The environmental impact of cloth nappies compared to disposable nappies, from the Life Cycle Assessment by the University of Queensland in 2009.
This study considered the 'life cycle' impact: from the growing of cotton (for the cloth nappies) and timber (for the wood pulp used in disposables), the manufacture of the nappies and transportation, through to use (including water & energy used in washing cloth nappies) and disposal.
- Kimberly-Clark Australia (manufacturer of Huggies) supplied most of the data regarding disposable nappies.
- Different average number of nappy changes a day were used to reflect the fact that many people change disposables less frequently than cloth: The study considered low to high impact figures depending on the number of nappy changes. The low impact figure for disposables was 4 changes a day (compared to 5 for cloth) and for high impact - like at the newborn stage - 7 changes a day (cloth was 9).
- As far as water & energy used in washing cloth nappies, the study included the difference in the total energy used in home washed nappies if you use hot water compared to cold, and a top loader compared to a front loader, and also examined the difference between home washing and using a nappy service.
- The study considered nappies made of cotton fabric only. Hemp and bamboo fabrics are generally considered more environmentally friendly crops to grow (using less water, pesticides and land space).
- The researchers included covers (of the plastic pants variety) in their energy/water/waste figures for cloth nappies.
- The costs for the cloth nappies included energy & fuel transportation costs assuming the cotton would be grown in Australia, transported to Asia for processing and milling into fabric, and shipped back to Australia.
- Disposable nappies are composed of 40% cellulose (wood pulp), with Australian pine forest plantations the source.
- Pulp production is responsible for 75% of the non-renewable energy required over the life-cycle of disposable nappies, even though 46% of energy used in pulping is renewable.
- Home-washed reusable nappies were found to use less non-renewable and total energy over the life cycle than any other nappy system, regardless of the number of nappies used, the mass of nappies, or the type of washing machine.
- Reusable nappies washed in a top-loading washing machine were found to use more water than disposable nappies or reusable nappies washed in a more efficient front-loading machine.
- Water resource depletion associated with the softwood production for disposable nappies was higher than for the cotton growing stage of home-washed nappies. This is despite the fact that forestry is typically much less water intensive (on a per-area basis) than cotton growing – indicating that it was the much larger mass of raw material required for the production of disposable nappies over the 2.5 year lifecycle that was the driver for this result.
- The study assumed that cloth nappies would be soaked in warm water and noted that "heating water for soaking nappies consumes 30-56% of the energy used over the life cycle of home-washed reusables" and that "using solar water heating could substantially reduce the non-renewable resource depletion. More energy is, and hence more greenhouse gas
emissions generated, if the nappies are tumble-dried or washed in hot water, particularly if a solar hot water system is not used."