Exploring the Reusability of Oil Refinery Sludge Post Blending With Natural Bulking Agents: Comparing the Suitability of Rice Husk and Cow Dung Manure

ABSTRACT Oil refinery sludge (ORS) is a chemically heterogeneous industrial waste with known environmental risks. However, there is a scarcity of knowledge pertaining to its reutilization. The present study proposes an eco‐friendly approach toward resource recovery from ORS by blending it in equal proportions with natural bulking agents viz. rice husk (RH) and cow dung manure (CDM) (i.e., ORS + RH 1:1 and ORS + CDM 1:1). The structural, thermal, and chemical attributes were studied in detail through scanning electron microscopy‐energy dispersive X‐ray (SEM‐EDX), carbon, hydrogen, and nitrogen elemental analyzer (CHN), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis‐derivative thermogravimetry (TGA‐DTG), atomic absorption spectroscopy (AAS), and gas chromatography‐mass spectrometry (GC‐MS) analyses to choose the superior blend. Additionally, the pollution potential of the blended ORS was computed to ascertain its relative eco‐toxicity. The pH, C:N and C:P ratios of ORS + RH were optimum with lesser heavy metal contents than ORS + CDM. SEM‐EDX revealed good microstructural integrity, porosity, and higher SiO 2 bi‐layers on the surface of RH mixed ORS. We also observed a thermal reactive profile in ORS + RH with better combustion efficiency (5.2 2 × 10 −07 % 2 °C −3 min −2 ) than ORS + CDM (2.30 × 10 −07 % 2 °C −3 min −2 ). GC‐MS detected 581 compound signatures in total, where 63 and 139 were unique to ORS + RH and ORS + CDM, respectively. Notably higher pollution potential was also depicted by CDM blended ORS than its RH counterpart. Overall, our findings infer that RH is a suitable alternative in ORS reusability and valorization.