Hello slate people
“Is there really nothing we can do with this?” Probably, this is the question I have heard the most times since I work on roofing slates. Roofing slate mining has some characteristics. Slate only needs some cuts to be ready, not like other natural rocks that require further manufacturing such as polishing, consolidating or chemical treatment. On the other hand, the amount of waste in roofing slate mining is rather high. Only between 9-7% of what is extracted is finally transformed into shingles. The rest goes directly to the pit. Thus, everyone that visits a slate quarry for his/her first time makes the same question, why nobody has thought on doing something with all this? Well, in fact there has been several attempts to take advantage of the enormous volume of wastes. Some researchers put their attention in this question and published several papers on obtaining ceramic foams using the slate powder. Other researchers have tried to produce rock wool using this powder mixed with mussel’s shells. More authors have tried producing concrete, bricks or different ceramic materials using wastes. In all these cases, the results showed that it is possible to create new materials coming from slate powder. Well, it is possible to fabricate these materials with slate, but this does not mean a real solution to the wastes problem. The amount of powder required is ridiculous compared with the total amount of wastes, and the slate powder did not have any special advantage for any of these industries. It is not really worth for them to use it. In addition, if you want to use these wastes, you would have to carry them to the fabrics, which is not very cheap.
Perhaps the researchers that have studied this problem with the most realistic approach was the group headed by J.E. Oti from the University of Glamorgan, UK. They admit the limitations expressed so far (waste volume vs. used volume, distance) but they also specify all the possible uses for the slate wastes. In any case, it is not possible to provide an outlet for the massive pits. It is something we have to live with. On the other hand, technology and environmental legislation have improved very much the design and arrangement of the pits. Nowadays companies cannot just throw away the wastes wherever they want, and they must provide a restoration plan, which includes seeding. Roofing slate industry is becoming more and more aware of environment; do not forget that CO2 emissions are the lowest of all roofing materials.