Rock wool has long been a popular media for growing hydroponic fruits, vegetables and herbs. However, I’m going to make the case against rockwool and argue why you should never use rockwool again because rockwool is harmful.
This post has gotten a lot of attention recently, and as a result is in the process of being updated to include more information. I cite studies and in no way reference any particular company – I am talking about mineral wool as a growing media in this post.
If you want better alternatives to rockwool, please check out my hydroponic media guide.
It’s Not Environmentally Friendly
I believe in environmental sustainability – it’s one of the reasons I’ve chosen to grow hydroponically. Rockwool doesn’t score well on the environmental scale. It’s not a natural material. Manufacturers use combine chalk and rock and then heat them up to around 3,000 degrees Fahrenheit. Next a stream of air is blown through it, resulting in extremely thin fibers of the rocky material. As the strings are blown out, they bunch together and form the material that you see for sale at the local hydroponics store.
Basically, they are taking two materials that are 100% natural (chalk and rock) and turning them into a hybrid material that will remain in that form forever. When you throw away your old rockwool it’s going to sit in a landfill looking just like that for a long, LONG time. If you absolutely insist on using it, try to save your rockwool in between your growing season and reuse it.
