Glass–ceramics from vitrified sewage sludge pyrolysis residues and recycled glasses

► Sinter-crystallization of vitrified sewage sludge pyrolysis residues is feasible. ► Waste-derived glass–ceramics are strong and chemically durable. ► The durability is improved by the mixing with recycled glasses. ► Sintering temperatures of waste-derived glass are particularly low. Pyrolysis of urban plant sewage sludge has been demonstrated to be an effective way to produce fuel gas. However, a complete disposal of this particular waste is not achieved if the solid residues from the treatment are not considered. In this paper we discuss the feasibility an integrated pyrolysis/vitrification/sintering approach, aimed at a “full” disposal: the pyrolysis residues are first converted into a glass, then transformed into glass–ceramics, by simple viscous flow sintering treatments, with or without additions of inexpensive recycled glasses and kaolin clay. The obtained products were demonstrated to constitute an alternative to natural stones, in terms of both mechanical strength and chemical stability.