AskPablo: Napkins

napkin.jpgThis weeks question is from Nick Gruber: “My question has to do with linen napkins vs. paper napkins. Is it more efficient to use linen napkins (factoring in the energy for picking them up and washing them) or paper napkins (recycled paper napkins)?”

Let’s start with some very basic assumptions to frame this analysis. I am assuming that the paper napkin is made from 100% recycled paper content and that the fabric napkin is made from conventionally grown cotton (it is much easier to find data on cotton than on flax, from which linen is made). The weight of each alternative is also critically important in terms of its material input intensity, but negligible in terms of transportation. The paper napkin is assumed to weigh 5 g and the cotton napkin is assumed to weigh 32 g. The paper napkin is used only once, while the cloth napkin will be reused 50 times over its lifetime.
Recycled paper fiber has a significantly lower material intensity than virgin paper. 1.75 g of CO2 per gram of bleached virgin paper vs. 0.05 g of CO2 per gram of recycled paper. The difference in water use is also impressive, 303 g vs. 15 g. The cotton is even worse than the bleached paper at 2.74 g of CO2 per g and 6814 g of water used per g. (Source: MIPS data tables, Wuppertal Institute)
Based on our assumption and factors stated above the paper napkin results in 0.25 g of CO2 emissions (or 8.75 g for non-recycled paper) and the cotton napkin is responsible for 87.68 g of CO2 emissions.
In terms of water used during the manufacturing of both napkins we get 75 g of water for the recycled paper napkin (or 1515 g for non-recycled paper) and the cotton napkin is responsible for 218,048 g of water use (that’s 218 liters!).
The results for the cotton napkin are higher not only because of its higher water and carbon emissions factors but also because it weighs more. But we are not simply comparing napkins here, we are comparing lip wiping and hand cleaning services. Therefore we need to compare the cloth napkin with a comparable amount of paper napkins, based on its fifty-use lifespan. Multiplying the paper napkin results by 50 results in 3,750 g of water and 12.5 g of carbon emissions. End of story? Well, from a material intensity perspective the result is clear the 100% recycled paper napkin is the environmentally superior decision (even the non-recycled paper napkin used less water, 75,750 g, but it did emit more CO2, 437.5 g).
For the paper napkin we have almost reached the end of the line. The average ton of landfill trash will emit 1.8 tons of CO2-equivalent (mostly methane) over 50 years (B. Davis, Ze-Gen, at CleanTech2007 conference, May 24, 2007). While the average ton of landfill waste is not 100% paper this gives us an idea of the emissions that can be expected from landfill waste. If we just assume this factor to be accurate for our paper napkin, we can add 450 g of CO2e to our fifty paper napkins.
Since the cloth napkin will be reused fifty times we need to consider the impact of washing and drying. Washing and rinsing the cloth napkin probably uses around 2.8 to 5 gallons of water per pound of fabric. If we assume a highly efficient machine this means 250 g of water per napkin, so 12,500 g ( 12.5 kg) of water over its lifetime. Add to that the use of soap and the energy used in drying.
Assume that we are using a 5000 W machine that can dry fifty napkins in twelve minutes, using 1 kWh. Using the CA average emissions factor ( 0.51 mT CO2 / MWh) we get 510 g of CO2 (0.001 MWh x 0.51 mT CO2 / MWh). If we go back and assume a 500 W washing machine this would add around 50 g of CO2.
So, here’s the final tally: Fifty paper napkins are responsible for 3,750 g of water use, and 462.5 g of CO2 emissions (although we can’t assume the landfill emissions factor to be quite accurate) and the cloth napkin is responsible for 240,548 g of water use, and 648 g of CO2 emissions.
Here are my recommendations… Cotton is very damaging from an environmental aspect (we didn’t even discuss pesticides and defoliants) so purchasing organic cotton is a good decision. Since Linen is made from flax we can assume that the environmental impact of linen napkins would be less. If you need to buy napkins, the 100% recycled ones clearly have a lower environmental impact. If you use cloth napkins, use biodegradable, phosphate-free soap, use the energy-saving settings, and line-dry them.
This is my best quick analysis of this question and I hope that Nick is happy with the result. If you have any better assumptions or additional comments to make please feel free to post them below. I look forward to an interesting discussion. Thanks for reading AskPablo!

Pablo Päster
Sustainability Engineer