexes bearing a bulky Salen ligand and diverse steroidal alkoxy moieties to synthesize novel biodegradable aliphatic polyesters end‐capped with steroidal building blocks. At first, three new aluminum metal complexes ( 9 – 11 ) were synthesized with good yields of 80–90%, bearing cholesterol and diosgenin derivatives as functional alkoxy moieties. By means of nuclear magnetic resonance (NMR) spectrometry, matrix‐assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI–FTMS), and Fourier transform infrared spectrometry, the molecular structures of 9 – 11 were characterized. Furthermore, new biodegradable aliphatic polyesters, poly(ε‐caprolactone) and poly(δ‐valerolactone) end‐capped with diverse steroidal moieties, were synthesized through the ring‐opening polymerization of ε‐caprolactone and δ‐valerolactone catalyzed by these new metal complexes under 100 °C in toluene, and they were also characterized by gel permeation chromatography, NMR, MALDI–FTMS, differential scanning calorimetry, and thermogravimetric analysis. Very narrow molecular weight distributions were revealed for these new polymer products, and their thermal crystallization and stability strongly depended on the degree of polymerization of the polyester building blocks and the distinct steroidal moieties. Because of the nature of the steroidal moieties, these biodegradable polymers may pave a path to new possibilities as potential biomaterials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2045–2058, 2006     

Biodegradable liquid-crystalline aromatic polyesters

Two strategies designed for the mechanical reinforcement of biodegradable polyesters, such as poly-(ε-caprolactone), poly (L-lactide) and their copolyesters, are described. Both strategies utilize more or less biodegradable thermotropic aromatic polyesters as reinforcing component. However, the structures of the aromatic polyesters differ largely. For strategy I polyesters composed of substituted hydroquinones and substituted terephthalic acids are used (which may contain anhydride groups), whereas the polyesters of strategy II are made up of natural nontoxic monomers such as β-(4-hydroxyphenyl) propionic acid and 4-hydroxybenzoic acid.     

Nature or Petrochemistry?—Biologically Degradable Materials

Naturally occurring polymers have been utilized for a long time as materials, however, their application as plastics has been restricted because of their limited thermoplastic processability. Recently, the microbial synthesis of polyesters directly from carbohydrate sources has attracted considerable attention. The industrial-scale production of poly(lactic acid) from lactic acid generated by fermentation now provides a renewable resources-based polyester as a commodity plastic for the first time. The biodegradability of a given material is independent of its origin, and biodegradable plastics can equally well be prepared from fossil fuel feedstocks. A consideration of the overall carbon dioxide emissions and consumption of non-renewable resources over the entire life-cycle of a product is not necessarily favorable for plastics based on renewable resources with current technology-in addition to the feedstocks for the synthesis of the polymer materials, the feedstock for generation of the overall energy required for production and processing is decisive.     

PBS基生物降解材料的研究进展

PBS(聚丁二酸丁二醇酯 )是一种具有良好生物降解性的聚酯塑料。本文简述了PBS的基本特性、降解机理和制备方法 ,对各种PBS基生物降解材料的特性进行了分析 ,介绍了PBS基生物降解材料的研究进展     

Plastics of the Future? The Impact of Biodegradable Polymers on the Environment and on Society

In recent years the littering of plastics and the problems related to their persistence in the environment have become a major focus in both research and the news. Biodegradable polymers like poly(lactic acid) are seen as a suitable alternative to commodity plastics. However, poly(lactic acid) is basically non‐degradable in seawater. Similarly, the degradation rate of other biodegradable polymers also crucially depends on the environments they end up in, such as soil or marine water, or when used in biomedical devices. In this Minireview, we show that biodegradation tests carried out in artificial environments lack transferability to real conditions and, therefore, highlight the necessity of environmentally authentic and relevant field‐testing conditions. In addition, we focus on ecotoxicological implications of biodegradable polymers. We also consider the social aspects and ask how biodegradable polymers influence consumer behavior and municipal waste management. Taken together, this study is intended as a contribution towards evaluating the potential of biodegradable polymers as alternative materials to commodity plastics.     

A novel process for anaerobic composting of municipal solid waste

A novel process has been developed and evaluated in a pilotscale program for conversion of the biodegradable fraction of municipal solid waste (MSW) to methane via anaerobic composting. The sequential batch anaerobic composting (SEBAC) process employs leachate management to provide organisms, moisture, and nutrients required for rapid conversion of MSW and removal of inhibitory fermentation products during start-up. The biodegradable organic materials are converted to methane and carbon dioxide in 21–42 d, rather than the years required in landfills.     

Production of PHAs from agricultural waste material

Polyhydroxyalkanoates (PHAs) are biodegradable substitutes to fossil fuel plastics that can be produced from renewable raw materials such as saccharides, alcohols and low-molecular-weight fatty acids. They are completely degradable to carbon dioxide and water through natural microbiological mineralization. Consequently, neither their production nor their use or degradation have a negative ecological impact. By keeping closed the cycle of production and re-use, PHAs can enable at least part of the polymer-producing industry to switch from ecologically harmful end-of-the-pipe production methods towards sounder technologies. Up to now such polyesters have been produced biotechnologically from refined raw materials (e.g. glucose and sodium propionate), but they can as well be produced much cheaper from agricultural waste materials (e.g. molasses, maltose, glycerol phase from biodiesel production, whey), as long as these materials have a known composition and are available in appropriate quantities. Yield factors and specific rates for growth and PHA accumulation are shown for 3 strains of Alcaligenes latus for different agricultural waste carbon sources.     

Structural Effects on the Biodegradation of Aliphatic Polyesters

In advance of a discussion on structural effects on biodegradation, aliphatic polyesters as biodegradable structural materials were classified into four types regarding chemical structure, that is poly(ω-hydroxy acid), poly(β-hydroxyalkanoate), poly(ω-hydroxyalkanoate) and poly(alkylene dicarboxylate), and reviewed on synthesis route, thermal and physical properties, and biodegradability. The biodegradation mechanism of these aliphatic polyesters were discussed on the major mode of hydrolysis reaction in regard whether it was enzyme-catalyzed or not, and the substrate specificities of enzymes, such as lipases or PHA depolymerases, were discussed on the hydrolysis of the aliphatic polyesters in respect of primary structure. Moreover, the biodegradation behaviors were exceedingly influenced by solid-state morphology in addition to primary structure. The rate of enzymatic degradation of polycaprolactone fibers drawn with various draw ratios was dependent on draw ratios, suggesting that crystallinity and orientation of them affected biodegradability by lipase. In the study of enzymatic degradation of films made from butylene succinate – ethylene succinate copolymer, the dependence of degradation rate on polymeric compositions was ascribed to the degree of crystallinity rather than the primary structure. These studies revealed that the degree of crystallinity was the major rate-determining factor of biodegradation of solid polymers. © 1997 John Wiley & Sons, Ltd.     

Liquid chromatography under limiting conditions of desorption 4 separation of blends containing low-solubility polymers

Low solubility polymers, poly(ethylene terephthalate), PET and poly(butylene terephthalate), PBT were mutually separated at ambient temperature with help of a novel method, liquid chromatography under limiting conditions of desorption, LC LCD. The results demonstrate high selectivity of LC LCD, which enabled discrimination of macromolecules of well similar chemical structure, irrespectively of their molar mass. Above poly(terephthalate)s were also readily base-line separated from the aliphatic biodegradable polyesters poly(l-lactic acid) and poly(butylene adipate). The experimentally feasible LC LCD method produces narrow, focused peaks of polymers eluted behind the adsorption promoting barrier of appropriate liquid. This merit of LC LCD enables discrimination and identification of minor macromolecular constituents of multicomponent polymers and facilitates the application of method as an integral part of two-dimensional liquid chromatography for comprehensive molecular characterization of complex polymer systems.