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.