Application of biosurfactants in enhanced oil recovery ex-situ: a review

With a growing focus on environmentally friendly solutions, biosurfactants derived from plants or microorganisms have gained attention for Enhanced Oil Recovery (EOR) applications. Biosurfactants offer several advantages over existing options, including biodegradability, low toxicity, availability of raw materials, resistance to harsh reservoir conditions, and improved water/oil interfacial tension reduction. Different organisms, such as bacteria, fungi, and plants, can produce these natural surfactants. Bacillus sp. and Pseudomonas sp. bacteria are extensively studied for their ability to produce biosurfactants using low-cost carbon and nitrogen sources, exhibiting excellent surface activity and low critical micellar concentration (CMC). Fungi, though less commonly used, can also produce biosurfactants, albeit with lower interfacial activity. Plant-derived natural surfactants find wide application in laboratory tests for EOR, despite having higher CMC. This review not only summarizes the current knowledge on biosurfactants but also offers a novel comparative analysis of those produced by bacteria, fungi, and plants, examining their CMC, surface tension, and interfacial tension properties. Additionally, it quantifies the number of publications on the use of biosurfactants for Microbial Enhanced Oil Recovery ex-situ (MEOR ex-situ) over the past 30 years and compares these with biosurfactants derived from plant sources. Our study is unique in its comparative approach and the quantification of literature on MEOR ex-situ. The findings reveal that biosurfactants produced by bacteria generally exhibit superior surface activity, even at lower concentrations, compared to those produced by plants or fungi. This new comparative perspective and thorough literature analysis highlight the distinctive contributions of this study. Overall, the use of biosurfactants for EOR represents a promising approach to cleaner energy production, with the potential to reduce environmental impact while improving oil recovery.