Grodan, as a company, consistently tests its stone wool for heavy metal content through a third-party laboratory known as Bureau Veritas, which operates numerous locations in North America.
In their commitment to provide growers with a reliable substrate adhering to high standards, Grodan empowers growers with better control over their crop inputs. This not only upholds the integrity of cannabis brands and benefits their customers but also positions operators ahead of potential new regulations resulting from increased government scrutiny on soil health. By transitioning from peat or coco to stone wool, operators can save both time and effort in their testing and compliance processes while preemptively addressing concerns related to substrate contaminants.
In a world where an array of consumer products, from baby food to clothing textiles, are revealing alarming levels of heavy metal concentrations, cannabis operators can offer an extra layer of reassurance with a straightforward choice of using stone wool, a growing medium with proven, negligible levels of heavy metals.
Testing Stone Wool Substrates for Heavy Metals
It's crucial to note that there are different methods for testing growing media, depending on whether they are organic (i.e., "living" material) or inert (like stone wool).
For organic media, such as soil, peat, and coco, the acid digestion process proves useful in determining heavy metal concentrations. This method involves using various acidic chemicals to break down organic compounds in a sample, allowing for the better observation and quantification of elements, including heavy metals. It helps identify what hidden components of an organic substrate might be absorbed by plants.
However, when it comes to inert mineral substrates like perlite and stone wool (rock wool), applying the acid digestion process produces inaccurate results. It releases 100% of all elements in the stone wool material, not just the elements naturally available to plants under typical temperature and pH conditions during the growing cycle.
For inorganic growing media, the most suitable testing process is the Toxicity Characteristic Leaching Procedure (TCLP). TCLP simulates the leaching of metals over a standard growing season, providing an accurate understanding of the bioavailability and mobility of various compounds in mineral substrates. This method aligns with the process specified by the EPA when it established federal standards for hazardous and industrial waste disposal in the 1970s.
Cannabis operators can rely on TCLP results because they typically slightly overestimate the total level of leaching occurring over a full growing season. When examining mineral substrates through electron micrographs, the physical degradation of stone wool fibers can be observed after several years of use, compared to similar fibers subjected to the TCLP extraction process, which degrades the fibers even more than they would naturally degrade during the growing cycle.
This high level of accuracy, coupled with the additional degradation during testing, is the reason why Grodan consistently conducts TCLP analysis of their products as part of their stringent quality control standards. While various types of basalt rock, the raw material for stone wool growing media, naturally contain variable levels of heavy metals, Grodan can demonstrate that any heavy metals are detectable well below legal limits, if they are detected at all.
For more information:
Grodan
www.grodan.com