Purnell

Operational vs. embedded carbon p& energy

Wi h f hWith a cameo appearance from the functional unit

Phil Purnell: Director iRIPhil Purnell: Director iRI

Water@Leeds Confluence, 10 March 20102010

The iRIThe iRI

• Institute for ResilientInfrastructure– to provide the knowledge

to ensure that the physical infrastructure systems • The iRI has a unique, infrastructure systems underpinning our way of life can adapt to change, b th i th

world‐class combination of Engineering Science

both in the way we use them and in the social and physical environment in

research with Management expertise,

li d h h i d i lp ywhich they are designed, built and operated.

applied through industrial collaboration

The Poetry of D H RumsfeldThe Poetry of D.H. Rumsfeld

Th U kThe UnknownAs we know,There are known knownsThere are known knowns.There are things we know we know.We also knowThere are known unknowns.That is to sayWe know there are some things —Feb. 12, 2002, We know there are some thingsWe do not know.But there are also unknown unknowns,

Department of Defense news briefing. http://www.slate.com/

The ones we don't knowWe don't know.

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iRI Research & StrategyiRI Research & Strategy

• 20+ academic staff

• structural behaviour of

• finance, safety and management in complex i f t t j tmasonry and composite

structures

infrastructure projects

• numerical optimisation

• cement chemistry and microstructure

• carbon accounting and whole life cycle costing

• geotechnical structures

• construction materials

• digital information standards

including recycled and waste materials

• flood risk management and resilience

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Operational : EmbeddedOperational : Embedded

O i l b• Operational carbon or energy– heating, lighting, a/c, pumping, decommissioning and di l t it t ‘ i t ’disposal etc; site to grave; ‘running costs’

• Embedded carbon or energy– materials, manufacture etc; cradle to site ; ‘capital cost’

• Ratio O:E determines where eco‐£££ should be spent– E.g. occupied buildings O >> E: spend on insulation etc– infrastructure O ≈ E: need to analyse more carefully

Structural materials: CO headlinesStructural materials: CO2 headlines

• “1 m3 of wood replacing steel or concrete saves 1.1 tonne of CO2” [1]2 [ ]

• “Concrete's carbon footprint is fairly large…” [2][2]

• “Steel construction has no equal in sustainability. The recycling and reuse rate… in the UK is 94% [3]”the UK is 94% [3]

[1] Wood in Green Building: Sylvain Labbé, Q‐WEB. Canada Wood Group (2007). http://www.unece.org/timber/docs/tc‐sessions/tc‐65/md/presentations/12Labbe.pdf[2] A concrete solution to climate change?: Hayley Birch, Royal Society of Chemistry (2009). h // / h i ld/N /2009/M /26050901http://www.rsc.org/chemistryworld/News/2009/May/26050901.asp[3] Sustainable construction ‐ The bigger picture. Steel Construction Institute/Corus. http://www.corusconstruction.com/en/reference/publications/sustainability_and_environment/

Structural materials: the factsStructural materials: the facts

Material eCO2 eE (MJ/kg) ±

Timber (Glulam) 0.7 12 40%( )

Steel: virgin 2.8 37 30%

Steel: recycled 0.4 10 30%

Concrete (RC50, CEM1) 0.2 1.4 30%Concrete (RC50, CEM1) 0.2 1.4 30%

Concrete (RC50, 50% PFA) 0.1 0.9 30%

• So who’s right?Hammond, Geoffrey P. and Craig I. Jones, 2008. 'Embodied energy and carbon in construction materials', Proc. Instn Civil Engrs: Energy, 161 (2): 87‐98. [DOI:10 1680/ener 2008 161 2 87][DOI:10.1680/ener.2008.161.2.87]

The functional unitThe functional unit

• Cannot directly compare china vs. paper cupsp p p– supply, lifespan, maintenance, disposal…maintenance, disposal…

• Compare functional units– e.g. energy/CO2 per 1000 cups of coffee

– e.g. coffee consumption per employee p.a.

http://www.faqs.org/photo‐dict/phrase/382/cup.html; http://www.javapackaging.ca/media/ccp0/cat/biodegradable_paper_cup.JPG

Functional unit: exampleFunctional unit: example

• Beam to span a 9m gap– Max depth = 700 mmp

– 6 kN/m dead load

8 kN/m live load– 8 kN/m live load

– Ultimate limit state

– 50 year life

• RC v Steel v Timber…RC v Steel v Timber…

http://www.tgp.co.uk/services/projects/king.html; http://www.mainroads.qld.gov.au/~/media/files/business‐and‐industry/technical‐publications/queensland‐roads‐technical‐journal/march‐2006/qr_mar06_taromeocreek.pdf

Functional unit: exampleFunctional unit: example

RC Ti b• RC– b = 0.225 m40

• Timber– UK pine glulam grade C24 ρ ≈ 600 kg m‐3– 40 mm cover

– steel ratio 0.029assume 90% recycled

C24, ρ ≈ 600 kg m 3

– b = 0.14 m• NB in real life would– assume 90% recycled

high‐yield steel– 50% PFA replacement

NB in real life would probably need to be wider: LTB

– rectangular section50% PFA replacement

• Steel– char. yield = 270 MPa

– rectangular section

• Part 1: How do embodied energy andchar. yield 270 MPa

– UB 385 x 165, 54 kg/m– assume 60% recycled

embodied energy and CO2 compare?

y

Beam: eCO & eEBeam: eCO2 & eE…eCO2 / kg eE / GJ

12

14

800

1000 eCO2 / kg eE / GJ

8

10600

800

GJ

/ kg

4

6

8

400 eE / G

eCO2 /

2

4200

00

RC Steel Timber RC Steel Timber

cf Materials: eCO & eE…cf Materials: eCO2 & eE…eCO2 eE /MJ/kg

25

302 eCO2 eE / MJ/kg

201.5

J/kg

O2

10

151

eE / M

J

eCO

50.5

e

00

Conc. Steel Timber Conc. Steel Timber

Other embodied considerationsOther embodied considerations

if i f b• Lifetime of beam– e.g. if timber beam only lasts 25 years, will need 2 double the embodied energy/CO2

• Transport to site– RC: 2100 kg, Steel: 500 kg, g gTimber: 530 kg

• On‐site operationsO s te ope at o s– in‐situ casting, welding etc.

http://www.telegraph.co.uk/news/uknews/6004724/Lorry‐stuck‐on‐bridge‐for‐two‐days‐after‐diversion.html; http://www.okladot.state.ok.us/newsmedia/i40bridge/gifs/pics‐020717/Welding_on_steel_beams_b.gif

Part 2: Operational energyPart 2: Operational energy

i• Maintenance– Steel: painting, Timber: preservative– RC: hopefully none if QC ok, else CP etc.

• Disposal– Steel: recycled with high energy cost, or reused– Timber: possible recycled if OK else landfill– RC: partly recycled or landfill– Note: landfill = zero energy/CO2 cost!f gy 2

• importance of ‘weighting’ different impacts: LCA

• All fairly small (?) so O:E prob <1y ( ) p

Case study: domestic housingCase study: domestic housing

H i ht t (HC)• Heavyweight concrete (HC) vs. lightweight timber frame (LTF)

• eCO (ton) HC 37 LTF 32• eCO2 (ton): HC = 37, LTF = 32– carpets ≈ 6 !

• Total CO : HC 180 LTF 220• Total CO2: HC = 180, LTF = 220• ‘spending’ +5 t during building saves 40 t over 100ybuilding saves 40 t over 100y– thermal inertia reduces heating/cooling load

2‐bed, SE England. 65m2

100 year lifespan: climate change factored inheating/cooling load

• O:E = 4 – 5 change factored in

Hacker et al, Embodied and operational carbon dioxide emissions from housing:

d h ff f h lA case study on the effects of thermal mass and climate change. Energy & Buildings 40 (‘08) 375‐384

Case study: rooftop wind turbineCase study: rooftop wind turbine

80% f f i l• >80% of E from materials esp. Al, CFRP

• Payback time: time whenE + ∫O(t) = 0 – 8%: 4.2y (energy), 3.3y (CO2)– 30%: 1.1y (energy), 0.8y (CO2)– i.e. 20 year O:E –ve, ‐5 > O:E > ‐18

• Intensity (kgCO2/MWh): 27‐41 max 1.5 kW (13 MWh/ )

y ( g 2/ )– cf inland, coastal wind ≈ 25, 9coal ≈ 900, PV ≈ 100, nuclear ≈ 5

(13 MWh/year)eCO2 = 2400 kgeE = 23000 MJ

R K Rankine, J P Chick, and G P Harrison , Energy and carbon audit of a rooftop wind turbine. Proc. IMechE Vol. 220 Part A: J. Power and Energy pp643‐654.

20 year lifespan

The Water contextThe Water context

• UK water industry: total 5 Mt CO2 equiv pa– ⅔ waste water, ⅓ potable, p

– 0.29 tCO2 / Ml potable water• 1:1 pumping:treatment• 1:1 pumping:treatment

– 0.74 tCO2 / Ml waste water1 2 i• 1:2 pumping:treatment

– 80% gas & electricity, 20% direct emissions from sludge and other waste: CH4 ‘GWP’

Environment Agency (2009) report SC070010/R2 “Transforming wastewater treatment to reduce carbon emissions”; Scottish Water Carbon Footprint Report 2007‐2008.


• Water Framework Directive (WFD) likely to increase emissions by ≈100 kt CO2 pay 2 p– Addition of end‐of‐pipe processes to achieve required water quality can double operational andrequired water quality can double operational and embodied CO2 of individual plant

Against background of Carbon Reduction– Against background of Carbon Reduction Committment (‐26% by 2020)

l i l h il b ll• Multiple strategy approach: no silver bullet…


• Source control– avoid substance contact with water in first place

• Increased operational efficiency– SUDS: divert runoff to avoid pumping storm water p p g(‐100 kt CO2)

• Switch existing treatment to low‐Energy processesg gy p

• Renewable energy generation– CHP from anaerobic sludge digestion (‐100 kt CO )CHP from anaerobic sludge digestion (‐100 kt CO2)

• Least carbon end‐of‐pipe strategy…

Environment Agency (2009) report SC070010/R2 “Transforming wastewater treatment to reduce carbon emissions”; Scottish Water Carbon Footprint Report 2007‐2008.

E:O Treatment processesE:O – Treatment processes

b d d k l20‐yeartreatment type

Embodied CO2 kg equiv/Ml

Operational CO2kg equiv/Ml

O:E

Trickling filters 10 – 21 224 >10Trickling filters 10 21 224 >10

Reed beds 16 ? (low) <1

Activated carbon 62 66 – 78* ≈1

Reverse osmosis 2‐31 370 – 470 >10

Biological filters 22 224 >10

Activated sludge 10 224 >10

Process level: operationally intensive – focus on O‐CO2, p y 2,not E‐CO2 in mitigation strategies

Environment Agency (2009) report SC070010/R2 “Transforming wastewater treatment to reduce carbon emissions”. * does not include regeneration of carbon

Case study: treatment plantCase study: treatment plant• Water treatment works Isle ofWater treatment works, Isle of Man, 37 Ml/day

Floc DAF/Mn contactors– Floc‐DAF/Mn contactors

• LCA: 40 year life O:E ≈ 7:1– Embodied: 13 kt CO2

• 80% materials, 20% M&E

– Operational: 85 kt CO2• 70% electricity & sludge, 30%

b d d h lembodied in chemicals• Treated water pumping:>30 kt CO

Calculating the carbon footprint of a water treatment plant. Paul Hunt et al. Northern Water Conference and Exhibition November 2008, Manchester. >30 kt CO2

,http://www.envirolinknorthwest.co.uk/Envirolink/Events0.nsf/0/8025739B003AADE3802574AA002778CF?OpenDocument

ConclusionsConclusions

• Simple comparisons based on materials’ ‘renewability’ or ‘recyclability’ are not valid –y y ydefine a functional unit

• Cannot generalise about O:E ratio• Cannot generalise about O:E ratio– ‘Spend’ E to reduce O

• Embodied carbon ≈ 2:1 waste:potable water

• Most treatment processes & plant O >> E• Most treatment processes & plant O >> E– Operational focus give greater CO2 benefit

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