Synergistic Closed-Loop System for Oily Sludge Valorization via Biomass-Assisted Pyrolysis: Bridging Waste Management to Sustainable Soil Revitalization

Oily sludge (OS) and saline-alkali soil (SAS) are two interconnected environmental challenges that persist in petroleum-producing regions, yet conventional remediation strategies address them in isolation. This study innovatively presents a closed-loop system integrating biomass-assisted pyrolysis (BAP) of OS with SAS revitalization using pyrolysis residues. The addition of biomass to OS reduces its viscosity and enhances porosity, lowering pyrolysis activation energy by 8.3-12.8% and increasing oil recovery by 25-30 wt %. Simultaneously, BAP mitigates environmental risks by reducing heavy metal release (∼50%) and residual total petroleum hydrocarbons to ≤3‰, meeting regulatory thresholds. The resulting biochar-rich residue transforms SAS into arable land, improving water retention, microbial activity, and ion exchange capacity. This enables robust <i>Ryegrass</i> growth with plant height, survival rate, and dry biomass increasing by 2.2-2.4, 5.6-7.0, and 10.0-14.2 times, respectively. BAP achieves a 10 times greater carbon reduction than individual OS pyrolysis. By bridging petroleum waste valorization with soil restoration, this work pioneers a circular economy paradigm that simultaneously advances renewable resource recovery and sustainable agriculture, aligning with the United Nations Sustainable Development Goals.