

Dear Pablo: A few of my co-workers and I are wondering what we should tell people when they refuse to use ceramic plates for lunch meetings, etc. They want to use paper plates. Do you have any information on the comparison between resources used for dish-washing vs. paper production?

This question has been asked by many people in many different forms. Years ago I was asked if it's better to wash dishes by hand or use the dishwasher. I collected some empirical data on my clunky old dishwasher to find that washing by hand is better. Meanwhile, a German study using the new energy-efficient dishwashers showed that they can use half the energy, one sixth the water, AND less soap.The question of disposable dishes, cups and cutlery has been a recurring theme as well. In my very first Ask Pablo article ever I did a life cycle analysis of sorts comparing paper cups, ceramic mugs, and metal coffee mugs. Later I revisited the matter in more detail.

The key to the question of durable vs. disposable lies both in the production of the product and in its use. The eco-efficiency of a reusable plate depends on the plate being used many times over many years to take the place of hundreds of paper plates. Where the disposable plate beats the reusable is in the fact that it does not need to be washed. In fact, the plates manufacture becomes so insignificant over time that we can say that it is negligible. The comparison therefor turns into the energy and water required to wash the reusable plate vs. the energy and water used to produce, transport and dispose of a paper plate.

Washing the Plate

The impact of washing a plate has many dimensions. If washed by hand it will require less energy and water than using an old dishwasher, but more than a brand new state-of-the-art model. The efficiency with which you load the machine becomes important because every cubic centimeter counts but you don't want it packed so full that dishes come out still dirty. The California Energy Commission has the following tips on their website:

Avoid using the "rinse hold" setting on your dishwasher. "Rinse hold" uses three to seven gallons of hot water for each use, and heating water takes extra energy. Never use "rinse hold" for just a few dirty dishes.

Try to wash only full loads-the savings will surprise you.

Use short cycles for everything but the dirtiest dishes. Short cycles use less energy and work just as well.

If your dishwasher has an air-dry setting, choose it instead of the heat-dry setting. You will cut your dishwasher's energy use from 15 percent to 50 percent. If there's no air-dry setting, turn the dishwasher off after its final rinse and open the door. The dishes will dry without using any extra electricity.

If you rinse dishes before loading them, use cold water. Don't waste water by letting it run continuously, either.

Install your dishwasher away from your refrigerator. The dishwasher's heat and moisture make the refrigerator work harder. If you have to put them next to each other, place a sheet of foam insulation between them.

The Bottom Line

I could go through a lengthy quantitative exercise that would end up being either approximately correct or precisely wrong. The problem is that an analysis using my dishwasher and one particular plate would result in an answer that is completely different from your dishwasher and your disposable plates. In most cases the reusable plates and the dishwasher will win over disposables. Disposables do have their place; at the company picnic, or any other event that is far removed from modern plumbing. Ultimately trust that little green voice inside your head that tells you that disposable plates are the wrong choice for the office meeting. If other people don't share your values and are too lazy to load their plate into the dishwasher, perhaps the committed few can organize and volunteer for dish patrol. Eventually your corporate culture can evolve and everyone will be on board with the new status quo.