In recent years, more and more potters are turning to the search for a new way of making pottery with a greater awareness of work and respect for the environment and health.
Rising raw material prices have spurred the search for cheaper alternatives and the use of recycled materials.
In Sicily and Portugal, experiments have been initiated to develop a clay slurry made from eggshells used in food production. There is also a great rediscovery of ash glazes by using waste ashes from garden mowing and food waste so as to obtain personal and original glazes by reusing material that would otherwise be thrown away as waste.
Regarding the issue of energy and high fuel consumption, more and more people are turning to stoneware clay slurries with temperatures ranging around 1100 degrees thus trying to reduce consumption or using monofiring, all methods to achieve reduced energy consumption, economic savings and less impact on the environment.
In recent years I have dedicated myself within my laboratory to research, for example, recycling egg shells and baking them in an earthenware container at 980 degrees when I do cookie bakes. After taking them out of the kiln they have to be finely crushed and sieved, thus obtaining a calcium oxide powder to be used in clay mixtures or inside glazes to make excellent Matts. 
Of course, all these grinding and sieving practices should always be done with safety glasses, gloves and ffp2 mask.
You can also recover glass obtained from broken glasses and jars to use in place of the thick crystalline but it is important to always test first because not all glass melts the same way.
Glasses that melt well include medicine vials, which, after being ground and, if desired, colored with iron or copper oxide, can excellently replace commercial thick crystalline. 
Copper can be obtained by recovering the scraps of electrical wires after removing the plastic sheath that covers the wire. These wires can be used as is or by bending them and also creating very beautiful designs. Or they can be ground thus obtaining a copper oxide powder. The same process can be done with iron from rusty nails or pieces of metal. Master Gaetano Scalese recycles the scrap from the soldering of copper-rich microchips to make beautiful raku glazes for his works.
Faenza-based master Giovanni Cimatti recycles spent Portland cement to make striking glazes from Gres.
In research, it is always important to consider the furnace as a reaction chamber where changes in matter occur at the chemical level that can develop gases that are harmful to us and the environment as well as to the furnace itself. So it is always good to first do your research and find out if the substances we use release chlorine, sulfur or other harmful substances.
It would be good to set up a forum where those with chemistry experience can also answer various questions and through sharing and exchanging knowledge build a better way to minimize the impact of our work on the environment and our health.