Frequently Asked Questions

General Questions

What are carbon offsets?

See our Offset Information page for detailed information on what carbon offsets are.

From what projects do the tons originate?

DCOI's carbon offset tons originate from a variety of projects. The Initiative's goal is to deliver offsets that provide environmental, social, and economic co-benefits for North Carolina and the Southeast region.

DCOI currently manages two projects that generate carbon offsets. DCOI has been working with Google and Duke Energy on the Innovative Swine Waste Management project since May 2011. Now, the Initiative is piloting a home energy efficiency retrofit project targeted towards Duke employees.

DCOI also manages external offset purchases in order to meet the University's demand. Offsets have been purchased from the capture and destruction of nitrous oxide (N2O) at a nitric acid plant in East Dubuque, IL, and residential energy efficiency projects in South Carolina. DCOI is exploring purchases from avoided forest conversion and other regional residential energy efficiency projects.

How is the University's greenhouse gas (GHG) footprint calculated?

Duke University's GHG footprint is calculated annually by Sustainable Duke and compared to a 2007 baseline. The three main sources of carbon emissions for the University are electricity, stationary fuel, and transportation. More information on the GHG inventory methodology can be found on the Sustainable Duke website's Climate Action Inventory page.

Purchasing Offsets

Who can purchase offsets from DCOI?

DCOI provides offsets to members of the Duke community for individual purchase. Students, faculty, staff, and departments are all encouraged to purchase offsets through DCOI's Purchase Carbon Offsets page.

What price does DCOI charge for personal offsets?

DCOI charges a flat rate of $10 per offset, or ton of CO2 equivalent. This value reflects the average price of offsets in DCOI's portfolio and DCOI's portfolio management costs. Carbon offset prices vary depending on project type and DCOI assembles a diverse portfolio to provide high quality offsets at a competitive price. In addition, DCOI works to advance innovation and reliability in the field of offset development and receives funding from The Duke Endowment and other sources. This funding helps support DCOI carbon offset projects and decrease the price of innovative carbon offsets generated.

Offset Calculations

How do I calculate how many offsets to purchase?

DCOI provides online calculators to help individuals and departments determine how many carbon offsets they should purchase in order to offset their events and travel. These calculators can be found on DCOI's Purchase Carbon Offsets page.

How are air travel emissions for personal offset purchases calculated?

DCOI uses the Clean Air - Cool Planet (CACP) Campus Carbon Calculator to estimate total emissions from air travel. Table 1 provides an overview and example of CACP's methodology. The final emissions total is a factor of the number of miles traveled, an air travel emissions factor, and the Radiative Forcing Index (a measure of the non CO2-related warming effects of air travel.)

Table 1. Overview and example of the Clean Air- Cool Planet Campus Carbon Calculator air emissions calculation methodology.

  CACP Campus Carbon Calculator TM
Emissions Factors Single air travel emissions factor of 0.000276 mTCO2e/passenger mile
Radiative Forcing Index (RFI) 2.81
Greenhouse Gases included in Calculation CO2, N2O and CH4
Calculation method (distance based) GHG (CO2e)
emissions = Distance travelled * emissions factor * RFI
Examples @ 645 miles traveled (RDU to ORD) and @ 2,390 miles traveled (RDU to SFO) 0.498 mTCO2e = (645 miles * 0.000276 mTCO2e/passenger mile) * 2.8 1.847 mTCO2e = (2,390 miles * 0.000276 mTCO2e/passenger mile) * 2.8
Institutions that use Calculator/Tool Duke University, ACUPCC recommended tool

1. Derived from IPCC's best estimates of the ratio of total radiative forcing from air travel to that from CO2 emissions alone.

How are automobile travel emissions for personal offset purchases calculated?

Automobile travel emissions are calculated by multiplying the number of miles traveled by the car's gas mileage and a carbon emissions factor of 0.00892 tons/ gallon. The emissions factor was obtained from the EPA's Clean Energy calculations.

How are meeting and special event emissions for personal offset purchases calculated?

Emissions for meetings and special events are calculated by multiplying the number of participants by a multiplier that is based on the average emissions required to travel from the selected distance. If there are a variety of distances from which participants are traveling, the user can choose the average distance participants are coming from. The user can also fill out the form in shifts, one for each travel group, and then add up the results to find the event's total footprint. Tables 2 and 3 display emissions multipliers for different distances and an example of how meeting and special event emissions are calculated, respectively.

Table 2. Carbon emissions multipliers for different travel distances.

Multipliers
Locally 0.01
Regionally 0.1
Nationally 1
Globally 6

Table 3. Example meeting and special event carbon footprint calculation.

Special Event calculator
Field text Example Input Formula
How many people will participate in the event? 100 Multiply by the number of participants by the corresponding multiplier in Table 2, depending on what is selected in the following input
Will most of the participants be traveling locally, regionally, nationally, or globally? Regionally (multiplier = .1)
Example Output 10 100*.1 = 10

How are departmental emissions for personal offset purchases calculated?

Departmental emissions calculations are based on the average carbon footprint of Duke faculty, staff, and students. Departments that have obtained the Duke Green Workplace Certification will have lower average emissions. Table 4 provides an example of how the departmental emissions are calculated.

Table 4. Example departmental carbon footprint calculation.

Department calculator
Field text Example Input Formula
# of Staff in your Department or Workplace 15 Multiply by 3, or 2.5 if Green Workplace Certification is completed
# of Faculty in your Department or Workplace 10 Multiply by 4.5, or 4 if Green Workplace Certification is completed
# of Students in your Department or Workplace 100 Multiply by 3, or 2.5 if Green Workplace Certification is completed
Will your department complete the Green Workplace Certification? Yes  
Example Output 328 (15*2.5)+(10*4)+(100*2.5) =
327.5 round up to 328