Your microwave oven could be as polluting as your car!

Microwaves in Britain generate as much carbon dioxide as 1.3 million cars, while across the European Union, the emissions equal almost seven million cars, scientists have concluded, as they call on people to use their ovens more efficiently.

Researchers from the University of Manchester in England arrived at the figure after studying the broad environmental impact of microwaves, taking account of their manufacture, use, and end-of-life disposal.

The findings indicated that microwaves emit 7.7 million tonnes of carbon dioxide per year in the EU, which is equivalent to the annual emissions of 6.8 million cars.

There are around 23 million microwaves in homes across the UK, but despite their huge popularity, little is known about the effect of the devices on the environment, said the researchers.

Microwaves across the EU consume an estimated 9.4 terawatts per hour (TWh) of electricity every year. This is equivalent to the annual electricity generated by three large gas power plants.

Dr Alejandro Gallego-Schmid from the university's School of Chemical Engineering & Analytical Science explained, ''Rapid technological developments and falling prices are driving the purchase of electrical and electronic appliances in Europe.''

''Consumers now tend to buy new appliances before the existing ones reach the end of their useful life as electronic goods have become fashionable and 'status' items'', Gallego-Schmid added.

Efforts to reduce consumption should focus on improving consumer awareness and behaviour to use appliances more efficiently, he said.

Altogether, the research team investigated 12 different environmental factors, including climate change, depletion of natural resources and ecological toxicity.

The research shows that the manufacturing process alone contributes more than 20 per cent to depletion of natural resources and to climate change.

The study also found that, on average, an individual microwave uses 573 kilowatt hour (kWh) of electricity over its lifetime of eight years, which is equivalent to the electricity consumed by a seven watt LED light bulb, left on continuously for almost nine years.

This is despite the fact that microwaves spend more than 90 per cent of their lifetime being idle, in the stand-by mode.

Dr Gallego-Schmid stated that it is increasingly important to start addressing the impacts of microwaves on resource use and end-of-life waste

The study's authors suggest consumers should use microwaves more efficiently by sticking to cooking instructions rather than just guessing, or always using the highest setting.

The lifespan of modern microwaves is nearly seven years shorter than it was almost two decades ago, said the scientists whose findings appear in the journal Science Of The Total Environment.

In 2005, 184,000 tonnes of electrical and electronic (EE) waste was produced by discarded microwaves, the study found.

But not everybody agreed with the findings. Prof David Reay, Professor of Carbon Management at the University of Edinburgh, said, ''To say microwave ovens are 'as bad for the environment as cars' is an apples to oranges comparison, because one (the microwaves) is for a full life-cycle assessment and the other (cars) is just their direct emissions from being driven.

''Yes, there are a lot of microwaves, and yes they use electricity.  But their emissions are dwarfed by those from cars – there are around 30 million cars in the UK alone and these emit way more than all the emission from microwaves in the EU.''

Latest data show that passenger cars in the UK emitted 69 million tonnes of CO2 equivalent in 2015.