Session: Transport

Life Cycle Assessment of Energy and Greenhouse Gas Emissions of Ground Shipping in the United States: U.S. Postal Service Case Study
Aweewan Mangmeechai,  
H. Scott Matthews,^* CMU

A significant increase in the use of shipping services has drawn public attention to energy consumption and associated air emissions. Despite the transportation sector being an important contributor to fossil energy consumption and greenhouse gas emissions, few detailed studies on the system-wide impacts of shipping exist. The U.S. Postal Service (USPS), a part of the federal government subject to public reporting requirements, represents a case study that can better inform the energy and emission impacts from shipping. Unlike other previous studies, this study takes both energy consumption and emissions from highway vehicles and support services such as buildings and equipment into account. A life cycle assessment (LCA) of the USPS is quantified in this paper by using a hybrid LCA model involving process and an input-output modeling. Existing vehicle-only shipping emissions and energy use are estimated at 600 to 630 grams of CO2 per ton-mile (8,300 to 8,900 BTU per ton-mile), while the hybrid LCA’s emission factor for direct energy consumption is 2,500 to 2,700 grams per ton-mile (21,500 to 23,000 BTU per ton-mile). The hybrid LCA emission factor for the whole supply chain is 7,000 to 7,600 kg per ton-mile (85,700 to 91,600 BTU per ton-mile). These numbers prove that the previous studies, which do not include overall impacts of shipping, greatly underestimate actual emission impacts, by up to a factor of 30. This underestimate is important and relevant for decision makers considering the energy and environmental impacts of shipping e.g. purchases of carbon offset. The LCA of USPS shows that USPS’s focus should be to decrease electricity consumption in buildings to accomplish CO2 reduction goal.

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