SGGC (SchaumGlas Global Consulting GmbH) installed a production line for cellular glass gravel in the USA. The line is used for hydroponic applications. This is a subset of hydroculture where plants are grown without soil. In this case, the roots are supported by the (cellular glass) gravel and have access to much more oxygen and exactly the amount of water they need.
The above production line runs with fine powder waste glass, mixed with calcium carbonate and is heated with gas from landfill. The plant is built next to this landfill reducing transport to the minimum. The product they produce is called Growstones.
In fact, the roots of plants are settled into the Growstones, while all neceassary ingredients are introduced diluted in water. It seems that Growstones are the best material for this kind of hydroculture due to the best balance of water holding capacity and air filled porosity.
An in principle objective paper is given in this link.