Thursday, October 29, 2015

Are Electric Cars Really as Green as Advertised?

Life cycle air quality impacts of conventional and alternative light-duty transportation in the United States (6 page pdf, Christopher W. Tessuma, Jason D. Hillb,1, and Julian D. Marshall, Proceedings of National Academy of Sciences(PNAS), Dec. 30, 2014)

Also discusses here: Electric Vehicle Batteries: Clean and Green, or Something Less?(Al Bredenberg, Contributing Writer, Design News, Sep. 7, 2015)

Today we review research into the life cycle costs in terms of GHG emissions and ptrematurte deaths resulting from the use of electric vehicles (EV) compared to conventional vahicles using gas which is a factor not only of the tailpipe emissions on the road but also on the source of the electricity used to charge the batteries and what emissions come from them. Results indicate that EVs using electricity generated from coal (which is true for southeastern USA) produce more than three times the mortalities than from conventional vehicles burning gas – and over 90% of this comes from the battery production. On the other hand, EVs using electricity from wind/solar/water have almost insignificant damages compared to gasoline powered vehicles. EVs using electricity form biofuels such as corn ethanol have impacts about 50% higher than ordinary gasoline powered vehicles. All of this underlines the importance of considering the pollution costs of the manufacture of the Lithium batteries that power many EVs, in addition to the fuel economy on the road.

Key Quotes:

“powering vehicles with corn ethanol or with coal-based or “grid average” electricity increases monetized environmental health impacts by 80% or more relative to using conventional gasoline. Conversely, EVs powered by lower emitting electricity from natural gas, wind, water, or solar power reduce environmental health impacts by 50% or more.”

“production of copper and other raw materials for batteries occurs far from people…copper ore smelting, which causes the majority of battery production SO2 emissions, mainly occurs in the sparsely populated southwestern United States.”

 “In 2011, the Chinese government began shutting down graphite mines for environmental and resource protection. Stricter controls were imposed to prevent a pollution problem called “graphite rain.” USGS explains that “dust emissions from the mining of crystalline flake graphite had become a major issue, and although graphite is inert and not harmful, the air pollution from dust had become a problem to local residents and farmers.”

“Excluding battery production, impacts from wind, water, and solar (WWS) EVs .. are notably lower than from the other scenarios because WWS electrical generators do not produce emissions while in use. Emissions from battery production for the EV scenarios are tracked separately. The main emission sources for EV battery production .. are coal mining inWyoming and the Appalachian Mountains and the extraction and refinement of raw material inputs, including copper”

Air pollution-related human health impacts for each scenario (PM2.5 and O3-related mortalities, and the corresponding monetized damages) ..range from 230 mortalities per year ($0.14 per gallon gasoline-equivalent) for the WWS EV scenario to 3,200 mortalities per year ($1.94 per gallon gasoline-equivalent) for the coal EV scenario. Estimated mortality impacts from PM2.5 are approximately an order of magnitude greater than those from O3”

“Previous studies ..have argued that to meet stated goals for GHG emission reductions, it is necessary to both electrify vehicles and decarbonize electricity generation, for example through WWS electric generation. Our results suggest that such a strategy would have the strong cobenefit of substantially reducing air quality-related mortalities (by ∼70%).”

No comments:

Post a Comment