Quantification of water content in biocrude oil emulsions using a low-cost electrical response method

Biocrude oils derived from sewage sludge, agricultural residues, and biodiesel processing streams commonly form stable water-in-oil emulsions with high water content. Accurate determination of water content is essential for efficient upgrading to renewable fuels; however, conventional analytical methods can be costly and impractical for frequent use. In this study, a low-cost, electrical response-based method was developed to quantify water content in biocrude oil emulsions. Measurements were conducted using a calibrated, in-house electrical measurement system comprising two-electrode cells integrated with a temperature sensor and microcontroller. The voltage response of emulsions was recorded under controlled near-ambient conditions and correlated with water volume fraction (ϕ), supported with GC-MS and FTIR analysis. Results showed a systematic increase in voltage with increasing water content up to ϕ = 0.6, with a strong correlation coefficient (R 2 = 0.995). An empirical model was developed for water-content estimation, achieving a prediction accuracy of up to 98.8% within the investigated range. FTIR analysis showed corresponding changes in the O–H and C–H spectral features, while GC-MS characterisation provided qualitative support for the influence of polar and surface-active compounds on the interfacial and charged-droplet behaviour. These findings demonstrate the potential of the electrical response method as a reliable, reproducible, and chemical-free approach for monitoring the biocrude emulsions investigated in this study. The method offers a low-cost basis for offline monitoring and has potential for future adaptation to process monitoring in biocrude upgrading and sustainable biofuel production.