Study seeks to spin new use for stone wool substrate
- 6 hours ago
- 3 min read
By Luke Edwards
Used substrate in Ontario’s greenhouses may offer value for farmers and outdoor growers.
With the help of a grant from the Greenbelt Foundation, researchers at Vineland Research and Innovation Centre are conducting a study to see how valuable used stone wool is as a soil amendment. And while Mother Nature’s whims during this year’s trials may not yield as much information on one of the main proposed benefits as researchers hoped, Jason Henry is nonetheless optimistic for a future benefit.
“The industry is moving to waste recovery because landfilling these types of materials is becoming more costly. It’s becoming a lot more costly,” said Henry, a research scientist for plant responses and the environment at VRIC.
Finding creative reuse of greenhouse waste is nothing new for Vineland researchers. Much work has gone into finding ways to divert the vines, leaves and unusable fruit away from landfills. However, Henry’s project takes that research underground, in a sense.
Substrate makes up a small but still significant amount of the overall greenhouse waste, something in the neighbourhood of 15 per cent, Henry said.
Reuse of other greenhouse material has helped add nutrients back into the soil. While previous research found stone wool doesn’t offer the same kind of nutrient infusion, Henry said it does show significant promise when it comes to water retention.
“It acts like a sponge,” he said.
That water retention could be valuable during summer droughts when plants are thirsty. Adding used stone wool into the soil could keep water available to plants when it’s really needed.
VRIC’s study is looking at sweet corn and broccoli, utilizing self-contained growing boxes at the Vineland campus. Four different treatments see researchers comparing plants grown in basic soil, plants grown with different rates of stone wool applied, plants grown with composted hen manure, and finally, plants grown with a mix of manure and stone wool applied.
While it’s too early to know the results, Henry said he’s optimistic.
In addition to water retention, Henry said they think the stone wool can similarly act as a sponge for the nutrients in the hen manure, holding them for later use by the plants.
Unfortunately, the wet spring and summer means they’ll gain limited insight on water retention. However, Henry said one of the concerns is the possibility the used stone wool could introduce disease into fields where it’s applied. The project will help researchers gain insight into that potential issue.
To conduct the study, VRIC partnered with Grodan, a company that produces soilless growing media such as stone wool. If they’re able to scale up the success they’ve found in the lab to real life scenarios, Henry said the industry can begin looking at processes to make it viable.
Yianni Monahan, product manager, lifecycle North America at Groden, called the project foundational.
“This project will provide important foundational research to evaluate the potential of this material as a soil amendment,” Monahan said.
One of the side issues Henry said they face is confusion over regulatory standards. Henry said they want to provide more information to farmers and greenhouse growers on the rules to help make things easier as well.
Public and industry events are planned for the future, as well, to help inform growers about the project and its results.
The project began in April and is scheduled to last nine months. Henry said he’d love another chance to conduct the trials when there’s less rain. In a future trial they could install covers in the self-contained boxes to control how much water the plants, giving them a better idea of the water retention qualities.
As tipping fees rise dramatically and landfill space in Ontario dwindles, finding creative ways to reuse greenhouse waste is becoming more and more important.
Henry said they’re grateful for the Greenbelt Foundation’s funding, calling it a “huge honour” to be selected.
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