Integrating Life-cycle Environmental and Economic Assessment with

Sep 20, 2013 - Civil, Environmental, & Sustainability Engineering, Arizona State University, 501 E Tyler Mall, Room 252, mail code 5306, Tempe, Arizon...
80 downloads 13 Views 3MB Size
Download PDF
Policy Analysis pubs.acs.org/est

Integrating Life-cycle Environmental and Economic Assessment with Transportation and Land Use Planning Mikhail V. Chester,*,† Matthew J. Nahlik,† Andrew M. Fraser,† Mindy A. Kimball,§ and Venu M. Garikapati† †

Civil, Environmental, & Sustainability Engineering, Arizona State University, 501 E Tyler Mall, Room 252, mail code 5306, Tempe, Arizona 85287-5306, United States § School of Sustainability, Arizona State University, 501 E Tyler Mall, Room 252, mail code 5502, Tempe, Arizona 85287-5502, United States S Supporting Information *

ABSTRACT: The environmental outcomes of urban form changes should couple life-cycle and behavioral assessment methods to better understand urban sustainability policy outcomes. Using Phoenix, Arizona light rail as a case study, an integrated transportation and land use life-cycle assessment (ITLU-LCA) framework is developed to assess the changes to energy consumption and air emissions from transit-oriented neighborhood designs. Residential travel, commercial travel, and building energy use are included and the framework integrates household behavior change assessment to explore the environmental and economic outcomes of policies that affect infrastructure. The results show that upfront environmental and economic investments are needed (through more energy-intense building materials for high-density structures) to produce long run benefits in reduced building energy use and automobile travel. The annualized life-cycle benefits of transit-oriented developments in Phoenix can range from 1.7 to 230 Gg CO2e depending on the aggressiveness of residential density. Midpoint impact stressors for respiratory effects and photochemical smog formation are also assessed and can be reduced by 1.2−170 Mg PM10e and 41−5200 Mg O3e annually. These benefits will come at an additional construction cost of up to $410 million resulting in a cost of avoided CO2e at $16−29 and household cost savings.

■

INTRODUCTION An integrated transportation and land use (ITLU) life-cycle assessment (LCA) framework that includes behavioral changes from urban form changes is needed for assessing the environmental outcomes of urban infrastructure policy. Such a framework would lead to a stronger understanding of the outcomes of urban form redesign and the household and travel changes that it creates, and how up-front environmental costs (e.g., in deployment of new transit lines and construction of mixed-use high-density buildings) may lead to opportunities for long-run environmental benefits. Using Phoenix, Arizona as a case study, this framework is developed and applied to land use densification strategies currently being considered near the city’s new light rail line. It requires the joining of building and transportation infrastructure and technology changes using existing methods developed by LCA practitioners with assessment of behavioral changes. A prospective assessment is used to evaluate how physical changes to transportation and land use result in long-term household and transportation © 2013 American Chemical Society

energy use that ultimately affect air emissions. By developing the ITLU-LCA at the neighborhood scale, it becomes possible to recommend land use changes that are sensitive to the sociodemographic and economic needs of the local community while reducing air emissions and household costs. Environmental LCA of transportation and land use systems has so far focused on understanding how vehicle movement and building use require other infrastructure and supply chain processes.1−3 The state-of-the-art approaches have sought to understand the interdependencies of infrastructure and quantify indirect impacts. It is uncommon for LCA practitioners to develop behavioral analyses. A framework that links infrastructure design with behavioral outcomes and the resulting energy use and environmental impacts can help planners, city Received: Revised: Accepted: Published: 12020

July 8, 2013 September 14, 2013 September 20, 2013 September 20, 2013 dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028

Environmental Science & Technology

Policy Analysis

Figure 1. Phoenix light rail infrastructure. The existing light rail line is shown as a thick black line and the yellow circles are the existing stations. The expansion lines and stations are shown as blue lines and blue circles. The three expansion stations evaluated are the small red circles with a 1/2 mile buffer to illustrate the typical catchment area for transit riders. A 3/4 mile buffer around the current and expansion is shown in color to identify the transit-accessible household region that was studied for TOD household travel characteristics. For each TOD, the planned train station is shown as a train icon in a white square with the catchment area. Blue parcels are vacant and dedicated surface parking lots. Yellow area is low value residential parcels. The solid red area is low value commercial parcels. The striped red area is commercial parcels that would likely be part of focused transit improvement zones given their proximity to stations.

predominantly either low-density residential (West and North) or commercial (East). New neighborhoods are designed for each TOD with sensitivity to the socio-economic profiles of current residents. Furthermore, interviews with local officials were conducted to understand what the long-term housing, economic activity, and job goals were in each region.10−14 The West station has many vacant lots and is a predominantly lowincome community. At the North station, the site is currently dominated by middle-income single-family homes with few vacant lots. There is demand along the North extension for commercial establishments.15 The East station is in downtown Mesa’s Main Street neighborhood, an area that has been targeted for revitalization. The site has many vacant lots including an 11 acre parcel. Mesa city officials are advocating mixed-use developments that will attract regional light rail transit (LRT) riders.10,16 Neighborhood Design. Each site is modeled with four different growth scenarios that range from single-family home infill to more aggressive mixed-use high-density infill through either adaptive reuse or new construction. Land use characteristics are detailed in the Supporting Information (SI) Table S4. Adaptive reuse is the process of reusing existing buildings (sometimes abandoned) where the structure and major architectural features are kept while the interiors are reconstructed. In each scenario the primary criteria for land selection is that development must be within walking distance of the LRT station, 0.5 miles, consistent with distances cited in previous TOD literature.17,18 The current socio-economic conditions, potential for commercial activity, and need for office versus retail at each site were considered in the design of the TODs. These considerations resulted in the inclusion of affordable housing that replaces the building stock removed, and commercial deployment strategies that meet the needs of the residents (e.g., markets and low-rent commercial space in lower-income neighborhoods and higher-end retail in the highincome East neighborhood). Public green space is also included. For each neighborhood, the number of current

managers, engineers, and policymakers identify the characteristics of urban design that produce less environmental impacts and more economic stability in cities. To advance this concept, an ITLU-LCA framework is developed using potential new development around three proposed LRT extension line stations in Phoenix. The framework builds upon an initial model of the existing LRT line and its 28 stations that focused on residential construction.4 In this study, we improve the framework by creating methods that (i) assess new building construction as well as building reuse, (ii) are sensitive to residential and mixed-use development and the transportation impacts for both residential and commercial travel, and (iii) allow for socially and economically sensitive land use configurations that result in the deployment of particular building designs that maintain affordability and local community needs. The assessment includes energy use and greenhouse gas (GHG) emissions as well as the potential for human health respiratory impacts and smog formation.

■

NEIGHBORHOOD CHANGES AND INFILL POTENTIAL Changes in energy consumption and air emissions of GHGs and conventional air pollutants are assessed over a 60 year lifetime from the investment in transit-oriented developments (TOD) in place of low-density outward growth. This time frame is consistent with typical building lifetimes in existing LCA literature.5−7 Midpoint life-cycle impact assessment methods are used to assess human health respiratory and photochemical smog stressors that result from air emissions.8 Site Selection. The light rail stations are selected to assess different TOD design goals along several new rail lines that are planned for 2023.9 TOD is high-density mixed residential and commercial land use around high capacity transit. Each of the three sites selected has unique infrastructure characteristics, residential profiles, and commercial (retail and office) activity needs and the TODs are designed differently to meet these. The three sites are shown in Figure 1 and are currently 12021

dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028

Environmental Science & Technology

Policy Analysis

high-density designs: a single family detached home, single story commercial building, three story apartment building, four story mixed-use building, six story mixed-use building, six story commercial building, and a 12 story mixed-use building. The four and six story mixed-use building each feature one floor of commercial space at street level and the 12 story mixed-use features two floors of commercial space. Below-market-rate residential buildings are also considered through a lower-cost design that can ultimately pass along ownership/rental savings to low-income residents. Development in Scenarios 2, 3, and 4 were designed with consideration for residential dwelling units, commercial retail, commercial office, grocery and restaurant space. Previous LCA’s of neighborhoods have used a one size fits all approach that does not allow for an understanding of environmental effects in neighborhood design trade-offs.3,22 The ratio of commercial properties to residential properties is based on an assessment of TODs in Los Angeles, a city that has also sought to transition lower-density auto-oriented neighborhoods to high-density around new rail systems.23,24 Building Construction. Energy use and air emissions are produced during the construction of buildings as a result of raw material extraction, processing, transport, and construction activities. The impacts from building construction were modeled using Athena Impact Estimator.25 Material inputs for each of the seven buildings were estimated through engineering material and cost estimation approaches.26 The designs are validated through personal communications with local developers who are actively constructing TODs.27 Additionally, the impacts associated with providing parking are included in the construction of each building.28,29 For multifamily and mixed-use buildings, a parking structure with 1.5 parking spaces per residential dwelling unit and per-squarefoot zoning requirements for commercial space are included.30 Building Use Phase. Residential and commercial building energy use was determined from analysis of several surveys and forecasts are developed for energy use changes into the future. Previous LCA studies of buildings have found that approximately 90% of a building’s environmental impacts can be attributed to the use phase.31 For residential buildings, an analysis of the American Housing Survey (AHS) was developed to show how energy use has changed with building age in the Phoenix metro area. AHS reports the average monthly consumption of electricity and natural gas.32,33 To forecast building energy use changes, an exponential function was fit for the relationship between building age and energy use following Kimball et al. (2013). Energy consumption per floor area has been decreasing with newer buildings (for both single and multifamily buildings) and energy use in 2040 was estimated (halfway through the 60 year analysis time frame). AHS also shows that the use of natural gas in newer buildings is diminishing and it is assumed that TOD buildings will not use natural gas. The forecasted annual electricity demand for a single-family home is 12 300 kWh and for a multifamily dwelling unit 11 400 kWh. CBECS (2003)14 is used to estimate the annual electricity demand for each commercial business type. The most recent local building energy codes have increased insulation requirements for exterior walls, roofs, windows, and efficiency requirements for heating, ventilating, and air-conditioning.34 However, there is evidence to suggest that increased plug loads have counteracted efficiency gains.35,36 It is assumed that new commercial establishments meet 2009 International Energy Conservation Codes (IECC). Electricity

parks were assessed and where none existed space was allocated. The land use assessment is shown in Figure 1. The four scenarios capture increasing commitments to density. Scenario 1 uses low-density development on vacant and surface parking lots through the construction of singlefamily homes. This scenario is designed to assess transportation benefits (both in shifting of automobile trips to transit and reduced trip distances) and evaluates policy outcomes that shift the next new home from suburban growth to infill. Scenario 2 models both high-density homes (apartments) and multistory commercial spaces integrated into mixed-use buildings, again on vacant and surface parking lots. In Scenario 3, in addition to new construction on vacant and surface lots, adaptive reuse of existing buildings is assessed. Commercial and industrial buildings that are in the lowest quartile of market value are identified and reconstructed into high-density mixed-use. Lastly, in Scenario 4, all residential, commercial, and industrial buildings in the lowest quartile of market value are demolished and new high-density mixed-use buildings are constructed. For each site, residential and commercial buildings are placed by first meeting the below-market-rate housing needs of the neighborhood, then meeting the commercial office space needs of the city, and last placing mixed-use commercial retail and additional residential. For each of the four scenarios, the infill proposals are referred to as TOD and the neighborhoods are compared to a corresponding suburban growth business-as-usual (BAU) counterpart. The BAU counterparts assume that the same number of dwelling units and commercial space that are modeled in the TOD scenario is instead constructed as lowdensity single-family homes and single-story commercial spaces not within walking distance to LRT systems, consistent with typical suburban Phoenix construction. Environmental Impact Assessment. The energy use and emissions (NOx, SOx, PM10, PM2.5, CO, VOCs, CO2, CH4, and N2O) from all buildings and transportation life-cycle processes in both the TOD and BAU configurations are first assessed. Emissions are converted into equivalent midpoint impact potentials using the U.S. Environmental Protection Agency’s Tool for the Reduction and Assessment of Chemical Impacts (TRACI).19 Greenhouse gas (GHG) emissions (CO2e), human health respiratory impact potential (PM10e), and photochemical smog formation potential (O3e) are assessed, the latter two using TRACI. GHG emissions include CO2, CH4, and N2O and are normalized to CO2e using IPCC 100 year radiative forcing factors of 24 and 298 for CH4 and N2O.20 The human health respiratory emissions (PM10, PM2.5, SOx, and NOx) are normalized to particulate matter (10 μm and smaller)-equivalent (PM10e) and potential smog-forming emissions (CH4, CO, VOC, and NOx) are normalized to ozone-equivalent (O3e). These impact potentials were chosen for their significance to the Phoenix metropolitan area.21 TRACI midpoint equivalency factors are provided in the SI Table S1. Changes in the Use of Residential and Commercial Buildings. Through GIS, an analysis of Maricopa County’s building assessor database was used to identify available land for development, and later joined with LCA modeling tools for assessing building designs. Building Designs. Residential, commercial, and mixed-use building prototypes are created to capture the variety of building designs that could be used within the TODs. Seven building models are developed and span from low-density to 12022

dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028

Environmental Science & Technology

Policy Analysis

demand for the five major commercial establishments are Grocery, 51 kWH/ft2/yr; Sitdown Resturants and Fast Food, 47.5 kWh/ft2/yr; Retail, 17.85 kwh/ft2/yr; and Office, 11.9 kWh/ft2/yr. Future changes in energy consumption resulting from efficiencies in building systems or electronics and appliances are uncertain and future research in this area will be valuable. For the future power generation mix it is assumed that Arizona meets their 2025 renewable energy goal of 15% but does not pursue more renewables afterward. An uncertainty assessment of the changing electricity mix is presented in the SI. GREET electricity pathways are used to assess the upstream impacts from extraction, processing, transport of fuel inputs, and combustion processes.37 Changes in Automobile Travel. Changes in residential and commercial neighborhood design with access to light rail may produce changes in travel behavior. Residents, shoppers, and workers, who would in the BAU scenarios not have public transit alternatives and would likely have to travel further to access destinations, now have the opportunity to shift household trips to transit and experience less household travel. To assess the transportation energy and environmental changes that occur from the deployment of the TODs, travel analysis of the National Household Travel Survey (NHTS) is used.38 NHTS is used widely for travel behavior analysis as it provides information about daily travel at a disaggregate level. Like many major urban regions, Maricopa County paid for oversampling in the 2009 survey. In addition to travel characteristics, sociodemographics and household characteristics are collected in the survey. Each household is geocoded in the survey response sheet. With this information, two cohorts are identified: (i) suburban households and (ii) light-rail accessible urban core households. There is no true TOD resident in Phoenix yet, as dense developments near the light rail line that began operation in 2009 are still emerging. For the purpose of this study, the travel behavior of residents living in a 0.75 mile buffer around the current LRT stations were considered as transit-oriented residents. It is anticipated that because these households are in the urban core with access to high-capacity transit a greater fraction of their trips will occur by transit and their automobile travel will be less. It was assumed that future TOD residents would have the same characteristics of the people around the current LRT stations. To assess the travel behavior of residents in low-density auto-oriented BAU scenarios, a suburban boundary was used that follows the ring freeways of the metropolitan area. These ring freeways are roughly 10−15 miles from the urban core and the newest low-density growth is anticipated outside of this region. Household travel characteristics inside these freeways but outside of the 0.75 mile light rail buffer were not assessed. Light rail and bus changes are not quantified because the changes that result to these networks as a result of the three TOD stations is estimated to be small. Even with redevelopment near the three stations, light rail is currently operating with significant excess capacity. Additionally, regardless of TOD implementation, bus route realignments will likely occur. As a result, it is not obvious that TODs will result in changes in rail and bus service that will lead to changing air quality effects. Furthermore, Kimball et al (2013)4 show that if new bus service were to expand, the air quality effects are small compared to automobile and building energy use effects. Household Travel. There are significant differences in travel characteristics between households in the core and suburban areas. The average household size and the number of

trips per household do not differ significantly, but the average trip length per day for a suburban household is 38% more than that of the core resident. The average suburban household travels about 20 miles more per day than the core resident. Furthermore, core households have three times more transit trips. This can be due to a variety of reasons including access to higher capacity transit lines, proximity to employment centers, and proximity to retail. Furthermore, a higher density of jobs exist in the core area.39 These benefits may not be due purely to proximity to services but may include parking policy that reduces incentivizes for automobile ownership near transit lines.40 The differences in travel characteristics between the core and suburban households are shown in the SI Tables S5 to S7. Of the total trips made by the NHTS Phoenix-area survey respondents, 24% were shopping, 10% work and 66% noncommercial.38 These three trip types were considered separately so the travel characteristics could be modeled appropriately for each of the three TODs. Given the uncertainty in travel behavior changes that result from the placement of a household in the core instead of suburbs, a mode shift bounding analysis was developed. There is a dearth of data for Phoenix on how household travel changes with access to light rail. The NHTS data set does not have sufficient temporal coverage since light rail began operation. Using a synthesis of household travel behavior changes by Cervero and Arrington (2008),41 an uncertainty analysis is developed for mode shifts. Based on surveys from TODs in the U.S., Cervero and Arrington (2008),41 found that the maximum mode shift experienced was 44%. Based on results from an onboard light rail survey in Phoenix, a baseline shift of 30% is determined, and is similar to a density-based mode shift assessment developed by Kimball et al. (2013) for the existing rail line.4,42 The effects of induced demand are considered but have negligible effects on results. TOD residents may make more trips given their proximity to commercial establishments, however, the impacts of these additional trips are small compared to the reduced trip distances by nonresidents to the same commercial establishments. Commercial Trip Reduction. To estimate commercial trip changes, trip generation rates for each retail purpose were used with TOD adjustment methods.43 As mixed-use developments are constructed near light rail, automobile travel throughout the city may change. If the commercial establishment is placed in the TOD to meet the new household demand instead of in the suburbs then travel may occur by transit, biking, or walking, and those that still access by car may have shorter trip distances given the TOD’s centralized location. The Institute of Transportation Engineer’s (ITE) trip generation manual is the state-of-the-art method for estimating automobile travel from commercial and office establishments.44 However, the manual is based on data largely from suburban sites that may inflate the actual travel that results from a centrally located TOD.43 Therefore, an adjustment methodology developed by Nelson-Nygaard (2005) was applied to adjust to TOD-specific trip generation.43 Assessments of below market rate housing, number of jobs created per household in the TOD, intersection density, sidewalk density, and bike path density were developed to estimate the adjustments. These factors compensate for overprediction of vehicular trips in dense neighborhoods by the ITE trip generation manual and shorter commercial trip lengths in densely developed areas. The reduction in commercial travel is therefore a result of shorter commercial trip lengths of TOD residents (3.76 miles) than the fringe residents (6.87 miles) and 12023

dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028

Environmental Science & Technology

Policy Analysis

Figure 2. Energy and environmental effects for three LRT stations over 60 year life-cycle. The red segments are the residential building phases and the orange segments are the commercial buildings. The purple segments are the transportation phases associated with home-based nonshopping (HBNS, commuting and leisure travel not associated with shopping) and the blue segments are the transportation phases associated with homebased shopping (HBS). Black lines are the uncertainty in both the buildings (future building energy use and energy mixes) and transportation (mode-shift) technologies as well as the percentage of household trips shifted to light rail in the case of TOD.

to occur. However, mode-shifting to light rail coupled with shorter trips by both TOD residents and commercial activity leads to substantial transportation and building use phase benefits as well as significant benefits in the supply chain. Figure 2 shows the total life-cycle energy consumption, GHG emissions, respiratory impact potential, and smog formation potential for all three sites over 60 years. These three LRT stations capture just a fraction of potential larger effects that may occur along more than 18 miles of planned rail line extensions in the Phoenix metropolitan area.9 By designing the TODs to the specific needs of the neighborhood, environmental changes occur for different reasons. Understanding where in the life-cycle these changes occur will enable planners and engineers to augment the neighborhood design with an understanding of the maximum possible environmental benefits. The uncertainty bars are based on optimistic and pessimistic cases for the electricity mix, fleet fuel economy, building energy use, household trip shifting to light rail, and commercial travel distance reduction. The overlapping portions of the uncertainty bars represent futures where TOD deployment produces environmental impacts equivalent or greater than BAU scenarios. For this to occur, TOD users would need to consume more energy in their homes, have less efficient vehicles, and not change their behavior relative to counterparts living away from the urban core. While possible, this outcome seems unlikely given that the TODs and their commercial establishments would be more centrally located in Phoenix. This is discussed in more detail in the SI. Energy Consumption and Greenhouse Gas Emissions. Automobile (22−51% of total) and building (22−44%) use phases constitute the majority of energy consumption and GHG emissions, however, life-cycle processes add 26−30%. Furthermore, the impacts from commercial activities are 1.9− 3.3 times larger than those from residential. The impacts from commercial activities decrease relatively more than residential activities for all scenarios, showing how the benefits of TODs extend beyond those who live in the neighborhoods by reducing both the number of trips by automobile and the trip distance. In Scenario 1, life-cycle energy consumption is reduced by 31% and total GHG emissions are reduced by 27% over BAU. When mixed-use residential and commercial infill occurs in Scenarios 2−4, the energy savings and GHG

also the reductions warranted by the adjustment methodology which predicts about 20% fewer vehicle trips in the TODs. Transportation Energy and Environmental Assessment. Energy use and air emissions from vehicle operation, fuel production, and vehicle manufacturing (to capture the effect of reduced automobile travel on displacing the production of new vehicles) were estimated using the GREET1 (fuel cycle) and GREET2 (vehicle cycle) models.37,45 To assess transportation effects over 60 years, vehicle manufacturing and fuel efficiency changes were modeled with goals for future fuel economy standards. Currently, Phoenix light duty vehicles average 23.4 mi/gal38 and future fuel economy standards of 35 mi/gal by 2020 and 55 mi/gal by 2050 were used to build changing emissions profiles into the future.46 A 60 year average fuel economy of 43.5 mi/gal was calculated by developing a time series for fuel economies from 2012 to 2071 assuming that the 35 and 55 mi/gal standards will be met on time. Using the NHTS, a 7 year fleet turnover was calculated for the Phoenix metropolitan statistical area. The material composition of vehicles is assumed to change over time to reach the 55 mi/gal goal.45 Fuel production methods are expected to change with the increase use of unconventional crude oil sources (e.g., oil sands). Currently, 8% oil sands are used and this is forecast to increase to 15.7% by 2020. Vehicle manufacturing effects are modeled with GREET2 and fuel production with GREET1. An uncertainty assessment that includes fuel economy is presented in the SI.

■

LIFE-CYCLE ENVIRONMENTAL IMPACTS OF URBAN INFILL The ITLU-LCA results show that urban infill where transit infrastructure has already been deployed has the potential to reduce life-cycle energy consumption, GHG emissions, and respiratory and smog stressors, and the majority of benefits are found in different life-cycle phases depending on the TOD design. The benefits increase with more aggressive land use scenarios, particularly when commercial activity is promoted, as shown in Figure 2. Regardless of the TOD design (mixed-use emphasizing middle-income and commercial office, mixed-use emphasizing low-income with retail, or residential), larger upfront energy and environmental effects will occur during building construction than if low-density suburban growth were 12024

dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028

Environmental Science & Technology

Policy Analysis

buildings processes. There are also significant contributions from vehicle manufacturing, the result of bauxite mining for aluminum parts and the production of carbon-fiber plastics that are necessary for lightweighting. While much focus thus far has been related to the use phases (electricity generation or gasoline combustion), respiratory stressors are significantly impacted by upstream processes such as mining of raw materials, producing building materials, manufacturing vehicles, or generating and producing energy. The buildings phases are 70−83% of the total respiratory potential impacts, but account for at most 23% of the savings. TOD infill should be accompanied by parallel efforts to establish renewable energy goals and LRT adoption to ensure reduced exposure to respiratory impacts. In Scenarios 2−4, if TODs are constructed but Arizona fails to meet renewable energy targets and few residents shift to LRT, then respiratory impacts will not be reduced from the BAU scenarios. The TOD benefits are realized when a confluence of planning policies and technology improvements come together. It is important that policy and decision makers recognize that the full benefits of TODs are achieved when changes to transportation, land use, and energy systems are managed concurrently. Particulate emissions in the region are currently estimated to be 92 Gg PM10e/yr,48 and the avoided emissions from TOD infill at just 3 stations has the potential to reduce these emissions by 0.2%. These three stations (74 total acres) are 0.0007% of the 10.6 million acres in the metro area. Smog Formation Potential. The Phoenix metropolitan area is routinely out-of-attainment for ozone and each of the TOD designs offers opportunities for reducing smog-forming precursors. Filling vacant and surface lots with low-density single-family homes in Scenario 1 produces a 23% potential savings over BAU and higher-density designs (Scenarios 2−4) produce up to 34% savings. The buildings phases constitute 50−67% of the total emissions, and are dominated by air emissions from electricity generation (26−39%of the total emissions). In the transportation phases, the smog precursors from gasoline production (which occur remotely) and combustion are nearly equal, and together make up 23−39% of the total emissions. The dominating share of remote impacts occur in gasoline production and are largely due to VOCs emitted by industrial boilers used in recovering petroleum and by transporting crude oil to refineries. The potential for local smog formation is estimated at 3.8 Tg O3e/yr,49 and Scenario 4 can reduce emissions by 0.1%.

emissions reductions can be as high as 42% and 40% respectively, from both travel savings and decreases in household energy consumption. The construction of buildings, manufacturing of automobiles, and production of energy in the life-cycle are significant and will not occur within the TOD neighborhoods or where travel occurs. These upstream phases are 26−30% of the total lifecycle effects in each scenario. These remote emissions occur for several reasons in building construction (the raw materials extraction, materials manufacturing, and transport are assumed to happen outside the region such as aggregate mining in Utah or lumber mills in northern Arizona), vehicle manufacturing (automobile parts manufacturing and vehicle assembly plants), building energy feedstock provision (raw material extraction for the fuel used in power generation and transport to the plants), and gasoline production (petroleum extraction, fuel refining and transport of both crude oil and refined gasoline). The results show that for every 10 Mg of TOD life-cycle GHG emissions in Scenario 4, 7.1 Mg result from electricity generation and vehicle operation emissions near or in the metro area. Building construction emits an additional 0.5 Mg in the metro area while 0.7 Mg occur in Arizona due to electricity feedstock production and 1.7 Mg occur outside of Arizona’s borders (from vehicle manufacturing and gasoline production). While local use-phase effects are often the focus of mitigation efforts, actions that reduce upstream emissions can have significant benefits outside the region. The Arizona Climate Change Advisory Group (CCAG) projects that Arizona’s GHG annual emissions will be 147 Tg by 2020.47 Infilling the 74 acres in Scenario 4 has the potential to reduce this state-wide footprint by 0.2 Tg/yr by targeting only three of the ultimately 42 total stations that are planned in the system by 2023. While the benefits of TOD in Scenario 1 (shifting the next 424 single family homes constructed near light rail) are small compared to other scenarios, the strategy is expected to lead to energy (1.4PJ) and GHG (99 Gg) benefits at little to no additional cost. Scenario 1 highlights how policies that focus on the development of vacant and underutilized land in the urban core (and near transit services) before new development occurs in outlying areas has significant transportation benefits. While housing construction and energy use impacts stay the same (since it is assumed that the same house is shifted from the suburbs to the core), locating households along transit and near services produces an opportunity to shift automobile travel to transit and results in shorter automobile trip distances. With aggressive land-use calculations, more mixed-use development yields greater potential savings over low-density BAU growth. In scenario 2, the substitution of mixed-use high-density for single family home infill in TOD1 produces energy and GHG benefits 38 times greater. Adding to this adaptive reuse in low-value parcels (TOD3) results in 41 times more savings and the most aggressive infill practices (TOD4) results in 140 times more savings over scenario TOD1. These life-cycle benefits are contingent on several key technological and behavioral factors and it is important to understand how the results change with uncertainty. Human Health Respiratory Potential. Respiratory impact stressors from primary and secondary particle formation can be reduced by as much as 23% in the most aggressive TOD infill scenario, and in all scenarios the total life-cycle respiratory emissions are dominated by the buildings phases. The mining of coal (in electricity feedstock production) for building energy use is the largest portion of total respiratory emissions from

■

BENEFITS OF NEIGHBORHOOD-SPECIFIC INFILL DESIGNS The results are specific to the designs of the neighborhoods. The placement of below-market-rate residential buildings to replace existing low-value homes, and the placement of commercial office space based on the needs expressed by the cities produces energy use and environmental benefits while maintaining social and economic goals. Air emissions within Phoenix will also decrease, however, epidemiological research is needed to assess public health trade-offs between neighborhood designs. The results show that high-density residential buildings produce 1.5−3 times the energy impacts per dwelling unit in construction but result in 10% reductions in energy use over low-density single-family homes in the 60 years, a net benefit. Ensuring that long-run user benefits are realized through upfront financing and development requirements will be critical. 12025

dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028

Environmental Science & Technology

Policy Analysis

Figure 3. Investments in User Savings and GHG Reductions. The left chart shows the total costs of BAU and TOD in each scenario and the economic benefits of TOD. The benefits of TOD increase with land area developed, largely the result of increasing commercial activity. The right chart shows the cost of conserved GHG emissions. The chart shows how much it will cost (in $/Mg CO2e) to reduce GHG emissions by a desired amount. Note that the cost of GHG reductions drops from Scenario 2 to 3, signifying that 3 is preferable to 2 provided that financial resources are available.

East TOD will reduce GHG emissions by 131 Gg CO2e/yr compared to the same commercial space in a typical lowdensity configuration. To maximize the environmental benefits of neighborhood-specific TOD design requires financial investments and these investments can be prioritized to the infrastructure changes that produce the greatest impact reductions.

Financing, development incentivizes, construction requirements and building energy audits could be established to ensure that developers take on energy-efficiency savings and that these benefits will be passed along to inhabitants over the long-term. The benefits of adaptive reuse are largely contingent on the changes in a household’s building energy use, however, transportation benefits alone are significant. Scenarios 3 and 4 contrast investments along light rail that either reuse and upgrade existing low value building stock (TOD3) or demolish that building stock and construct new buildings (TOD4). Adaptive reuse reduces residential building construction impacts by 4−9% for energy use, 22−50% for GHG emissions, 14−28% for respiratory stressors, and 18−44% for smog. For commercial structures, impacts are reduced by 4−19% for energy use, 22−42% for GHG emissions, 14−27% for respiratory stressors, and 18−43% for smog. There is uncertainty as to whether adaptive reuse of structures results in the same building envelope characteristics as new construction, and are used by inhabitants with behavior profiles that ultimately result in energy savings. Additional research is needed to better understand this dynamic. The reductions in transportation impacts in each scenario are dominated by changes in commercial travel that results from activity changes from both inside and outside of the TOD. The results show how the locating of a commercial establishment closer to the urban core and with transit access (i) creates an opportunity for residents along the entire transit network to access the establishment without automobiles, (ii) reduces the average trip distance to that commercial service, and (iii) creates greater reductions in automobile use outside of the TOD than from residents within the TOD. In all of the scenarios, commercial travel is roughly 80−87% of total travel. In the TOD scenarios, only 7−14% of commercial travel is the result of TOD residents. The TODs reduce residential travel by 47% and commercial travel by 51%. For Scenarios 2−4, the reductions in energy use and environmental impacts from nonresidents are 2.2−4.4 times larger than from those living in the TODs. The commercial benefits are largely the result of shorter automobile trip distances to commercial establishments (accounting for 79% of the total reductions). This shows the city-wide benefits that infill can achieve. Focusing on commercial office space, there are significant environmental benefits per job. It is estimated that the 6.6 million ft2 in the

■

VALUING URBAN FORM The deployment of TODs will require up-front financial investments that will lead to life-cycle economic changes in addition to environmental changes. Using the ITLU-LCA framework, a benefit-cost analysis is developed to assess the economic and environmental efficiencies that result from each strategy. Building construction, building use, vehicle ownership, and vehicle use costs are determined in 2012 dollars. Engineering estimation approaches are used to determine the construction costs for each building model. These costs are based on data from RS Means (2011)26 and Phoenix-specific adjustment factors are used. Residential building use phase costs include water, sewer, and energy and are estimated from Phoenix-specific households in AHS (2011).33 For commercial buildings, natural gas, and electricity costs are based on CBECS (2003).36 CBECS does not include water costs and other surveys are used.50 Changes from commercial activity are not included given the uncertainty in estimating how shopping and office services will change. AAA (2012)51 is used for vehiclerelated costs assuming a midsize sedan. Gasoline, electricity, and natural gas cost projections from EIA (2013)52 are used to find each fuel’s average price over the 60 year analysis period. EIA (2013)52 forecasts the future costs (due to changing methods of extraction, production, generation, and distribution) of producing these energy sources. For each of the lifecycle phases, costs were calculated over 60 years for each TOD and BAU and can be allocated to private developers and users. Figure 3 shows that the benefit-cost ratios in all scenarios are economic advantages for TOD infill, and up to 14 Tg CO2e can be avoided if TOD financial commitments are made. Higherdensity residential buildings and mixed-use buildings cost more than single-family homes (per dwelling unit) and single-story commercial structures (per unit area), but these investments produce opportunities for less automobile driving and building energy expenditures in the long run. The savings in Scenario 1 are on average $10,100 per household per year. In Scenarios 2− 12026

dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028

Environmental Science & Technology

Policy Analysis

(2) Chester, M. V.; Horvath, A. Environmental assessment of passenger transportation should include infrastructure and supply chains. Environ. Res. Lett. 2009, 4 (2), 024008 DOI: 10.1088/17489326/4/2/024008. (3) Norman, J.; MacLean, H. L.; Kennedy, C. A. Comparing high and low residential density: Life-cycle analysis of energy use and greenhouse gas emissions. J. Urban Plann. Dev. 2006, 132 (1), 10− 21, DOI: 10.1061/(ASCE)0733-9488(2006)132:1(10). (4) Kimball, M.; Chester, M.; Gino, C.; Reyna, J. Transit-oriented development infill in phoenix can reduce future transportation and land use life-cycle environmental impacts. J. Plann. Educ. Res. 2013, DOI: 10.1177/0739456X13507485. (5) Aktas, C. B.; Bilec, M. M. Impact of lifetime on US residential building LCA results. Int. Jo. Life Cycle Assess. 2012, 17 (3), 337−349, DOI: 10.1007/s11367-011-0363-x. (6) Ochsendorf, J.; Norford, L. K.; Brown, D.; Durschlag, H.; Hsu, S. L.; Love, A.; Santero, N.; Swei, O.; Webb, A.; Wildnauer, M. Methods, Impacts, And Opportunities in the Concrete Building Life Cycle; Massachusetts Institute of Technology: Cambridge, MA, 2011. (7) Athena Ecocalculator; Athena Sustainable Materials Institute, 2011. (8) Bare, J. C.; Norris, G. A.; Pennington, D. W.; McKone, T. TRACI: The tool for the reduction and assessment of chemical and other environmental impacts. J. Ind. Ecol. 2002, 6 (3−4), 49−78, DOI: 10.1162/108819802766269539. (9) Valley Metro Projects and Planning. http://www.valleymetro. org/metro_projects_planning/ (10) City of Mesa Arizona. Mesa, Arizona Form-Based Zoning Code; City of Mesa, Arizona: Mesa, AZ, 2012. (11) City of Phoenix Arizona. Economic Development Strategic Plan, Phoenix City Council Policy Session, February 28, 2012; City of Phoenix: Phoenix, AZ, 2012. (12) Dayal, A. Personal Communication, Project Manager for Valley Metro, September 27, 2012; Phoenix, AZ, 2012. (13) Graves, J. Personal Communication, Project Manager for the Office of Economic Development, Mesa, AZ, October 15, 2012; Mesa, AZ, 2012. (14) Tetreault, C. Personal Communication, Senior Policy Advisor for Sustainability, CIty of Phoenix, October 25, 2012; Phoenix, AZ, 2012. (15) Gehrke, A.; Srivastava, S. Sustainable Land Use and Transportation Strategy Market Study; Maricopa Association of Governments: Phoenix, AZ, 2011; p 59. (16) Maricopa Association of Governments. Minutes of the Maricopa Association of Governments Transportation Review Committee: October 25, 2012; Maricopa Association of Governments: Phoenix, AZ, 2012; pp 1−15. (17) Cervero, R.; Ferrell, C.; Murphy, S. Transit-Oriented Development and Joint Development in the United States: A Literature Review; Transit Cooperative Research Program: Washington, DC, 2002. (18) Cervero, R., Transit-oriented development in the United States: Experiences, challenges, and prospects; Transportation Research Board, 2004; Vol. 102. (19) Bare, J. TRACI 2.0: The Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts 2.0. Clean Technol. Environ. Policy 2011, 13 (5), 687−696, DOI: 10.1007/ s10098-010-0338-9. (20) Intergovernmental Panel on Climate Change. Climate Change 2007: The Physical Science Basis; Cambridge University Press: Cambridge, United Kingdom, 2007. (21) United States Environmental Protection Agency The Green Book Nonattainment Areas for Criteria Pollutants. http://www.epa. gov/oaqps001/greenbk/ (22) Frijia, S.; Guhathakurta, S.; Williams, E. Functional unit, technological dynamics, and scaling properties for the life cycle energy of residences. Environ. Sci. Technol. 2012, 46 (3), 1782−1788, DOI: 10.1021/es202202q.

4, the per-household savings are $8,900-$9,300. For Scenarios 2−4, the larger up-front investment costs diminish the perhousehold savings, however, savings are passed along to more residents in the city. These additional up-front building construction costs must be spent to set the appropriate TOD conditions that result in transportation life-cycle savings. The benefit-investment ratios range from 101:1 in Scenario 2 to 149:1 in Scenario 3. The cost investments lead to both economic and environmental benefits. Commonly cited social costs for CO2 emissions range from $10/Mg to $100/Mg (with a median of $30/Mg).53 Arizona’s Climate Change Advisory Group (CCAG) estimates that reducing CO2 emissions will result in economic benefits from job creation and economic development at $12/Mg.47 The drop in $/Mg CO2e costs in Scenario 3 is the result of the significant cost savings that are realized in adaptive reuse over new construction. The results show that for every additional dollar invested in development around the light rail line, it is possible to generate between $84−149 in household energy and transportation savings realized by those living in the neighborhoods.

■

LCA AND URBAN FORM CHANGES The findings, while focused on the energy and environmental benefits of TODs, provide insight into urban infill designs and policies. The ITLU-LCA framework is valuable for compartmentalizing changes in impacts so that policymakers can craft focused goals for each component of the highly interdependent transportation and land use systems. From building construction to electricity generation to vehicle travel, each component of the system has the potential to reduce or increase environmental impacts. Understanding the interfacing of these components is critical for developing policies that recognize and support the long-run benefits of upfront investments and the cobenefits across the systems. Ultimately, however, commitment to more efficient infrastructure alone is insufficient. Policymakers should recognize that infrastructure can affect the environmental outcome of behaviors, however, incentivizes are needed (e.g., employer transit programs, revisiting of minimum parking standards, public financing of high-density structures, electricity pricing, etc.) to support these behaviors in the long-run.

■

ASSOCIATED CONTENT

S Supporting Information *

Additional information as noted in the text. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*(M.V.C.) Phone:1-480-965-9779; fax: 1-480-965-0557; email: [email protected]. Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS The authors received no financial support for this research. REFERENCES

(1) Chester, M.; Pincetl, S.; Elizabeth, Z.; Eisenstein, W.; Matute, J. Infrastructure and automobile shifts: positioning transit to reduce lifecycle environmental impacts for urban sustainability goals. Environ. Res. Lett. 2013, 8 (1), 015041 DOI: 10.1088/1748-9326/8/1/015041. 12027

dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028

Environmental Science & Technology

Policy Analysis

(46) Department of Transportation. Federal Register; National Archives and Records Administration: Washington, DC, 2012; Vol. 77, pp 62623−63200. (47) limate Change Advisory Group. Phoenix Climate Change Action Plan Phoenix; Arizona Climate Change Advisory Group: Phoenix, AZ, 2006. (48) Maricopa County. 2008 Maricopa County PM10 Emission Inventory; Maricopa County Air Quality Department: Phoenix, AZ, 2011. (49) Maricopa County. 2005 Periodic Emission Inventory for Ozone Precursors; Maricopa County Air Quality Department: Phoenix, AZ, 2008. (50) Morales, M.; Heaney, J. Predominant commercial sectors in Florida and their water use patterns. Fla. Water Resour. J. 2010, 62 (8), 29−34. (51) AAA. Your Driving Costs; AAA Association Communication: Heathrow, FL, 2012. (52) United States Energy Information Administration. Annual Energy Outlook 2013 with Projections to 2040; US Energy Information Administration, US Department of Energy: Washington, DC, 2013. (53) National Research Council. Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use; The National Academies Press, 2010.

(23) Wachs, M. Learning from Los Angeles: Transport, urban form, and air quality. Transportation 1993, 20 (4), 329−354, DOI: 10.1007/ BF01100463. (24) Center for Transit-Oriented Development. Creating Successful Transit-Oriented Districts in Los Angeles: A Citywide Toolkit for Acheiving Regional Goals; Center for Transit-Oriented Development, 2010. (25) Athena. Athena Impact Estimator for Buildings; Athena Sustainable Materials Institute, 2012. (26) Balboni, B.; Babbitt, C.; Baker, T.; Bastoni, R. A.; Chiang, J. H., RS Means Square Foot Costs 2011; R. S. Means Company, Incorporated, 2011. (27) Lafferty, M. J. Personal Communication, General Contractor, Lafferty Development Inc, September 19, 2012; Phoenix, AZ, 2012. (28) Chester, M.; Horvath, A.; Madanat, S. Parking infrastructure: energy, emissions, and automobile life-cycle environmental accounting. Environ. Res. Lett. 2010, 5 (3), 034001 DOI: 10.1088/1748-9326/5/3/ 034001. (29) Horvath, A. Pavement Life-Cycle Assessment Tool for Environmental and Economic Effects; University of California, Berkeley: Berkeley, CA, 2003. (30) Maricopa County. Maricopa County Zoning Ordinance; Maricopa County Planning and Development Department: Phoenix, AZ, 2013. (31) Sharma, A.; Saxena, A.; Sethi, M.; Shree, V. Life cycle assessment of buildings: A review. Renewable Sustainable Energy Rev. 2011, 15 (1), 871−875, DOI: 10.1016/j.rser.2010.09.008. (32) United States Energy Information Administration. Electric Power Monthly Table 5.6.A: Average Retail PRive of Electricity to Ultimate Customers by End-Use Sector; United States Energy Information Administration: Washington, DC, 2013. (33) United States Census Bureau. American Housing Survey; United States Census Bureau, US Department of Commerce: Washington, DC, 2011. (34) Pacific Northwest National Laboratory Analysis of IECC (2003, 2006, 2009) and ASHRAE 90.1−2007 Commercial Energy Code Requirements for Mesa, AZ; U.S. Department of Energy: Washington, DC, 2011. (35) United States Department of Energy Buildings Energy Data Book; United States Department of Energy: Washington, DC, 2011. (36) United States Energy Information Administration Commercial Buildings Energy Consumption Survey (CBECS); US Energy Information Administration, US Department of Energy: Washington, DC, 2003. (37) Argonne National Laboratory The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Fuel Cycle Model Version GREET 1 2012 rev2; Argonne National Laboratory, US Department of Energy: Argonne, IL, 2012. (38) Federal Highway Administration. National Household Travel Survey; U.S. Department of Transportation, Federal Highway Administration: Washington, DC, 2009. (39) Leslie, T. F. Identification and differentiation of urban centers in Phoenix through a multi-criteria kernel-density approach. Int. Reg. Sci. Rev. 2010, 33 (2), 205−235, DOI: 10.1177/0160017610365538. (40) Chatman, D. G. Does TOD Need the T? J. Am. Plann. Assoc. 2013, 79 (1), 17−31, DOI: 10.1080/01944363.2013.791008. (41) Cervero, R.; Arrington, G. Vehicle trip reduction impacts of transit-oriented housing. J. Public Transp. 2008, 11 (3), 1−17. (42) Valley Metro. 2010−2011 Transit On-Board Survey; Valley Metro: Phoenix, AZ, 2011. (43) Nelson\Nygaard Consulting Associates. Crediting Low-Traffic Developments: Adjusting Site-Level Vehicle Trip Generation Using URBEMIS; Nelson\Nygaard Consulting Associates: San Francisco, CA, 2005. (44) Institute of Transportation Engineers. Trip Generation Manual. 8th ed.; Institute of Transportation Engineers, . (45) Argonne National Laboratory. The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Vehicle Cycle Model Version 2 2012 rev1; Argonne National Laboratory, US Department of Energy: Argonne, IL, 2012. 12028

dx.doi.org/10.1021/es402985g | Environ. Sci. Technol. 2013, 47, 12020−12028