A New Trend in Diesel Adulteration Emerging in South Africa – A Look at Biodiesel, Commercial Diesel and Adulterated Diesel

A comparative analysis of biodiesel produced, that aligns with the SANS 1935:2011 standard, with commercial petroleum diesel samples indicated that some of the commercial diesel samples met the SANS 342:2016 standard quality, while some diesel samples contained high paraffin levels, indicative of contamination.Diesel adulteration with paraffin additions raises concerns about combustion efficiency, engine reliability, and possible environmental impacts.The biodiesel samples were prepared by using waste cooking oil (WCO) through transesterification, using alkaline (KOH) and acid (H2SO4) catalysts, where the effects of catalyst loading and catalyst type, on the yield and the density, flashpoint, high heating values (HHV), GC-MS measurements were used to determine optimal biodiesel production conditions.The results demonstrate that biodiesel quality and yield depend significantly on catalyst type and loading with KOH producing biodiesel that aligns with the SANS standards, while H2SO4 show less consistent compliance.Four commercial diesel samples and a pure paraffin sample were sources from fuel stations in the area around Potchefstroom, South Africa.Two samples showed a paraffin content of up to 60%, much higher than the allowed standard of 5%, resulting in the lowering of the density, flashpoint, HHV and cetane number of the diesel.Laboratory prepared mixtures of 1:0.1 up to a 1:1 diesel-paraffin ratios were made to determine whether an easy way could be found to determine the paraffin content of any commercially available diesel.At a ratio of 1:06 diesel-paraffin the flashpoint dropped significantly from 60C to less than 40C, whilst the density showed a steady decrease from 0.83 kg.m-3 to 0.81 kg.m-3.The HHV stayed relatively constant.The correlation of diesel-paraffin ratios with n-alkane peak areas shows a clear and predictable increase in the n-alkane peak area and the ratio of n-alkane peak area to the internal standard area as the paraffin concentration increases, with a linear relationship between diesel-paraffin mixture ratio and n-alkane/internal standard area ratio, making it easy to determine the paraffin content in any adulterated diesel sample.