OVERVIEW

Greenhouse Gas Emissions Accounting at Duke University 

Duke created its first GHG inventory in 2007 and has conducted rigorous emissions accounting every year since that time. Duke does its GHG accounting on an annual, fiscal year basis. The GHG boundary and inventory are managed according to the best practices established by the Greenhouse Gas Protocol’s Corporate Standard. 

Greenhouse Gas Emissions Boundary

When Duke signed the American College and University Presidents’ Climate Commitment in 2007, the University committed to set a carbon neutrality target for various emission-generating activities. The CAP categorized Duke University’s overall emissions in three distinct scopes (outlined in the figure below) to address the unique attributes and extent of each. 

Three circles showing what sources are included in Duke's scope 1, 2, and 3 emissions.


Duke's Geographic Boundary

In addition to an emissions source boundary, Duke also has to define a geographic boundary for its GHG emissions accounting. Both the 2009 and 2019 Climate Action Plans identified targets for entities that the university directly owns and operates. These plans outlined emission reduction strategies for the University, including the School of Medicine, the School of Nursing, and the Duke Marine Lab. 

Two circles showing what phyiscal elements are included and excluded from Duke's GHG accounting

Fiscal Year 2025 Update

New methodologies

FY25 saw the inclusion of several new quantification methodologies in Duke's GHG inventory. These new methodologies update the way Duke calculates emissions from two key scope 3 sources, namely its air travel emissions and emissions from employee commuting.

  • For air travel emissions, Duke previously used a financial accounting model that estimated emissions based on the amount of air travel expenditures over the previous year. Duke now estimates flight distance by using a formula to model the distance between airports.
  • Duke has updated the emissions factor it uses to calculate emissions from employee commuting. This EPA emissions factor was suggested by the third-party auditor Duke engaged to verify its FY24 GHG inventory and is specific to employee business travel.

Annual GHG update

Duke’s FY25 GHG emissions represent a 33% reduction from the previous baseline (2007) and a 2.3% reduction from FY24, however comparisons to the carbon neutrality era (2007-2024) are of limited accuracy because of how Duke's accounting methods changed in FY25. 

Duke historic GHG emissions

Duke's Scope 1 and 2 emissions both went up by roughly 3.5% in FY25, however this is within the standard range of annual variability that has been historically observed. Scope 1 emissions are projected to gradually decline as more buildings are converted to hot water from steam. Scope 2 emissions are projected to decline as deeper campus efficiencies are realized and Duke Energy continues its grid decarbonization. Scope 3 emissions fell by over 13% compared to FY24, however new calculation methodologies for both employee commuting and air travel emissions make these categories difficult to compare to previous years.

New emissions baseline

A greenhouse gas baseline year establishes the reference point against which emissions reductions are measured, making it essential for tracking progress and ensuring accountability over time. FY07 served as Duke's baseline for its 2024 carbon neutrality goal, during which time it reduced overall emissions by 31% and energy emissions by 42%. Using a more recent baseline year provides a more accurate picture of current emissions, making progress tracking and future reductions more credible. For this reason, Duke is exploring an updated baseline year for use as a part of its net zero framework.