This study proposes magnetically recoverable biological-nanocomposite comprising photosynthetic bacteria , husk biochar, and Fe 3 O 4 nanoparticles to facilitate biomass and commercial product recovery after waste cooking oil removal from water bodies. The photosynthetic bacterium Rhodopseudomonas faecalis PA2 removes oil and produces commercially valuable products such as carotenoids , lipase , and microbial lipids. Biochar serves as a carrier for bacterial adsorption, while synthesized Fe 3 O 4 imparts superparamagnetism to the nanocomposite. Different types of biochars—rice straw, husk, and coconut coir dust—were tested; husk biochar (HB) nanocomposite was preferred owing to its high cell immobilization efficiency. Brunauer–Emmett–Teller analysis indicated that Fe 3 O 4 increased specific surface area of the Fe 3 O 4 /biochar nanocomposite compared with that of biochar alone. The results of X-ray diffractometry and Fourier transform infrared spectroscopy confirmed the presence of Fe 3 O 4 and biochar in the biological nanocomposite, whereas field emission scanning electron microscopy and transmission electron microscopy demonstrated the three components were combined as a composite . After the treatment, the biological nanocomposites could be easily recovered from an aqueous environment using an external magnetic field . Oil removal and recovery of beneficial products were higher in the biological nanocomposite (photosynthetic bacteria/Fe 3 O 4 /HB nanocomposite) than in the Fe 3 O 4 /HB nanocomposite and free cell treatments. Moreover, compared to the free cell experiments, the biological nanocomposite showed an increase in biomass, carotenoid production, and lipase activity by 65.0%, 84.9%, and 31.5%, respectively, with 70.31% oil reduction. This study presents a sustainable treatment for the removal of waste cooking oil and synthesis and recovery of microbial products. • Biological nanocomposites degrade waste oil. • Biological nanocomposites enhance biomass and microbial product recovery. • Rhodopseudomonas faecalis PA2 degrades oil and synthesizes microbial products. • Biochar made from lignocellulosic biomass is used as a microbial cell carrier. • Fe 3 O 4 serves as an inexpensive process for biomass and microbial product recovery.