W.L. Rathje

After a two-week tour of talks to environmental groups, universities, K—12 teachers, businesses, and consumer groups, that same old question is still ringing in my ears. I should probably give garbage professionals my answer and see what they say about it.

We tend to think of disposable diapers as being made of plastic, though by weight only about 8% or 9% of a disposable diaper–the waterproof backsheet–is plastic. About three-fifths of a disposable diaper’s constituent weight is plain cellulose, which goes into the diaper’s absorbent padding; the padding infused with a nontoxic polymer that turns into a gel when contact is made with urine.

In considering the pluses and minuses of disposable and cloth diapers, the major bones of contention involve these matters: the relative amount of energy that the use of each type of diaper requires, the relative volume of raw materials that the use of each type of diaper requires, the relative volume of discard, the relative amount of water consumed, the relative threat of pollution, the relative threat to public health, and the relative cost per diaper.

During the past decade and a half, there have been a number of studies that bear on these issues. Most were commissioned either by companies that manufacture disposable diapers, such as Procter & Gamble, or by the National Association of Diaper Service Industries, which for obvious reasons promotes the use of cloth diapers. The studies are all examples of what is known as "product life cycle analysis" or "cradle-to-grave analysis"–a controversial and slippery methodology in which an attempt is made to gauge the full range of costs that arise from the creation, use, and disposal of a product. The two sides are at loggerheads on many issues. But let’s look at what almost everyone can agree on.

Energy, Water, Pollution

For disposable diapers, the bulk of the energy use occurs during manufacturing, and at this stage there is also a likelihood that some pollution will occur. The resources required for disposable diapers are mostly renewable–cellulose from trees–but plastic too goes into the diaper and goes into the packaging as well. Disposable diapers obviously create more MSW than cloth ones do, and they create a possible pollution problem when they are dumped in landfills (a third of all diapers contain fecal matter, and all contain pathogens–at least initially) and perhaps even when they are incinerated. As for expense, if one simply looks at per-diaper cost, disposable diapers drain the pocketbook faster than cloth diapers (the per-diaper cost for each use of a disposable is about 25 cents, versus 7-9 cents for a cloth diaper laundered at home and 13-17 cents for a cloth diaper from a diaper service).

For cloth diapers, the largest amounts of energy are consumed in the growing of cotton (which requires large quantities of irrigated water and pesticides) and then in the 180 or so washings that the average diaper laundered at home goes through in its lifetime. Diapers last more than twice as long at home as they do in the employ of diaper services (which only about 15% of households on a cloth-diaper regime use), largely because services, for aesthetic reasons rather than purely practical ones, limit the number of times they will reuse a cloth diaper.

The material resources required for participation in a cloth-diaper system (cotton primarily) are almost completely renewable, but don’t forget about the chemicals used to make detergent (or the ones used to grow cotton, for that matter). The washing of cloth diapers requires vast amounts of water and turns the water filthy; it all goes into the sewage system. Diaper services, because of economies of scale and other efficiencies, use somewhat less energy per diaper and produce less dirty water than in the case with home laundering. But continue to consider that many, if not most, disposable diapers are woven in Asia from American cotton and make the long trip to and from at both a financial and environmental expense.

Also, don’t forget that diaper services pick up and deliver cloth diapers using trucks that burn gas and generate pollutants in their numerous roundtrips, often covering many dozens of miles both ways. In one early morning drive to a talk north of Minneapolis/St. Paul, I swooshed past a caravan of diaper service trucks for at least 40 minutes.

When everything is added up, which diaper regime comes out ahead, environmentally speaking? That’s the rub: It is impossible to say. Minor differences in assumptions–for example, small variation in how often cloth-diaper users "double diaper"–deflect any easy analysis.

The most striking fact overall, however, is how small the differences between the two diaper systems really are, no matter whose studies one accepts. And in absolute rather than comparative terms, one is not dealing with a major blight upon the land in either case.

For example, regardless of which type of diaper requires the most energy, the overall amount of energy under discussion is not very large. In real terms, and using high-end estimates for both energy consumption and number of diapers worn, all the energy invested in disposable diapers that a typical child uses in a year is equivalent to about 54 gal. of gasoline. That amount of gas is what would be consumed by driving from Boston, MA, to Little Rock, AR. We might never determine conclusively which kind of diaper, all things considered, is the more efficient, but neither kind is a major drain on our nation’s energy resources.

The Garbage Concern

What about the filling-up-of-landfills issue? Critics of disposables always hammer home the same point. To quote Carl Lehrburger, author of the two key pro—cloth diaper documents: "No other single consumer product–with the exception of newspapers and beverage and food containers–contributes so much to our solid waste." This statement is not exactly accurate; tires and textiles are just two other items that consume three times or more space as disposable diapers. Besides, Lehrburger’s statement seems like quite an indictment, though in fact it might be a little like saying that birds would be the biggest animals on earth if there were not mammals, reptiles, or fish.

Nevertheless, because disposable diapers loom so large in casual litter, one tends to assume that they loom large in garbage as a whole. They don’t. The Garbage Project’s excavations at 21 US landfills have documented that the volume taken up by disposable diapers varies from 0.53% to 1.82%. Disposable diapers might be a big-ticket item in landfills compared with toothpicks and check stubs, but they are simply not in the same league with paper of various kinds (especially newspapers) or items such as foodwaste, yardwaste, and construction and demolition debris–all of which fill up landfills at a rate many times greater than that of diapers. It is certainly an illusion to believe that eliminating disposable diapers would have anything but an imperceptible effect on the larger garbage picture.

As for the possible deleterious effects of landfilled diapers on public health, the issue does not merit great concern. Even if disposable diapers do represent a problem, their addition to a landfill does not suddenly poison a pristine environment. The so-called "bioload" of a typical landfill–the census of its microorganisms, many of which are pathogenic–is so enormous that the contributions made by diapers are relatively insignificant. Landfills already receive about 20% of the sludge from America’s sewage treatment plants. They receive 8% of the septage from the country’s septic tanks. Normal household garbage fairly brims with foodwaste, with the residues of personal hygiene, and with pet feces. Medical waste of every imaginable kind finds its way into landfills, even if much of it should not.

It is worthwhile still to figure out whether adding diapers to landfills makes any noticeable difference. Trying to do so seems to have turned into one of environmental science’s minor cottage industries. In the past 15 years, scores of scientific studies have been done on the subject. The propensity of bacteria and viruses in diapers to expire in landfills has been widely documented, and the few that do not die tend not to migrate very far.

The myriad disposable diaper studies conducted by Chuck Gerba of the University of Arizona, the world’s leading expert on such affairs, conclude that there are no active viruses, bacteria, or parasites in diapers retrieved from landfills.

What do we make of this information? The decision to bring infants into this chaotic world is a momentous one. Deciding what type of diaper to use is not. Use what fits you best.

I guess that the question between cloth and disposable diapers is a "wash"–you do what you need to do. Train well the ones you bear and watch your discards–you and our world will be OK!

Archeologist W.L. Rathje is founder and director of the Garbage Project.

MSW - September/October 2002