Flawed Impact Studies Review
“Studies show that
the impact of cloth diapers and disposable diapers is equal.”
Let’s start with the conclusion. You are being lied to and products are being greenwashed when you hear a version of this claim. This claim exploits a small overlap found in a two UK studies between the environmental impact of disposable diapers and reusable cloth diapers. The studies are really one study, and the data and assumptions are flawed. Even with all of the flaws, the overlap found was not the overwhelming evidence that disposable diaper manufacturers claim. Even these studies show that impact of cloth diapers and disposable diapers is not equal.
One problems is, few who cite the studies have actually read them.
There are important points to understand about the two-part UK study:
- the boundaries of lifecycle studies can vary and do determine outcomes;
- externalizing (that is, ignoring) costs of non-renewable resources skews results;
- cited data for disposable diapers included optimistic future projections from the absorbent hygiene and non-wovens industries; and
- cited data for reusable cloth diapers was so limited that it didn’t even include the most basic and by far the most commonly used cloth diapers, prefolds.
Whether these are overlooked flaws in the design of the study or deliberate manipulations, the best they could do was to find a minor overlap—less of an overlap in the 2008 addendum, which shows that reusable cloth diapers have 40% less impact than disposable diapers when laundered correctly. Parents are in control of environmental impact of cloth diapers.
If the flaws in the study were corrected—adding data for low-impact cloth diapers (prefolds and flats) that weren’t even considered in the study and not using projected future data for disposables—there would be no overlap whatsoever in impact.
For those concerned about environmental impact, even this skewed study makes it clear that using cloth diapers and careful washing and drying result in the lowest impact diapers.
2005 UK STUDY
The first study was Life Cycle Assessment of Disposable and Reusable Nappies in the UK published by the Environment Agency in May 2005 (SC010018), a 203-page report that billed itself as a Life Cycle Assessment (LCA). The Environment Agency is a UK government agency. They set up an advisory board that consisted of representatives of absorbent hygiene products (disposable diapers) and reusable products (cloth diapers). Ann Link, representing the Women’s Environmental Network (WEN) on the advisory board, protested vigorously the conclusions they reached, saying the final study was unduly influenced by corporate interests.
The report issued not a comparison of disposable and reusable diapers but a study focusing on the environmental impact of disposable or one-time use diapers. More than 2,000 parents using disposable diapers were questioned. Only 183 parents using reusable diapers were surveyed, 37% of whom used relatively high-impact terry nappies not commonly used in the U.S. Commercial laundry (diaper service) data were provided by Procter and Gamble and others. The Women’s Environmental Network of the UK issued a statement further detailing flaws in the study.
The results of this study showed not that impacts of disposable diapers and reusable cloth diapers were equal in the comparison but that there was some overlap in environmental impact between the highest impact reusable diapers and the lowest impact disposable diapers.
The conclusion provided within this study was: “There is no significant difference between any of the environmental impacts of the disposable, home use reusable and commercial laundry systems that were assessed. None of the systems studied is more or less environmentally preferable” (2005, p120). This conclusion is not, however, consistent with the data within the study itself, which is why so many participants in the advisory process protested the study.
Up to this point in the study, authors seemed to be fairly thorough. They use USDA data on cotton production, but they also state the assumption that diapers used in the UK are made in Asia. The data used are not necessarily representations of sources for UK reusable cloth diapers but are data sets used for estimation. They stated their assumption that reusable diaper equals cotton, so they did not address non-cotton reusable diapers. They did not mention Egyptian cotton nor organic cotton. So, perhaps they have been accurate but not thorough.
It is obvious to someone who knows about the manufacture and use of reusable cloth diapers that study authors were not quite able to wrap themselves around reusable diapers. The paucity of data about reusable diapers seems to me a reflection of that particular industry. Manufacture of disposable diapers is a highly technical process about which there is an abundance of engineering, manufacturing, and other data. Not so, cloth diapers. Although, since conventional cotton is also an industry with an abundance of production data, it makes sense that they would focus on data available for conventional cotton in place of data accurately representing the actual range of reusable cloth diapers on the market and in common use. In the conclusions, it is clear that this lack of data about reusable diapers hampered the authors’ ability to make useful comparisons.
Despite that lack of useful comparisons, those who are looking for a quick conclusion go right to the end (which is halfway, since disposable diaper appendices comprise nearly half of the study’s length), and they find a statement that they may or may not realize bears very little relation to the data that comes before. This is the one paragraph that disposable diaper manufacturers use to boost their claims.
Even using the study’s self-acknowledged weak assumptions, the conclusion does not reflect the significant reduction of environmental impact resulting from use of energy-efficient washing, as shown within the body of the report. The study shows that users of home-laundered cloth diapers can reduce environmental impact up to 38% through their laundering choices. Energy rating, washing temperature, and number of diapers laundered have a significant impact on results. This study shows careful laundering can reduce environmental impact considerably.
2008 UK STUDY
The second study is a 37-page addendum to the first: Using Science to Create a Better Place: An updated lifecycle assessment study for disposable and reusable nappies (SC010018/SR2), published October 2008 by the UK Environment Agency. It was funded by the Environment Agency (EA), Department for Environment, Food and Rural Affairs (Defra), all government agencies, and Waste & Resources Action Programme (WRAP), a private not-for-profit company backed by UK government funding with the purpose of developing markets for waste materials. This update was based on new developments in the manufacture of disposable products and updated assumptions about reusable products.
Again, though, the sampling of reusable cloth diaper types and manufacturing methods was too small to be more than generally informative. Though prefold diapers are mentioned, there is no manufacturing data included for them, so the presumably lowest impact reusable diapers were not included in the data. Authors used data for the highest-impact cotton from the farthest away treated with the most extreme chemical inputs. The study does, though, include predicted assumptions of future disposable diaper technologies.
The disposable “lightweighting scenario” in the study was not an assessment of current disposable diapers but a “predicted change.” There was no “predicted change” included for reusable diapers. This is similar to energy comparisons that use the assumed predictions of “clean coal,” scrubbing technology that is not actually yet in use, while still using information about existing technologies of renewable energy, no predicted advances included. Both situations compare the prediction of non-renewables against the reality of renewables.
Note this well. The studies included no research on available data for lowest impact cloth diapers, but they did include predictions for lower impact disposable diapers.
And, again, the study addendum finds that “the impacts for reusable nappies are highly dependent on the way they are laundered.” Reusable cloth diapers only just overlapped with disposable diapers in some, not all, of their graphs.
Life Cycle Assessments (LCAs) are useful in understanding and lowering the impact of one product. Manufacturers use this type of study to improve their own production. When LCA is used for comparison, there are too many variables to result in an accurate comparison. The UK studies tried to control for these variables, but those controls don’t resolve the issues of what impacts count. These are the foundational assumptions inevitable in any study. Compare two such different groups of products, and the assumptions will determine outcomes. Altogether, Life Cycle Assessment (LCA) is not a particularly accurate or helpful way to compare cloth diapers and disposable diapers.
Still, studies can be generally informative, and this study is informative despite its flaws.
Because studies necessarily draw boundaries, it is important to ask what information lacking in the study is still necessary for parents to make informed decisions about diapering. Environmental renewability and availability of petroleum resources are not a consideration in the study. There is no mention of costs and impacts oil and gas exploration or the acquisition, defense, and protection of foreign sources. It is not made clear which industries providing materials for diaper production are subsidized, externalizing even more of their costs. Other studies have raised concerns about the negative impact on babies’ health of disposable diaper use. And, financial costs to parents can be much lower with use of cloth diapers. None of this information is considered as the UK LCA was bounded.
And, what about waste? What are the costs of waste, both financial and environmental? The study does not cover the massive costs of disposable of diapers.
All of these costs would be included if we were genuinely concerned with overall impact of a product. Boundaries allow shifting and hiding of real costs.
Despite all of the flaws, conclusions in the studies remain the same:
- High-impact laundering of reusable cloth diapers means some overlap in environmental impact between reusable diapers and one-time-use diapers.
- Low-impact laundering of reusable cloth diapers means no overlap in environmental impact between reusable diapers and one-time-use diapers.
Authors conclude that the scope for improving disposable diaper impact is with manufacturers, while the scope for improving reusable diaper impact is with those who wash the diapers. They grant no credit for improvement to manufacturers of reusable cloth diapers. That wasn’t one of the parameters they even considered.
The takeaway is obvious: wash with care; care how you wash.
Reusable cloth diapers leave disposable diapers sitting, fuming in the landfill when it comes to real impacts and the way real parents wash their cloth diapers.
How do you lower impacts of reusable cloth diapers?
- Use Energy Star rated washing machines.
- Wash diapers at 140 degrees.
- Air dry.
- Use washable wipes and liners.
- Use low-impact detergent.
- Use organic products.
- Reuse diapers for the next child, then give them away or sell them to another.
Criticisms and recommendations have not changed since Real Diaper Association first published our response to the initial UK study five years ago.
Nevertheless, manufacturers of disposable products continue to misuse these studies to claim that the impact of reusable cloth diapers and disposable diapers is equal. The impact is not equal.
Parents control the impact of cloth diapers through their washing. At worst, there is a slight overlap when you compare highest-impact reusable cloth diapers with lowest-impact future technologies of disposable diapers. That is at worst. At best, even with the flawed data, cloth diapers have 40% less impact than disposable diapers. If the data used were to reflect diapering choices more accurately, the difference would be even more obvious. Cloth diapers have lower environmental impact than disposable diapers.
Do not accept greenwashing. Cloth diapers are the clear winner.