Microwaves could be as bad for the environment as cars, suggests new research

January 17, 2018, University of Manchester
Credit: CC0 Public Domain

Microwaves usage across the EU alone emits as much carbon dioxide as nearly seven million cars according to a new study by The University of Manchester.

Researchers at the University have carried out the first ever comprehensive study of the environmental impacts of microwaves, considering their whole life cycle, from 'cradle to grave'.

The study found:

  • Microwaves emit 7.7 million tonnes of equivalent per year in the EU. This is equivalent to the annual emissions of 6.8 million cars.
  • Microwaves across the EU consume an estimated 9.4 terawatt hours (TWh) of electricity every year. This is equivalent to the annual electricity generated by three large gas power plants.
  • Efforts to reduce consumption should focus on improving and behaviour to use appliances more efficiently

Microwaves account for the largest percentage of sales of all type of ovens in the European Union (EU), with numbers set to reach nearly 135 million by 2020. Despite this, the scale of their impacts on the environment was not known until now.

The study used life cycle assessment (LCA) to estimate the impacts of microwaves, taking into account their manufacture, use and end-of-life management. Altogether, the research team investigated 12 different environmental factors, including climate change, depletion of natural resources and ecological toxicity. They found, for example, that the microwaves used across the EU emit 7.7 million tonnes of carbon dioxide equivalent per year. This is equivalent to the annual emission of 6.8 million cars.

The research shows that the main environmental 'hotspots' are materials used to manufacture the microwaves, the manufacturing process and end-of-life waste management. For example, the manufacturing process alone contributes more than 20% to depletion of natural resources and to climate change.

However, it is by microwaves that has the biggest impact on the environment, taking into account its whole life cycle, from production of fuels to generation of electricity. In total, microwaves across the EU consume an estimated 9.4 terawatts hours (TWh) of electricity every year. This is equivalent to the annual electricity generation by three large gas power plants.

The study found that, on average, an individual uses 573 kilowatt hour (kWh) of electricity over its lifetime of eight years. That is equivalent to the electricity consumed by a 7 watt LED light bulb, left on continuously for almost nine years. This is despite the fact that microwaves spend more than 90% of their lifetime being idle, in the stand-by mode.

The study's authors suggest that efforts to reduce consumption should focus on improving consumer awareness and behaviour to use appliances more efficiently. For example, consumption by microwaves can be reduced by adjusting the time of cooking to the type of food.

Waste is another major problem. Due to their relative low cost and ease of manufacture, consumers are throwing more electrical and electronic (EE) equipment away than ever before, including microwaves.

In 2005, across the EU, 184,000 tonnes of EE waste was generated from discarded microwaves. By 2025 this is estimated to rise to 195,000 tonnes, or 16 million individual units being sent for disposal.

Dr Alejandro Gallego-Schmid, from the School of Chemical Engineering & Analytical Science, explains: '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.

'As a result, discarded electrical equipment, such as microwaves, is one of the fastest growing waste streams worldwide.'

Another major contributing factor to the waste is a reduced lifespan of microwaves. It is now nearly seven years shorter than it was almost 20 years ago. Research shows that a microwave's has decreased from around 10 to 15 years in the late 90s to between six to eight years today.

Dr Gallego-Schmid added: 'Given that microwaves account for the largest percentage of sales of all type of ovens in the EU, it is increasingly important to start addressing their impact on resource use and end-of-life waste.'

The study also shows that existing regulation will not be sufficient to reduce the environmental impacts of microwaves. It recommends that it will be necessary to develop specific regulations for these devices targeting their design. This will help to reduce the amount of resources used to make microwaves and waste generated at the end of their lifetime.

Explore further: Saving the planet, one microwave at a time

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27 comments

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Nik_2213
5 / 5 (9) Jan 17, 2018
Okay, how much power does it take to warm a gas oven to 'Mark 6' or '8', then keep it thus for half an hour or more ? With much of that heat belching from the vent ?? Or heat several pans on the hob ?? You can squeeze two or even three borosilicate 'Pyrex' jugs into a big microwave, cover, give them a five minute zap, drain and and serve...

FWIW, one of our microwaves is thirty years old, now mostly used for storing spacers and other accessories. The others are five and ten years old respectively. Last time I cooked a serious Christmas dinner, we had both gas ovens and all three microwaves busy at the same time. Careful planning required to get 'time on target'...
daqman
5 / 5 (12) Jan 17, 2018
Total rubbish. A microwave is more efficient than a conventional stove. It is powered by electricity and one has to consider the source of that electricity which may be renewable zero carbon. The implication here is that microwaves are somehow bad because the sum of all the microwaves use a lot of power. This is clearly untrue if what they replace is something that used more power.

There is the factor of microwaves having a shorter life than conventional stoves but, from personal experience of family and friends, microwaves seem to be owned at least as long as the conventional stoves and are smaller, taking less material to manufacture. This "study" doesn't pass the "feels right" test.
ddaye
5 / 5 (7) Jan 17, 2018
The ovens can be that bad in the absolute, but as commenters are saying, the comparison to the alternative traditional large electric and gas ovens is what's missing. Furthermore, the higher the percentage of electric power is renewable generated, the less the carbon emitted by microwave oven use.
TrollBane
4.8 / 5 (5) Jan 17, 2018
Keep in mind the life span of a microwave versus conventional stove, recycling, the encouragement of microwavable meals that might have more/worse packaging, etc. It's not just about the power consumption.
NoStrings
5 / 5 (6) Jan 18, 2018
I don't know where to even start. "Microwaves could be as bad for the environment as cars?" Is Dr Alejandro Gallego-Schmid that delusional, or was it an article planned to be released on April First Day? A statement like this is not even wrong!

Let me just join in support of the above commenters, they covered the details fairly.
antialias_physorg
5 / 5 (3) Jan 18, 2018
However, it is electricity consumption by microwaves that has the biggest impact on the environment

So? Electricity should come from renewable sources as much as possible in any case.

Microwaves probably have their uses for small servings or heating up a cup of water (I dunno - I find the food that is prepared in microwave ovens somehow tastes terrible, so I don't use 'em)...but as others have noted: one should look at the alternatives and compare whether those aren't even worse.

Due to their relative low cost and ease of manufacture, consumers are throwing more electrical and electronic (EE) equipment away

This is a valid criticism. Consumer should be more aware that investing in quality products that have a longer lifetime has benefits.
Not only do you spend overall less because you replace stuff less often. You also have a nice-looking product all the while instead of some cheap junk.

But this should go for all things one buys - not just microwaves.
antialias_physorg
5 / 5 (2) Jan 18, 2018
Keep in mind the life span of a microwave versus conventional stove, recycling, the encouragement of microwavable meals that might have more/worse packaging, etc. It's not just about the power consumption.

Good point. I guess that's also a part of the consumer behavior one could influence. Using less packaging is a mindset change worth fostering (in all areas). Particularly with microwave dinners: Using less pre-prepared foods is also a health issue.

As with my previous post: Don't invest in junk. This doesn't just go for gadgets but also for foodstuffs. It's amazing how tasty high quality food can be - and you don't even have to spend more than for the junk, because suddenly stuff like simple potatoes or greens become fabulous meals where otherwise you have to dump in meat and fats just to get any semblance of taste.
mackita
5 / 5 (2) Jan 18, 2018
A microwave is more efficient than a conventional stove. It is powered by electricity and one has to consider the source of that electricity which may be renewable zero carbon
In addition, usage of microwaves is the only way, how to heat the food only without heating any other ballast matter (pot, head of stove, air, water etc..) during cooking. In addition, the character or its heating disfavors the prolonged usage, whereas on the stove someone can cook and heat food whole hours - sometimes needlessly. What the people proposing the replacement of microwaves are recommending as an alternative? Every other alternative solution is more expensive and less efficient one.
katesisco
not rated yet Jan 18, 2018
I think I would like to see the comparison with normal heating. Maybe we should all get an AGA that is constantly on.
MR166
4 / 5 (4) Jan 18, 2018
Good God, before microwave dinners there were TV dinners. You heated these in your oven for 20 mins. or so. Now you zap something for a short time and have a meal instead of heating up the whole kitchen and uning AC to cool the home back down in the summer. These professors should stop writing papers on such easily debunked topics and go back to their climate models where they will be safe and warm with conclusions that cannot be proven wrong until way after they retire.

MR166
2.5 / 5 (6) Jan 18, 2018
But their research does prove one thing, there is way too much grant money available and it is going to way too many incompetent researchers.
MR166
not rated yet Jan 18, 2018
Well the green solution to this problem will be to lower the power of these ovens and use "less" electricity. Green dishwashers now take twice as long to wash dishes 1/2 as well as the older models.
mackita
3 / 5 (2) Jan 18, 2018
It's the "green" solution because the longer the water is heated, the more energy is also wasted by its cooling. Bellow some power threshold it may not be possible to reach required temperature at all.
SwamiOnTheMountain
5 / 5 (2) Jan 18, 2018
Bologna
EnricM
5 / 5 (3) Jan 19, 2018
Total rubbish. A microwave is more efficient than a conventional stoveThis "study" doesn't pass the "feels right" test.


Exactly my point. Sure, it's interesting to know how much CO2 is liberated by the different appliances but the idea that the title gives is that the microwaves somehow produce CO2 when working.

And the big issue is that they miss to compare it with conventional stoves. A gas stove does not only liberate CO2 during it's production process, gas does liberate CO2 during it's whole active live.

And the comparison with cars is also silly: They are comparing the production costs in CO2 of the microwaves with the _emissions_ of cars, but not with the cost of _producing_ the car. Sure, useless comparison too as both serve different purposes...

MR166
5 / 5 (2) Jan 19, 2018
Perhaps we should go back to using dung for cooking or perhaps even "research" papers like this since they both look and smell the same.
mackita
5 / 5 (1) Jan 19, 2018
The above research argues by shortened lifespan of microwaves and amount of electronic waste resulting from it - not by their consumption of electricity as such. But I don't think, that other kinds of electric stoves have substantially longer lifespan and their efficiency is still lower. The article appeal to manufacturers for to reduce planned obsolescence is indeed correct and praiseworthy - but I don't think that plain replacement of microwave ovens by another type of product could remove it: the producers would just utilize their obsolescence elements in another products, which would have even worse economy as a whole.
mackita
5 / 5 (1) Jan 19, 2018
BTW In near future the microwave ovens could get significant technological facelift by utilization of silicon transistors for generation of microwaves instead of magnetrons. These transistors would be able to dynamically shape/modulate the field inside the oven, so that the rotating plate will not be even necessary and the construction of oven will become as simple as induction cooker.
Eikka
4.5 / 5 (2) Jan 19, 2018
1) the common microwave oven is not particularily efficient. The magnetron isn't optimal, and the cavity absorbs a great deal of the radiated energy or returns it back to the magnetron especially when heating small food items. I've seen quotes at about 50% efficiency.

2) higher quality microwave ovens come with unnecessary vanity electronics that consumer large amounts of "phantom power", consuming severall Watts just to stay idle, which leads to the high overall energy consumption. It's the same problem as leaving a wall-wart plugged in when not in use - the simpler mechanical timers in cheap microwaves avoid this problem, but negate it by being otherwise inefficient and breaking sooner.

If you want to boil a cup of tea, a small kettle with a mechanical switch uses less energy. If you want to heat up your lunch, likewise an appropriately sized and insulated sandwich oven would do you better - but it would be slower.
Eikka
5 / 5 (2) Jan 19, 2018
If you take a closer look at the construction of a cheap microwave oven, it's actually designed to overheat. There's a simple blower that cools the magnetron, but since it's rarely used for longer than 2-3 minutes, the thermal mass of the part is enough to absorb the heat. If used for longer periods of time, the power is usually adjusted down to avoid burning the food on the surface.

If you use a cheap microwave oven at full power repeatedly, like heating a cup of water one after another at full power, the magnetron will overheat and the oven will soon fail. Industrial/professional units are different: they employ a sort of cavity diode that re-directs the returning reflected microwave energy into a dummy load, avoiding damage to the magnetron.
Eikka
5 / 5 (2) Jan 19, 2018
These transistors would be able to dynamically shape/modulate the field inside the oven, so that the rotating plate will not be even necessary and the construction of oven will become as simple as induction cooker.


That problem is already solved with older designs of microwave ovens that have a rotating reflector at the top of the oven cavity, often hidden under a microwave transparent shield. It scrambles the field inside the oven.

The reason why a rotating glass plate is used instead in cheap microwaves has to do with the returned energy problem. The glass tray actually acts as a sort of dummy load for when a less-absorbent food item (or less food) is placed inside the oven. If the plate didn't rotate, some hot spot would develop anyways and that could crack the glass.

Having both a spinning diffuser, and a spinning tray, is more expensive, so the cheap models omit the diffuser. Then people came to expect the spinning tray, and didn't trust ovens without it.
Eikka
4.5 / 5 (2) Jan 19, 2018
The way a microwave oven works, not all of the microwave energy is absorbed in one go. The impedance mismatch between the free air and the food means that a lot of the microwave energy bounces off the food, bounces from the cavity wall, and gets absorbed over multiple passes.

The glass plate absorbs the energy weakly, but over multiple passes it too heats up. If a more absorbent item is placed in the oven, the energy goes mostly to the food. If no food is present, the glass absorbs the energy, meaning the magnetron sees less returned power and so the cheap microwave doesn't need a separate dummy load - again saving cost.
anthonys
5 / 5 (1) Jan 22, 2018
Researchers like this should get fired for producing "research" like this - as should the journalists who perpetuate these babblings without a critical or scientific neuron in their heads.
Using a conventional stove uses far more electricity except when cooking large amounts all together. I have specific uses for my pressure cooker (stews, etc), my SMALL oven for things that cannot be satisfactorily by cooked in a microwave, such as roasts, and my microwave.
BTW my microwave is over 30 years old and my small oven over 25 years. I recently bought an electric pressure cooker because I feel they are safer and also lighter for older people. My electric food mixer is 50 years old, but then again, I have always believed in utility, not fashion.
Please critically examine articles before publishing this rubbish.
mackita
not rated yet Jan 22, 2018
But just such an articles produce lively discussion and ads impressions, so that positive feedback exists there...
crlMidi
not rated yet Jan 22, 2018
I agree with everyone else that the article is not well argued. In addition, one should not forget that, in much of the populated World, the heating is on for about half the year.
4528623
not rated yet Jan 23, 2018
Why stop at microwaves? Why not also washing machines, tumble dryers (much higher energy use) and of course, all forms of cooking. Yes, carbon emissions are important but this seems like something of a fool's errand. Nevertheless, I agree if would be good for us all (and indeed certainly good for the planet) if we were able to repair rather than scrap appliances (of all types) when a faulty develops. Perhaps the real problem is that in our supposedly affluent society, we simply cannot afford the labour costs to repair, when it becomes cheaper to replace many items. Unfortunately as robotic manufacturing grows, the economics are likely to remain unviable.
mackita
not rated yet Jan 23, 2018
The government can always impose excise tax to commodities, which may be considered harmful with respect to consumers, life environment of social "order and equality" and the scientists who are living from these taxes are therefore motivated in pointing to these commodities - so we have positive feedback here again...

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