Commercial microwave suppliers have hit back at a report branding microwaves an environmental scourge by releasing their own figures showing it is a more efficient way of cooking food than traditional methods.
Last week the University of Manchester published a study arguing that microwaves emit as much ‘carbon dioxide equivalent’ annually as 6.8 million cars.
The tone of the report angered commercial microwave firms, who said that it failed to provide comparisons with other methods of cooking and did not acknowledge that food needs to be cooked somehow.
Sources told FEJ they were confident that heating or cooking food in a microwave was more efficient than traditional methods but wanted time to investigate before officially issuing a comment.
The category’s main body, the Microwave Technologies Association (MTA), has now done that – and struck out at the “misleading” headlines which emanated from the University of Manchester study.
“Compared to microwave heating, hot air heating [involving gas, electric or fan-assisted ovens] is a relatively inefficient process, since in microwave ovens electricity is converted to microwave energy and this then directly penetrates and heats the food itself, meaning much less energy is wasted heating the oven itself or the air inside or the packaging,” explained Jennipher Marshall-Jenkinson, chairman of the MTA.
“So although the article draws attention to the energy and emissions associated with microwave ovens, this is far less than the energy used and associated emissions from using conventional hot air ovens.”
To investigate the potential energy saving of using a microwave oven compared to a conventional hot air oven, the MTA’s technical officer Gordon Andrews used an energy metre to measure the electrical energy consumed during the heating of a frozen ready-meal product.
The heating times developed to safely cook a c.400g chicken and vegetable ready-meal were used for both a 900W microwave oven and a fan-assisted electric oven set at 180°C.
The results found that a fan-assisted electric oven used 0.43 kilowatt hours (KWh) in a 15-minute pre-heat to reach 180°C, and then took 51 minutes to cook a c.400g chicken, using an additional 0.67 KWh in the process.
The same product in a 900W microwave took 12 minutes on full power and used 0.25 KWh versus the 1.10 KWh consumed by the oven.
“What was surprising was that the fan-assisted electric oven used almost twice as much energy as the microwave oven in just the pre-heat,” said Mrs Marshall-Jenkinson. “Over the whole cooking process, the microwave oven used over four times less electrical energy compared to the fan-assisted oven and also cooked the meal over four times faster.”
The MTA acknowledges that it performed a “limited” range of tests, but said the results helped to bring context to the narrative used in the University of Manchester report.
On the basis of the original report’s claim that microwaves emit 7.7 million tonnes of carbon dioxide equivalent, using a microwave rather than a conventional fan-assisted electric oven would save 23 million tonnes of carbon dioxide a year if the same calculations were applied to its own findings, the MTA said.
Furthermore, the University of Manchester report stated that microwaves across the EU consume an estimated 9.4 terawatt hours (TWh) of electricity per year, equivalent to the annual power generated by three large gas power plants.
Referring to its own tests, which suggest the energy efficiency of microwaves is four times greater than fan-assisted ovens, the MTA insists that using microwave ovens oven a conventional fan-assisted electric oven would actually save 28 terawatt hours (TWh) of electricity per year, equivalent to the annual power generated by nine large gas power stations.
Kris Brearley, sales of director RH Hall, the exclusive UK supplier of Sharp commercial microwaves to the foodservice industry, told FEJ that the company went through the MTA’s report last week and “fully endorses” its findings.
Mrs Marshall-Jenkinson added that there were a number of important steps that users can take to prolong the lifetime of their microwaves, including keep it clean inside, allowing it to dry inside after use, ensuring the oven is well ventilated and never operating it empty.