Our plastic age

Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production. In this Theme Issue of Philosophical Transactions of the Royal Society, we describe current and future trends in usage, together with the many benefits that plastics bring to society. At the same time, we examine the environmental consequences resulting from the accumulation of waste plastic, the effects of plastic debris on wildlife and concerns for human health that arise from the production, usage and disposal of plastics. Finally, we consider some possible solutions to these problems together with the research and policy priorities necessary for their implementation.     

Plastics recycling: challenges and opportunities

Plastics are inexpensive, lightweight and durable materials, which can readily be moulded into a variety of products that find use in a wide range of applications. As a consequence, the production of plastics has increased markedly over the last 60 years. However, current levels of their usage and disposal generate several environmental problems. Around 4 per cent of world oil and gas production, a non-renewable resource, is used as feedstock for plastics and a further 3–4% is expended to provide energy for their manufacture. A major portion of plastic produced each year is used to make disposable items of packaging or other short-lived products that are discarded within a year of manufacture. These two observations alone indicate that our current use of plastics is not sustainable. In addition, because of the durability of the polymers involved, substantial quantities of discarded end-of-life plastics are accumulating as debris in landfills and in natural habitats worldwide.Recycling is one of the most important actions currently available to reduce these impacts and represents one of the most dynamic areas in the plastics industry today. Recycling provides opportunities to reduce oil usage, carbon dioxide emissions and the quantities of waste requiring disposal. Here, we briefly set recycling into context against other waste-reduction strategies, namely reduction in material use through downgauging or product reuse, the use of alternative biodegradable materials and energy recovery as fuel.While plastics have been recycled since the 1970s, the quantities that are recycled vary geographically, according to plastic type and application. Recycling of packaging materials has seen rapid expansion over the last decades in a number of countries. Advances in technologies and systems for the collection, sorting and reprocessing of recyclable plastics are creating new opportunities for recycling, and with the combined actions of the public, industry and governments it may be possible to divert the majority of plastic waste from landfills to recycling over the next decades.     

Recent Advances in Sustainable Plastic Upcycling and Biopolymers

Advances in scientific technology in the early twentieth century have facilitated the development of synthetic plastics that are lightweight, rigid, and can be easily molded into a desirable shape without changing their material properties. Thus, plastics become ubiquitous and indispensable materials that are used in various manufacturing sectors, including clothing, automotive, medical, and electronic industries. However, strong physical durability and chemical stability of synthetic plastics, most of which are produced from fossil fuels, hinder their complete degradation when they are improperly discarded after use. In addition, accumulated plastic wastes without degradation have caused severe environmental problems, such as microplastics pollution and plastic islands. Thus, the usage and production of plastics is not free from environmental pollution or resource depletion. In order to lessen the impact of climate change and reduce plastic pollution, it is necessary to understand and address the current plastic life cycles. In this review, “sustainable biopolymers” are suggested as a promising solution to the current plastic crisis. The desired properties of sustainable biopolymers and bio‐based and bio/chemical hybrid technologies for the development of sustainable biopolymers are mainly discussed.     

微生物降解塑料的研究进展

塑料广泛应用于人类的生活中,其中约80%的塑料垃圾被填埋,最终成为陆地和海洋垃圾。由于管理与处置不善,这些废弃物造成了巨大的环境污染,目前回收再利用是较好的处置方式,但对某些塑料废弃物并没有妥善的处置方式。生物降解作为环境友好的处置方式,具有巨大的应用潜力。本文对聚对苯二甲酸乙二醇酯、聚乙烯、聚氯乙烯、聚丙烯、聚苯乙烯和聚氨酯这6种常用塑料的降解微生物及生物降解机制进行了总结,对目前微生物降解塑料存在的问题进行了分析,并提出了促进微生物降解塑料应用的途径,为生物降解塑料菌株和降解酶的开发应用、降解机制研究提供理论参考。     

Fungal bioremediation of polyethylene: Challenges and perspectives

Plastics have become ubiquitous in both their adoption as materials and as environmental contaminants. Widespread pollution of these versatile, man-made and largely petroleum-derived polymers has resulted from their long-term mass production, inappropriate disposal and inadequate end of life management. Polyethylene (PE) is at the forefront of this problem, accounting for one-third of plastic demand in Europe in part due to its extensive use in packaging. Current recycling and incineration processes do not represent sustainable solutions to tackle plastic waste, especially once it becomes littered, and the development of new waste-management and remediation technologies are needed. Mycoremediation (fungal-based biodegradation) of PE has been the topic of several studies over the last two decades. The utility of these studies is limited by an inconclusive definition of biodegradation and a lack of knowledge regarding the biological systems responsible. This review highlights relevant features of fungi as potential bioremediation agents, before discussing the evidence for fungal biodegradation of both high- and low-density PE. An up-to-date perspective on mycoremediation as a future solution to PE waste is provided.     

Accumulation and fragmentation of plastic debris in global environments

One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic products commenced in the 1950s, plastic debris has accumulated in terrestrial environments, in the open ocean, on shorelines of even the most remote islands and in the deep sea. Annual clean-up operations, costing millions of pounds sterling, are now organized in many countries and on every continent. Here we document global plastics production and the accumulation of plastic waste. While plastics typically constitute approximately 10 per cent of discarded waste, they represent a much greater proportion of the debris accumulating on shorelines.Mega- and macro-plastics have accumulated in the highest densities in the Northern Hemisphere, adjacent to urban centres, in enclosed seas and at water convergences (fronts). We report lower densities on remote island shores, on the continental shelf seabed and the lowest densities (but still a documented presence) in the deep sea and Southern Ocean. The longevity of plastic is estimated to be hundreds to thousands of years, but is likely to be far longer in deep sea and non-surface polar environments. Plastic debris poses considerable threat by choking and starving wildlife, distributing non-native and potentially harmful organisms, absorbing toxic chemicals and degrading to micro-plastics that may subsequently be ingested. Well-established annual surveys on coasts and at sea have shown that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing: rather stable, increasing and decreasing trends have all been reported. The average size of plastic particles in the environment seems to be decreasing, and the abundance and global distribution of micro-plastic fragments have increased over the last few decades. However, the environmental consequences of such microscopic debris are still poorly understood.     

可降解塑料的微生物降解研究进展

塑料材料的广泛使用给环境带了巨大的污染和处理压力,使用可降解塑料替代传统塑料是解决这一问题的重要途径。可降解塑料的生物降解是由相应的微生物和降解酶来完成的。综述了目前常见的生物降解塑料的微生物降解研究和进展情况,明确了微生物在可降解塑料生物降解中的重要性。     

Biodegradable and compostable alternatives to conventional plastics

Packaging waste forms a significant part of municipal solid waste and has caused increasing environmental concerns, resulting in a strengthening of various regulations aimed at reducing the amounts generated. Among other materials, a wide range of oil-based polymers is currently used in packaging applications. These are virtually all non-biodegradable, and some are difficult to recycle or reuse due to being complex composites having varying levels of contamination. Recently, significant progress has been made in the development of biodegradable plastics, largely from renewable natural resources, to produce biodegradable materials with similar functionality to that of oil-based polymers. The expansion in these bio-based materials has several potential benefits for greenhouse gas balances and other environmental impacts over whole life cycles and in the use of renewable, rather than finite resources. It is intended that use of biodegradable materials will contribute to sustainability and reduction in the environmental impact associated with disposal of oil-based polymers.The diversity of biodegradable materials and their varying properties makes it difficult to make simple, generic assessments such as biodegradable products are all ‘good’ or petrochemical-based products are all ‘bad’. This paper discusses the potential impacts of biodegradable packaging materials and their waste management, particularly via composting. It presents the key issues that inform judgements of the benefits these materials have in relation to conventional, petrochemical-based counterparts. Specific examples are given from new research on biodegradability in simulated ‘home’ composting systems. It is the view of the authors that biodegradable packaging materials are most suitable for single-use disposable applications where the post-consumer waste can be locally composted.     

Transport and release of chemicals from plastics to the environment and to wildlife

Plastics debris in the marine environment, including resin pellets, fragments and microscopic plastic fragments, contain organic contaminants, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, petroleum hydrocarbons, organochlorine pesticides (2,2′-bis(p-chlorophenyl)-1,1,1-trichloroethane, hexachlorinated hexanes), polybrominated diphenylethers, alkylphenols and bisphenol A, at concentrations from sub ng g^–1 to µg g^–1. Some of these compounds are added during plastics manufacture, while others adsorb from the surrounding seawater. Concentrations of hydrophobic contaminants adsorbed on plastics showed distinct spatial variations reflecting global pollution patterns. Model calculations and experimental observations consistently show that polyethylene accumulates more organic contaminants than other plastics such as polypropylene and polyvinyl chloride. Both a mathematical model using equilibrium partitioning and experimental data have demonstrated the transfer of contaminants from plastic to organisms. A feeding experiment indicated that PCBs could transfer from contaminated plastics to streaked shearwater chicks. Plasticizers, other plastics additives and constitutional monomers also present potential threats in terrestrial environments because they can leach from waste disposal sites into groundwater and/or surface waters. Leaching and degradation of plasticizers and polymers are complex phenomena dependent on environmental conditions in the landfill and the chemical properties of each additive. Bisphenol A concentrations in leachates from municipal waste disposal sites in tropical Asia ranged from sub µg l^–1 to mg l^–1 and were correlated with the level of economic development.     

Biological degradation of plastics: a comprehensive review

Lack of degradability and the closing of landfill sites as well as growing water and land pollution problems have led to concern about plastics. With the excessive use of plastics and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. Awareness of the waste problem and its impact on the environment has awakened new interest in the area of degradable polymers. The interest in environmental issues is growing and there are increasing demands to develop material which do not burden the environment significantly. Biodegradation is necessary for water-soluble or water-immiscible polymers because they eventually enter streams which can neither be recycled nor incinerated. It is important to consider the microbial degradation of natural and synthetic polymers in order to understand what is necessary for biodegradation and the mechanisms involved. This requires understanding of the interactions between materials and microorganisms and the biochemical changes involved. Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. This paper reviews the current research on the biodegradation of biodegradable and also the conventional synthetic plastics and also use of various techniques for the analysis of degradation in vitro.     

Comparison of Plastic Packaging Waste Management Options: Feedstock Recycling versus Energy Recovery in Germany

Plastics recycling, especially as prescribed by the German Ordinance on Packaging Waste (Verpackungsverordnung), is a conspicuous example of closing material loops on a large scale. In Germany, an industry‐financed system (Duales System Deutschland) was established in 1991 to collect and recycle packaging waste from households. To cope with mixed plastics, various “feedstock‐recycling” processes were developed. We discuss the environmental benefits and the cost‐benefit ratio of the system relative to municipal solid waste (MSW) incineration, based on previously published life‐cycle assessment (LCA) studies. Included is a first‐time investigation of energy recovery in all German incinerators, the optimization opportunities, the impact on energy production and substitution processes, an estimation of the costs, and a cost‐benefit assessment. In an LCA, the total environmental impact of MSW incineration is mainly determined by the energy recovery ratio, which was found on average to reach 39% in current German incineration plants. Due to low revenues from additional energy generation, it is not cost‐effective to optimize the plants energetically. Energy from plastic incineration substitutes for a specific mixture of electric base‐load power, district heating, and process steam generation. Any additional energy from waste incineration will replace, in the long term, mainly natural gas, rather than coal. Incineration of plastic is compared with feedstock recycling methods in different scenarios. In all scenarios, the incineration of plastic leads to an increase of CO2 emissions compared to landfill, whereas feedstock recycling reduces CO2 emissions and saves energy resources. The costs of waste incineration are assumed to decrease by about 30% in the medium term. Today, the calculated costs of CO2 reduction in feedstock recycling are very high, but are ex‐pected to decline in the near future. Relative to incineration, the costs for conserving energy via feedstock recycling are 50% higher, but this gap will close in the near future if automatic sorting and processing are implemented in Germany.     

生物可降解塑料在不同环境条件下的降解研究进展北大核心CSCD

当前社会塑料制品的使用需求持续增加,塑料垃圾处理压力不断增大,减缓塑料污染成为当务之急,生物可降解塑料因可在一定生物活性环境下较快降解而备受关注,具有广阔的应用前景。生物可降解塑料降解条件复杂,影响因素众多,对不同生物可降解塑料降解规律,降解微生物和功能酶的透彻掌握,是实现其全面利用和高效资源化处理处置的基础和前提。文章系统梳理了常见生物可降解塑料的种类、性能、优缺点和主要用途,全面综述了生物可降解塑料的降解机理、降解微生物和功能酶,以及生物可降解塑料在不同环境条件下的降解周期和程度,以期为生物可降解塑料的微生物降解研究提供借鉴,为生物可降解塑料废弃物的高效处理处置和彻底降解提供科学参考。     

Enhancement of biodegradability of disposable polyethylene in controlled biological soil

Plastics as polyethylene are widely used in packaging and other agricultural applications. They accumulate in the environment at a rate of 25 million tons per year. Thus, the development and use of degradable plastics was proposed as a solution for plastic waste problem. Because of the ever-increasing use of plastic films, nowadays, biodegradability has become a useful characteristic for plastics. Conversely, the introduction of biodegradable plastics has generated a need for methods to evaluate the biodegradation of these polymers in landfills and solid waste treatment systems such as composting or anaerobic digestion treatment plants. The purpose of this study was to investigate the biodegradation of disposable low-density polyethylene bags containing starch (12%), autoxidizable fatty acid ester and catalytic agents in soil. Structurally this work intended to evaluate the capacity of Phanerochaete chrysosporium (ATCC 34541) to enhance polyethylene film biodegradation in soil microcosms. Soil samples inoculated with P. chrysosporium were mixed with LDPE/starch blend films and biological changes of the films and soil were monitored for 6 months. The biodegradation of polyethylene starch blend film has been determined by the physical, chemical and biological properties of the samples such as pH, biomass, CO₂ formation, percentage elongation, relative viscosity and FTIR spectrum.     

Synthesis of polyhydroxyalkanoate from palm oil and some new applications

Polyhydroxyalkanoate (PHA) is a potential substitute for some petrochemical-based plastics. This biodegradable plastic is derived from microbial fermentation using various carbon substrates. Since carbon source has been identified as one of the major cost-absorbing factors in PHA production, cheap and renewable substrates are currently being investigated as substitutes for existing sugar-based feedstock. Plant oils have been found to result in high-yield PHA production. Malaysia, being the world’s second largest producer of palm oil, is able to ensure continuous supply of palm oil products for sustainable PHA production. The biosynthesis and characterization of various types of PHA using palm oil products have been described in detail in this review. Besides, by-products and waste stream from palm oil industry have also demonstrated promising results as carbon sources for PHA biosynthesis. Some new applications in cosmetic and wastewater treatment show the diversity of PHA usage. With proper management practices and efficient milling processes, it may be possible to supply enough palm oil-based raw materials for human consumption and other biotechnological applications such as production of PHA in a sustainable manner.     

Sustainable synthesis and applications of polyhydroxyalkanoates (PHAs) from biomass

Polyhydroxyalkanoates (PHAs) belong to group of biopolymers that have in recent times received growing research interest as a result of being eco-friendly and close characteristics with petrochemical based plastics. Alternatives to utilization of synthetic plastics are being explored since synthetic plastics are non-recyclable and non-biodegradable in nature. One of the innovations of Green Chemistry is utilization of renewable feedstocks such as biomass to achieve sustainable development with future circular economy. Bio-based products are of great interest to sustainable development as a result of diminishing fossil fuel reserves and rising environmental concerns. This review summarizes the productions of PHAs from renewable feedstocks such as lignocellulose, crude glycerol, levulinic acid (LA), palm-oil mill effluents (POME) and waste oils. The production of bio-based polymers has become much more professional and differentiated in recent years. Presently, there are bio-based alternatives for practically every application, therefore, this review presents applications of PHA in bio-refinery, medical sectors, agriculture sector, construction industry, and in packaging industry. The cost analysis of PHA from renewable sources with commercially available ones and potential to attain circular economy were also stressed. The reasons for this shift are connected to the non-renewability of fossil-based resources, the deteriorating environmental impacts, and the lack of biodegradability of the petroleum-produced materials.     

Metabolic engineering for the synthesis of polyesters: A 100-year journey from polyhydroxyalkanoates to non-natural microbial polyesters

As concerns increase regarding sustainable industries and environmental pollutions caused by the accumulation of non-degradable plastic wastes, bio-based polymers, particularly biodegradable plastics, have attracted considerable attention as potential candidates for solving these problems by substituting petroleum-based plastics. Among these candidates, polyhydroxyalkanoates (PHAs), natural polyesters that are synthesized and accumulated in a range of microorganisms, are considered as promising biopolymers since they have biocompatibility, biodegradability, and material properties similar to those of commodity plastics. Accordingly, substantial efforts have been made to gain a better understanding of mechanisms related to the biosynthesis and properties of PHAs and to develop natural and recombinant microorganisms that can efficiently produce PHAs comprising desired monomers with high titer and productivity for industrial applications.Recent advances in biotechnology, including those related to evolutionary engineering, synthetic biology, and systems biology, can provide efficient and effective tools and strategies that reduce time, labor, and costs to develop microbial platform strains that produce desired chemicals and materials. Adopting these technologies in a systematic manner has enabled microbial fermentative production of non-natural polyesters such as poly(lactate) [PLA], poly(lactate-co-glycolate) [PLGA], and even polyesters consisting of aromatic monomers from renewable biomass-derived carbohydrates, which can be widely used in current chemical industries.In this review, we present an overview of strain development for the production of various important natural PHAs, which will give the reader an insight into the recent advances and provide indicators for the future direction of engineering microorganisms as plastic cell factories. On the basis of our current understanding of PHA biosynthesis systems, we discuss recent advances in the approaches adopted for strain development in the production of non-natural polyesters, notably 2-hydroxycarboxylic acid-containing polymers, with particular reference to systems metabolic engineering strategies.     

A life cycle assessment of residential waste management and prevention

Purpose

The oft-cited waste hierarchy is considered an important rule of thumb to identify preferential waste management options and places waste prevention at the top. Nevertheless, it has been claimed that waste prevention can sometimes be less favorable than recycling because (1) recycling decreases only the primary production of materials, whereas waste prevention may reduce a combination of both primary and low-impact secondary production, and (2) waste prevention decreases the quantity of material recycled downstream and the avoided impacts associated with recycling. In response to this claim, this study evaluates the life cycle effects of waste prevention activities (WPAs) on a residential waste management system.

Methods

This life cycle assessment (LCA) contrasts the net impacts of a large residential solid waste management system (including sanitary landfilling, anaerobic digestion, composting, and recycling) with a system that incorporates five WPAs, implemented at plausible levels (preventing a total of 3.6 % of waste generation tonnage) without diminishing product service consumption. WPAs addressed in this LCA reduce the collected tonnage of addressed advertising mail, disposable plastic shopping bags, newspapers, wine and spirit packaging, and yard waste (grass).

Results and discussion

In all cases, the WPAs reduce the net midpoint and endpoint level impacts of the residential waste management system. If WPAs are incorporated, the lower impacts from waste collection, transportation, sorting, and disposal as well as from the avoided upstream production of goods, more than compensate for the diminished net benefits associated with recycling and the displaced electricity from landfill gas utilization.

Conclusions

The results substantiate the uppermost placement of waste prevention within the waste hierarchy. Moreover, further environmental benefits from waste prevention can be realized by targeting WPAs at goods that will be landfilled and at those with low recycled content.     

Quantity,Components, and Value of Waste Materials Landfilled in the United States

The current system of production and consumption needs end‐of‐life disposal to function, but the linkage between upstream production‐consumption with the downstream landfill as terminus is, at best, a tenuous, one‐way relationship, suggesting a partial system failure. A starting point to fix this link is to confront, systematically, the messy “black box” that is mixed waste landfilling, interrogate its contents locally, and determine a baseline that can be used to scale up results. Here, we develop a detailed model characterizing landfilled municipal solid waste (MSW) in the United States across the dimensions of material quantity, quality, location, and time. The model triangulates measurements spanning 1,161 landfills (representing up to 95% of landfilled MSW) and 15,169 solid waste samples collected and analyzed at 222 sites across the United States. We confirm that landfilled quantities of paper (63 million megagrams [Mg]), food waste (35 million Mg), plastic (32 million Mg, textiles (10 million Mg), and electronic waste (3.5 million Mg) are far larger than computed by previous top‐down U.S. government estimates. We estimate the cost of MSW landfill disposal in 2015 (10.7 billion U.S. dollars [USD]) and gross lost commodity value of recyclable material (1.4 billion USD). Further, we estimate landfill methane emissions to be up to 14% greater (mass basis) than the 2015 U.S. inventory. By principally relying on measurements of waste quantity and type that are recorded annually, the model can inform more effective, targeted interventions to divert waste materials from landfill disposal, improve local, regional, and national emission estimates, enhance dissipative loss estimates in material flow analyses, and illuminate the dynamics linking material, energy, and economic dimensions to production, consumption, and disposal cycles.     

Waste Treatment and Assessment of Long-Term Emissions (8pp)

Goal, Scope and Background The disposal phase of a product’s life cycle in LCA is often neglected or based on coarse indicators like ‘kilogram waste’. The goal of report No. 13 of the ecoinvent project (Doka 2003) is to create detailed Life Cycle Inventories of waste disposal processes. The purpose of this paper is to give an overview of the models behind the waste disposal inventories in ecoinvent, to present exemplary results and to discuss the assessment of long-term emissions. This paper does not present a particular LCA study. Inventories are compiled for many different materials and various disposal technologies. Considered disposal technologies are municipal incineration and different landfill types, including sanitary landfills, hazardous waste incineration, waste deposits in deep salt mines, surface spreading of sludges, municipal wastewater treatment, and building dismantling. The inventoried technologies are largely based on Swiss plants. Inventories can be used for assessment of the disposal of common, generic waste materials like paper, plastics, packaging etc. Inventories are also used within the ecoinvent database itself to inventory the disposal of specific wastes generated during the production phase. Inventories relate as far as possible to the specific chemical composition of the waste material (waste-specific burdens). Certain expenditures are not related to the waste composition and are inventoried with average values (process-specific burdens). Methods The disposal models are based on previous work, partly used in earlier versions of ecoinvent/ETH LCI data. Important improvements were the extension of the number of considered chemical elements to 41 throughout all disposal models and new landfill models based on field data. New inventories are compiled for waste deposits in deep salt mines and building material disposal. Along with the ecoinvent data and the reports, also Excel-based software tools were created, which allow ecoinvent members to calculate waste disposal inventories from arbitrary waste compositions. The modelling of long-term emissions from landfills is a crucial part in any waste disposal process. In ecoinvent long-term emissions are defined as emissions occurring 100 years after present. They are reported in separate emission categories. The landfill inventories include long-term emissions with a time horizon of 60’000 years after present. Results and Discussion As in earlier studies, the landfills prove to be generally relevant disposal processes, as also incineration and wastewater treatment processes produce landfilled wastes. Heavy metals tend to concentrate in landfills and are washed out to a varying degree over time. Long-term emissions usually represent an important burden from landfills. Comparisons between burdens from production of materials and the burdens from their disposal show that disposal has a certain relevance. Conclusion The disposal phase should by default be included in LCA studies. The use of a material not only necessitates its production, but also requires its disposal. The created inventories and user tools facilitate heeding the disposal phase with a similar level of detail as production processes. The risk of LCA-based decisions shifting burdens from the production or use phase to the disposal phase because of data gaps can therefore be diminished. Recommendation and Perspective Future improvements should include the modelling of metal ore refining waste (tailings) which is currently neglected in ecoinvent, but is likely to be relevant for metals production. The disposal technologies considered here are those of developed Western countries. Disposal in other parts of the World can differ distinctly, for logistic, climatic and economic reasons. The cross-examination of landfill models to LCIA soil fate models could be advantageous. Currently only chemical elements, like copper, zinc, nitrogen etc. are heeded by the disposal models. A possible extension could be the modelling of the behaviour of chemical compounds, like dioxins or other hydrocarbons.     

A review of plastic waste biodegradation

With more and more plastics being employed in human lives and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. This review looks at the technological advancement made in the development of more easily biodegradable plastics and the biodegradation of conventional plastics by microorganisms. Additives, such as pro-oxidants and starch, are applied in synthetic materials to modify and make plastics biodegradable. Recent research has shown that thermoplastics derived from polyolefins, traditionally considered resistant to biodegradation in ambient environment, are biodegraded following photo-degradation and chemical degradation. Thermoset plastics, such as aliphatic polyester and polyester polyurethane, are easily attacked by microorganisms directly because of the potential hydrolytic cleavage of ester or urethane bonds in their structures. Some microorganisms have been isolated to utilize polyurethane as a sole source of carbon and nitrogen source. Aliphatic-aromatic copolyesters have active commercial applications because of their good mechanical properties and biodegradability. Reviewing published and ongoing studies on plastic biodegradation, this paper attempts to make conclusions on potentially viable methods to reduce impacts of plastic waste on the environment.