Hybrid biodegradation of petroleum drill waste through vermitechnology integrated with hydrocarbon degrading microbial consortia: Promoting enhanced vermicomposting and waste valorization

Abstract

The potential for valorizing petroleum drill waste (PW) through enhanced vermicomposting process has yet to be investigated. This research investigated the efficacy of PW waste valorization using enhanced vermicomposting with the earthworm species Eisenia fetida, in conjunction with hydrocarbon-degrading microbial consortia (HDM) across five different mixtures of PW and cow dung (CD), compared to vermicomposting without added HDM, referred to as standard vermicomposting. Metal concentrations (Cd, Cr, Cu, Pb, Ni, and As) decreased up to 92% through bioaccumulation and biotransformation. Notably, hydrocarbon concentrations decreased significantly by up to 98%. The worms experienced a decline in both their fertility and growth in the CD + PW (0:100) substrate mixture initially but demonstrated progress at a later stage. The pH, electrical conductivity, and carbon concentrations were stabilized. The levels of macronutrients, namely nitrogen, phosphorus, and potassium (NPK), have shown a rise of as much as 59% through enhanced vermicomposting. Furthermore, the vermicompost produced was subjected to seed germination tests to validate the findings. The analysis reveals that the end product compositions of CD + PW in ratios of 70:30, 50:50, and 30:70 from enhanced vermicomposting exhibited exceptional germination results compared to all five standard vermicomposts. As a result, these findings shed new light on the potential of enhanced vermicomposting as a hybrid method for biodegrading PW into nutrient-rich fertilizer, thereby promoting green hybrid waste valorization.