Developmental Investigation of Recycled Color Mixed Glass in Engineered Soils

This project will develop an engineered soil product and process that repurpose waste-stream glass into soil suitable for horticultural and green infrastructure projects. The project supports the EPA's goal to improve sustainable materials management. Recycling of solid waste materials, like glass, remains challenging to cities due to costs of recycling in comparison to landfill disposal. Process costs for glass cullet have increased, while products made from cullet have marginal commercial value. This makes glass recycling economically non-viable for most cities. A practical solution for converting local solid waste to local usable infrastructure effectively is therefore critical to improving use of recycled materials. OLIN is partnering with the City of Philadelphia to significantly reduce the landfilling of glass. The project will develop an engineered approach to converting glass waste into a refined soil product that can serve the needs of the city in urban development of green spaces. The technology consists of an engineered soil, and an engineered process plan, that cities can implement to utilize pulverized glass, soil, and amendments, to produce a clean, functional, soil product with demonstrated plant growth, and water draining potential comparable to sand-based soil blends. By replacing sand with pulverized glass, the project addresses shortages of construction-grade sand, and the costs of sand use in soil preparations. This efficiency is further improved by facilitating local processing, soil blending and installation, improving the value for mixed-color, small-particle glass cullet. The comparative life cycle assessment (LCA) that our team completed in 2019 demonstrated that recycled glass-sand may reduce greenhouse emissions by 67% compared to virgin sand. A Phase I greenhouse study assessed horticultural performance and found it to be comparable to that of sand-based soil. A Phase I Technical Plan proved the economic benefits of diverting municipal glass waste to glass-based soil production. A 2021 material analysis, and mesocosm study tested the material�s infiltration performance and leachate, critical to maintaining water quality in urban green stormwater infrastructure (GSI) and found glass-based soil to be a feasible alternative to conventional GSI soil. By creating a workable, engineered plan for municipalities to cost effectively repurpose glass waste streams for local production of glass-based soil products, this project will reduce need, and therefore environmental impact, of sand mining, while significantly reducing city landfilling costs for glass. The market for this product and process includes all urban and suburban regions that are focusing efforts on green space development and water management.