Low-temperature alkaline pyrolysis of sewage sludge for enhanced H2 production with in-situ carbon capture

Abstract

Pyrolysis has been recognized as one of the promising thermal technologies on the account of satisfying the principles of waste reduction, resource recovery, and detoxification. This study proposed the alkaline thermal treatment of sewage sludge of enhanced H2 production and in-situ carbon capture. The maximum H2 yield of ∼10 mmol g−1 biomass was achieved at 1:3 sludge: NaOH ratio, 10 °C min−1 heating rate, and 500 °C temperature, with the H2 purity of 79.1% in the gaseous products. The presence of NaOH significantly promoted H2 production and substantially suppressed CO and CO2. Temperature also played an important role in cracking of CC and CH bonds and gave H2-rich gas (H2 formation rate 0.34 mmol min−1 g−1) with a high yield of 10.3 mmol g−1 at 500 °C. The solid residue analysis via XRD verified the existence of Na2CO3 in the solid, implying the inherent carbon management potential of the NaOH during the sludge pyrolysis process.