Assessing the feasibility of biodegradable diaper alternatives for sustainable waste management

Abstract

The growing environmental burden of plastic waste has become a global concern, particularly in low- and middle-income countries, where inadequate waste collection systems contribute to uncontrolled dumping. A significant proportion of household waste in these regions consists of disposable diapers, which are composed of non-biodegradable polymers such as low-density polyethylene (LDPE), especially in the backsheet layer. These plastics can persist in landfills for over 500 years, raising urgent concerns around long-term environmental sustainability. Despite increasing awareness, there remains a critical gap in identifying and validating biodegradable polymer alternatives that can maintain product functionality while reducing ecological impact. This dissertation aims to investigate and evaluate polylactic acid (PLA) as a viable biodegradable substitute for LDPE in disposable diaper backsheets. The study comprises two components: a literature-based review (Article 1) that assesses commercially available biodegradable polymers for diaper applications, and an experimental investigation (Article 2) that characterises the backsheets of three commercial diapers and compares their thermal, morphological and biodegradation behaviour to that of PLA. In the review, PLA emerged as the most promising candidate due to its commercial availability, cost-effectiveness, and favourable processing characteristics relative to other biodegradable polymers such as polyhydroxyalkanoates and polybutylene succinate. However, its brittleness limits its direct use in flexible films such as diaper backsheets. The literature highlights modification strategies, including blending, plasticisation, and reinforcement, to enhance the ’mechanical properties of PLA. The experimental study employed differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron, and soil burial biodegradation testing. Diaper C, which contained cellulose-infused PE, showed altered thermal and surface properties compared to conventional LDPE backsheets but did not significantly improve biodegradability. The cellulose degraded early during composting, while the polyethylene matrix remained intact. In contrast, PLA demonstrated lower decomposition temperatures and gradual biodegradation over time, confirming its classification as a compostable polymer. The growing environmental burden of plastic waste has become a global concern, particularly in low- and middle-income countries, where inadequate waste collection systems contribute to uncontrolled dumping. A significant proportion of household waste in these regions consists of disposable diapers, which are composed of non-biodegradable polymers such as low-density polyethylene (LDPE), especially in the backsheet layer. These plastics can persist in landfills for over 500 years, raising urgent concerns around long-term environmental sustainability. Despite increasing awareness, there remains a critical gap in identifying and validating biodegradable polymer alternatives that can maintain product functionality while reducing ecological impact. This dissertation aims to investigate and evaluate polylactic acid (PLA) as a viable biodegradable substitute for LDPE in disposable diaper backsheets. The study comprises two components: a literature-based review (Article 1) that assesses commercially available biodegradable polymers for diaper applications, and an experimental investigation (Article 2) that characterises the backsheets of three commercial diapers and compares their thermal, morphological and biodegradation behaviour to that of PLA. In the review, PLA emerged as the most promising candidate due to its commercial availability, cost-effectiveness, and favourable processing characteristics relative to other biodegradable polymers such as polyhydroxyalkanoates and polybutylene succinate. However, its brittleness limits its direct use in flexible films such as diaper backsheets. The literature highlights modification strategies, including blending, plasticisation, and reinforcement, to enhance the ’mechanical properties of PLA. The experimental study employed differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron, and soil burial biodegradation testing. Diaper C, which contained cellulose-infused PE, showed altered thermal and surface properties compared to conventional LDPE backsheets but did not significantly improve biodegradability. The cellulose degraded early during composting, while the polyethylene matrix remained intact. In contrast, PLA demonstrated lower decomposition temperatures and gradual biodegradation over time, confirming its classification as a compostable polymer. The combined findings underscore that partial material substitution, for example, adding cellulose to LDPE, is insufficient to address the environmental impact of diaper waste. PLA-based backsheets offer a more effective alternative, with the potential to reduce long-term waste accumulation. However, successful implementation will require material innovations, supportive policy frameworks, and increased consumer and industry engagement, especially in low- and middle-income countries where waste management infrastructure is limited. This dissertation contributes valuable knowledge toward the development and adoption of biodegradable diaper materials and lays the foundation for future research on improving the performance of sustainable polymers in hygiene applications.