Life Cycle Assessment of flax fibre

for the reinforcement of composites

Nilmini Dissanayake,John Summerscales, Stephen Grove and Miggy Singh

Fibre-reinforced composites:typical applications

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Content

Flax Life Cycle Assessment (LCA)

goal and scope system boundaries

Life Cycle Inventory analysis (LCI) 3 scenarios energy

Environmental Impact Classification Factors (EICF) Life Cycle Impact Assessment (LCIA) - results Conclusions

Flax• Linum usitatissimum • temperate zone plant• flax – grown for fibre linseed – grown for seed oil• sown in March-May in UK• life cycle of the plant 45-60 day vegetative period 15-25 day flowering period 30-40 day maturation

period

Why Flax ?

• flax is the most agro-chemical intensivebast fibre used as reinforcement

• other bast fibres may be “greener”provided yield/hectare andperformance/durability are satisfactory

Growth stages• Life cycle of the flax plant consists of

• a 45 to 60 day vegetative period, • a 15 to 25 day flowering period and • a maturation period of 30 to 40 days

• From J A Turner “Linseed Law” BASF (UK) Limited, 1987via http://www.flaxcouncil.ca/images

UK harvest

Flax grown on campus

• 4 x 4 x 2 replicates behind Portland Villas• three fertilisers (N, P, K) or none• 0, 0.5, 1.0 or 2.0 times recommended level• no significant differences (soil too good ?)

Flax: from plant to fibre

• tillage and growth• harvest (combining or pulling)• retting

(dew-, wet-, stand- or enzyme-retting)– enzymes (e.g. pectinase digests pectin

binder)• decortication/scutching

(hammer mill, fluted rollers, willower)• cleaning (removal of shive)• carding (brushing/combing aligns fibres)

> sliver• spinning (twisting binds fibres)

> yarn/filament

Life Cycle Assessment (LCA)

Goal and Scope

Definition

Goal and Scope

Definition

InventoryAnalysis

InventoryAnalysis

Impact Assessmen

t

Impact Assessmen

t

Interpretation

Goal and Scope To determine the sustainability of natural fibres as reinforcement in polymer matrix composites (referenced to glass fibres)

Cradle-to-factory gate • agricultural operations (from ploughing to harvest)• fibre extraction operations (retting and decortication)• fibre preparation operations (hackling and carding)• fibre processing operations (spinning or finishing)

The functional unit : “one tonne of flax fibres for reinforcement in polymer matrix composites” (assumes Eflax = 42 GPa equal specific modulus)

Co-products allocated burdens only for post-separation handling

System Boundaries

Crop ProductionCrop Production

RettingRetting

ScutchingScutching

HacklingHackling

Wet SpinningWet Spinning

seed, fertiliser,pesticides, dieselmachinery

diesel, machinery, water

electricity

electricity

electricity, water

atmospheric emissions,emissions into water,co-products and waste

Dry, green flax stems

Dry, retted flax

Scutched long fibre

SLIVER

YARN

Life Cycle Inventory (LCI)

Three scenarios linkingdifferent tillage and retting methods:

1. No-till & water retting - minimum impact?2. Conservation till (chisel) & stand/dew retting

- average impact?3. Conventional till (mouldboard) & bio-retting

- maximum impact?

Tillage Methods

Fibre Processing

Mass loss during the production

LCI results – energy consumption

Energy consumption - breakdown

Scenario 1- Sliver (54 GJ/tonne)

LCI results – energy consumption

Energy consumption - breakdown

Scenario 1- Yarn (80GJ/tonne)

Energy consumptionMat .. sliver GJ/t

Glass fibre mat 54.7

No-till & water retting 54.4

Conservation & stand retting

113

Conventional & bio-retting

119

Continuous fibre … yarn GJ/t

Glass fibre 31.7

No-till & water retting 80.4

Conservation & stand retting

142

Conventional & bio-retting

148

Energy consumption

Energy source % in UK % in France

Coal/Solid fuels 25.8 5

Natural Gas 47.7 14

Oil - 33

Nuclear 18.0 40

Renewables 6.6 6

Other 1.9 2

UK: http://www.decc.gov.uk/en/content/cms/statistics/fuel_mix/fuel_mix.aspxFrance: http://ieepa.org/news/Other/20100917174353200.pdf

Environmental Impact Classification Factors

From Adisa Azapagic (and ISO 14047)

1. Acidification Potential (AP)

2. Aquatic Toxicity Potential (ATP) – ecotoxicity

3. Eutrophication Potential (EP) - nitrification

4. Global Warming Potential (GWP) - climate change

5. Human Toxicity Potential (HTP)

6. Non-Renewable/Abiotic Resource Depletion Potential

(NRADP)

7. Ozone Depletion Potential (ODP)

8. Photochemical Oxidants Creation Potential (POCP) –

smog

Draft BS8905 adds “land use”

EICF definitions I• Acidification Potential (AP)

consequence of acids (and other compounds which can be transformed into acids)

being emitted to the atmosphere and subsequently deposited in surface soils and water

• Aquatic Toxicity Potential (ATP) – ecotoxicity

based on the maximum tolerable concentrations

of different toxic substances in water by aquatic organisms

what about insects and birds ?

• Eutrophication Potential (EP) – nitrification

the potential of nutrients to cause over-fertilisation of water and soil

which in turn can result in increased growth of biomass

• Global Warming Potential (GWP) - climate change

caused by the atmosphere's ability to reflect some of the heat radiated from the earth's surface:

reflectivity is increased by the greenhouse gases (GHG) in the atmosphere

relatively difficult to quantify climate change

EICF definitions II• Human Toxicity Potential (HTP)

persistent chemicals reaching undesirable concentrations in each of the three elements of the

environment (air, soil and water) leading to damage to humans, animals and eco-systems

• Non-Renewable/Abiotic Resource Depletion Potential (NRADP)

depletion of fossil fuels, metals and minerals

• Ozone Depletion Potential (ODP)

potential for emissions of chlorofluorocarbon (CFC) compounds

and other halogenated hydrocarbons to deplete the ozone layer

• Photochemical Oxidants Creation Potential (POCP) – summer smog

related to the potential for VOCs and oxides of nitrogen to generate photochemical or summer smog

Environmental Impact for Flax fibre:

See also http://www.netcomposites.com/downloads/03Thurs_Summerscales.pdf - slide 15

Life Cycle Inventory Analysis (LCI)INPUTS

Materials Value (per tonne of yarn)

SeedFertilisers: Lime Ammonium nitrate Triple superphosphate Potassium chloridePesticidesDiesel (using no-till & water retting)Electricity

423 kg2445 kg (4GJ)444 kg (25 GJ)400 kg (6GJ)305 kg (3 GJ)9 kg (2 GJ)

5 GJ36 GJ

OUTPUTS

YarnCo-products : Short Fibres Shive Dust Coarse plant residuesDirect Emissions : CO2

NH3

N2O NOx

SO2

1000 kg4497 kg7104 kg2824 kg2304 kg9334 kg

68 kg14 kg6 kg3 kg

Life Cycle Impact Assessment – LCIA

methodologyIn the impact assessment interpretation of the LCI data,Environmental impact potential,

where: Bjx = burden (release of emission j or consumption of resource j per functional

unit)ec1 = characterisation factor for emission j

continues …

Non-renewable/abiotic resource depletion potential is calculated using :

Where: Bj = burden (consumption of resource j per functional unit) ec1 = estimated total world reserves of

resource j.

As defined by Adisa Azapagic et al (2003, 2004) in Polymers, the Environment and Sustainable Development and Sustainable Development in practice –case studies for engineers and scientists

For the production of flax sliver

Life Cycle Impact Assessment (LCIA)

continues …

For the production of flax yarn

Life Cycle Impact Assessment (LCIA)

No-till/water-ret flax vs glass fibres…

GF data from Sustainability at Owens Corning – 2008 Summary Progress Report

This study did not address:• sequestration of CO2

• use phase – assumed comparable to glass• disposal – flax could be composted

but degradation leads to “biogas [which] is typically 60-65% methane, 35% carbon dioxide and a small amount of other impurities” [Jana et al, 2001]

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).

A Le Duigou et al, JBMBE, 2011.

• environmental impact analysis onFrench flax fibers using different underlying assumptionsto Dissanayake et al for UK fibersconcluded that“without the allocation procedurethe results from the two studieswould be similar.”

Le Duigou vs Dissanayake key differences

• UK plants desiccated at mid-point flowering but French plants allowed to set seed

• UK yield only 6000 kg/ha but French yield 7500 kg/ha at harvest

• UK study excluded photosynthesis and CO2 sequestration

• Higher level of nuclear power in the French energy mix• UK study allocated all burdens to fiber

French study allocated on mass of product and co-products

Conclusions I no-till and water retting scenario

• lowest global warming potential

using bio-retting process• increased global warming• reduced eutrophication, acidification and toxicity

fibre mass as % green flax stems • 5% in bio-retting• 4% in water retting • 2% in dew retting

the embodied energies for flax (no-till agriculture): 54 GJ/tonne for sliver (55 GJ/tonne for glass mat) 80 GJ/tonne for yarn (32 GJ/tonne for continuous glass)

However ….

• Analysis uses 100% burden to long fibre• Economic apportionment:

If long fibre = 10% weight at 90 p/kgand short fibre/dust = 90% at 10p/kg,then burdens on long fibre halved

• Mass apportionment (indefensible?), then long fibre burden reduced to 10%

Burdens from … minimum < average < maximum

• no till < conservation agriculture< mouldboard

plough• organic fertiliser < agro-chemicals• biological control of pests

< pesticides• water- < dew- < bio-retting• sliver < spun yarn

Conclusions II

the validity of the “green” case for substitution of glass fibres by natural fibres is dependent on the chosen reinforcement form and associated processes

no-till with water retting is identified as the most environmental friendly option

conservation agriculture, organic fertiliser and biological control of pests will improve environmental credentials of flax

PhD thesis as free download:

http://pearl.plymouth.ac.uk/handle/10026.1/483

Thank you for your attention.Any questions?

http://www.tech.plym.ac.uk/sme/acmc/lca.htm