Anu Ramaswami

Greenhouse gas emission footprints and energy use benchmarks for eight U.S. cities.

A hybrid life cycle-based trans-boundary greenhouse gas (GHG) emissions footprint is elucidated at the city-scale and evaluated for 8 US cities. The method incorporates end-uses of energy within city boundaries, plus cross-boundary demand for airline/freight transport and embodied energy of four key urban materials [food, water, energy (fuels), and shelter (cement)], essential for life in all cities. These cross-boundary activities contributed 47% on average more than the in-boundary GHG contributions traditionally reported for cities, indicating significant truncation at city boundaries of GHG emissions associated with urban activities. Incorporating cross-boundary contributions created convergence in per capita GHG emissions from the city-scale (average 23.7 mt-CO(2)e/capita) to the national-scale (24.5 mt-CO(2)e/capita), suggesting that six key cross-boundary activities may suffice to yield a holistic GHG emission footprint for cities, with important policy ramifications. Average GHG contributions from various human activity sectors include buildings/facilities energy use (47.1%), regional surface transport (20.8%), food production (14.7%), transport fuel production (6.4%), airline transport (4.8%), long-distance freight trucking (2.8%), cement production (2.2%), and water/wastewater/waste processing (1.3%). Energy-, travel-, and key materials-consumption efficiency metrics are elucidated in these sectors; these consumption metrics are observed to be largely similar across the eight U.S. cities and consistent with national/regional averages.

A Social‐Ecological‐Infrastructural Systems Framework for Interdisciplinary Study of Sustainable City Systems

Summary Cities are embedded within larger-scale engineered infrastructures (e.g., electric power, water supply, and transportation networks) that convey natural resources over large distances for use by people in cities. The sustainability of city systems therefore depends upon complex, cross-scale interactions between the natural system, the transboundary engineered infrastructures, and the multiple social actors and institutions that govern these infrastructures. These elements, we argue, are best studied in an integrated manner using a novel social-ecological-infrastructural systems (SEIS) framework. In the biophysical subsystem, the SEIS framework integrates urban metabolism with life cycle assessment to articulate transboundary infrastructure supply chain water, energy, and greenhouse gas (GHG) emission footprints of cities. These infrastructure footprints make visible multiple resources (water, energy, materials) used directly or indirectly (embodied) to support human activities in cities. They inform cross-scale and cross-infrastructure sector strategies for mitigating environmental pollution, public health risks and supply chain risks posed to cities. In the social subsystem, multiple theories drawn from the social sciences explore interactions between three actor categories—individual resource users, infrastructure designers and operators, and policy actors—who interact with each other and with infrastructures to shape cities toward sustainability outcomes. Linking of the two subsystems occurs by integrating concepts, theories, laws, and models across environmental sciences/climatology, infrastructure engineering, industrial ecology, architecture, urban planning, behavioral sciences, public health, and public affairs. Such integration identifies high-impact leverage points in the urban SEIS. An interdisciplinary SEIS-based curriculum on sustainable cities is described and evaluated for its efficacy in promoting systems thinking and interdisciplinary vocabulary development, both of which are measures of effective frameworks.

Two Approaches to Greenhouse Gas Emissions Foot-Printing at the City Scale

C greenhouse gas (GHG) accounting is confounded by the relatively small spatial size of cities compared to nations, due to which • Essential infrastructures—commuter and airline transport, energy supply, water supply, wastewater infrastructures, etc.—cross city boundaries, hence energy use to provide these services often occurs outside the boundary of the cities using them. • Significant trade of other goods and services also occurs across cities, with associated embodied GHGs. Consequently, human activity in cities—occurring in residential, commercial, and industrial sectors—stimulates in-boundary GHG emissions occurring within the geopolitical boundary of the community, as well as trans-boundary emissions (occurring outside). Allocating in-boundary and trans-boundaryGHG emissions to communities can be achieved using different approaches described below.

Progress toward low carbon cities: approaches for transboundary GHG emissions’ footprinting

Cities are home to a large proportion of the world’s population and as a result, are being recognized as major contributors to global GHG emissions. There is a need to establish baseline GHG emission accounting protocols that provide consistent, reproducible, comparable and holistic GHG accounts that incorporate in-boundary and transboundary GHG impacts of urban activities and support policy intervention. This article provides a synthesis of previously published GHG accounts for cities by organizing them according to their in-boundary and transboundary considerations, and reviewing three broad approaches that are emerging for city-scale GHG emissions accounting: geographic accounting, transboundary infrastructure supply chain (TBIS) footprinting, and consumption-based footprinting. The TBIS and consumption-based footprints are two different approaches that result in different estimates of a community’s GHG emissions, and inform policies differently, as illustrated with a case study of Denver, CO, USA. The conceptual discussions around TBIS and consumption-based footprints indicate that one single metric (e.g., GHG/person) will probably not be suitable to represent GHG emissions associated with cities, and it will take a combination of variables for defining a low-carbon city.

Meta-principles for developing smart, sustainable, and healthy cities

Policy directives in several nations are focusing on the development of smart cities, linking innovations in the data sciences with the goal of advancing human well-being and sustainability on a highly urbanized planet. To achieve this goal, smart initiatives must move beyond city-level data to a higher-order understanding of cities as transboundary, multisectoral, multiscalar, social-ecological-infrastructural systems with diverse actors, priorities, and solutions. We identify five key dimensions of cities and present eight principles to focus attention on the systems-level decisions that society faces to transition toward a smart, sustainable, and healthy urban future.

Implementing Trans‐Boundary Infrastructure‐Based Greenhouse Gas Accounting for Delhi, India

Community‐wide greenhouse gas (GHG) emissions accounting is confounded by the relatively small spatial size of cities compared to nations—due to which, energy use in essential infrastructures serving cities, such as commuter and airline transport, energy supply, water supply, wastewater infrastructures, and others, often occurs outside the boundaries of the cities using them. The trans‐boundary infrastructure supply chain footprint (TBIF) GHG emissions accounting method, tested in eight U.S. cities, incorporates supply chain aspects of these trans‐boundary infrastructures serving cities, and is akin to an expanded geographic GHG emissions inventory. This article shows the results from applying the TBIF method in the rapidly developing city of Delhi, India. The objectives of this research are to (1) describe the data availability for implementing the TBIF method within a rapidly industrializing country, using the case of Delhi, India; (2) identify methodological differences in implementation of the TBIF method between Indian versus U.S. cities; and (3) compare broad energy use metrics between Delhi and U.S. cities, demonstrated by Denver, Colorado, USA, whose energy use characteristics and TBIF GHG emissions have previously been shown to be similar to U.S. per capita averages. This article concludes that most data required to implement the TBIF method in Delhi are readily available, and the methodology could be translated from U.S. to Indian cities. Delhis 2009 community‐wide GHG emissions totaled 40.3 million metric tonnes of carbon dioxide equivalents (t CO‐eq), which are normalized to yield 2.3 t CO‐eq per capita; nationally, India reports its average per capita GHG emissions at 1.5 t CO‐eq. In‐boundary GHG emissions contributed to 68% of Delhis total, where end use (including electricity) energy in residential buildings, commercial and industrial usage, and fuel used in surface transportation contributed 24%, 19%, and 21%, respectively. The remaining 4% of the in‐boundary GHG emissions were from waste disposal, water and wastewater treatment, and cattle. Trans‐boundary infrastructures were estimated to equal 32% of Delhis TBIF GHG emissions, with 5% attributed to fuel processing, 3% to air travel, 10% to cement, and 14% to food production outside the city.

Tracking urban carbon footprints from production and consumption perspectives

Cities are hotspots of socio-economic activities and greenhouse gas emissions. The aim of this study was to extend the research range of the urban carbon footprint (CF) to cover emissions embodied in products traded among regions and intra-city sectors. Using Xiamen City as a study case, the total urban-related emissions were evaluated, and the carbon flows among regions and intra-city sectors were tracked. Then five urban CF accountings were evaluated, including purely geographic accounting (PGA), community-wide infrastructure footprint (CIF), and consumption-based footprint (CBF) methods, as well as the newly defined production-based footprint (PBF) and purely production footprint (PPF). Research results show that the total urban-related emissions of Xiamen City in 2010 were 55.2 Mt CO2e/y, of which total carbon flow among regions or intra-city sectors accounted for 53.7 Mt CO2e/y. Within the total carbon flow, import and export respectively accounted for 59 and 65%, highlighting the importance of emissions embodied in trade. By regional trade balance, North America and Europe were the largest net carbon exported-to regions, and Mainland China and Taiwan the largest net carbon imported-from regions. Among intra-sector carbon flows, manufacturing was the largest emission-consuming sector of the total urban carbon flow, accounting for 77.4, and 98% of carbon export was through industrial products trade. By the PBF, PPF, CIF, PGA and CBF methods, the urban CFs were respectively 53.7 Mt CO2e/y, 44.8 Mt CO2e/y, 28.4 Mt CO2e/y, 23.7 Mt CO2e/y, and 19.0 Mt CO2e/y, so all of the other four CFs were higher than the CBF. All of these results indicate that urban carbon mitigation must consider the supply chain management of imported goods, the production efficiency within the city, the consumption patterns of urban consumers, and the responsibility of the ultimate consumers outside the city.

What metrics best reflect the energy and carbon intensity of cities? Insights from theory and modeling of 20 US cities

Three broad approaches have emerged for energy and greenhouse gas (GHG) accounting for individual cities: (a) purely in-boundary source-based accounting (IB); (b) community-wide infrastructure GHG emissions footprinting (CIF) incorporating life cycle GHGs (in-boundary plus trans-boundary) of key infrastructures providing water, energy, food, shelter, mobility–connectivity, waste management/sanitation and public amenities to support community-wide activities in cities—all resident, visitor, commercial and industrial activities; and (c) consumption-based GHG emissions footprints (CBF) incorporating life cycle GHGs associated with activities of a sub-set of the community—its final consumption sector dominated by resident households. The latter two activity-based accounts are recommended in recent GHG reporting standards, to provide production-dominated and consumption perspectives of cities, respectively. Little is known, however, on how to normalize and report the different GHG numbers that arise for the same city. We propose that CIF and IB, since they incorporate production, are best reported per unit GDP, while CBF is best reported per capita. Analysis of input–output models of 20 US cities shows that GHGCIF/GDP is well suited to represent differences in urban energy intensity features across cities, while GHGCBF/capita best represents variation in expenditures across cities. These results advance our understanding of the methods and metrics used to represent the energy and GHG performance of cities.

Optimization of Cementitious Material Content for Sustainable Concrete Mixtures

AbstractUtilization of fly ash in concrete reduces the use of virgin materials and offers benefits of reduced landfill materials and CO2 emissions avoidance—fly ash therefore contributes to industrial sustainability. This paper presents a method to optimize the cement and fly ash contents in concrete on the basis of the hardened concrete properties testing and environmental effects. Such fly ash concrete would develop an adequate 1-day and 28-day compressive strength and would be as durable as the ordinary portland cement concrete. Nine concrete mixtures with fly ash contents ranging from 15–60% and cementitious material contents from 338–391  kg/m3 (570-705  lbs/cu yd) were investigated. Environmental life cycle assessments (LCA) were completed by using a model developed for Denver, Colorado. The optimized fly ash concrete was selected to yield a similar 28-day compressive strength and durability to that of Colorado Department of Transportation (CDOT) Class D structural concrete. The durability aspects i...

Quantifying carbon mitigation wedges in U.S. cities: near-term strategy analysis and critical review.

A case study of Denver, Colorado explores the roles of three social actors-individual users, infrastructure designer-operators, and policy actors-in near-term greenhouse gas (GHG) mitigation in U.S. cities. Energy efficiency, renewable energy, urban design, price- and behavioral-feedback strategies are evaluated across buildings-facilities, transportation, and materials/waste sectors in cities, comparing voluntary versus regulatory action configurations. GHG mitigation impact depends upon strategy effectiveness per unit, as well as societal participation rates in various action-configurations. Greatest impact occurs with regulations addressing the vast existing buildings stock in cities, followed by voluntary behavior change in electricity use/purchases, technology shifts (e.g., to teleconferencing), and green-energy purchases among individual users. A portfolio mix of voluntary and regulatory actions can yield a best-case maximum of ~1% GHG mitigation annually in buildings and transportation sectors, combined. Relying solely on voluntary actions reduces mitigation rates more than five-fold. A portfolio analysis of climate action plans in 55 U.S. cities reveals predominance of voluntary outreach programs that have low societal participation rates and hence low GHG impact, while innovative higher-impact behavioral, technological, and policy/regulatory strategies are under-utilized. Less than half the cities capitalize on cross-scale linkages with higher-impact state-scale policies. Interdisciplinary field research can help address the mis-match in plans, actions, and outcomes.