The University of Michigan and Michigan-based Whirlpool Corp., the nation’s largest dishwasher manufacturer, recently cooperated to produce guidelines for environmentally conscious consumers who want to make their daily dishwashing chores as “green” as possible.
Their research looked at the environmental burdens of both washing dishes by hand and different types of machine dishwashing in terms of greenhouse gas emissions, water and energy consumption, solid waste production and cost. The study also compared common practices used for hand and machine dishwashing in American households.
It found that when typical manual and machine practices were followed, machine dishwashers produced less than half the greenhouse gas emissions – and used less than half the water – of most manual dishwashing techniques.
However, there was one manual washing technique – the “two-basin” method, in which dishes are soaked and scrubbed in a sinkful of hot water and then rinsed in cold water – that was associated with fewer greenhouse gas emissions than machine dishwashing.
On the other hand, the increasingly common “running tap” method of manual dishwashing, which involves washing and rinsing dishes under a steady stream of hot water, used both more energy and more water than any other dishwashing method tested. If by-hand dishwashers switched from the running tap to the two-basin method, they could reduce greenhouse gas emissions associated with washing their dishes by about two-thirds, the researchers said.
For the majority who prefer the time savings and convenience of an automatic dishwasher, the study offered several tips to reduce their environmental impact. They include not pre-rinsing dishes before loading them into the dishwasher; avoiding the “heat dry” setting; and selecting the “normal” wash cycle for most loads, except for heavily soiled dishes.