Two starting clarification: the study is focused on U.S. context and considers global warming pollution sources only. Particulate emission, for instance, are not considered, since they’re not related to global warming. UCS (that of course, as the name declares, is deeply committed to environment issues) points out that heavy-duty vehicles, including buses, make up only 5 percent of all vehicles on the road today but contribute 25 percent of global warming emissions in the transportation sector and a significant amount of air pollution. Most of U.S.’ carbon dioxide emissions that cause climate change come from transportation. The study by UCS has the merit of taking into consideration the life cycle global warming emissions for battery electric buses: a definition that includes those from generating electricity and extracting, processing, and transporting the fuels used to generate electricity. These emissions were compared to the life cycle emissions of diesel and natural gas buses, which include tailpipe emissions and emissions from extracting, refining, and transporting the oil and natural gas.
UCS had already demonstrated in another study that, for buses charged on California’s grid, battery electric buses had 70 percent lower global warming emissions than a diesel or a natural gas. The reason is simple: California is the country leader in electricity generation from non-hydroelectric renewable energy source (geothermal, wind, solar). 29 per cent of electric generation in 2017 has come from renewable sources
