The 2025 PHS Flower Show installation is the culmination of over a decade of research and collaboration between OLIN Labs, local partners and national funders. Since 2011, OLIN Labs has been investigating the use of alternative materials in its soil specifications to improve overall soil sustainability. Through numerous greenhouse trials, studies, and literature reviews, research determined the suitability of glass-sand to support healthy plant growth. OLIN Labs began collaborating with local partners Bottle Underground and Bennett Compost to produce locally-sourced glass-sand combined with food-waste compost, and also biochar, drawing upon concurrent Labs research supported by the EPA and USDA. The glass-based soil has been tested through in-situ installations, in several OLIN built projects. The beautiful creations of Remark Glass included in the installation are made from the same upcycled glass as the glass-sand.

Why Does this Matter?

Soil is foundational to creating thriving gardens and landscapes, but its environmental footprint is often overlooked.

The sourcing and extraction of soil components, such as topsoil, sand, and organic matter like peat moss, are associated with negative environmental, social, and human health impacts worldwide. It depletes non-renewable materials formed over hundreds to thousands of years, contributes to soil erosion, nutrient depletion, and habitat destruction, and causes significant water, air, and noise pollution.

What if we could create a soil with the same performance as conventional soils while simultaneously reducing these negative impacts?

Our vision is a future where Circular Soil transforms landscapes of all sizes—from backyard gardens to public parks and green stormwater infrastructure projects—throughout Philadelphia and beyond, fostering robust ecosystems, enhancing biodiversity, and diverting reusable materials from landfills.

Components

Glass-Sand

Glass waste is crushed and sieved to create sand, a critical component of engineered soil blends, is one of the most heavily extracted materials on the planet. In many parts of the world, construction-grade sand is running out, and its extraction disrupts ecosystems. Meanwhile, approx. 7 million tons of glass is landfilled in the U.S. annually. OLIN Labs, along with Bottle Underground and other local partners, developed a glass-based horticultural soil that reduces reliance on mined sand while matching the performance of sand-based soil.

See more about Lab’s Circular Soil research here: https://olinlabs.com/soil-less-soil

Food-Based Compost

Food waste is combined with oxygen, water and microbes to break down scraps and make compost is the result of managed, aerobic decomposition of organic materials by microorganisms. As an alternative to non-renewable organic amendments, food-waste compost provides essential nutrients, retains soil moisture, and supports plant health, while reducing the amount of food in the local waste stream. Nationwide, 30-40% of our food supply is landfilled, generating potent methane emissions through decomposition while wasting the fossil fuels used in its transport and disposal. Bennett Compost operates Philadelphia’s first composting operation focused on food waste.

Biochar

Wood waste is chipped and heated without oxygen to make biochar is a carbon-rich soil amendment produced through pyrolysis—the heating of organic materials in an oxygen-free environment. Biochar sequesters carbon by storing it for long periods of time in a stable form rather than releasing it back into the atmosphere as the harmful greenhouse gas carbon dioxide. As a soil amendment, it can improve water retention, nutrient availability, plant growth, and soil structure. In collaboration with the USDA, OLIN Labs has successfully produced a biochar prototype using local wood waste, transforming a costly municipal burden into a valuable resource.

See more about Lab’s Biochar research here: https://olinlabs.com/biochar