Contrary to popular belief, small diesel vehicles are more environmentally friendly than their lithium-ion battery counterparts, a study suggests.

According to a report appears in the American Chemical Society journal by Swiss government research lab EMPA, tests showed that the manufacture and disposal of batteries presents no obstacle to the concept of electric-powered motoring.

However, the group also concluded that there is also a major eco-burden involved in the burning of coal or gas to produce electricity which is not required by diesel vehicles.

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It is the operation phase that remains the dominant contributor to the environmental burden caused by transport service as long as the electricity for the [battery car] is not produced by renewable hydropower, read one section of the report.

A break even analysis shows that an [internal combustion engined vehicle] would need to consume less than 3.9 litres/100km to cause lower [environmental impacts] than a [battery car].

The study, which appears in the American Chemical Society journal and is entitled Contribution of Li-Ion Batteries to the Environmental Impact of Electric Vehicles, noted that consumptions in this range are already achieved by some small diesel cars.

CO2 emissions from hybrids and electric cars are similar, while diesel cars emit 8% more carbon. Emissions from petrol cars, on the other hand, are around 35% higher due to less efficient use of energy compared to diesel.

The study demonstrates that while electric cars have the lowest 'tail-pipe' emissions, they cannot attain the same travel ranges or top speeds as conventional cars.

An electric car that could cover a similar distance with one charge would in fact produce more CO2 emissions than diesel vehicles, as it is heavier and requires more energy, it says.