Gasification of paper mill waste: a low-value feedstock for sustainable energy production

In the papermaking industry billions of tonnes of paper mill waste are globally produced every year. In the present work, the preliminary compositional analysis of the paper mill sludge has been carried out highlighting a high content of CaCO3 (70 wt%) and a minor amount of cellulosic fibre (30 wt%).Due to its features, the thermochemical treatment of paper mill sludge through gasification for syngas production could represent an innovative and strategic valorisation route. The gasification was carried out in a fixed bed (downdraft) reactor (≈100 kWTH), employing a mixture of O2/H2O or air as gasifying agents. Moreover, the characterization of the side products, as ash and tar, which is a mixture of condensable hydrocarbon and aromatic molecules, has been also performed. In conclusion, for the first time, this work proposes the integrated valorization of paper mill waste through the gasification process producing both the syngas for energetic purposes and ash that can be valorized recycling it within the same papermaking process.