Economics of plastics processing

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Figure 1: Comparative Costs and Production Volumes For Processing of Plastics Wiki fig 1.png
Figure 1: Comparative Costs and Production Volumes For Processing of Plastics


The economics of plastics processing is determined by the type of process. Plastics can be processed with the following methods: machining, compression molding, transfer molding, injection molding, extrusion, rotational molding, blow molding, thermoforming, casting, forging, and foam molding. Processing methods are selected based on equipment cost, production rate, tooling cost, and build volume. High equipment and tooling cost methods are typically used for large production volumes whereas low - medium equipment cost and tooling cost methods are used for low production volumes. [1] Compression molding, transfer molding, injection molding, forging, and foam molding have high equipment and tooling cost. [1] Lower cost processes are machining, extruding, rotational molding, blow molding, thermoforming, and casting. [1] A summary of each process and its cost is displayed in figure 1.

Contents

Aspects of plastic processing

Degradable plastics

Oxo-degradable plastics: [2] these are petroleum-based plastics with additives such as transition metals and metals salts that promote the process of fragmentation of the plastic when exposed to a particular environment, such as high temperature or oxygen rich one, for a prolonged period of time. Fragmentation exposes a larger surface area of the plastic to colonies of bacteria that eventually decompose the polymer into its lower energy state components: carbon dioxide and water.

Some aspects to take into account regarding this method to dispose of end-of-life plastics are:

Classifying a polymer as bio-degradable requires specifications regarding these aspects.

Important economic aspects that need to be considered when disposing of degradable polymers include:

Reusable plastic containers

The implementation of reusable plastic containers arises as a consequence of concerns with sustainability and environmental impact. Use of recyclable plastic packages is beneficial environmentally but is more expensive. [6] The adoption of reusable plastic containers will amount to an approximate annual increase of 0.058 euros/kg of delivered goods. [6] The cost associated with reusable plastic containers are packaging purchasing costs, transportation costs, labor/handling costs, management costs, and costs resulting from losses. [6] Packaging purchasing costs encompasses the cost of the containers as well as any associated service costs. This cost is reoccurring but is only relevant once every 50 cycles, which is the typical lifetime of reusable plastic containers. One cycle consists of the initial stages of processing plastic containers all the way to the use and recycling of these containers by the consumers. Transportation costs are slightly higher for reusable plastic containers as compared to traditional use and throwaway plastic containers in that these reusable containers need additional transportation to recycling facilities. Reusable plastic containers also require work loading and unloading from trucks as well as quality inspection, this adds additional labor costs. [6] Management costs exists because reusable plastic container stock count needs to be managed. The final cost of reusable plastic containers is the cost incurred when packages are lost or there are errors within the management system. [6] Figure 2 provides a detailed summary of the costs associated with adopting reusable plastic containers.

Incineration of plastics

Recycling plastics presents the difficulty of handling mixed plastics, as unmixed plastics are usually necessary to maintain desirable properties. Mixing many plastics results in diminished material properties, with even just a few percent of polypropylene mixed with polyethylene producing a plastic with significantly reduced tensile strength. [7] An alternative to recycling of these plastics and those which can’t be easily recycled such as thermosets is to use degradation to break the polymers down into monomers of low molecular weight. The products of this process can be used to make high quality polymers however energy stored in the polymer bonds is lost during this process. [7]

An alternative to economically dispose of plastics is to burn them in an incinerator. Incinerators capable of cleanly burning polymers exist and while they require significant capital investment, the energy produced offsets the economic impact. [8] Since most plastics are produced from petroleum, their molecules consist exclusively or primarily of carbon, oxygen, and hydrogen atoms. With proper design, an incinerator can completely combust these plastics allowing the recovery of energy stored in the original petroleum feedstock which would otherwise escape during processes such as degradation. Some polymers contain chlorine or nitrogen which can result in undesirable combustion products however the use of scrubbers can remove such products. The end result is that many polymers burn more cleanly than coal and as clean as most oils. [7]

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<span class="mw-page-title-main">Polyvinyl chloride</span> Common synthetic polymer

Polyvinyl chloride (alternatively: poly(vinyl chloride), colloquial: polyvinyl, or simply vinyl; abbreviated: PVC) is the world's third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene). About 40 million tons of PVC are produced each year.

<span class="mw-page-title-main">Biodegradation</span> Decomposition by living organisms

Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradation occurs under a specific set of circumstances.

<span class="mw-page-title-main">Recycling</span> Converting waste materials into new products

Recycling is the process of converting waste materials into new materials and objects. This concept often includes the recovery of energy from waste materials. The recyclability of a material depends on its ability to reacquire the properties it had in its original state. It is an alternative to "conventional" waste disposal that can save material and help lower greenhouse gas emissions. It can also prevent the waste of potentially useful materials and reduce the consumption of fresh raw materials, reducing energy use, air pollution and water pollution.

<span class="mw-page-title-main">Polystyrene</span> Polymer resin widely used in packaging

Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to air and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used plastics, with the scale of its production being several million tonnes per year. Polystyrene is naturally transparent, but can be colored with colorants. Uses include protective packaging, containers, lids, bottles, trays, tumblers, disposable cutlery, in the making of models, and as an alternative material for phonograph records.

Thermal depolymerization (TDP) is the process of converting a polymer into a monomer or a mixture of monomers, by predominantly thermal means. It may be catalysed or un-catalysed and is distinct from other forms of depolymerisation which may rely on the use of chemicals or biological action. This process is associated with an increase in entropy.

<span class="mw-page-title-main">Polyethylene terephthalate</span> Polymer

Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins.

<span class="mw-page-title-main">Bin bag</span> Disposable bag used to contain solid waste material

A bin bag, rubbish bag, garbage bag, bin liner, trash bag or refuse sack is a disposable bag used to contain solid waste. Such bags are useful to line the insides of waste containers to prevent the insides of the receptacle from becoming coated in waste material. Most bags today are made out of plastic, and are typically black, white, or green in color.

<span class="mw-page-title-main">Plastic recycling</span> Processes which convert waste plastic into new items

Plastic recycling is the processing of plastic waste into other products. Recycling can reduce dependence on landfill, conserve resources and protect the environment from plastic pollution and greenhouse gas emissions. Recycling rates lag those of other recoverable materials, such as aluminium, glass and paper. Through 2015, the world produced some 6.3 billion tonnes of plastic waste, only 9% of which has been recycled, and only ~1% has been recycled more than once. Additionally, 12% was incinerated and the remaining 79% sent to landfill or to the environment including the ocean.

<span class="mw-page-title-main">Municipal solid waste</span> Type of waste consisting of everyday items discarded by the public

Municipal solid waste (MSW), commonly known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste, as in a garbage disposal; the two are sometimes collected separately. In the European Union, the semantic definition is 'mixed municipal waste,' given waste code 20 03 01 in the European Waste Catalog. Although the waste may originate from a number of sources that has nothing to do with a municipality, the traditional role of municipalities in collecting and managing these kinds of waste have produced the particular etymology 'municipal.'

<span class="mw-page-title-main">Waste-to-energy</span> Process of generating energy from the primary treatment of waste

Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of generating energy in the form of electricity and/or heat from the primary treatment of waste, or the processing of waste into a fuel source. WtE is a form of energy recovery. Most WtE processes generate electricity and/or heat directly through combustion, or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels, often derived from the product syngas.

<span class="mw-page-title-main">Biodegradable plastic</span> Plastics that can be decomposed by the action of living organisms

Biodegradable plastics are plastics that can be decomposed by the action of living organisms, usually microbes, into water, carbon dioxide, and biomass. Biodegradable plastics are commonly produced with renewable raw materials, micro-organisms, petrochemicals, or combinations of all three.

<span class="mw-page-title-main">Textile recycling</span> Method of reusing or reprocessing used clothing, fibrous material and rags

Textile recycling is the process of recovering fiber, yarn, or fabric and reprocessing the material into new, useful products. Textile waste is split into pre-consumer and post-consumer waste and is sorted into five different categories derived from a pyramid model. Textiles can be either reused or mechanically/chemically recycled.

<span class="mw-page-title-main">Commodity plastics</span> Inexpensive plastics with weak mechanical properties

Commodity plastics or commodity polymers are plastics produced in high volumes for applications where exceptional material properties are not needed. In contrast to engineering plastics, commodity plastics tend to be inexpensive to produce and exhibit relatively weak mechanical properties. Some examples of commodity plastics are polyethylene, polypropylene, polystyrene, polyvinyl chloride, and poly(methyl methacrylate) .Globally, the most widely used thermoplastics include both polypropylene and polyethylene. Products made from commodity plastics include disposable plates, disposable cups, photographic and magnetic tape, clothing, reusable bags, medical trays, and seeding trays.

Waste management in Japan today emphasizes not just the efficient and sanitary collection of waste, but also reduction in waste produced and recycling of waste when possible. This has been influenced by its history, particularly periods of significant economic expansion, as well as its geography as a mountainous country with limited space for landfills. Important forms of waste disposal include incineration, recycling and, to a smaller extent, landfills and land reclamation. Although Japan has made progress since the 1990s in reducing waste produced and encouraging recycling, there is still further progress to be made in reducing reliance on incinerators and the garbage sent to landfills. Challenges also exist in the processing of electronic waste and debris left after natural disasters.

<span class="mw-page-title-main">Plastic</span> Material of a wide range of synthetic or semi-synthetic organic solids

Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.

Recycling can be carried out on various raw materials. Recycling is an important part of creating more sustainable economies, reducing the cost and environmental impact of raw materials. Not all materials are easily recycled, and processing recyclable into the correct waste stream requires considerable energy. Some particular manufactured goods are not easily separated, unless specially process therefore have unique product-based recycling processes.

<span class="mw-page-title-main">Ecobricks</span> Environmentally friendly building method

An ecobrick is a plastic bottle densely packed with used plastic to create a reusable building block that achieves plastic sequestration. Ecobricks can be used to produce various items, including furniture, garden walls and other structures. Ecobricks are produced primarily as a means of managing consumed plastic by sequestering it and containing it safely, by terminally reducing the net surface area of the packed plastic to effectively secure the plastic from degrading into toxins and microplastics. Ecobricking is a both an individual and collaborative endeavour. The ecobricking movement promotes the personal ecobricking process as a means to raise awareness of the consequences of consumption and the dangers of plastic. It also promotes the collaborative process as a means to encourage communities to take collective responsibility for their used plastic and to use it to produce a useful product.

<span class="mw-page-title-main">Packaging waste</span> Post-use container and packing refuse

Packaging waste, the part of the waste that consists of packaging and packaging material, is a major part of the total global waste, and the major part of the packaging waste consists of single-use plastic food packaging, a hallmark of throwaway culture. Notable examples for which the need for regulation was recognized early, are "containers of liquids for human consumption", i.e. plastic bottles and the like. In Europe, the Germans top the list of packaging waste producers with more than 220 kilos of packaging per capita.

China's waste import ban, instated at the end of 2017, prevented foreign inflows of waste products. Starting in early 2018, the government of China, under Operation National Sword, banned the import of several types of waste, including plastics. The ban has greatly affected recycling industries worldwide, as China had been the world's largest importer of waste plastics and processed hard-to-recycle plastics for other countries, especially in the West.

<span class="mw-page-title-main">Plastic sequestration</span> Securing plastic out of industry and out of the environment

Plastic sequestration is a means of plastic waste management that secures used plastic out of industry and out of the environment into reusable building blocks made by manual compaction. Plastic sequestration is motivated by environmental protection and modeled on the Earth's process of carbon sequestration. Emerging out of the struggle of towns and communities in the Global South to deal with plastic pollution, plastic sequestration compaction methods are characterized by being locally based, non-capital, non-industrial and low-tech. Plastic sequestration is defined by the goals of securing plastic out of the environment and out of high energy/carbon industrial systems. Based on eliminating the chemical and physical and abiotic and biotic degradation pathways, plastic sequestration aims to achieve these goals, by terminally reducing the net surface area of thin film plastics. The building blocks that emerge from plastic sequestration are used in applications that further protect from degradation and permanently keep plastic out of industrial processes, thereby preventing their carbon emissions.

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