http://www.designnews.com/author.asp?section_id=1386&doc_id=278535&cid=nl.dn14.20150908&dfpPParams=ind_182,industry_auto,industry_alt,kw_36,aid_278535&dfpLayout=blog
Electric Vehicle Batteries: Clean and Green, or Something Less?
Al Bredenberg, Contributing Writer
9/7/2015
As I wrote in my previous article, the operation of electric vehicles
(EVs) is relatively “clean,” especially when powered by renewably
generated electricity. However, the emissions from simply operating a
vehicle are not the only environmental concern. For EVs, what makes them
go is the battery, a piece of highly refined technology that comes with
its own environmental impacts.
A recent study, led by biosystems engineering researcher Christopher W.
Tessum and published by the National Academy of Sciences, examined the
air-quality impacts of light-duty vehicles on human health in the US.
Tessum and colleagues compared the emissions by traditional
gasoline-powered vehicles with various alternatives, including battery
electric vehicles (BEVs).
In the analysis, Tessum considered the lifecycle air-quality impacts of
BEV battery production and found their impacts relatively small in terms
of population mortalities and externality damages. For example, for an
EV powered by an average US power-generation mix, battery production
accounted for only about 10 percent of lifecycle emissions of fine
particulate matter (PM2.5, or particles of 2.5 microns or less).
Tessum admitted that his team's results showed a smaller impact from
battery production than previous research by Jeremy J. Michalek and
colleagues did. Tessum pointed out that Michalek assumed that “processes
upstream from EV battery manufacturing are colocated with automobile
manufacturing facilities.” However, according to Tessum, “production of
copper and other raw materials for batteries occurs far from people,” so
the potential harm is reduced. For example, he said, “copper ore
smelting, which causes the majority of battery production SO2 emissions,
mainly occurs in the sparsely populated southwestern United States.”
However, US air-quality impacts are not the only environmental concerns
raised about EV battery production. Not all materials and components
used in lithium-ion batteries are produced in the US, and they can have
environmental impacts other than air pollution.
Graphite, for example, is a key material used for negative electrodes in
Li-ion batteries. Researchers estimate that a BEV battery requires about
50 kilograms of graphite. By far, graphite is mined in China, according
to the US Geological Service (USGS). The agency says batteries are the
fastest-growing market for graphite, increasing at between 15 and 25%
growth per year.
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.”
Bloomberg New Energy Finance reports that the environmental problems in
China have depressed graphite production and pushed up prices. Aside
from illuminating the concerns about graphite rain, Bloomberg also
points to problems arising from the hydrochloric acid used to process
raw graphite. Poor disposal practices have resulted in the release of
the corrosive chemical into wastewater.
As with any manufactured product, end-of-life disposal is a concern with
EV batteries. Since the EV market is comparatively young, relatively few
batteries have reached mortality. However, that will change over the
next 15 to 20 years. The US Department of Energy says processes for
battery recycling are under development, including smelting processes to
recover basic elements or salts, and direct recovery, which involves
separating materials for re-use, is being investigated.
Even though old batteries might lose their suitability for electric
cars, some experts point out that they could still be useful for other
purposes. A study by the Mineta National Transit Research Consortium
explored the feasibility of remanufacturing Li-Ion batteries for re-use
in vehicles, repurposing them for stationary uses, and disassembling
them to recover materials. “Remanufacturing was shown to be profitable,”
the organization determined, “primarily due to the avoided costs of
producing new batteries when a remanufactured battery could be used
instead.” While the economic feasibility of repurposing and recycling
batteries was harder to pin down, the report stressed that “recycling
can support closed-loop supply chains reusing materials in the
production of new batteries as well as supporting the principles of
environmentalism and sustainability.”
Obviously, the environmental impacts of Li-Ion EV battery production are
not zero. However, battery efficiency is improving and new battery
technologies are in the works. These improvements could make BEVs even
more attractive compared to conventional gasoline vehicles. A future
article will discuss trends in EV battery technology and how they might
affect the environmental picture.
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