There's a plethora of debate about WHAT you should eat if you're trying to be environmentally friendly, but I'm going to try and answer HOW you should eat it. I suppose the least wasteful way to go would be to cook your entire dinner in one pot and have everyone dig straight into the pot with their hands, saving the hassle of using dishes at all. While I'd be totally fine with that method, others might have an issue with such an animalistic method.
So hand-shoveling aside, the methods I am going to consider are using dishes and washing them in a regular dishwasher, washing them by hand, and finally using paper plates.
What other folks think
I'm by no means the first person to ask this question. And so far the scientists are pretty much in agreement on the issue of hand-washing versus using a dishwasher (clicking link will download a paper done by scientists at the University of Bonn in Germany); as long as you only run your dishwasher when it's full and your machine is less than 14 years old, you're better off using the dishwasher. Your dishwasher uses only 7-10 gallons of water per cycle. It is possible to be very very careful, and use less than this by hand-washing. However, the studies show that hand washing generally uses 20+ gallons per load because people leave the water running the whole time they wash. Hand-washing is also less effective in sanitizing dishes. So dishwashers are usually the way to go. This was a pleasant surprise for me, as I'm sure it is for all of you out there who support the cause of minimizing your chore time. For once being lazy is actually good for the environment.
And if you really want to boost the energy and water saving potential of your dishwasher, don't rinse your dishes before putting them in the washer, and skip the pre-rinse and drying cycles. I could gather data and do my own analysis on how to wash your dishes to reduce your environmental impact, but I'm going to stick with the theme of laziness, and accept the German scientists' work as accurate. Plus by doing this I'll spend less time on the computer and save energy, so really I'm helping the environment.
Some people claim that the answer to this question gets a little murky if you consider the pollution and energy use that results from producing a dishwasher. If you already have a dishwasher you should continue using it, but if your dishwasher is broken and you're considering buying a new one, or if you don't have a dishwasher yet, it's been suggested that it's better to stick with hand washing.
Luckily those thorough German scientists have already considered this. They looked at the energy use of dishwashers over the dishwashers' complete life-cycle. They found that 95% of the product's environmental impact comes from the use phase, with about 4% coming from the production phase, and 1% coming from the disposal phase after the machine has worn out, assuming a 15 year lifespan. Since, according to the Bonn study, dishwashers use 50% as much energy as hand-washing and a fraction of the water, the machines still win, even when you consider the materials and energy used to produce and transport them.
What I think
What if you can cut out washing your table dishes, and just wash pots and pans by using paper plates? For this comparison, I'm going to assume that you're using biodegradable paper dishes made from recycled paper and cutlery and cups made from corn like these or these.
As far as the plates, they are made from recycled paper and don't waste materials in production. They do, however, require energy to produce. In your dishwasher's 15 year lifecycle, it will use about 24,000 kWh of energy, according to the Germans. By using paper plates, lets say you only have to run your washer 1/3 as much to clean your pots and pans. This reduces your dishwasher's energy consumption to 8700 kWh. For a normal family, you're going to use about 12 plates or bowls, 10 cups and 20 pieces of cutlery each day. Over 15 years, this comes out to 65,700 plates, 64,750 cups, and 129,500 forks, spoons and knives.
I can't find good information on the environmental impact of producing biodegradable plates, but it would require about 2000 kWh, and produce 247 kg of carbon emissions to make that many regular paper plates and bowls. According to the EarthShell website, their production methods use less energy and have lower greenhouse emissions than those of traditional paper plate manufacturers. So the plates and bowls should require less than 2000 kWh of energy.
There's much better information available about the production of biodegradable PLA plastic cups. According to a report by Franklin Associates, producing 10,000 PLA plastic cups requires about 4000 kWh of energy and 500 kg of carbon emissions. I'm assuming you would use around 65,000 cups in 15 years, which would require 26,000 kWh of energy and 3250 kg of carbon emissions. While this energy usage outweighs the energy saved by not using the dishwasher, the types of energy used in producing the cups result in less carbon emissions than the energy that your dishwasher uses. I'm assuming you save 15,300 kWh by reducing your dishwasher usage, which translates to 9 tonnes of carbon according to carbonfund. Cup production results in 3 tonnes of carbon, and accounts for about 1/3 of the reduction in dishes to wash, so in terms of greenhouse gasses, there's little to no difference between using glasses and PLA plastic cups.
I can't find a study like the Franklin Associates one that deals with biodegradable cutlery, but since it's made from the same material as the cups, its going to require a comparable amount of energy and carbon emissions.
Disposable cups and cutlery are probably out, but plates and bowls could be an energy and emissions saving option, assuming you compost all the disposable dishes you use. Taking all the plates and bowls out of your dishwasher could reduce the number of loads you do by, say, 40%. This would save around 9000 kWh, which converts to a savings of 5470 kg of carbon emissions from not using the dishwasher, while requiring less than 2000 kWh and 250 kg of carbon to produce the disposable plates and bowls you would use over 15 years. This translates to a savings of 5 tonnes of carbon over 15 years.
Conclusions?
I also don't have data about water use in producing biodegradable disposable dishes, so I can't make any comparisons on that basis. But from what I've got here, it looks like there is an argument for biodegradable plates and bowls, but not cups or cutlery. If you don't have a dishwasher, and are currently washing all your dishes by hand, biodegradable plates and are almost certainly a good option. But if you're in the majority of people who use dishwashers, it's arguable whether switching to disposable plates is better or not. Just make sure you jam that dishwasher as full as you can, and look for environmentally friendly detergents.
Of course I haven't talked about cost at all in this post. You could end up spending about $300 per year if you switch to EarthShell plates. Some of this cost is offset by saving on water, detergent and energy that goes into washing dishes, but in the end you have to decide for yourself whether it's worth it or not.
