Operational carbon refers to emissions from running infrastructure like heating and lighting, while embedded carbon refers to emissions from materials and construction. The ratio of operational to embedded carbon determines where efforts should focus to reduce emissions. A functional unit is needed to properly compare infrastructure options by accounting for lifespan, maintenance needs, disposal, etc. Case studies show operational carbon can be several times higher than embedded depending on factors like insulation, climate, and lifespan.

1. Operational vs. embedded carbon
p
& energy
With a cameo appearance from the
Wi h f h
functional unit
Phil Purnell: Director iRI
Phil Purnell: Director iRI
Water@Leeds Confluence, 10 March
2010

2. The iRI
The iRI
• Institute for Resilient
Infrastructure
– to provide the knowledge
to ensure that the physical
infrastructure systems
infrastructure systems • The iRI has a unique,
underpinning our way of world‐class combination
life can adapt to change, of Engineering Science
both in the way we use
b th i th research with
them and in the social and
Management expertise,
p y
physical environment in
which they are designed, applied through industrial
li d h hi d i l
built and operated. collaboration

3. The Poetry of D.H. Rumsfeld
The Poetry of D H Rumsfeld
The Unknown
Th U k
As we know,
There are known knowns.
There are known knowns
There are things we know we know.
We also know
There are known unknowns.
That is to say
—Feb. 12, 2002,
We know there are some things
We know there are some things
Department of Defense
We do not know. news briefing.
But there are also unknown unknowns, http://www.slate.com/
p // /
The ones we don't know id/2081042/
We don't know.

4. iRI Research & Strategy
iRI Research & Strategy
• 20+ academic staff • finance, safety and
• structural behaviour of management in complex
masonry and composite infrastructure projects
i f t t j t
structures • numerical optimisation
• cement chemistry and • carbon accounting and
microstructure whole life cycle costing
• geotechnical structures • digital information
• construction materials standards
including recycled and • flood risk management
waste materials and resilience

5. A disclaimer
A disclaimer
http://clovisonline
eschool.files.wo
ordpress.com/
/2010/01/yoda
a.jpg

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

7. Structural materials: CO
Structural materials: CO2 headlines
• “1 m3 of wood replacing steel or concrete
saves 1.1 tonne of CO2” [1]
[ ]
• “Concrete's carbon footprint is fairly large…”
[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).
http://www.rsc.org/chemistryworld/News/2009/May/26050901.asp
h // / h i ld/N /2009/M /26050901
[3] Sustainable construction ‐ The bigger picture. Steel Construction Institute/Corus.
http://www.corusconstruction.com/en/reference/publications/sustainability_and_environment/

8. Structural materials: the facts
Structural 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)
Concrete (RC50, CEM1) 0.2 1.4 30%
Concrete (RC50, 50% PFA) 0.1 0.9 30%
Hammond, Geoffrey P. and Craig I.
Jones, 2008. 'Embodied energy and
• So who’s right? 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]

9. The functional unit
The functional unit
• Cannot directly compare
p p p
china vs. paper cups
– 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

10. Functional unit: example
Functional unit: example
• Beam to span a 9m gap
– Max depth = 700 mm
p
– 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

11. Functional unit: example
Functional unit: example
• RC • Ti b
Timber
– b = 0.225 m – UK pine glulam grade
– 40 mm cover
40 C24, ρ ≈ 600 kg m 3
C24 ρ ≈ 600 kg m‐3
– steel ratio 0.029 – b = 0.14 m
– assume 90% recycled
assume 90% recycled • NB in real life would
NB in real life would
probably need to be
high‐yield steel wider: LTB
– 50% PFA replacement
50% PFA replacement – rectangular section
rectangular section
• Steel • Part 1: How do
– char. yield = 270 MPa
char. yield 270 MPa embodied energy and
embodied energy and
– UB 385 x 165, 54 kg/m CO2 compare?
– assume 60% recycled
y

12. Beam: eCO & eE…
Beam: eCO2 & eE
1000 eCO2 / kg
eCO2 / kg eE / GJ
eE / GJ 14
12
800
10
/ kg
600
GJ
8
eE / G
eCO2 /
400 6
4
200
2
0 0
RC Steel Timber RC Steel Timber

13. …cf Materials: eCO2 & eE
cf Materials: eCO & eE…
2 eCO2
eCO2 eE / MJ/kg
eE / MJ/kg 30
25
1.5
20
J/kg
O2
eE / MJ
eCO
1 15
10
e
0.5
5
0 0
Conc. Steel Timber Conc. Steel Timber

14. Other embodied considerations
Other embodied considerations
• Lifetime of beam
if i fb
– 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 g
Timber: 530 kg
• On‐site operations
O 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

15. Part 2: Operational energy
Part 2: Operational energy
• Maintenance
i
– 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 <1
y ( ) p

16. Case study: domestic housing
Case study: domestic housing
• H
Heavyweight concrete (HC) vs.
i ht t (HC)
lightweight timber frame (LTF)
• eCO2 (ton) HC 37 LTF 32
(ton): HC = 37, LTF = 32
– carpets ≈ 6 !
• Total CO2: HC 180 LTF 220
Total CO : HC = 180, LTF = 220
• ‘spending’ +5 t during
building saves 40 t over 100y
building saves 40 t over 100y 2‐bed, SE England. 65m2
– thermal inertia reduces 100 year lifespan: climate
heating/cooling load
heating/cooling load change factored in
change factored in
• O:E = 4 – 5 Hacker et al, Embodied and operational
carbon dioxide emissions from housing:
A case study on the effects of thermal
d h ff f h l
mass and climate change. Energy &
Buildings 40 (‘08) 375‐384

17. Case study: rooftop wind turbine
Case study: rooftop wind turbine
• >80% of E from materials esp.
80% f f i l
Al, CFRP
• Payback time: time when
E + ∫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
y( g / ) max 1.5 kW
(13 MWh/year)
(13 MWh/ )
– cf inland, coastal wind ≈ 25, 9 eCO2 = 2400 kg
coal ≈ 900, PV ≈ 100, nuclear ≈ 5 eE = 23000 MJ
20 year lifespan
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.

18. The Water context
The 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 water
• 12
1:2 pumping:treatment
i
– 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.

19. The Water context
The Water context
• Water Framework Directive (WFD) likely to
increase emissions by ≈100 kt CO2 pa
y p
– Addition of end‐of‐pipe processes to achieve
required water quality can double operational and
required 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)
• Multiple strategy approach: no silver bullet…
li l h il b ll

20. The Water context
The Water context
• 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 processes
g gy p
• Renewable energy generation
– CHP from anaerobic sludge digestion (‐100 kt CO2)
CHP from anaerobic sludge digestion (‐100 kt CO
• 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.

21. E:O – Treatment processes
E:O Treatment processes
20‐year Embodied CO2 k Operational CO2
b d d kg l O:E
treatment type equiv/Ml kg equiv/Ml
Trickling filters
Trickling 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 ,
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

22. Case study: treatment plant
Case study: treatment plant
• Water treatment works Isle of
Water treatment works, Isle of
Man, 37 Ml/day
– Floc DAF/Mn contactors
Floc‐DAF/Mn
• 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%
embodied in chemicals
b d d h l
Calculating the carbon footprint of a water treatment
• Treated water pumping: plant. Paul Hunt et al. Northern Water Conference and
>30 kt
>30 kt CO2 Exhibition November 2008, Manchester.
,
http://www.envirolinknorthwest.co.uk/Envirolink/Events0
.nsf/0/8025739B003AADE3802574AA002778CF?OpenDo
cument

23. Conclusions
• Simple comparisons based on materials’
y y y
‘renewability’ or ‘recyclability’ are not valid –
define 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