A few other alternatives
Urban sewage sludge management

This technique involves the thermal decomposition of dried sludge in the absence of oxygen (O ₂ < 2% and at temperatures between 400 and 700°C). At the end of this process, a combustible gas is obtained as well as a solid residue (ash), also known as biochar. The recovered gas can be reused as an energy source, however, this requires additional facilities to harness the energy contained in these produced gases.

As for biochar, it can be used for soil improvement, since it contributes to enriching the soil's chemical, physical and biological characteristics, and promotes water retention in the soil.