Trans-boundary Carbon Emission Footprints and A Framework for Sustainable Cities

Dr. Anu RamaswamiProfessor of Civil Engineering and Director

IGERT Program on Sustainable Urban Infrastructure Center for Sustainable Infrastructure Systems

Sustainability Outcomes

Eg: Low Carbon, Resilient and Healthy Cities

Energy & Buildings

Transport Construction Materials

Water/ Waste

Policy Actors

Firms & Businesses

Citizens & Community

UC

D C

ente

r for

Sus

tain

able

In

frast

ruct

ure

Syst

ems

Food

Trans-boundary Issues in Measuring Urban Environmental Sustainability:- City-scale Carbon Emission Footprints - City-scale Water Footprints (ongoing)

Greenhouse Gas (GHG) Inventory

• The first step in undertaking climate action planning at the city-scale is to conduct a baseline greenhouse gas (GHG) inventory for the city in a base year

• What are Greenhouse Gases (GHGs?)– CO2– CH4– N2O– Plus three CFC replacements– Aggregated in terms of global warming potential

as CO2e (carbon dioxide equivalent)

City or

Urban Region w/ Buildings, Vehicles, Industries (Scope 1)

The Urban Trans-Boundary Challenge

Commuter

Airline Travel

Freight & Goods

Key Urban Flows

-Food

- Water

- Energy Electricity

….(Scope 2)Transp Fuel

- ShelterCement

…

What to Include in a City’s GHG Account?

• GHG Accounting at the city scale is confounded by the small spatial scale of cities, due to which:– Trans-boundary commuter travel and airline travel are

artificially truncated at the city boundary– Essential infrastructures transcend city boundaries

• so electricity production GHG are emitted outside the boundary of the city that uses that electricity

– Beyond infrastructures, there is also trade of goods and services across cities

• Larger-scale National Inventories: More inclusive of all human activities (agriculture, fuel refining, electricity production, etc.)

Emerging Issue: Not All CO2 is the Same

• Although a global climate forcer, we may want to know spatially WHERE CO2 is emitted.

• CO2 “domes” over cities affect atmospheric mixing that increases concentrations of short-lived climate forcers - SLCF (e.g., ozone) locally

Illustration OnlyJacobson et al., Environ. Sci. Tech., 2010

Methodological Approaches: Community-Wide GHG Accounting

Geographic-based, Boundary-Limited• In-Boundary direct GHG emission only

(Scope 1) – good for national inventories• GHG from trans-boundary purchased

Electricity (Scope 2) – reqd. for corporations • Other Trans-boundary?(Scope 3, optional)• Relates to measures of productivity

Consumption-Based Using EIO-LCA• Household Consumption $• Government Expenditures• Business Capital Investment

Geographic-Plus Trans-boundary Infrastructure Supply Chain Footprint for Cities

• Identifies Scope 3 GHG contributions important in all cities: transboundary travel life cycle impacts of producing key urban materials relating to water, fuel, shelter, food (infrastructures)

• Benchmarking with National data

Scope 1+2 underestimates GHG impact of cities

Data challenges in down-scaling to cities Test convergence

EPA Climate Leaders & WRI Protocols for Corporate GHG Reporting

• Scope 1 + Scope 2 are required reporting

• EPA and WRI recommend reporting on a few Scope 3 emissions – Optional– But creates win-win climate actions

• Full Scope 1-2-3 Accounting yields an expanded inventory that becomes a “Carbon Footprint”

• But we needed insight/research on what Scope 3 items are most important for cities

City-Scale GHG Inventory Methods –Developments from 2006-2011

• Only about 10 cities completed inventories in 2006

• No standardization on what to include/exclude:– Airports – included by Seattle and Aspen– Transport Fuel Wells-to-Pump (production) emissions

ignored by all – Upstream energy use in producing other key urban

materials – ignored by most cities (although asphalt included in some)

• Focus on “direct end-use of energy” within a city’s polygon area - tailpipe transport emissions, emissions from electricity use in buildings and credit for material recycling.

Denver, CO – Location and Goals

Denver seeks to reduce its annual per capita Greenhouse Gas (GHG) emissions by 10% from 1990 baseline levels, by 2012.

Denver, within the Denver Regional County of Governments (DRCOG) Region

Denver’s GHG Inventory Method –Geographic Plus

• Spatially-allocates travel-related GHG across cities

• Key Material Flows: Views the city as a demand-center for energy, transport and key materials– Functionality of cities led to choice of key urban material

flows in cities :water, food, fuel and shelter (concrete).– Supported by major home-scale expenditures and MSA-

level material flows

• Applies Material flow Analysis (MFA) and Life Cycle Assessment (LCA) to quantify upstream indirect GHG emissions of key urban materials– Analogous to electricity indirect GHG

Transportation Energy Use: Separating Trips to and from Denver

Denver's Resident

Workforce41%Workers

Commuting into Denver59%

Demand Centered Approach - DRCOG regional transportation model was analyzed to isolate trips to and from Denver, and, to ignore pass-through trips. [Dr. Bruce Janson]

Transportation Energy Use: Airport Fuel Use Allocated to Denver• Trips from Denver to the

Airport were isolated from all trips to the Airport to allocate airline fuel use to Denver – Road Trip Ratio = 0.22

• Tracked well with population ratio of Denver versus DRCOG region– Denver/DRCOG

Population Ratio = 0.22

Road Trip Ratio To Airport vs. Population Ratios for 25 U.S. Cities

y = 0.99x

R2 = 0.96

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70

Regional Population Ratio

Airp

ort T

rip R

atio Portland

Austin

Denver

Hillman, Janson, & Ramaswami, ASCE J. Transportation Engineering, 2010

SeattleMinneapolis

Hybrid LCA of Key Urban Materials

• Department of Energy’s GREET model was used for upstream wells-to-pump GHG emissions associated with fuel processing for all transport fuels

• Regional cement production and transport data was used to model cement LCA [Reiner & Ramaswami]

• Denver Water data showed upstream energy use for trans-boundary water supply to be small (this is not the case for all cities)

• Economic Input-Output LCA used for food

Denver GHG Inventory Results

Trans-Boundary GHG Emissions Denver, CO

• A Trans-boundary GHG emissions footprint facilitates holistic bio-physical infrastructure systems design.– Cross sector strategies like

Tele-presence vs Airline Travel– Cross-scale Supply Chain

strategies such as “green concrete”

– Shifts in nature of demand in cities (e.g., healthy foods)

– Connects consumption-production

• Prevents shifting of GHG burden from within boundary to outside boundary– Hydrogen-cars are “zero”

emitting in-boundary, but with significant CO2 from fuel production outside boundaries

Comparison w/ National, State and Other City Data

DenverPer Capita

GHG Emissions (mtCO2e/person

)

National, State & Other CitiesPer Capita

GHG Emissions (mtCO2e/person)

Direct energy use plus airline travel and key urban materials

Denver:25.3

National; State:25; 25.5

Direct energy use (no airline travel, no fuel refining, noproduction of concrete, food and food packaging)

Denver:18.9

Other Colorado Cities

18.4 – 19.6

Key Question: Do the trans-boundary inclusions lead to scale consistency in inclusions from the city-scale to national-scale?

Measuring Sustainability: Greenhouse Gas Footprints of 8 US Cities

Hillman and Ramaswami, Environ. Sci. Technol., 2010

UCD Scope 3 Inclusions Increased Per Capita Emissions by 46% on Average

0

5

10

15

20

25

Denve

r, CO

Boulde

r, CO

Fort C

ollins

, CO

Arvada

, CO

Portlan

d, OR

Seattle

, WA

Minnea

polis,

MN

Austin

, TX

Averag

eGH

G E

mis

sion

s pe

r Cap

ita (m

t-CO

2e/c

apita

)

Long Distance FreightWater / WW / WasteCementFoodFuel Processing (W2P)Airline (P2W)Surface Transport (P2W)Buildings Energy Use

Hillman and Ramaswami, Environ. Sci. Technol. 2010

Scale-Convergence w/ National Data?

0.0

5.0

10.0

15.0

20.0

25.0

30.0

Per

Cap

ita G

HG

Em

issi

ons

(mt-C

O2e

/cap

ita)

City per Capita GHG Emissions (with Scope 3 Inclusions and U.S. Average Electricity Emissions Factor)

U.S. GHG Emissions = 24.5 mt-CO2e/cap

Hillman & Ramaswami, Environ. Sci. Technol., 2010

Consistency Across Scale

• Convergence between city-scale and national per capita demonstrate that the UCD expanded inventory method may be approaching a footprint with these inclusions.– Deviations from national per capita could be explained by unique

characteristic, e.g., low commercial-industrial activity in Arvada

• Cities need to track and report benchmark metrics in individual sectors to better understand their footprint and assess progress. (See examples next page)

• GHG per-capita is not be the best metric for inter-city comparisons in the geographic-plus method– Consider outliers with very low or very high industrial-commercial

activity– Consider easy metrics to indentify highly producing cities,

consuming cities and roughly carbon trade-balanced cities.

Examples of ConsumptionMetrics & Benchmarks

Sample Consumption Metrics for Tracking Over Time

National or (CO State)

BenchmarkDenver, CO

Commercial-Industrial Energy Use Intensity

(kBtu/sf)138 122

Residential Electricity Use(kWh/hh/mo)

(667) 545

Jet Fuel per passenger (gallons/enplaned passenger)

22 19

Road Transport(VMT/capita/day)

(28) 24

* (Hillman & Ramaswami, 2010)

Policy Relevance: Geographic-Plus vs Consumption-Based Carbon Footprints for Cities

Geographic-Plus: Policy Relevance

• Pro: Well suited to show impacts of local infrastructure policies and trans-boundary changes/policies across scale

• Pro: Well suited to link local energy use to local climate change impacts like urban heat island effect, local public health

• Pro: Able to link energy use to economic measures (GDP, local jobs created)

• Con: Needs better blended metrics for inter-city comparability, e.g., GHG/[resident plus jobs] – to be studied

Consumption-Based: Policy Relevance

• Pro: Most rigorous method of comparing per capita GHG emissions

• Pro: Facilitate shifting government and household expenditures toward “cleaner” products/regions of the world

• Con: City is split up – with household consumption emphasized Ignores local commercial-industrial activity that is exported elsewhere even though these create local jobs and can be governed locally

• Con: IO data unavailable at sub-county level for smaller county/towns, therefore needing approximations

Denver Final Demand Consumption GHG’s, by Scope: Geographic Plus Captures ~81% in this IMPLAN Run

0.0 1.0 2.0 3.0 4.0

Energy/UtilitiesPersonal Transport: Cars & …

ServicesFood Manufacturing

Industry/ManufacturingWholesale and Retail

Transport: Air and otherMiningHealth

Restaurants/HotelsGovernment Services

CommunicationsEducation

Furniture, Misc GoodsRecreationElectronics

Alc Bevs/TobaccoApparel

AgricultureOther Textiles

mt-CO2e/capita

Scope 1: Natural Gas Combustion

Scope 1: Petroleum Combustion

Scope 2: Electricity Generation

Scope 3: Geographic Plus

Remainder

Meta Analysis of 45 US Counties

• Goal: Identify improved Carbon-emission metrics for Intercity Comparisons and Public Communication.

• Consider various typologies of cities – highly producing cities (e.g., resort towns); highly-consuming cities (suburbian towns) and balanced (metro) communities

Example: Denver vs Routt County

26.424.2

26.1

39.8

0

5

10

15

20

25

30

35

40

45

Denver: C-B Denver: G-P Routt: C-B Routt: G-P

mt-

CO2e

/cap

ita

C-B: Consumption-BasedG-P: Geographic-Plus

Denver GHGTrade Balance = 3% of G-P total

Routt GHGTrade Balance = 39% of G-P total

Ramaswami et al., 2011, submitted ES&T

Impact on Developing a Common Community-wide GHG Protocol

• ICLEI-USA is releasing a draft community-wide protocol for cities to report energy use and GHG emissions, based on some of these studies:

• Community-wide distinguishes from municipal government energy use

• Recommends a Basic and Comprehensive community impact report based on Geogrphic Plus method (this presentation)

• Separate Consumption-based report is recommended where resources and data are available.

Conclusions• Transboundary challenges can be overcome

by developing two different types of energy use or carbon emission footprints for cities:

• Infrastructure Based expanded Geographic Footprint– Detailed data available by infrastructure sectors

• Consumption Based Footprint (Input-output) – data challenges

• Conduct societal learning experiments – how do people use footprint information?

Our Work in U.S. Cities

*Hillman, T; Ramaswami, A. . ES&T 2010

Our Work in Global Cities

Cities in India: Hyderabad, Rajkot and Coimbatore

Our Global City Network*:

• Bangkok (city)• Barcelona (city)• Cape Town (city)• Denver (city and county)• Geneva (Canton)• London (GLA)• Los Angeles (county)• New York City• Prague (GPR)• Toronto (GTA)

*Kennedy, C et al. “Greenhouse Gas Emissions from Global Cities.” Environmental Science & Technology 2009, 43, 7297-7302, August 20, 2009.

Sponsored Program:National Science Foundation

• Integrative Graduate Education & Research Traineeship– $3.2 Million grant– 26 total PhD students

• Engineering, Public Affairs, Planning, Health & Behavioral Sciences

– ~ 20 Masters students from many disciplines (MS Associates)

– Certificate in Sustainable Infrastructure

Other Program Sponsors and Partners: Public Sector

• Colorado Cities:

• Governor’s Energy Office• Colorado Municipal League (CML)• National Civic League • Urban Drainage and Flood Control District• Colorado Department of Public Health &

Environment• Office of Naval Research• US EPA – P3 Program

- Denver, Arvada, Central City, Broomfield, Aurora, Durango, Lafayette, Thornton

• AT&T Foundation: Faculty Fellowship in Industrial Ecology

• Wal-Mart Foundation: Outreach to Colorado Cities in partnership with CML

• MWH: Sponsored project with funded student

• Clinton Global Initiative University Outstanding Commitment Award: funding student outreach

Other Program Sponsors and Partners: Private Sector