Composites Design and Manufacture (Plymouth University teaching support materials)
Environmental implications of polymers and composites.
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Concern for environmental issues is not a new phenomenon: key dates ..and.. definitions of eco-efficiency.
A key political concept in this context is Sustainability and a major tool is Life Cycle Assessment/Analysis (LCA).
A major business tool is Environmental Management Systems, especially ISO 14001.
EuCIA have launched a Eco Impact Calculator to provide an easy way to calculate the environmental impacts of composite products from “cradle to gate”.

Wesley Stephenson, All the plastic you can and cannot recycle, BBC News Science and Environment, 21 September 2018.

Table 1 presents some data on the tonnage of materials produced or consumed each year:

Table 1:  Annual consumption data for key materials
 Material  Total World Annual Production/Consumption  Census date  Reference
 Steel  1107.1 million tonnes (MT)  2005  World Steel Review - 2006, accessed 27 February 2006.
 Aluminium  23.423 million metric tonnes  2005  Primary Aluminium Production, accessed 27 February 2006.
 Copper  12.4 million tonnes  2003  Joël PT Kapusta, JOM World Nonferrous Smelters Survey, Part I: Copper, July 2004.
 Zinc  >10 million metric tonnes  2005  Sucden, Metals - Base and Precious, accessed 27 February 2006.
 Timber  EU-25: 21.8 MT# (industrial roundwood)  2003  E. Mäki-Simola & Imola Panagopoulos, The production of wood and forest industry products in EU-25, 4 October 2005.
 Timber  UK: 7.5 MT# (supplied from Britain’s forests)  2004  Forestry Commission, Timber Statistics, 18 January 2006.
 Plastics  100 million tonnes  "today"  Plastics recycling information sheet, Waste Online, February 2006.
 Plastics  UK: 4.7 million tonnes  2002  Introduction to plastics, British Plastics Federation, 2003.
 Composites  Western Europe: 1.54 million tonnes  2000 (estimate)  UK Polymer Composites Sector Foresight Study and Competitive Analysis, October 2001.
 Composites  UK: 0.21 million tonnes  2000 (estimate)  UK Polymer Composites Sector Foresight Study and Competitive Analysis, October 2001.

# The conversion factor used for this data was the figure for wood of 1000 metric tonnes = 1480 cubic meters [1].

Analyses of the composition of municipal solid waste (MSW) are available for the United States of America [2] and the principality of Wales [3].  The US Environmental Protection Agency (EPA) defines MSW to include durable goods, containers and packaging, food wastes, yard wastes, and miscellaneous inorganic wastes from residential, commercial, institutional, and industrial sources.  EPA excludes industrial waste, agricultural waste, sewage sludge and all categories of hazardous wastes (the latter including batteries and medical wastes).  The proportion of plastics in MSW in each case was 9.5% and up to 11% respectively.

The BBC website presents "Seven charts that explain the plastic pollution problem"

Graph of the US market for composites

Figure 1:  The growth of the reinforced plastics market in the USA.

Figure 1 shows the growth of the market for reinforced plastics.  The data up to 1996 is from the Society for the Plastics Industry with the more recent data from the American Composites Manufacturers Association (e.g. US market statistics for 2005 [4]).  Note that in spite of the apparent discontinuity in sector sizes between 1996 and 1997 due to reallocation of categories, the total market figures appear to follow a sensible trend.

At the design state of any product do consider the possibility of re-use and, if that is not practical, do design for dis-assembly or recycling.

Any (re-)processing of materials will require energy. That raises issues of collection and transport, fuel efficiency and the ethics of global sourcing.  Unnecessary use of energy costs money and potentially contributes to climate change.  A European project, RECIPE: Reduced Energy Consumption In Plastics Engineering, aims to help the plastics processing industry to reduce their energy consumption.  The RECIPE best practice guide [5] provides a structured and practical approach to improving energy efficiency in the processing of plastics.

Article 4 of the revised EU Waste Framework Directive [6] sets out five steps for dealing with waste, ranked according to environmental impact - the waste hierarchy (Columns 1 and 2 of Table 1 [7]).

The potential routes for dealing with waste composites are summarised in Figure 2.

recycling options
Figure 2: The options for end-of-life composites

A list of review papers on recycling composites can be found here.  Halliwell [8] has recently produced an excellent best practice guide on End-Of-Life options for composite waste.  Liu et al [9] have reported an eco-audit comparison for end-of-life wind turbine blades.

There is increasing interest in reclamation of high-value materials.  In particular, technologies for the recovery of short carbon fibres are being developed [10].

Composting

One alternative for bio-based materials (natural fibres and plant-based resins) is disposal by composting.  Hermann et al [10] classify "composting" into four categories as shown in Table 3 where chemical/mechanical pulp is for paper and cellulose production (and hence probably appropriate for natural fibres).  Specific benefits of compost [11] are that:

Table 3: Four types of biological waste treatment (after Hermann et al [11])

 bacteria (no fungi)Anaerobic digestor  Aerobic composting bacteria and fungi
temperature: 50-60°Cchemical pulp - starch - starch/PCL- PHA - PLA thermophilic digestion industrial compostingchemical pulp - mechanical pulp - starch - starch/PCL - PBAT -PHA - PLA
temperature: ≤35°Cchemical pulp - starch - starch/PCL- PHAmesophilic digestion home compostingchemical pulp - mechanical pulp - starch - starch/PCL - PBAT -PHA
outputsCO2 - humusdigestate compostCO2 - CH4 - N2O - humus

There are essentially two options (a) aerobic: carried out either in open air windrows or in enclosed vessels, or (b) anaerobic: required when animal by-products or catering wastes are included [12].  A typical value for mass loss during composting (for grassland in Austria) is 56% [13].  A demonstration-scale anaerobic digestion (AD) plant is operating at Dufferin (Toronto) solid waste transfer station with a mass balance (based on 100 metric tons/day) of 50% biogas and effluent, 25% digestate and 25% residue [14].  The biogas varies due to the batch operation but is typically 110 m3/metric ton with an average of 56% methane (ranges from 45-73%) by volume.  Jana et al [15] suggest that the biogas is typically 60-65% methane, 35% carbon dioxide and a small amount of other impurities".  Similarly, "pure landfill gas can contain up to 35% carbon dioxide, 65% methane and no oxygen" [16].  Further resources include BioCycle magazine and the Composting Association.

Life Cycle Assessment (LCA) studies have suggested that composting is preferable to incineration when the compost is used to enhance the carbon content of agricultural soils [11, 17].

A biodegradable material is expected to reach a defined extent of degradation by biological activity under specific environmental conditions within a given time under standard test conditions [18].  Krzan et al [19] have recently reviewed the standards and certification appropriate to environmentally degradable plastics.  The biodegradation of a polymeric materials under controlled composting conditions is the subject of a number of standard methods, including ASTM D 5338 [20], ASTM D6400 [21], ASTM D6868 [22], EN 13432 [23] or ISO 14852 [24].  The EU Directive on Packaging and Packaging Waste (94/62/EC) criteria for biodegradability are set out in BS EN 13432 while the criteria in North America are set out in ASTM D6400.  The requirements of the standard include:

Organisms that possess cellulase (the enzyme which cleaves sugar from the cellulose molecule) include bacteria, some flagellate and ciliate protozoa, and fungi [25].  If an animal is to digest cellulose, it must enter into an alliance with such an organism.  For example, termites have a symbiotic relationship with fungi which provides the symbionts with a rich source of cellulose for food in return for access to glucose cleaved from the cellulose and additionally to protein, vitamins and essential amino-acids produced by the fungi.  Termites hatch without this essential intestinal flora and are inoculated with it by being fed faeces and regurgitant that contain the symbionts.  The fungal deterioration of cellulosic textiles has been reviewed by Montegut et al [26].

Milner et al [27, 28] have reported a new strain of thermophylic bacteria that can break down cellulose waste to produce useful renewable fuels for the transport industry. The Geobacillus family normally synthesise sugars and produce lactic acid as a by-product when they break down biomass in a compost heap. The re-engineered TM242 strain is claimed to produce ethanol more efficiently (yields of 10 to 15%) and cheaply than in traditional yeast-based fermentation.

Gómez and Michel [29] investigated the relative biodegradability of a range of polymeric materials and natural fiber composites under composting, soil incubation and anaerobic digestion conditions.  The validity of the tests was confirmed in that positive controls (cellulose paper) biodegraded by more than 70% in all three systems in a reproducible manner.  While some of the bio-based plastics and natural fibers biodegraded to an appreciable extent, plastics containing additives that supposedly confer biodegradability to polymers such as polyethylene and polypropylene did not improve the biodegradability of the polymers.  SEM analysis confirmed that substantial biodegradation of polyhydroxyalkanoate-based (PHA) plastics occurred and that some surface changes occurred in co-polyester/corn-based plastic and coconut coir materials.  However, SEM confirmed that no degradation of polypropylene and polyethylene occurred, even after amendment with additives meant to confer biodegradability.  The relative biodegradability of the materials during long-term soil incubation was PHA>co-polyester/corn-based plastic>composted cow manure>plastarch>paper pulps>natural fibers>conventional plastics containing additives to enhance biodegradability = conventional plastics.

Environmental impact classification factors

Azapagic has presented an analysis which permits the quantification of environmental impact classification factors.  Any (re-)processing of materials will require energy.

The discipline of biomimetics, may have much to teach us here.  Biological systems create wastes which are raw materials for other plants and/or animals.  For an insight into how complex natural systems can evolve, see the life cycle of Maculinea Arion (large blue butterfly) and its dependence on Myrmica Sabuleti (red ant).

References:

  1. B Michie and P Wardle, EFI/WFSE Trade Flow Database, European Forest Institute, Joensuu - Finland, 2000, updated 2002.
  2. Municipal Solid Waste Profile, 16 April 1997.
  3. The Composition of Municipal Solid Waste in Wales, December 2003.
  4. Composites Industry Statistics, American Composites Manufacturers Association, 2006.
  5. Best Practice Guide for Low Energy Plastics Processing from the European Community funded RECIPE project (supported by the Intelligent Energy Europe programme) contract no. EIE/04/153/S07.38646.
  6. S Halliwell, End of Life options for composite waste - recycle, reuse or dispose?, National Composites Network Best Practice Guide, 2006.  MooDLE.  (NCN registrants can download the guide from NCN Best Practice Guide - Composites recycling guide).
  7. Directive 2008/98/EC on waste (Waste Framework Directive), accessed on 06 June 2014.
  8. Waste legislation and regulations, accessed on 06 June 2014.
  9. P Liu, F Meng and CY Barlow, Wind turbine blade end-of-life options: an eco-audit comparison, Journal of Cleaner Production, 1 March 2019, 212, 1268-1281.
  10. R Mehta, A lifeline for waste carbon fibres, Materials World, January 2010, 18(1), 6-7.
  11. BG Hermann, L Debeer, B de Wilde, K Blok and MK Patel, To compost or not to compost: carbon and energy footprints of biodegradable materials’ waste treatment, Polymer Degradation and Stability, June 2011, 96(6), 1159-1171.
  12. Jeremy Jacobs, The Compositing Association, private communication (e-mail), Monday 26 June 2006 08:45
  13. M Narodoslawsky and A Niederl, Chapter 10: The Sustainable Process Index (SPI), pp 159-172 in Jo Dewulf and Herman van Langenhove (editors), Renewables-Based Technology: Sustainability Assessment, Wiley, Chichester, 2006.  ISBN 978-0-470-02241-2.  PU CSH Library.
  14. N Goldstein, Source separated organics as feedstock for digesters, BioCycle, August 2005, 46(8), 42.
  15. S Jana, NR Chakrabarty and SC Sarkar, Removal of Carbon Dioxide from Biogas for Methane Generation, Journal of Energy in Southern Africa, August 2001, 12(3), 412-414.
  16. L Greenham and P Walsh, Carbon Dioxide Detectors For Health & Safety Applications, Petro Industry News, December 2004, pp 34-35 (page no longer available).
  17. HH Khoo, RBH Tan and KWL Chng, Environmental impacts of conventional plastic and bio-based carrier bags - Part 1: Life cycle production, International Journal of Life Cycle Assessment, 2010, 15(3), 284-293.
  18. Richard Murphy and Ian Bartle, Biodegradable Polymers and Sustainability: Insights from Life Cycle Assessment, Summary Report presented at the National Non-Food Crops Centre seminar, London, 25 May 25 2004.
  19. Andrej Krzan, S Hemjinda, S Miertus, A Corti and E Chiellini, Standardization and certification in the area of environmentally degradable plastics, Polymer Degradation and Stability, December 2006, 91(12), 2819-2833.
  20. ASTM D5338-98(2003): Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions.
  21. ASTM D6400-04: Standard Specification for Compostable Plastics
  22. ASTM D6868-11: Standard Specification for Labeling of End Items that Incorporate Plastics and Polymers as Coatings or Additives with Paper and Other Substrates Designed to be Aerobically Composted in Municipal or Industrial Facilities
  23. BS EN 13432:2000 Packaging. Requirements for packaging recoverable through composting and biodegradation. Test scheme and evaluation criteria for the final acceptance of packaging, December 2000.
  24. ISO 14852 (1999): Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous medium - Method by analysis of evolved carbon dioxide.
  25. J Scott Turner, The Extended Organism: The Physiology of Animal-built Structures, Harvard University Press, September 2002. ISBN 0-674-00985-1.  PU CSH Library.
  26. D Montegut, N Indictor and RJ Koestler, Fungal deterioration of cellulosic textiles: a review, International Biodeterioration, 1991, 28(1-4), 209-226.
  27. P Milner, SM Martin, KL Eley, R Cripps, E Firth, C Mercier, J Robinson and T Atkinson, Development of a second generation bioethanol process using TM242 – a thermophilic bacillus, Autumn Meeting, Society for General Microbiology, Trinity College Dublin, 08-11 September 2008, abstracts book page 23.
  28. Compost heap bacteria could help produce renewable fuel, BioTech International, September 2008, 20(4), 26.
  29. EF Gómez, and FC Michel, Biodegradability of conventional and bio-based plastics and natural fiber composites during composting, anaerobic digestion and long-term soil incubation, Polymer Degradation and Stability, available online 1 October 2013.

Further reading:

  1. B Adhikari, D De and S Maiti, Reclamation and recycling of waste rubber, Progress in Polymer Science , 2000, 25(7), 909-948.
  2. Adisa Azapagic, Alan Emsley and Ian Hamerton, Polymers: The Environment and Sustainable Development,
    John Wiley & Sons, March 2003, ISBN 0 471 87741 7 (1st edition soft-cover).  PU CSH Library
  3. Caroline Baillie, Green Composites: polymer composites and the environment, Woodhead Publishing Limited, Cambridge, 2004.
    ISBN 1-85573-739-6.  CRC Press LLC, Boca Raton FL, 2004.  ISBN 0-8493-2576-5.  PU CSH Library
  4. Jack Harris, Material matters: availability of uranium, Materials World, January 2006, 14(1), 56.
  5. L Henry, A Schneller, J Doerfler, WM Mueller, C Aymonier and S Horn, Semi-continuous flow recycling method for carbon fibre reinforced thermoset polymers by near- and supercritical solvolysis, Polymer Degradation and Stability, November 2016, 133, 264-274.
  6. J Howarth, SSR Mareddy and PT Mativenga, Energy intensity and environmental analysis of mechanical recycling of carbon fibre composite, Journal of Cleaner Production, 15 October 2014, 81, 46-50.
  7. Y Leterrier, Life Cycle Engineering of Composites, Comprehensive Composite Materials Volume 2: Polymer Matrix Composites, Elsevier, 2000, 1073-1102.
    ISBN 0-08-043720-6.
  8. X Li, R Bai and J McKechnie, Environmental and financial performance of mechanical recycling of carbon fibre reinforced polymers and comparison with conventional disposal routes, Journal of Cleaner Production, 20 July 2016, 127, 451-460.
  9. James Lovelock, The Revenge of Gaia: why the Earth is fighting back – and how we can still save humanity, Allen Lane, London, 2006.
    ISBN-13: 978-0-713-99914-3.  PU CSH Library
  10. TJ O'Neill, Life Cycle Assessment of Environmental Impact of Polymeric Products, Rapra Review Reports, 2003, 13(12), 1-133. ISBN 1-85957-364-9.  PU CSH Library
  11. Steve Pickering and Peter Hornsby, Polymer Composites: recycling and energy recovery, Materials World, September 1995, 3(9), 426-427.
  12. J Rybicka, A Tiwari, PA Del Campo and J Howarth, Capturing composites manufacturing waste flows through process mapping, Journal of Cleaner Production, 15 March 2015, 91, 251-261.
  13. Gerald Scott, Polymers and the Environment, Royal Society of Chemistry, Cambridge,  1999.  ISBN 0-85404-578-3.  PU CSH Library

Composting polymers:

Other resources:

Composites recycling companies


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Updated by John Summerscales on 06-Aug-2020 16:19. Terms and conditions. Errors and omissions. Corrections.