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Saving energy: Dishwashers vs. hand-washing and china vs. paper  Smart Choices Archive

Saving energy: Dishwashers vs. hand-washing and china vs. paper

Surprisingly, using a dishwasher saves water and energy over hand-washing dishes.

Energy Efficiency: Appliances

Martin Holladay, a blogger on greenbuildingadvisor.com, writes a regular column, “Musings of an Energy Nerd.” In a recent posting, he discusses energy implications of washing dishes by hand vs. a dishwasher, and serving foods and beverages on china dishware vs. paper.

Below are excerpts from his column; read the entire posting on greenbuildingadvisor.com.

A dishwasher vs. handwashing
The definitive research was performed in 2004 in Bonn, Germany, and the findings were published in Home Energy magazine. Researcher Rainer Stamminger found that a dishwasher uses about half the energy and one-sixth the water used by an average hand-washer. The appliances used in the study used an average of about 4 gallons of water and 1 kWh of electricity per load. The dishwasher also used less detergent and got the dishes cleaner. In the study, those washing by hand had to use an average 27 gallons of water and 2.5 kWh of water-heating energy.

China versus paper
He says, “Most environmentalists are scornful of those who use disposable coffee cups or paper plates. Such people take pride in the fact that they always use a china coffee cup at the office (washing it out in the sink, of course, when necessary). So is there any logic to preferring china plates and cups to paper plates and cups? Which approach uses less energy?”

He cites a number of studies comparing the options. Several points of interest:

  • Studies looked at the environmental impact using a life cycle assessment tool. One study reported that the minimum number of reuses for china is about 50, when compared to a single-use biodegradable plate.
  • Another study concluded that paper plates and bowls make more sense than paper cups and plastic forks. The conclusion was based on taking plates and bowls out of the dishwasher, thus reducing the number of loads run by about 40%. Comparing the kWh and carbon emissions in savings by not running the dishwasher vs. the amount of energy (kWh and carbon) used to produce single-serve items was the basis for this recommendation. As part of this study, it was noted that if a consumer hand-washes dishes, biodegradable single-serve plateware is definitely a good option.
  • An analysis made by the Dutch Ministry of Environment claims that in ceramic vs. polystyrene cups in terms of energy and water consumption, you would have to use the ceramic cup 640 times to equal a polystyrene one, and 294 times to equal a paper/cardboard one. In terms of air pollution, it takes 1,800 uses of ceramic to best polystyrene and 48 to do better than paper/cardboard. As for waste, it’s 126 and 99 uses respectively. However, because a ceramic cup can be used indefinitely, or “for more than 3,000 slurping sessions,” it is still ranked as the best option.
  • A classic life-cycle energy analysis, performed in 1994 by Martin B. Hocking, a Canadian chemistry professor, compared ceramic, glass and reusable plastic and two types of disposable cups (paper and polystyrene foam). He calculated the energy of manufacture as: china at 14 MJ, paper at only .55 MJ and polystyrene, surprisingly, at .20 MJ (less than that of a paper cup). Using Hocking’s break-even matrix,  “You would have to use (and wash) a ceramic cup 1,006 times to break even with the energy used to manufacture 1,006 polystyrene cups, but you would only have to use a ceramic cup 39 times to break even with the energy used to make 39 paper cups. Since the energy needed to wash a cup or plate once is less than the energy required to manufacture one disposable cup or plate, using a china cup or plate wins the race, as long as it is used for more times than required to reach the “break even” point.” The variable, though, is the efficiency of the dishwasher.

Martin Holladay’s comments

His “winner”: China plates, bowls and cups are better than paper, but only slightly, and only under certain conditions:

  • China fails this comparison if your cabinets are full of more china plates and cups than you use regularly. After all, if you have 40 coffee mugs in your cabinet, that’s a lot of embodied energy. You have to use each cup dozens or hundreds of times before you’ve broken even.
  • China fails this comparison if you have clumsy family members who break china often.
  • China fails this comparison if you wash your dishes by hand.

His suggestions
Buy and use an energy efficient dishwasher; ENERGY STAR models use no more than 295 kWh/year (assuming that the washer is run 215 cycles per year, that is 1.37 kWh/cycle) and no more than 4.25 gallons of water per cycle. Look for a list of ENERGY STAR models at the ENERGY STAR website.  Also check out Consumer Reports for details and ratings on dishwashers.

His tips for using an automatic dishwasher

  • Simply scrape off food scraps, no need to pre-rinse dishes.
  • Wait until the dishwasher is full before running it.
  • Avoid enhanced settings like “super wash” or “pots and pans.”
  •  Use a good detergent. He says that Consumer Reports recommends Cascade Complete with Dawn ActionPacs, Cascade Complete All-in-1 Powder, or Walmart’s Great Value Powder Pacs.
  • If possible, don’t use the heated drying cycle. Heated drying uses an electric resistance heating element. If your dishwasher offers it, select unheated air drying, or just open the door when the dishes are still hot from the rinse cycle, to allow the dishes to dry into the room.

Source: Musings of an Energy Nerd blog


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