After escaping from the pile of waste material, the gas is a low Btu fuel gas that can be a source of heat for some other process. Sometimes this gas is oxidized to generate heat to make electricity. Alternatively, this gas can be used to provide process energy in materials manufacturing or heat treating. The molten oxides or glass in the melter is the residue of the waste feed materials. The ash from combustibles have many useful oxides needed in glass melting.
Wood products are frequently high in calcium and potassium that are used as fluxes.
Early man used the ash from selected trees to obtain these fluxes to make glass products. Soil or dirt is typically high in silica and alumina. These oxides are essential for making a durable glass and are also found in the residue of organics. However, if needed, soil or dirt can be added to make a chemically durable, higher silica glass. Sometimes the waste material does not have high organic content so additional fuel is needed to melt the glass.