Life-cycle assessment, comparison of biopolymer and traditional diaper systems

Growing space problems accompanying urbanisation and rise in the standard of living have motivated the development of measures to reduce waste production. One such measure is the development of biodegradable materials which can be treated in com-posts and so recycled. A lot of valuable space is thus saved. The polymer discussed in this study is also made from renewable raw-material, which increases its attraction and makes it particularly interesting from the life cycle point of view. The landfill capacity saved is counterbalanced by land needs and emissions of agricultural production. Thus, an objective judgement on the environmental performance of such a product needs to be based on its whole life cycle. In this study the environmental impacts of a new bio-polymer product over its whole life cycle were assessed and compared to those of a conventional plastic product. The study is built on diaper products, because they are assumed to have a significant role in the growth of the future markets of biodegradable materials. The biodegradable polymer, polylactide, is based on lactic acid produced by fermenta-tion from carbohydrate sources. Consequently, the appropriate system extends to agri-cultural production. The life cycle of conventional plastic starts from crude oil produc-tion and refining. Both product systems include the production of the diaper with its components. The phase of waste management comprises biological treatment, incinera-tion and landfilling as alternatives. Several scenarios were formed to study the effects of variable options in the life cycle of diapers, especially in that based on the new product. The characteristic variables chosen for the scenarios were technology, waste utilisation intensity, location and raw materials. Geographical or agricultural policy aspects were not considered. An important outcome of the study is that differences between the impacts of the tradi-tional and the biodegradable diaper systems are small. The fluff component (70%) of the diaper turned out to be dominant in most environmental stressors. In most scenarios a polyolefin based diaper is slightly better, but the results are not far from each other. The most important phases in the life cycle of polylactide are agricultural production and fermentation to lactic acid. The biodegradable diaper waste can be converted into compost products, which can be used to enhance soil quality and partly to substitute mineral fertilisers. Thus, the amount of landfill waste is substantially reduced. Another advantage is that the biopolymer made of annually renewable raw-material. In the pro-duction chain of conventional plastic the most important impacts are hydrocarbon emis-sions to air and water. Because polyolefin products cannot be composted, the only pos-sible way of saving landfill capacity by waste treatment is incineration. The results vary greatly according to scenario parameters. It should also be taken into account that the whole biopolymer chain is still under development, which obviously adds the uncertainty of the results obtained for the PLA system.