Scientists use recycled glass to grow plants without fertilizers, pesticides or fungicides

Tortilla chips and fresh salsa are already delicious, but imagine how much more satisfying they could be if the ingredients were grown sustainably. You might not think about it while enjoying cilantro, bell peppers, and jalapeños, but the way these ingredients are cultivated can make a significant difference.

In a recent study, researchers discovered that these essential salsa ingredients could be grown in a more environmentally friendly way by using recycled glass from discarded bottles, like those from beer or soda, as a partial substitute for soil.

The findings showed that this method not only speeds up plant growth but also reduces unwanted fungal growth, offering a potential new approach to sustainable agriculture.

This innovative research is being presented at the fall meeting of the American Chemical Society (ACS). The meeting, a hybrid event with both virtual and in-person sessions, features around 10,000 presentations covering a wide range of scientific topics.

The idea to use recycled glass in agriculture began when nanomaterial scientist Julie Vanegas, who had recently joined the faculty at The University of Texas Rio Grande Valley, was paired with faculty mentor Teresa Patricia Feria Arroyo.

Feria, an ecologist focused on food security and sustainability, became intrigued when Vanegas mentioned her work assessing recycled glass particles for coastal restoration projects, such as growing willow trees. This led Feria to wonder whether glass could also be used to grow produce. To explore this possibility, they designed experiments using foods that are familiar, quick to mature, and suitable for container or backyard gardens—specifically, the ingredients for pico de gallo.

“We’re trying to reduce landfill waste while also growing edible vegetables,” explains Andrea Quezada, a chemistry graduate student in the Nanoworld Vanegas lab who is presenting the team’s research at the ACS meeting. “If this approach proves viable, we could introduce glass-based soils into agricultural practices not only here in the Rio Grande Valley but across the country.”

For their experiments, the researchers sourced recycled glass particles from a company that diverts bottles from landfills. These bottles are crushed into particles and tumbled to smooth out any sharp edges, making the glass fragments safe to handle. Plant roots can grow around these smooth glass pieces without being harmed, which is a key feature for their use in agriculture.

In the initial tests, the team assessed the soil-like properties of the glass fragments, such as compaction and water retention, using three different sizes of particles. They found that glass particles similar in size to coarse sand grains had the best characteristics for plant growth, including good oxygen flow to the roots and adequate moisture retention.

As ACS explains in this video, putting recycled glass to use as a sustainable soil amendment could help address three problems:

Preliminary results indicate that plants grown in recycled glass tend to grow faster and retain more water compared to those grown in traditional soil. “A weight ratio of more than 50% of glass particles to soil seems to be the best for plant growth compared to other mixtures we tested,” says Vanegas. However, the team is waiting until harvest time to confirm which soil mixture yields the highest output and tastiest produce.

Currently, Quezada is testing the effectiveness of recycled glass as a soil substitute in a campus greenhouse. She’s growing cilantro, bell pepper, and jalapeño plants in various pots, some containing 100% commercial potting soil and others with varying proportions of recycled glass. While pots with more soil have higher levels of essential nutrients like nitrogen, phosphorus, and potassium, the glass-soil mixtures showed consistent pH levels—a promising sign, as plants generally thrive in a narrow pH range.

One particularly surprising result was the absence of fungal growth in pots containing any amount of recycled glass. In contrast, pots filled with 100% potting soil developed a fungus that stunted plant growth, likely by interfering with nutrient uptake by the roots. Feria is intrigued by this finding and the team is currently gathering data to understand why the glass-soil mixtures might inhibit fungal growth.

These findings are especially exciting for Quezada, who is passionate about sustainable agriculture. The study was conducted without the use of fertilizers, pesticides, or fungicides—chemicals that often have negative impacts on the health of farm workers and nearby communities.

“From my experience working in agriculture, I know that many chemicals used in farming can affect people, like my family members, who work or live near these areas,” Quezada says. “It’s important to try to minimize the use of harmful chemicals. If we can reduce them and also help the community by collecting recyclables, we can improve people’s quality of life.”

The use of recycled glass in agriculture represents a promising step toward a more sustainable future. By reducing waste and avoiding harmful chemicals, this approach could provide a healthier environment for both plants and people. As the team continues to refine their methods and analyze the results, they are hopeful that their work could lead to widespread adoption of glass-based soils, benefiting communities both locally and beyond.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

Like these kind of feel good stories? Get The Brighter Side of News' newsletter.