Salsa hack: 50% recycled glass mix boosts cilantro, pepper, jalapeño plant growth

Julie Vanegas, a nanomaterial scientist at The University of Texas Rio Grande Valley (UTRGV), and her team have pioneered this sustainable farming method. Vanegas was paired with ecologist Teresa Patricia Feria Arroyo, who has extensive experience in food security and sustainability. 

Their collaboration began with Vanegas’s work on using recycled glass for coastal restoration projects, such as growing willow trees. This led Feria to question whether glass could also be used for growing produce. Together, they devised experiments to test this hypothesis using common garden vegetables ideal for container and backyard gardens, such as those needed for pico de gallo.

Benefits and findings of recycled glass cultivation

The researchers sourced recycled glass particles from a company specializing in diverting bottles from landfills. The glass is crushed and smoothed to ensure safety for both users and plants.

Initial tests evaluated the soil-like properties of different glass fragment sizes, including their compaction, water retention, and oxygen permeability. The study found that fragments resembling coarse sand grains were particularly effective in providing optimal conditions for plant growth.

Andrea Quezada, a chemistry graduate student in the Nanoworld Vanegas lab, is presenting the team’s findings at the American Chemical Society (ACS) Fall 2024 meeting, held from August 18-22. The research suggests that glass-based soils could transform agricultural practices, particularly in the Rio Grande Valley and beyond. 

Quezada notes, “We’re trying to reduce landfill waste at the same time as growing edible vegetables. If this is viable, then we might be able to introduce glass-based soils into agricultural practices for people here in the Rio Grande Valley and across the country.”

In their experiments, the researchers found that a glass-to-soil ratio exceeding 50% significantly enhanced plant growth. In an interaction with Interesting Engineering (IE), Vanegas explains, “The optimal ratio of recycled glass to soil for maximizing plant growth and water retention was determined through a pilot study. This study prepared several samples with varying percentages of soil and recycled glass.” 

“The results indicated that samples with higher concentrations of recycled glass demonstrated significantly enhanced plant growth. While the project is tied to a developing patent and specific details cannot be disclosed, I can share that those concentrations exceeding 50% recycled glass showed the most substantial growth.”

Vanegas also points out that a forthcoming paper will detail how the shape and chemical composition of the recycled glass, including elements like sodium and iron, contribute to plant growth. This research initially focused on Gulf Coast restoration but has significant agricultural applications.

Challenges and future prospects

The research team encountered several challenges during their experiments. Maintaining plant health and managing fungal growth were key issues.

“During our pilot tests, we encountered several key challenges related to maintaining plant health and managing fungal growth. One of the main issues was ensuring that the recycled glass did not introduce any harmful effects on the plants, such as altering the pH levels of the soil or affecting nutrient absorption. Additionally, we observed instances of fungal growth, which posed a risk to the overall health of the plants,” Vanegas told IE.

To address these issues, the researchers closely monitored soil pH and nutrient levels and implemented antifungal treatments. Explaining it to IE, Vanegas added, “We introduced specific antifungal treatments and improved soil aeration techniques to create an environment less conducive to fungal proliferation.”

As a result, the scientists able to mitigate the risks associated with fungal infections and maintain the health of the plants throughout the experiments. This ultimately led to the positive results the team have achieved so far.

Quezada is currently testing the effectiveness of recycled glass as a soil substitute in a greenhouse. Preliminary results suggest that plants grown in a mixture with more than 50% glass exhibit faster growth and better water retention than those in 100% traditional soil.

Remarkably, pots with recycled glass showed no fungal growth, while those with only potting soil developed fungus that stunted plant development. Quezada emphasizes the broader implications of this research, particularly for agricultural communities.

“I think it’s really important to try to minimize the usage of any chemicals that can negatively affect our health,” she says in the press release. “If we are able to reduce them, and help the community by collecting recyclables, then we can give people a better quality of life.”

In the future, the team intends to broaden their research and conduct additional field trials. Their objective is to establish glass-based soils as a widely accepted and sustainable agricultural solution. They aim to improve soil health, conserve resources, and support a circular economy by advancing innovative recycling practices.