Glass Soil Amendments

Yes, you can use crushed/pulverized recycled glass sand with compost or soil. Glass mulch is a commonly used synthetic, or inorganic mulch. Using tumbled glass mulch made from used glass bottles, old windows, and other glass products keeps glass out of the landfills. The ground, tumbled glass, which may display minor flaws common to recycled glass, is available in various shades of amber, blue, and green. Clear glass mulch is also available.

Tumbled glass mulch has no jagged, sharp edges, which makes it useful for a variety of uses in landscaping including pathways, fire pits, or around potted plants. The mulch works well in beds or rock gardens filled with plants that tolerate rocky, sandy soil. Landscape cloth or black plastic placed under the glass keeps the mulch from working its way into the soil. Using landscape glass as mulch tends to be relatively expensive upfront, but the low maintenance and longevity help balance the cost.

Yes, you can use crushed/pulverized recycled glass sand with soil to grow things better. A comparative life cycle assessment (LCA) completed in 2019 demonstrated that recycled glass sand may reduce greenhouse emissions by 67% compared to virgin sand. A 2019 pilot greenhouse trial showed that glass-based soils supported plant growth as well as a control mined-sand mix.

The glass sand is easy to compact and mix with other materials. When mixed with compost and soils, this is great for drainage layers and backfills. The filtration rate for glass sand aggregate is up to ten times faster than natural aggregates. So, using crushed/pulverized recycled glass sand with soil can be a good way to grow things better.

Science Lesson: Silicon Dioxide (SiO2) is the next most common molecule on our planet, after H2O. It has three phases: crystalline, amorphous, and molten. Glass is amorphous silica, and a liquid; it just does not flow at room temperature. 

Plants need water to grow: Amorphous silica has a negative charge on the surface and will attract and retain water on the surface of the glass, making it available to the plants for their use.

Plants need silicon dioxide to grow: Making the SiO2 available in the amorphous/liquid form, instead of the crystalline form, will make it easier for the plants to absorb and metabolize into their plant structure.

Recycled glass sand surface area: In a fine granular form, glass has a lot of surface area with the available SiO2 the plants need for their growth.

Particle shape and properties: Recycled glass that is processed and sized into an angular particle size will provide superior filtration properties and will not break down over time. Glass is inert and the water will not leach minerals or break down the particles over time.

Recycled Engineered Soils: Mixing the glass sand with compost will provide an engineered soil with the nutrients available from the compost, mixed with the glass particles that provide water retention, and structural integrity.