What use can be made of recycled fibreglass?
This most obviously depends on the recycling method applied: With grinding, dimensions of small resulting pieces can range from 1 inch to powder. That material can then be then be integrated into cement, for instance. And therewith, be used in constructions.
Also, remainders can serve as energy provider for cement kilns. Quoting Eric Sponberg in his article “Recycling Dead Boats“: “Interestingly, recent findings in Scandinavia have proven that composites are a suitable fuel and feed-stock for cement kilns. Burning junk fiberglass laminate to create heat in the kiln (2,5520F/1,4000C) ensures its complete combustion, and the inorganic ash can be incorporated into new cement. Cement kilns, however, depend on large and steady quantities of feedstock to operate, and the recovery processes for composites are not mature enough to support the kilns’ voracious appetites. But, the potential for further development is certainly there.”
Then there is pyrolysis, we remember, “the process of chemically decomposing or transforming a material into one or more recoverable substances by heating it to very high temperatures in an oxygen-depleted environment”. This produces two interesting materials – pyro-gas and pyro-oil. Quoting the article again: “The pyrogas is very clean and has an energy content similar to natural gas. It can be sold as a natural gas replacement, and it fuels the burners of the pyrolysis reactor so that the reaction is self-sustaining. Pyro-oil is similar to heavy crude oil and, as such, it has less value than normal crude oil, but it can be blended with other fuel oils or incorporated into asphalt. Pyro-gas and pyro-oil comprise about 25% of the pyrolysis traction output in roughly equal amounts. These are free of sulfur, halogens, phosphorous, heavy metals, or other elements that can cause environmental problems.”
Still regarding above mentioned cement kilns, the recycling of fibreglass also appears to allow for the (partial) production of cement. Here follows a description of the cement kiln route, described in the article Recycling glass fibre reinforced composites – history and progress, written by Stella Job. Verbatim quote from this article:
“Cement kiln route – how does it work
Incineration of GRP is not practical since about 50-70% of the material is mineral and would be left as ash, which still needs to be landfilled. For co-processing in cement kilns, composite parts are size-reduced and mixed with other waste to feed into the kilns.
GRP typically contains E-glass, which is usually alumino-borosilicate, along with an organic resin and often calcium carbonate filler. When fed into a cement kiln the organic resin burns providing energy (about 12 MJ/kg of waste) and the mineral constituents provide feedstock for the cement clinker.
The clinker is ground to form cement. Any calcium carbonate calcines (releasing carbon dioxide) to calcium oxide, the primary component of Portland cement. Alumina and silica also have cementitious properties in an alkaline environment and are typically present in Portland cement at about 25%, and in much higher proportions in cement alternatives from fly-ash and slag. Boron, which is found in most E-glass, can cause a reduction in early strength during the setting of cement, but as long as proportions are kept low it is not considered a problem (ref: Pickering, Benson, Recovery of material and energy from thermosetting plastics, Proceedings, ECCM6 – Recycling concepts and procedures, 1993).”
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