The construction and demolition industry in the United States produces an extraordinary amount of waste, estimated by the EPA to be around 160 million tons per year. While most current waste management solutions focus on new construction and demolition, little is being done in renovation, where the smaller average project size creates significant cost barriers to designing and implementing a waste management solution. In order to address this issue, they have identified a key material with significant recycling potential in this problem space: window glass. While bottle glass is easily recyclable, window glass is frequently coated in a thin metal oxide film that absorbs certain UV wavelengths and helps regulate temperature at the cost of rendering the glass unrecyclable. In order to recycle the 320,000 tons of window glass that are thrown out each year in the U.S., there needs to be a process for removing this coating.
RENTEC proposes developing and implementing a chemical process that will remove the coating in a cost-effective and environmentally-friendly manner, designed in such a way that all process streams can be recycled back into their process units and no hazardous bi-products result. In the first phase of the process, an organic solvent will be used to clean the window glass and remove any impurities before the treatment phase begins. In the treatment phase, they propose using hot hydrogen chloride vapor to initiate the desorption of metal oxides from the glass. This step brings the coating components to the surface of the glass, where a water bath will dissolve them, leaving cleaned glass ready to be recycled by the conventional process used on other glass. They believe that a process with strong economic and environmental considerations such as this one will add value to the recycling industry and help divert a significant quantity of glass waste from landfills.
