Reusable vs. Disposable Cups: Saving Money and Energy

You might think that disposable tableware–such as plates, cups and flatware–are an affront to the environment and should be avoided at all costs. But the truth is more nuanced.

Assortment of disposable plastic cups
Image via Wikipedia

To compare the environmental impact of reusables (such as glass, porcelain or reusable-plastic cups) with disposables (such as plastic, paper or polystyrene foam cups), you first need to decide which environmental variables to focus on. Are you more concerned with the impact on the air, water or landfill, or is your prime concern energy consumption?

If you focus on energy, you need to consider the energy required to fabricate the cups as well as the energy required to wash resuable cups. The analysis is complicated by the question of how efficiently energy is generated in the area where the cups are manufactured verus where they are being washed. It’s also possible to consider the impact of recycling, and how recycling reusable cups might reduce their total energy and environmental footprint.

An Energy Analysis of Reusables versus Disposables

A classic study by chemistry professor Martin Hocking in the early 1990s took an energy-focused approach in comparing reusable and disposable cups. Hocking calculated the break-even point for pairs of different types of cups.

He found, for example, that manufacturing one glass cup and washing it 15 times used as much energy as the manufacture of 15 paper cups. Other pairs of materials had more challenging break-even points: reusable plastic cups needed 450 uses before they could compete with polystyrene foam. Ceramic cups (which are very energy intensive in their manufacture) vs. polystyrene foam: a whopping 1006 uses.

Paper Is an Energy Hog

He found that, among disposables, paper cups are energy hogs, whereas the much maligned polystyrene foam cups are relatively parsimonious energy users.

Hocking analyzed how sensitive his calculations were to changes in the inputs. An improvement in the energy efficiency of the manufacture of reusable cups reduces the break-even number proportionally. Of course, if you reduced the energy required to make disposable cups below the amount of energy it takes to wash cups, you would eliminate any break-even point, making the use of disposable cups superior, from an energy point of view, at any volume.

Hocking’s calculations are very sensitive to the energy efficiency of the washing process. If you reduce the energy in the washing process by 50%, the breakeven for reusable plastic versus polystyrene, for example, plunges to just 59 versus the 450 noted above.

Major Improvements in Dishwasher Efficiency

According to the Association of Home Appliance Manufacturers, dishwashers have gotten steadily more energy efficient over the years, with energy use dropping by move than 42 percent from 1990–around the time Hocking performed his study–to 2007. Assuming that the energy used in the manufacture of cups has not declined faster than the energy used by dishwashers, it may take just a few dozen uses for reusable cups to be more energy efficient than their disposable counterparts.

Hocking concluded that both reusables and disposables have their place:

For regular use in the home and in most cafeteria and restaurant settings where a reusable cup life of 500 or more uses can be expected, their use makes sense. From an energy consumption criterion, however, there is good reason to use the disposable cup types when the return rate is likely to be low or for situations of one-time use such as for large parties, because their total energy requirement for manufacture is less than, or so close to, the energy required to clean a reusable cup that there is not much to choose between them.

(Hocking also cited a Dutch study that evaluated the environmental breakevens for the other environmental variables I mentioned: air, landfill and water as well. The study found plausible conditions under which reusables excelled on air and landfill use as well, but not on water use. Again, that study was from the early 90s. The water efficiency of dishwashers has improved over the years as well but I don’t have that data handy. Please let me know if you do.)

The Financial Rationale

Regardless of the energy requirements, a food service operator will probably need to see an economic justification for adoption one type of tableware or another. This is where my model comes in. I look at the cost of reusables vs disposables, factoring in cost of cups, energy, water, disposal and even the dishwasher itself.

I built my analysis on top of an EPA model that calculates the operating costs of various types of dishwashers. I layered on top the costs of purchasing disposable and reusable cups, factoring in a reasonable assumption about the need to replace broken or worn out reusable cups.

To run an example, I compared the costs for using 12-oz reusable plastic tumbers, that sell for about $.95 in quantity with the costs of using 12-oz disposable plastic cups that cost about $.04 each.

Reusables Can Provide Rapid Payback

By my calculations, a facility that uses 200 cups a day saves over $2500 per year by using reusable cups rather than disposable. This amounts to about a three-year payback period including the cost of a commercial dishwasher (at $6,000) and an initial inventory of reusable cups. At 500 cups, the savings is over $6,000 per year and the payback time drops to under one year.

Reusables vs. Disposables

Reusables vs. Disposables

My model can be used to model the costs of other types of dinnerware or be customized to reflect other parameters. But broadly, it seems pretty easy to justify, on environmental grounds and economic ones, that food service establishments that have even modest volume and decent return rates, will be better of with reusable dinnerware.

If you have experience with this issue from your own operation, or have seen other data related to it, I would love to hear from you.

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12 Comments

Filed under efficiency, Life Cycle Assessment, sustainability, water

12 responses to “Reusable vs. Disposable Cups: Saving Money and Energy

  1. I assume most people will be washing their cups by hand…have you calculated the cost of the water, soap, etc. (bearing in mind that the water needed to be heated).

    I think there are quite a few factors that come into play here…

    • David Schatsky

      Hi Pinny,

      This analysis is aimed at commercial settings with large volumes of cups where automatic dishwashers almost always make sense. The model considers the cost of electricity, water, and gas, and does indeed reflect the costs of heating the water. Soap is not included because it’s cost is relatively small and doesn’t affect the overall conclusions in a significant way. (But I could easily add it to the model.)

      I believe all significant factors are considered here.

      Thanks for your question.

  2. Pranava Levine

    Soap is only needed when there is oily substances to be cleaned. Most drink do not contain oily substances so hot water alone wash it perfectly well.

    PS: Every one should have his/her own cup. You using the same cup all day long and rinse it lightly if you drink something different. You may do that at home or at work.

    Awarness should take over convenience!

  3. LT

    This was a helpful update to the Hocking paper. I wonder, though, how many times you can realistically wash those plastic cups in a commercial dishwasher before they start looking dingy.

  4. It’s absolutely true that the multitude of environmental factors complicates this decision. It’s good that life-cycle and embedded environmental impacts are becoming better understood. My firm recently published a piece on embedded environmental impact and the movement from building new infrastructure to retrofitting existing assets:

    “Embedded Environmental Impact: The Roman Coliseum vs. the New Yankee Stadium”

    http://civicus.com/uploads/425/Embedded_Environmental_Impact-The_Roman_Coliseum_vs_the_New_Yankee_Stadium.pdf

    In addition, we published a piece on green standards, and the fact that they are in their infancy.

    “Needed: Standards to Set Goals, Measure Progress and Enable Collaboration”

    http://civicus.com/uploads/301/2009-7_MRN25-eqsp-Needed-Standards_to_Set_Goals,_Measure_Progress_and_Enable_Collaboration.pdf

  5. greg hunt

    isn’t Hocking’s analysis flawed in that it doesn’t include disposal energy? How can you have a life-cycle analysis without, well, the whole life cycle?

  6. Pingback: Waste Not Want Not - Reducing waste and saving energy » Just ask for change.

  7. Jefferson Seaver

    What about these other costs associated with washing dishes?

    – Labor: a huge factor in overall cost

    – Real estate: additional square footage needed for equipment and storage, and utilities for this extra space

    • David Schatsky

      Hi Jefferson,

      Thanks for your comment. Labor is not a big factor in overall cost. I estimated that 1000 cups could be loaded into a dishwasher and unloaded in about a half hour. At the minimum of wage of $7.25 per hour, that adds a cost of $.004 per washed cup, about one tenth the cost of a reusable cub (which carry their own labor costs of receiving, unpacking and storing).

      The analysis is centered on power usage. Square footage for equipment and storage and utilities for the space (not operating the equipment) are probably about neutral. Reusable cups will require dishwasher space and cup space but disposable cups will require significant space for an inventory of cups.

      – David

  8. Pingback: Pragmatic Environmentalism

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