Green Dinner Parties: Nitty-gritty

August 31, 2011

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Q: I often host dinner parties for groups of six to 10 people, and I have always wondered: Should I purchase disposable plasticware or paperware, or is it better to use my flatware and run one or two dishwasher loads? Which uses fewer resources? Which has a less negative impact on the environment?

Asked by Alison Herson, ’08, Vancouver, Wash.

Paper plates or dishwasher?

While the ultimate answer is clear, quantifying every environmental impact from such different items is no simple task. We'll make some assumptions along the way, but here's the breakdown. Let's look at greenhouse gas emissions from energy use first, and then examine the water use for both types of plate.

First, let's consider running the dishwasher once. Energy use varies by model, but modern efficient dishwashers average about one or two kilowatt-hours. Dishwashers are powered with electricity, so estimating their carbon emissions requires examining electricity in your area. Luckily for you, Vancouver's electricity supply is relatively clean, with nearly half coming from hydropower (compared to a national average of less than seven percent) and nearly 50 percent coal. That means the running your dishwasher in Vancouver is greener than average, emitting about 700 grams of carbon emissions per load.

Making paper for plates, meanwhile, is a long process, and one explored in some detail in a SAGE column about paper towels. Each paper plate on average is responsible for about 3.8 grams of carbon emissions. Assuming 10 plates per party, we can estimate about 40 grams of carbon from plate production. This paltry emission pales in comparison to the dishwasher figure, so why should we use flatware?.

First, manufacturing the plates does not guarantee their presence on your dinner table. The plates have to make it there, first, and transportation is potentially the largest source of greenhouse gas emissions from paper plates. Assuming the primary mode of transportation is a diesel truck, as it is for 75 percent of the freight in the United States, estimated carbon emissions are around 800 grams per mile, per ton of cargo. Diesel trucks also generate about eight grams per mile of nitrous oxide. Nitrous oxide is about 300 times more potent as a greenhouse gas than carbon dioxide, so a diesel truck would generate more than 2,600 grams of carbon equivalent per mile.

Assuming a single-unit truck has about 1,400 cubic feet loading capacity, and that the dishware for one dinner party would occupy about 1 cubic foot, your disposable dishes are going to generate something like 1.8 grams of CO2-equivalent per mile. The distance your plates travel depends on your location, but for example, Dixie plates are manufactured in Kentucky. They travel across the country before reaching us on the West Coast, adding perhaps 4,000 grams of CO2-equivalent in transportation by the time they reach your local store, and dwarfing the 700 grams of CO2-equivalent it took to run your dishwasher.

Then, there's water. Making enough paper for one plate also uses about 8 gallons of fresh water, which means your 10-plate dinner party uses 80 gallons, without washing a thing. Running the dishwasher for one load uses much less water, between six and 10 gallons.

It's worth noting that even a basic lifecycle analysis, like the one I've attempted here, relies on a lot of assumptions and uncertainties. Without knowing the specifics of your situation—especially whether you've got an efficient dishwasher and whether you would compost any paper plates you use—it's impossible to say whether paper plates are 10 times worse for the environment than reusable plates, or 100 times. But by adding up all the environmental impacts along the way, it becomes very clear that by the time you've hosted more than a few parties, reusable flatware is the best way to go.

More environmental effects from making paper

When we compared carbon emissions from paper plates earlier, we left out a few further causes for concern.

Paper needs to be sourced from somewhere, and we did not account for the effects of obtaining the necessary wood. The potential impact from sourcing wood could be quite low, in the case of using recycled paper, or quite high, in the case of deforestation of a fresh forest. Trees contribute to carbon sequestration, or the intake of carbon dioxide from the atmosphere, so deforestation reduces the planet's ability to absorb our emitted carbon dioxide. We also did not account for the transport of the wood products throughout the papermaking process.

Though we did estimate the amount of water necessary to the manufacture of paper, we left out some important steps. For example, many paper plates are bleached to get their pristine white sheen, and depending on the type of bleach used, this step can be very environmentally detrimental.

In the Essential Answer, we were quick to criticize disposable plates because they eventually end up in landfills. While the landfill may be the ultimate home for the majority of disposable flatware, more environmentally friendly options are increasingly available. Many plastic plates, for example, could be recycled, even if many local recyclers don't want them. Most paper plates are compostable. Recycling and composting have their own associated emissions, but repurposing the used plates for a second life is a step in the right direction.

Manufacturing ceramic plates and reuse

We have addressed impacts from washing traditional flatware and from manufacture of disposable plates in our consideration of clean up from one dinner party, which would require either manufacture of paper plates or washing already-made traditional flatware.

I wondered, though, about the missing piece from this holistic assessment—the manufacture of the traditional flatware. Most flatware is made from ceramic, porcelain being one of the more popular types. To make porcelain, materials must be sourced, mixed, melted and formed, and then fired. The process is certainly energy-intensive, with the largest demand coming from the heat for drying and firing the plates. On average, each plate results in some 600 grams of CO2-equivalent.

That's a lot more than the 4 grams emitted for a paper plate. In fact, ceramic flatware takes so much more energy to make that it raises a whole new question: if I don't have any plates at all to start with, should I buy paper plates or porcelain plates to feed my hungry friends? A new porcelain plate would need to be used 150 times to before it starts to be the better climate option. My roommates and I use each of our plates at least once a day, but let's be generous to paper and assume for this calculation that each plate is used once every other day. Porcelain plates, then, must be in regular circulation for about a year before they become the greener choice.

How does this information impact our decision about the dishwasher, though? Well, assuming that you already have porcelain plates in your house, we can say that you have already made the choice addressed above—porcelain over paper plates. Use those porcelain plates 150 times, and they'll have paid off their carbon debt, so to speak. The greenhouse gases from porcelain manufacture have already been emitted, and it makes more sense to use them rather than buy new plates, which requires further emissions.

Either way, though, it is clear now that the dinner party has a number of unexpected environmental impacts. Cooking a great meal and sharing it with friends, avoiding a drive to a restaurant and encouraging getting in touch with food again, is what we're all about. Maybe at your next dinner party, around the table of porcelain china and seasonal, locally grown food, you can strike up a conversation about your efforts to be green. Happy cooking!

Jade Wang, ’10, plans to receive her master’s degree in earth systems in 2011.

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