Date of Award

Fall 11-5-2024

Document Type

Thesis

First Advisor

Dr. Edward Bush

Abstract

Louisiana’s coastal land loss results from complex interactions of anthropogenic and naturally occurring processes that impact sediment supply in the Mississippi river delta. Given the coastline's vital role in the state’s economy, Louisiana has made significant investments in coastal restoration projects, including planting native vegetation and adding borrowed sediments. The amount of sediment needed to maintain Louisiana’s existing coastline exceeds the available amount that could be extracted, and state officials have since identified this lack of sustainable sediment resources as a critical limitation for future restoration projects. One proposed solution to address this shortage is using recycled crushed glass cullet (RCGC), a sand-like material that is produced by grinding recycled glass bottles into particle sizes comparable to native sands.

However, additional research is necessary to evaluate the safety and suitability of RCGC for use in coastal restoration applications. Previous studies demonstrate that RCGC does not pose additional harm to aquatic life or vegetation communities. Building on prior feasibility studies, this work provides a more comprehensive assessment of how the native dune-building grass called bitter panicum (Panicum amarum) grows when asexually propagated in mixtures of crushed glass sand. We created five soil mixtures using varying amounts of RCGC to mason sand as the control (0%, 25%, 40%, 65%, and 80%) and added 20% peat moss by volume in all treatments to enhance water-holding capacity. In March, we planted bitter panicum cuttings in containers filled with these mixtures (45 plants per treatment) and arranged into a complete randomized block design in an irrigated plant nursery. From late March to early August, we measured plant height weekly, then assessed dry biomass for a subset of plants in August.

The results indicate that bitter panicum can be successfully propagated directly into mixtures containing RCGC. In treatments containing up to 80% RCGC, there were no significant negative effects for height (cm) or biomass (g). Additionally, there was evidence suggesting a slightly positive effect on growth parameters at higher RCGC concentrations. These findings support the safety and viability of using sand made from recycled glass as an alternative fill material for coastal restoration. By leveraging post-consumer recycled materials, use of RCGC addresses multiple sustainability goals: reducing dependence on finite sources of borrowed sediment and diverting glass waste from landfills through local recycling initiatives.

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