Can recycled soil blends support a more sustainable future?

In the basement of the Bok Building, a former technical school turned artist- and makerspace in South Philadelphia, Rebecca Davies walks through what’s known as the “rainbow room” at glass recycler Bottle Underground. The shelves are stacked neatly with empty bottles of all shapes, sizes and colors. There’s a space reserved for soft green water bottles, another for those of a deep blue, and so many empty bottles of gin, vodka and whiskey that it looks something like a liquor store gone dry. Rather than putting all this glass in recycling bins, where it would be commingled with other materials and broken down to the point that it can’t actually be recycled, community members, bars and restaurants have brought it here to be put back to use.

“We produce a lot of waste and recycled glass is not something we’re using here in the United States,” Vanegas says. In 2018, for example, the U.S. sent nearly 8 million tons of glass to landfills, accounting for 5 percent of all municipal solid waste, according to the Environmental Protection Agency. So, Vanegas says, “Why don’t we start to give a second life to this waste?”

Looking ahead, Vanegas is planning to collaborate with Crabtree Farms, a 22-acre urban farm in Chattanooga, Tennessee, that focuses on sustainable practices. The partners are in the early stages of determining what their project will look like, but the next steps will build on work being done in the farm’s greenhouse, where Crabtree has experimented with recycled glass in an effort to find a more sustainable horticultural medium. With glass provided by local recycler Overlooked Materials, Crabtree has tried replacing sand and perlite — a common growing medium — with glass sand, seeking to harness its capacity for both water retention and efficient drainage, as well its ability to make silica more available to plants, increasing the strength of their cell walls and their stress tolerance. The greenhouse has used glass to grow native perennials including aster, coneflower, milkweed and primrose, says greenhouse and gardens coordinator Sarah Wiatrek.

For Crabtree, where education is a priority, testing out the potential of glass sand is a way of demonstrating the need to reach for sustainable solutions, Wiatrek says. “It makes people question the status quo,” she says.

For Davies, the Gritty blend is the beginning of an environmental solution, as well as a waste and extraction solution. Scaling it to the point that it can also be an approachable solution for more people will require the growth of local initiatives like those developing in Philadelphia and Chattanooga. As Davies suggests, transporting even the most sustainable soil across vast distances will increase its carbon footprint to the point of undoing its benefits, so recycled soils should be treated as a local initiative — something a municipality could undertake with partners in its own community, perhaps. Already, though, Davies says, “What we have here shows that waste can be used entirely to recreate the things that we need in our landscapes and in our growth environment.”

At home, Davies has a prickly pear cactus potted in the soil blend, offering her a regular reminder that with a focus on sustainability and an open mind, we can find new ways to grow plants.

“If I kill it,” she says, “it will be because of my lack of a green thumb — not because of the soil.”

Top photo by Zara Neifield.