@article{160656,
  author = {T. Hillman and A. Ramaswami},
  title = {Greenhouse Gas Emission Footprints and Energy Use Metrics for Eight US Cities},
  abstract = { A hybrid life cycle-based trans-boundary greenhouse gas (GHG) emissions footprint is elucidated at the city-scale and evaluated for 8 US cities. The method incorporates end-uses of energy within city boundaries, plus cross-boundary demand for airline/freight transport and embodied energy of four key urban materials [food, water, energy (fuels), and shelter (cement)], essential for life in all cities. These cross-boundary activities contributed 47\% on average more than the in-boundary GHG contributions traditionally reported for cities, indicating significant truncation at city boundaries of GHG emissions associated with urban activities. Incorporating cross-boundary contributions created convergence in per capita GHG emissions from the city-scale (average 23.7 mt-CO<sub>2</sub>e/capita) to the national-scale (24.5 mt-CO<sub>2</sub>e/capita), suggesting that six key cross-boundary activities may suffice to yield a holistic GHG emission footprint for cities, with important policy ramifications. Average GHG contributions from various human activity sectors include buildings/facilities energy use (47.1\%), regional surface transport (20.8\%), food production (14.7\%), transport fuel production (6.4\%), airline transport (4.8\%), long-distance freight trucking (2.8\%), cement production (2.2\%), and water/wastewater/waste processing (1.3\%). Energy-, travel-, and key materials-consumption efficiency metrics are elucidated in these sectors; these consumption metrics are observed to be largely similar across the eight U.S. cities and consistent with national/regional averages. },
  year = {2010},
  journal = {Environmental Science \& Technology},
  language = {eng},
}