A Vanderbilt University professor and two undergraduate students in the School of Engineering are participating in an innovative research project that aims to use recycled glass to enhance building materials and infrastructure as well as reduce waste.
Juniors Emily Zeller and Nicole Witherell, both civil engineering majors, and research adviser Ravindra Duddu, an associate professor of civil and environmental engineering, are collaborating with the University of Alabama on the “Bottles to Bricks” project.
In 2018, the U.S. Environmental Protection Agency estimated that a total of 12.3 million tons of glass, roughly four percent of all municipal solid waste, was generated in the United States. Of that amount, only about 31 percent was recycled. Moreover, the amount of waste glass has gradually increased since 2018, due to an ever-growing use of glass products, and more waste glass being dumped in landfill sites.
“This is undesirable towards reaching a sustainable or environment-friendly consumer practice, as waste glass is not biodegradable and perhaps a safety hazard,” says Duddu. “Therefore, there is a need for developing solutions to use waste-glass materials and reduce their proliferation in landfills without resorting to expensive recycling.”
As a possible solution, the project seeks to use waste glass in construction, which researchers say can address the global need for advanced, multifunctional building materials, either as load bearing units or as cladding. Additionally, waste glass could be incorporated into building materials for either new high-performance construction or to repair and enhance the performance of existing structures.
The project goal is to develop a versatile building product, known as concrete masonry unit or simply concrete block/brick, which can incorporate waste glass at large weight fractions without significantly impacting its overall strength or performance. Thus, waste glass can be repurposed into a usable ingredient for typical concrete mixes by crushing or grinding unrecycled glass. Previously, glass has been successfully used in asphalt concrete mixtures as a partial aggregate replacement, as well as a fine aggregate in pipe bedding, landfill-gas venting systems, and gravel backfill for drains.
The University of Alabama team, led by Professors Sriram Aaleti and Armen Amirkhanian at the Center for Sustainable Infrastructure, is focused on mix design and strength/durability testing of the concrete bricks, while the Vanderbilt team is engaged in social and economic impact analytics, particularly how glass is recycled in Nashville and other major metro areas in the South. For instance, it costs about $40 per ton of glass to recycle it in Nashville, compared to $38.50 to put it in a landfill, which is frequently the destination because of the cheaper cost. However, these cost estimates do not include the externalities related to pollution and other negative environmental impacts.
“There are a lot of cities that do it better than us, and I think that we can definitely step it up,” says Witherell of recycling in Nashville.
If nothing else, Zeller says she hopes the project creates awareness about glass recycling in Nashville, and in general.
“People don’t know how little glass is recycled,” says Zeller. “Glass is 100 percent recyclable, so it doesn’t make sense to take up the space in landfills if we don’t have to.”
Funding support for the project is provided by Good Molecules, LLC.
Contact: Lucas Johnson, 615-343-0137
lucas.l.johnson@vanderbilt.edu