SEPTA's Greenhouse Gas Inventory (Goal 1)

February 18, 2011

Transportation is the single largest consumer of energy in the United States, also far outpacing any other industrialized country in the world. According to the U.S. Environmental Protection Agency (EPA), energy consumed by the U.S. transportation sector is highly carbon intensive, accounting for nearly one-third of total U.S. greenhouse gas (GHG) emissions. And it's growing: between 1990 and 2006, GHG emissions from U.S. transportation grew 27 percent, compared to just 15 percent across all sectors.

Mass transit is a solution to this growing problem. For transit, GHG emissions produced by diesel-burning motor buses, electricity-consuming trolleys and trains, and the operation of facilities is offset by the displacement of GHG emissions by taking cars off the road, reducing congestion, and supporting energy-efficient, transit-oriented development. Goal 1 of SEP-TAINABLE is to improve upon SEPTA's already impressive track record in this regard by expanding its role in displacing GHG emissions across the region.

To do so, last year SEPTA set out to quantify its GHG inventory and impact on the Greater Philadelphia region. Using an industry-standard methodology developed by the American Public Transportation Association (APTA) in conjunction with The Climate Registry (TCR), SEPTA found that its service displaces approximately three metric tons of regional GHG emissions for every metric ton it emits. Among the more interesting findings of this analysis is that when SEPTA's emissions increase, the region's transportation-related emissions actually decrease. The upshot of this paradox: when residents leave their car at home and use SEPTA, the entire region stands to benefit.

Scope of Analysis

SEPTA's GHG inventory was built upon APTA's "Recommended Practice for Quantifying Greenhouse Gas Emissions From Transit," which groups GHG emissions into three scopes for analysis:

  • Scope 1: Local emissions produced from combusted energy (for SEPTA: diesel and gasoline fuel, heating oil, and natural gas)
  • Scope 2: Non-local emissions produced from purchased energy (for SEPTA: electricity & steam)
  • Scope 3: Emissions displaced from transit effect (for SEPTA: lower levels of car use, congestion relief, and development patterns)

For SEPTA's GHG inventory, units are measured in carbon dioxide-equivalents (CO2-e) to normalize the global warming potential of three significant greenhouse gases: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Calendar 2009 was used as a base year for analysis.

Scope 1. SEPTA's local emissions account for 44 percent (202,480 metric tons CO2-e in 2009) of its GHG inventory. The lion's share (86 percent) is produced by SEPTA's fleet of 1,500 diesel-burning motor buses. Remaining emissions are produced by SEPTA's non-revenue supervisory and utility fleet (4 percent) as well as building heat generated by natural gas and heating oil (6 percent).

Scope 2. SEPTA's non-local GHG emissions account for 56 percent (262,675 metric tons CO2-e) of its GHG inventory. The lion's share (77 percent) is related to the purchase of electricity for propulsion-powered trolleys and trains. Another 21 percent is related stationary electricity consumption at SEPTA facilities, with an additional 1 percent related to the purchase of steam to power Center City administrative and regional rail facilities during cold winter months.

In 2009, SEPTA produced a total of 465,156 metric tons of CO2-e.

Source: SEPTA

Scope 3. In 2009, SEPTA displaced regional transportation-related GHG emissions by a ratio of 2.75-to-1. The 1,281,124 metric tons of CO2-e displaced were a result of cars taken off the road (23 percent), associated congestion relief (5 percent), and its role in promoting dense, compact development patterns that support shorter trips and lower car ownership levels (72 percent).

Key Findings

First, it is important to note that all of SEPTA's service modes outperform single-occupancy vehicles (SOV). According to the United States Department of Transportation, SOVs emit 0.96 pounds of CO2-e per mile. Each of SEPTA's modes is more GHG efficient than SOV by at least 30 percent.

But there is room for improvement. Compared with other U.S. transit agencies, only SEPTA's motor bus fleet is at or below the national average for GHG emissions per passenger mile. SEPTA's higher-than-average GHG emissions for propulsion-based fleets - heavy rail, light rail, and commuter rail - is largely driven by the carbon intensive nature of electricity generated and used to power SEPTA's service region.

Source: US DOT & SEPTA

Another key finding is the strong relationship between ridership and GHG performance. When gas prices spiked in 2008, SEPTA's ridership grew by six percent. But SEPTA's GHG displacement ratio spiked by 36 percent, from 2.60-to-1 in 2007 to 3.54-to-1 in 2008. The subsequent ridership lag in 2009, largely resulting from the impact of global economic recession on localized unemployment, reduced SEPTA's displacement ratio back under 3.00 to 2.75.

A Plan to Improve Performance

SEP-TAINABLE's plan for improving GHG performance focuses on measures of intensity: units of GHG per levels of service. The use of intensity performance measures, as opposed to gross emissions totals, focuses GHG initiatives on expanding upon SEPTA's already positive impact while at the same time focusing on opportunities to improve overall system efficiency.

SEPTA has established a goal to improve GHG performance by 5 percent annually and will track progress based on three measures of intensity against a 2009 baseline:

  • GHG Emissions/Passenger Mile Traveled: 0.661 lbs CO2-e
  • GHG Emissions/Vehicle Mile: 10.56 lbs CO2-e
  • GHG Emissions/Revenue Vehicle Hour: 148.46 lbs CO2-e

These metrics are designed to integrate SEPTA's GHG performance with other components of SEPTA's sustainability plan. For example, GHG emissions per passenger mile will benefit from ridership growth associated with SEPTA's objective to increase transit mode share per capita (Goal 9). GHG emissions per vehicle mile will benefit from improved fuel economy associated with SEPTA's objective to reduce energy intensity (Goal 3). And GHG emissions per revenue vehicle hour will benefit from reduced deadheading associated with SEPTA's goal to improve operating expense performance (Goal 11).

These intensity measures will ensure that SEPTA's GHG initiatives will not create a disincentive to expand service. Reduction strategies include:

Develop a Climate Action Plan (CAP). The CAP, based on APTA standards, will evaluate opportunities to decrease the carbon intensity of its system and services through a "plan-do-check-act" framework outlined in the chart below. A CAP can be a powerful tool to help transportation agencies identify and implement a cost-effective set of strategies to mitigate GHG emissions, increase GHG displacement, and adapt to future climate change risks.

Source: Booz Allen Hamilton

Pursue Alternative Fuels. Rising fuel prices and more stringent emissions regulations increases the risk of SEPTA's exposure to petroleum-based fuels. Emerging vehicle-based technologies, such as electric and hydrogen fuel cells, may be an opportunity to hedge against this exposure and demonstrate the viability of non-carbon based fuels to power a large-scale transit operation. In the interim, SEPTA will evaluate fuel-based technologies to improve the GHG performance of its diesel fleet.

Invest in Renewable Energy. SEPTA's real estate is a unique opportunity to leverage the potential of on-site energy production. In Pennsylvania's newly deregulated electricity market, SEPTA's demand for nearly hundreds of millions of kilowatt hours in annual electricity consumption is increasingly vulnerable to market-based price fluctuations. Due to the largely coal-based, carbon-intensive nature of the electricity it purchases, it is also the primary source of SEPTA's GHG emissions. Investments in off-grid renewable energy sources, such as solar and wind, through power purchase agreements are an opportunity to remove load from the grid, stabilize and reduce energy costs, improve power reliability, and reduce SEPTA's GHG emissions, all at the same time.

Complete a Vulnerability and Risk Assessment. As evidence mounts of global climate change, critical parts of the region's infrastructure are increasingly vulnerable to impending weather pattern shifts. In addition to steps towards climate mitigation, climate adaptation is becoming a more fundamental component of regional sustainability and emergency response planning. Infrastructure in the Philadelphia region, located at the convergence of two major rivers and dozens of tributaries, may be particularly at risk to rising sea levels and increased flooding. Through a vulnerability and risk assessment, SEPTA can assess this risk and evaluate how the Authority's systems would be affected by uncharacteristic operating conditions caused by climate change. Such a risk evaluation would assist the region's overall emergency preparedness.

What's Next

SEP-TAINABLE's goal to improve GHG emissions performance is coupled with a complimentary objective to improve regional air quality. To this end, SEPTA has become a regional leader over the past decade by drastically reducing its NOx and particulate matter emissions. Still, the region remains at risk - a non-attainment area for ozone and direct fine particulate matter. Next week, we'll describe the proactive steps that SEPTA is taking to work with partners and stakeholders in remedying this situation.

Next Week: SEPTA's Air Quality Performance and Clean Diesel Application