Environmental implications of composites
John Summerscales
Outline of lecture• raw materials• production• fitness for purpose• end-of-use
Consumption of materialsMaterial Production/Consumption (Mega Tonnes) Date
Steel 1107 2005
Aluminium 23.4 2005
Copper 12.4 2003
Zinc >10 2005
Timber EU-25 21.8 2003
Timber UK 7.5 2004
Plastics 100 2006
Plastics >300 20101
Plastics UK 4.7 2002
Bio-based polymers 0.7 20102
Bio-based polymers 1.7 20152
Composites WEur 1.54 2000
Composites UK 0.21 2000
1: http://dx.doi.org/10.1016/j.progpolymsci.2013.05.0062: http://dx.doi.org/10.1016/j.eurpolymj.2013.07.025
Mtonnes of composites in USA
Raw materials
• Thermoplastics, resins,carbon fibre, aramid fibreso primary feedstock = oilo potential for coal as feedstocko bio-based feedstocks
e.g. carbon fibres from rayon (cellulose)
• Glass (or basalt) fibreso primary feedstock = minerals
Production of materials
• carbon fibres pyrolysed at 1000-3000°C*
o higher temperatures for higher moduluso greenhouse gases produced
• aramid fibres spun from conc.H2SO4 solutiono strong acid required to keep aramid in solution
• glass fibres spun from “melt” at ~1375°Co greenhouse gases produced
http://www.answers.com/topic/carbon-fiberhttp://www.answers.com/topic/kevlarhttp://www.answers.com/topic/fiberglass
Component manufacture
• Net-shape production?o knitted preformso closed mould to avoid “overspray” or
equivalento dry fibres and wet resin (infusion vs prepreg)
for aerospace prepreg manufactureup to ~40% of material from roll may go to wastebecause fragment size and orientation not useful
resin film infusion uses unreinforced resinso orientation is not an issueand % usage only limited by labour costs
Fitness for purpose
• does lightweight structurereduce fuel consumption?
• what is the normal product lifetime?o can it be designed for extended life/ re-use
etc
• do safety factorsunnecessarily increase materials usage?
End of life: hierarchy of options: • first re-use
o consider re-use (or dis-assembly or recycling)at the design state
• re-cycleo potential for comminuted waste as filler
• Decompositiono pyrolysis/hydrolysis etco for materials recovery, e.g. Milled Carbon Ltd.o future: enzymes, ionic liquids, sub- and super-critical processes
• incinerationo with energy recovery
• finally landfillo only if all else fails.
PET: poly ethylene terephthalate
HDPE: high density polyethylene
PVC: poly vinyl chloride
LDPE: low density polyethylene
PP: poly propylene
PS: polystyrene
other: polycarbonate, ABS, nylon, acrylic or composite, etc
Plastic Resin Identification Codes
Plastic Resin Identification Codes
PA6 GF30/M20 FR: • polyamide-6
(caprolactam-based nylon)• 30% glass fibre• 20% mineral filler• flame retardant
An alternative is compostingfor bio-based materials
• composting: biodegradation of polymers under controlled composting conditions
• determined using standard methods including ASTM D 5338 or ISO 14852o aerobic (with air present):
in open air windrows or in enclosed vessels
o anaerobic (without air): animal by-products or catering wastes
• biogas is ~60-65% CH4 + 35% CO2 + others
• 100 year GWP of methane = 23x that for CO2
*
* according to the Stern Review “The Economics of Climate Change” (2006),
but the short term effect is even greater.
Digestion vs Composting
bacteria (no fungi)Anaerobic digestor
Aerobic composting bacteria and fungi
temperature:
50-60°C
chemical pulp - starch - starch/PCL-
PHA - PLA
thermophilic digestion
industrial compostingchemical pulp - mechanical pulp - starch - starch/PCL - PBAT -PHA -
PLA
temperature: ≤35°C
chemical pulp - starch - starch/PCL-
PHAmesophilic digestion home composting
chemical pulp - mechanical pulp - starch - starch/PCL - PBAT -PHA
outputs CO2 - humus digestate compost CO2 - CH4 - N2O - humus
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.
Political drivers (EC)
• End of Life Vehicles (ELV) Directive (2000/53/EC)o last owners must be able to deliver their vehicle
to an Authorised Treatment Facilityfree of charge from 2007
o sets recovery and recycling targetso restricts the use of certain heavy metals
in new vehicles
• Waste Electrical and Electronic Equipment (WEEE) Directive (2002/96/EC)
ELV targets• end of life vehicles generate 8-9 Mtonnes
of waste/year in the European Community
• 2006: o 85% re-use and recoveryo 15% landfill
• 2015:o 95% re-use and recoveryo 5% landfill
ELV targets
• ELV targets were set to minimise landfill• total lifetime costs may be increased
o e.g. for composites:o thermoset manufactured at use temperature
but recycling is difficult
o thermoplastic processed at use + ~200°C could be recycled by granulating/injection
mouldingfor lower grade use
but higher GreenHouse Gases (GHG) early in life?
Carbon fibres: incineration
• carbon fibres should burn to CO2
in the presence of adequate oxygen(with recovery of embedded energy)
• incomplete combustion may lead to surface removal and reduce diameter
• rescue services concerned by health riskof inhalable fibres released fromburning carbon composite transport structures
Life Cycle Assessment
ISO14040 series standards
•The goal & scope definition
•Life Cycle Inventory analysis (LCI)
•Life Cycle Impact Assessment (LCIA)
•Life Cycle Interpretation
Environmental ImpactClassification Factors:
ISO/TR 14047:2003(E) Azapagic et al
Acidification Acidification Potential (AP)
Ecotoxicity Aquatic Toxicity Potential (ATP)
Eutrophication / Nitrification Eutrophication Potential (EP)
Climate Change Global Warming Potential (GWP)
Human Toxicity Human Toxicity Potential (HTP)
Depletion of abiotic /biotic resources
Non-Renewable / Abiotic Resource Depletion (NRADP)
Stratospheric ozone depletion Ozone Depletion Potential (ODP)
Photo-oxidant formation Photochemical Oxidants Creation Potential (POCP)
Draft BS8905 adds Land Use
Environmental Impact for Glass fibre production:
Problem?Issue?No impact?
Recommended further reading• Y Leterrier, Life Cycle Engineering of
Composites, Comprehensive Composite Materials Volume 2, Elsevier, 2000, 1073-1102.
• W McDonough and M BraungartCradle to cradle: remaking the way we make things,North Point Press, New York, 2002.
• SJ Pickering, Recycling technologies for thermoset composite materials: current status, Composites Part A, 2006, 37(8), 1206-1215.