Assessment of a Novel Sludge Residue-Based Biochar with its Environmental Application Potentials

Abstract

Converting sewage sludge to biochar by pyrolysis is an environmentally sustainably method of sludge utilization. In this study, a novel sludge residue-based biochar (RBC) was prepared by pyrolysis of the sewage sludge after extracellular polymers (EPS) extraction, and the application potential of RBC as adsorbent and fertilizer was explored. The results indicated that in pyrolysis process to prepare biochar, the biochar yield by sludge residue was 9.3%-19.0% higher than that by raw sludge. Compared with the raw sludge-based biochar (SBC), a variety of new functional group structure and crystalline structure were formed in RBC, and the specific surface area and pore volume were significantly increased. Furthermore, a largest NH4+ adsorption capacity of 7.6 mg/g was achieved using modified RBC (MRBC) under an optimum pH value of 7. Moreover, both MRBC and RBC showed superior performance in germination rate of ryegrass by 15.2% and 3.0%, respectively, with also significant enhancement on height of ryegrass by 57.7% and 44.4%, respectively. In general, the residual sludge after EPS extraction exhibited great potential for biochar production and hence to optimize total value recovery from excess sludge.

Keywords: Sewage sludge, Biochar, NH4+ adsorption, Ryegrass germination, Resource utilization