Greenhouse gas emission footprints and energy use benchmarks for eight U.S. cities.
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(2)e/capita) to the national-scale (24.5 mt-CO(2)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.
Hillman
Tim
T
Sustainable Urban Infrastructure Program, Department of Civil Engineering, University of Colorado Denver, USA.
Ramaswami
Anu
A
D000397:Air Pollution / Q000706:statistics & numerical data*; D019985:Benchmarking / Q000379:methods*; D058572:Carbon Footprint / Q000706:statistics & numerical data*; D002947:Cities / Q000706:statistics & numerical data; D003247:Conservation of Natural Resources / Q000379:methods*; D017752:Greenhouse Effect; D011210:Power Plants / Q000706:statistics & numerical data*; D014481:United States