May/June 2012
Hands that do dishes ...
Most of us in the UK do our washing up by hand with only about 42% of us owning a dishwasher.(31)
The best selling brand is Fairy which boasts a seal of approval by the British Skin Foundation, though this claim is not all that it seems. The British Skin Foundation is a charity that Fairy’s owner, Procter & Gamble (along with many other product manufacturers) supports financially.(20)
Washing-up liquids do not contain phosphates so products labelled ‘phosphate-free’ are misleading. But conventional brands do contain petrochemical surfactants and synthetic fragrances, not to mention the increasing number that claim to be antibacterial.
“Using a dish detergent in hot water also creates another health hazard- chemical vapours. In hot water the chemicals vaporise and are inhaled as steam; and some ingredients can produce vapours that cause severe irritation to the eyes and respiratory tract.”(20)
Marigold versus machine
The great debate – is it better for the environment to do the washing up by hand or use a dishwasher?
One of the most detailed studies ever done was in 2004 by Professor Rainer Stamminger of the University of Bonn.(14) He found that dishwashers used less water and electricity than washing by hand. On average, human washers in his study each used 103 litres of water, 2.5kWh of water-heating energy and took 80 minutes. By comparison, the machines used 15 litres of water and 1-2kWh of electricity, taking between 80 and 160 minutes.
These days, the most efficient dishwashers on the market use only 6.5 litres of water and less than 1kWh.(22) Stop it before the drying cycle begins and let it air dry (or use the quick wash setting) and you’ll use even less energy.
So dishwashers seemed to come out top, but they had to be full for the figures to stack up. But this may not have been a robust conclusion. A better handwashing technique makes the figures more competitive.
The best human washers in the 2004 study were only using 30 litres and 1 kWh of energy by, for example, scraping not rinsing food scraps, not pre-rinsing under a running tap and rinsing in a second sink full of cold water. British washers were using even less water than average.(14)
The energy used for handwashing could be even less because he calculated the energy used based on electricity use. Whilst most dishwashers now, annoyingly, only have a cold fill and so have to use electricity to heat the water, many people have efficient gas condensing boilers, gas having a lower carbon footprint than electricity.(13) So carbon savings can be made there, even more if you are using solar-heated water.
In addition, Rainer Stamminger did not include the embodied energy of manufacturing and transporting the dishwasher in his figures nor the materials used to make it.
References
13 How bad are bananas?, Mike Berners-Lee, 2010 Profile Books 14 A good Life, Leo Hickman, Eden Project Books 2008 20 Behind the label: Fairy Liquid, The Ecologist, 5th February 2009 22 www.sust-it.net viewed 8th March 2010 31 Mintel Dishwashing Detergents - UK - April 2011