Petrol and diesel-driven hybrids, which use fossil fuel to charge their batteries, were not examined.
A solely plug-in EV "makes the lowest contribution to climate change over its life cycle, with the low operational impacts arising from low-carbon emissions in the New Zealand electricity mix," the study concluded.
That assessment would improve if New Zealand moved from producing around 80 percent of its electricity from renewable resources to a higher proportion.
It is easy enough to state with confidence the ameliorating effect on fossil fuel resource depletion of using (EV) technology.
The report debunks some widely held beliefs about the main minerals used for battery manufacture. For example, the lithium salts used in lithium-ion batteries are not rare and do not qualify as "rare earth metals".
While all engines used some rare earth materials, "the study findings show that the resource depletion impacts of rare earth metals was not a significant issue compared to other minerals or resources."
However, there are some surprises about the extent of resource depletion required in electric vehicle manufacture, including the fact that gold has recently been identified as an ingredient to lengthening the lifespan and storage capacity of lithium-ion batteries.
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"There are no significant differences across the technology types with regard to net resource depletion," the study found, "although it should be noted that the levels of uncertainty in these findings was high.
"It is easy enough to state with confidence the ameliorating effect on fossil fuel resource depletion of using (EV) technology," the study found, but quantifying depletion of minerals used in battery and electric motor manufacture was more difficult.
That said, "improvements in battery technology (such that battery life is extended) and in the rate of recycling of the materials used in batteries and motors will improve the comparative mineral resource performance of (EVs)."
It is easy enough to state with confidence the ameliorating effect on fossil fuel resource depletion of using (EV) technology.
Electric vehicles also "demand significant amounts of metal such as aluminium, copper and steel, above the levels commonly used in conventional vehicles," the study says. "This material demand is required by electronic componentry including motors, charger, batteries, wiring and circuitry etc, as well as the underlying chassis which is typically heavier also."
Compared with the conclusive benefits of EVs for CO2 emissions, the report warned of a high degree of uncertainty about the results that found a plug-in hybrid EV has a higher level of eco-toxicity than any of the other three types of car in the study, mainly because of the components required to manufacture both an internal combustion engine and energy-storing batteries in the one vehicle.
Likewise, EVs had higher lifetime levels of human health toxicity than conventional vehicles, although the differences were not dramatic.
"At any rate, human toxicity impacts were very small across the vehicles," the study found. On smog-producing photo-chemical oxidation, EVs came out way ahead, emitting "50 percent less photo-chemical matter", with battery-only EVs producing no exhaust and not even having a tail-pipe.
