Center for Earth Systems Engineering and Management

Vehicle trips presently account for approximately 50% of San Francisco’s greenhouse gas emissions (San Francisco County Transportation Authority, 2008). City and county officials have developed aggressive strategies for the future of passenger transportation in the metropolitan area, and are determined to move away from a “business as usual” future. This project starts with current-state source data from a life-cycle comparison of urban transportation systems (Chester, Horvath, & Madanat, 2010), and carries the inventoried emissions and energy usage through by way of published future scenarios for San Francisco.

From the extrapolated calculations of future emissions/energy, the implied mix of transportation modes can be backed out of the numbers. Five scenarios are evaluated, from “business as usual” through very ambitious “healthy environment” goals. The results show that when planners and policymakers craft specific goals or strategies for a location or government, those targets, even if met, are unlikely to result in the intended physical outcomes. City and state governments would be wise to support broad strategy goals (like 20% GHG reduction) with prioritized specifics that can inform real projects leading to the goals (for instance, add 5 miles of bike path per year through 2020, or remove 5 parking garages and replace them with transit depots). While these results should not be used as predictions or forecasts, they can inform the crafters of future transportation policy as an opportunity for improvement or a cautionary tale.

This LCA used data from a previous LCA done by Chester and Horvath (2012) on the proposed California High Speed Rail, and furthered the LCA to look into potential changes that can be made to the proposed CAHSR to be more resilient to climate change. This LCA focused on the energy, cost, and GHG emissions associated with raising the track, adding fly ash to the concrete mixture in place of a percentage of cement, and running the HSR on solar electricity rather than the current electricity mix. Data was collected from a variety of sources including other LCAs, research studies, feasibility studies, and project information from companies, agencies, and researchers in order to determine what the cost, energy requirements, and associated GHG emissions would be for each of these changes. This data was then used to calculate results of cost, energy, and GHG emissions for the three different changes. The results show that the greatest source of cost is the raised track (Design/Construction Phase), and the greatest source of GHG emissions is the concrete (also Design/Construction Phase).

The ultimate goal of this LCA is to give Arizona State University specific advice on possible changes in lighting systems that will reduce environmental impacts and support ASU’s sustainability efforts. The aim is to assess the potential for a decrease in specific environmental impacts (CO2 emissions and energy use) and economic impact (cost) from changing to a different type of lighting in a prototypical classroom in Wrigley Hall. The scope of this assessment is to analyze the impacts of T8 lamps lasting 50,000 hours. Thus, a functional unit was defined as 50,000 hours of use, maintaining roughly 825 lumens. To put this in perspective, 50,000 hours is equivalent to 8 hours of use per day, 365 days per year, for approximately 17.1 years.

Results are available here. 

The environmental life cycle assessment of electric rail public transit modes requires an assessment of electricity generation mixes. The provision of electricity to a region does not usually adhere to geopolitical boundaries. Electricity is governed based on lowest cost marginal dispatch and reliability principles. Additionally, there are times when a public transit agency may purchase wholesale electricity from a particular service provider. Such is the case with electric rail modes in the San Francisco Bay Area.

An environmental life cycle assessment of San Francisco Bay Area public transit systems was developed by Chester and Horvath (2009) and includes vehicle manufacturing/maintenance, infrastructure construction/operation/maintenance, energy production, and supply chains, in addition to vehicle propulsion. For electric rail modes, vehicle propulsion was based on an average electricity mix for the region. Since 2009, new electricity contract information and renewable electricity goals have been established. As such, updated life cycle results should be produced.

Using recent wholesale electricity mix and renewable electricity goal data from the transit agencies, updated electricity precombustion, generation, transmission, and distribution environmental impacts of vehicle propulsion are estimated. In summary, SFMTA Muni light rail is currently purchasing 100% hydro electricity from the Hetch Hetchy region of California and the Bay Area Rapid Transit (BART) system is purchasing 22% natural gas, 9% coal, 2% nuclear, 66% hydro, and 1% other renewables from the Pacific Northwest . Furthermore, the BART system has set a goal of 20% renewables by 2016. Using the GREET1 2012 electricity pathway, a life cycle assessment of wholesale and renewable electricity generation for these systems is calculated.

Chester and Horvath (2009)

Building energy assessment often focuses on the use of electricity and natural gas during the use phase of a structure while ignoring the energy investments necessary to construct the facility. This research develops a methodology for quantifying the “embedded” energy and greenhouse gases (GHG) in the building infrastructure of an entire metropolitan region. “Embedded” energy and GHGs refer to the energy necessary to manufacture materials and construct the infrastructure. Using these methods, a case study is developed for Los Angeles County.