Water quality issues and life-cycle energy consumption of glass container recycling in New Jersey

Alternative uses of cullet (crushed recycled glass containers) that is difficult to use as feedstock in new glass container production have grown rapidly. The cullet is mainly used as aggregate in construction projects and in landfills as daily cover, drainage layer, or road pavement. Despite the increasing use as aggregate, it is unclear if this practice is environmentally sustainable. In the first part of this study, water quality issues associated with this practice are assessed. Glass cullet that is stockpiled uncovered before use as aggregate can release leachate to the surrounding environment. Leachate is generated from rainwater that has percolated through the cullet stockpile and dissolved and suspended some of the contaminants, such as food/beverage residuals and paper. Field stockpiles were constructed to monitor leachate quantity and quality as well as to evaluate the cullet treatment within the stockpiles. The results of the leachate characterization showed that leachate is a potential source of water pollution. The analyzed pollutant levels were in most cases comparable to or higher than those of untreated domestic wastewater or urban stormwater. Both mechanical turning and forced aeration of cullet stockpiles can enhance the degradation of the organic constituents inside the stockpiles. However, active aeration needs to be combined with mechanical turning to be effective. The second part of the study assesses the life-cycle energy consumption associated with glass container recycling including its different end uses. A material flow and energy analysis quantifies glass container flows used and discarded in 2008 in New Jersey and its associated energy consumption from raw material extraction to final use and disposal. The results of the analysis showed that about five times more (255,600 tons) recycled glass containers were used as aggregate compared to use as feedstock in glass container or fiberglass production. Most likely this can be attributed to the quality of the cullet that cannot meet the industry specifications. However, the energy analysis confirmed the benefit of use as feedstock in glass container or fiberglass production. To allow the use of cullet as feedstock in glass container production, the quality of the cullet must be improved.Ph.D.Includes bibliographical referencesIncludes vitaby Ching-Ling Tsa