Environmental sustainability practice of sewage sludge and low-rank coal co-pyrolysis: A comparative life cycle assessment study

Abstract

This study attempts to bridge the current research gaps related to the environmental burdens of low-rank coal (LRC) and sewage sludge (SS) co-pyrolysis potentially. The life cycle assessment (LCA), energy recovery and sensitivity analysis were investigated for different proportions of LRC and SS (co-)pyrolysis. The results showed that the LRC/SS pyrolysis mitigated the environmental burden with an average improvement of 43 % across 18 impact categories compared with SS pyrolysis. The best net values of energy and carbon credits were identified in SL-4 with −3.36 kWh/kg biochar and −1.10 CO2-eq/kg biochar, respectively. This study firstly proposed an optimal LRC/SS co-feed proportion at 3 to 7, which achieves the acceptable environmental burden and satisfactory energy recovery. Moreover, sensitivity analysis demonstrated this proportion is robust and adaptable. LRC/SS co-pyrolysis is a promising and sustainable alternative for SS disposal, which could meet the imperative of carbon emission mitigation and resource recycling.