Possible environmental impacts of recycled glass used as a pavement base material

In theory, glass diverted or recovered from the municipal solid waste (MSW) stream can be used as feedstock (glass cullet) in the production of new glass containers. However, post-consumer glass typically contains a mixture of clear and coloured material and is often contaminated with other wastes; characteristics that are impediments to the production of new containers. Sorting and cleaning of glass diverted from MSW to make it feasible for use in bottle industries are also time consuming and costly tasks. There is, however, the potential to use recycled glass as a sub-base material for road pavement construction. Geotechnical investigations to date suggest that use of recycled glass as a roadway sub-base could be cost-effective, and thus preclude the need for expensive sorting. There is, however, the necessessity to further investigate the potential short- and long-term toxicity, health hazards, and/or environmental pollution associated with use of mixed glass cullet as an aggregate, considering conditions during stockpiled storage and after placement. The results of laboratory tests on recycled glass regarding its potential to release pollutants to the environment via leaching are presented herein. Five random samples of crushed glasses were collected from a recycling company in Melbourne, Australia. The parameters tested for each sample were total organic matter, heavy metals, sulfates, chlorides, conductivity, pH and surfactant levels. It wais found that in most cases, the contamination levels were within the State of Victoria's Environmental Protection Agency-specified limits for manual handling, thus indicating that recycled glass could probably be safely used in pavement sub-bases.