Before I became a parent the one question that everyone asked me was whether or not I would use disposable or reusable nappies. As an environmentalist, the natural assumption was that I would use reusables because reusing materials is good for the planet. After all, disposable nappies make up around 2-4% of UK household waste – that is 2-4kg out of every 100kg disposed – which in turn leads to an incredible nappy mound growing by 400,000 tonnes a year bubbling beneath the surface of our green and pleasant land (WRAP, 2013). Being a responsible parent should surely mean that I should therefore do something about this poo mountain silently polluting our landscape and waiting to take over the world… right? Like most things in the sustainability space, it turns out this is a bit more complicated than the single factoid bantered around on blogs.

The list of environmental issues and questions could be endless, but being busy means that we don’t have the time to necessarily look into each one. Personally, I’ve decided to look at most things through the carbon footprint lens because, for me, climate change is the most important environmental challenge facing my family and I believe carbon is a good indicator to use for other environmental issues.

Using just the carbon footprint as the deciding factor helps focus our questions on a specific output since it provides a number that will either be better or worse than another option.

Life Cycle Thinking

Life_Cycle_Thinking_Product_System

Image: Life cycle thinking (National Institute of Standards and Technology (NIST))

There are many different standardised ways to calculate a carbon footprint and the underlying method consistent with all of them is the use of something called life cycle assessment. This type of thinking asks us to consider the impacts of a product  for each part of a product’s life from raw material production to your use and disposal of them.

Life cycle thinking is an important process to go through as it helps show us where we should be concerned and focused for managing our own impacts. In the case of nappies, we’re fortunate to have quite a robust study commissioned by the UK Department for Environment, Food and Rural Affairs (Defra) and the Environment Agency that does just this and goes even further by including metrics beyond just carbon (e.g. ecotoxicity).

The UK government commissioned two life cycle assessment studies concerning the use of nappies. The first one, commissioned in 2002, took more than 3 years to complete and involved surveys of more than 1,000 households to determine how people used and disposed of both disposable and reusable nappies over an estimated 2.5 years worth of coverage from birth to toilet training. The results showed that there was negligible difference between the two formats from a carbon perspective, with a slightly higher footprint being associated with reusables due to the energy required to wash and dry the nappies. A number of groups immediately challenged the results because it diluted one of their core messages: reusables are always better than disposables.

Environmental groups rebel

The strong public backlash to the study led to a follow up analysis in 2005 to take account of changes to the sector and allow for alternatives to the assumptions used in the original by presenting 10 different use scenarios. For example, what happens if people wash their nappies below 60 degrees (which happens to go against health advice) or if they always line dry their nappies outside instead of putting them in a tumble dryer? The results of this new study were then presented in 2008 and the outputs were basically the same… there is no material difference in the carbon footprint between either method when using the most likely behaviours of people using reusable nappies; the primary difference between the two formats is in where the impacts are occurring, with the manufacturer for disposables and with households for reusables. However, as multiple scenarios were assessed, the best case scenario, which the authors state should be considered “extreme rather than general practice”, said that reusables could have a 40% carbon savings over the 2.5 years a child is in nappies if they are washed in full loads, always line dried outside and worn by a second child. The disposable format was also reassessed and although the numbers were slightly lower than before, the overall picture of them being roughly equivalent to reusables over their life from a carbon perspective remained.

After the results of the new study were announced the same groups that were previously so skeptical of the study embraced it in its full glory around the basic, unchanged, fact that the authors noted: parents using reusables have “control” over the environmental impact of nappies. Oddly enough, these same proponents ignore the rest of the paper where the authors demonstrate that this control could easily lead to reusables being worse should you undertake non-standard washing methods (e.g. washing at 90). If this occurs the carbon footprint of using reusables could increase by 75% and thus be far worse than using disposables.

Carbon footprint of using nappies for 2.5 years

Reusables – high wash temperatures and tumble drying (993 kgCO2e) 174%
Reusables – average behaviour (570 kgCO2e) 100%
Disposables (550 kgCO2e) 96%
Reusables – eco behaviour (342 kgCO2e) 60%

It is important to note that these studies are specifically for the UK market and the specific impacts of both products will be different in other countries (e.g. in France electricity is mostly produced from nuclear energy, which has a very low carbon footprint, whereas the UK uses more fossil fuels). Additional studies have also been carried out by manufacturers and universities, but the conclusions are basically the same.

Does it really matter which is “better”?

For arguments sake, we’ll ignore the evidence that says that for the majority of the population there is almost no difference in the carbon footprint of using either format and say that you can save 40% of the footprint by using reusables over disposables (as some organisations do). Even in this scenario it turns out that this savings isn’t very much at all: approximately 200kg CO2e.

driving to aberdeenThis amounts to a fraction of the average UK household footprint over this same period (~65,000 kg CO2e over the 2.5 years a child is in nappies) and equates to driving about 620 miles in an average car.

In other words, the amount of carbon savings that could be achieved by using renewable nappies over disposables in the most “extreme” scenario will save the same amount of carbon as taking one less road trip from Plymouth to Aberdeen… or cycling instead of driving for two weeks… or one flight from London to Rome (one way, one person).

So what did I decide to do? Well this environmentalist chose to use the most environmentally friendly disposable nappy I could find. One that uses renewable resources (from certified sustainable sources!) and is biodegradable (even though they probably will not biodegrade in landfill). Is it the most environmentally friendly thing a parent can do? No. But neither is using reusable nappies.

It turns out there are a lot bigger issues out there for parents to face. Contrary claims being made by some, the decision related to what nappy you will use for your ecobaby is nowhere near the “biggest environmental decision a new parent faces“. With every other choice, challenge and change that comes with being a parent, the decision about whether it is more responsible to use reusables or disposables is hardly worth the time of day in my opinion. Regardless of the system you use, there are opportunities for savings.

I will discuss the good things to look for in disposable nappies in another post, but to sum up the key things you can do to lower the impact of using reusables: (1) wash in fuller loads, (2) outdoor line dry after washing, and (3) reuse nappies on more than one child.