This month’s blog in the area of environmental-transportation sustainability is more technical in nature, as it relates to calculating a carbon footprint for the operation and maintenance of rest areas.  Rest areas are often overlooked by DOTs as a significant source of greenhouse gas emissions and energy consumption. DOTs need to be more aware and proactive in evaluating and implementing cost effective sustainable operations of rest areas to protect the environment and to anticipate upcoming federal and state greenhouse gas/climate regulations. The following discusses a carbon calculation methodology that can be used for rest areas:

TerraLogic and Colorado State University at Pueblo (CSU-Pueblo) is using an innovative and unique approach when assessing the sustainability of Colorado Department of Transportation Rest Areas (CDOT). There has been very limited if any research performed on carbon footprinting of rest areas so there limited opportunity to compare actual or estimated carbon loadings from other state Department of Transportation rest areas.  

The carbon footprint calculation approach used by TerraLogic and the CSU-Pueblo Team is consistent with an international standard established to calculate the emission of greenhouse gases known as the Green House Gas Protocol (GHGP). This standard was initiated by two major organizations; the World Resource Institute (WRI) and the World Business Council for Sustainable Development (WBCSD)

The GHGP identifies three main “scopes” to identify and delineate direct and indirect   emission sources.  These scopes are used to provide consistency in accounting for and mitigating greenhouse gas emissions.  The following summarizes the GHGP scopes as they relate to CDOT rest areas (WRI, 2004):

Scope 1- Direct GHG Emissions- these type of emissions come from combustion sources that are owned by the entity (CDOT) that are directly related to the operations of the rest area such as propane and natural gas for heating, and gasoline/diesel fuel for the transportation of materials, equipment, mowing  and personnel transportation to and from work.

Scope 2- Electrical Indirect GHG Emissions- accounts for GHG emissions from the generation of purchased electricity consumed by the company (CDOT). The actual emissions occur that the power facility where the electricity is generated. This type of indirect emission will be used for rest area heating/cooling and lighting and is expected to be the largest type of emission for rest areas.

Scope 3- Other Indirect GHG Emissions- these types of emissions are a consequence of activities of the company (CDOT) but occurs from sources not owned or controlled by the company (CDOT). The main rest area source for this type of indirect emission is from truck idling.   

Scope 1 Direct Emission Equation

Equation 1 is used for the direct emissions associated with the operation and maintenance of the rest areas. The equation basically uses emission factors (kg/gallon) for CO2, N2O, and CH4 that are referenced from the United States Environmental Protection Agency (EPA, 2005). These emission factors are multiplied by the amount of fossil fuel consumed and by the respective Global Warming Potential (GWP).  GWP is defined as the amount of impact or the degree of harm a particular gas has on the atmosphere (IPCC, 2007). When the GWP is multiplied by the amount emitted, it is converted to an equivalent amount of CO2 and that is called “Equivalent CO2” or CO2e .

Equation 1 is applicable to any type of fossil fuel, such as diesel fuel; however, emission factors will change whenever the type of fuel changes since emission factors are specific to the type of fuel being used in the carbon footprint calculations. 

Scope 2- Electrical Indirect GHG Emission Equation

Equation 2 is used to calculate the Scope 2 Electrical Indirect GHG Emissions for the Project rest areas. The equation involves the amount of electricity consumed in KWh. This electrical consumption information will be obtained directly from the electrical provider is based upon a 5 year average, whenever possible.  Equation 2 is based upon the consumption of electricity (KWh) multiplied by the emission factor and GWP, similar to Equation 1. The emission factors used in Equation 2 are based upon eGRID data developed by EPA (EPA, 2008), and since the EPA data are given in pounds rather than kilograms, an extra conversion factor is included in Equation 2. These factors are regional based within the United States and are dependent upon varying methods for generating electricity (coal, natural gas, nuclear or renewable).

Scope 3- Other Indirect GHG Emissions

Trucks idling in rest areas represent a significant greenhouse gas emission source that is associated with the operation and service of the rest area. It is estimated that greater than 500,000 heavy duty trucks (>26,000 lbs) travel more than 500 miles as an average daily trip within the United States. Long haul truck drivers are required by the Department of Transportation to rest 8 hours after a maximum of 10 hours driving (EPA, 2002). During this time most long haul truckers continue to idle their engines. Assuming that these 500,000 truck idle for 8 hours a day for 300 days per  year at fuel consumption rate of 0.8 gallons per hour, trucks can generate and emit over 10.9 million tons of CO2 per year (21.7 tons /year per truck) and 190,476 tons of NOX per year (0.38 tons per year per truck). Under this trucking scenario, heavy duty trucks would consume 960 million gallons of diesel fuel while idling (EPA, 2009).

Scope 3 Calculation (example Vail Pass Rest Area)

As a hypothetical example, it is assumed that the average heavy duty truck consumes 0.82 gallons per hour of diesel fuel while idling and there is an average of three trucks that individually idle 8 hours/per day at the rest area; therefore, 6.6 gallons of diesel would be consumed per truck with an overall consumption value of 19.7 gallons of diesel fuel for three trucks per day. It is assumed that the 3 trucks idle for 8 hours for 365 days per year, in which 7,183 gallons of diesel is consumed annually from idling at the Vail Pass Rest Area. The following is an example calculation for the truck idling carbon footprint. Equation 1 is again used to estimate the Scope 3 Indirect GHG Emissions for Vail Pass rest area.

Diesel fuel consumption per year(idling) = 7,183 gallons

Emission factor−CO2 =  10. Kg 𝐶𝑂/gallon
Emission factor−N2 O = 0.000199 Kg/gallon
Emission factor−CH4 =0.18 Kg/gallon
GWP−CO2 =1
GWP−N2 O=310
GWP−CH4 =21

The development of a rest area’s carbon footprint is a unique way of analyzing the rest areas’ energy consumption and air quality impact. By identifying the greenhouse gas emissions from rest area, potential mitigation schemes and recommendations can be developed toward making the rest area carbon neutral.  Potential mitigation techniques may include but not limited to changes in rest area operating procedures, reducing gas consumption, heating/energy conservation, vegetation/tree sequestration, truck electrification and alternative energy photovoltaic cells.

References

(EPA 2002) U.S. Environmental Protection Agency, Study of Exhaust Emissions from Idling Heavy-duty Diesel Trucks and Commercially Available Idle Reducing Devices, EPA420-R-02-025, October, 2002.

(EPA 2008) U.S. Environmental Protection Agency, Direct Emissions from Mobile Combustion Sources, EPA430-K-08-004, May, 2002.

http://www.epa.gov/climateleaders/documents/resources/mobilesource_guidance.pdf

(Jakubski, 2008) Jakubski, Paul. “Calculating and Reducing Your Carbon Footprint.” GATF World 20.3(2008):40-43

http://www.pneac.org/publicationoftheyear/Calculating-and-Reducing-Your-Carbon-Footprint.pdf

(EPA 2008) U.S. Environmental Protection Agency, eGRID2007 Version 1.1 Year 2005 GHG Annual Output Emission Rates, December 2008

http://www.epa.gov/cleanenergy/documents/egridzips/eGRID2007V1_1_year05_GHGOutputRates.pdf

(EPA 2009) U.S. Environmental Protection Agency, Appendix A: Carbon Footprint/Greenhouse Gas Inventory Analysis for Sediment, Floodplain, and Treatment/Disposition Alternatives, March 2009

http://www.epa.gov/region1/ge/thesite/restofriver/reports/cms/447141_Appendix_A.pdf

(EPA, 2005) Office of Transportation and Air Quality, Emission Facts; Average Carbon Dioxide Emissions Resulting from Gasoline and Diesel Fuel; EPA420-F-05-001, February 2005

(WRI, 2004) Bhata, Pankaj ; Janet Ranganathan, The Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard, March 2004

(DOE, 2005) Energy Information Administration, Documentation for Emissions of Greenhouse Gases in the United States, 2005, DOE/EIA 0638 (2005)

(JCI, 2010) Spreadsheets of electrical consumptions sent to Art Hirsch from Johnson Controls (Nichole Stennes), September, 2010

(IPCC, 2007) Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland, 2007: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf