Seed processing and oil quality of Jatropha curcas L. on farm scale: A comparison with other energy crops

• We utilize a single screw extruder for squeezing different oil seeds at farm level
• The Jatropha curcas is compared with sunflower and rapeseed
• We analyze the extrction performance parameters and the quality of the oil obtained
• The best results of J. curcas is a seed feed rate of 25.7 kg/h yielding 8 hg/h of oil
• Excessive temperarture during the extraction process alters the Jatropha oil quality

There are many examples of small-scale initiatives, based on exploitation of the jatropha-crude oil chain, to provide energy at local level, especially in the rural areas of a developing country, where mechanical pressing is currently the most widely used process to extract oil from seed. This study is a comparative analysis of the extraction performance parameters and the quality of the cold pressed oil obtained utilizing a commercial single screw extruder at the farm level for the extraction of Jatropha curcas, sunflower and rapeseed oil. In the case of J. curcas, the best operating results were obtained at a seed feed rate of 25.7 kg/h yielding about 8 kg/h of oil. This result, although satisfactory, was much lower than that of the rape and sunflower seeds. The levels of the main mineral contents (phosphorus, calcium and magnesium) in the jatropha oil, are significantly higher than those specified in the DIN V 51605 standard. Moreover jatropha oil showed high K and Na content (> 2 ppm), the elements that promote deposit formations in engines, while these were not detectable in rapeseed and sunflower oil. Preventive measures (optimizing harvest and storage condition) and avoiding an excessive rise in oil temperature (< 50 °C) during the extraction process are necessary to improve the quality of the jatropha crude oil. In order to meet the quality standards of the new DIN 51506, in order to reduce the mineral elements content in the jatropha oil (especially P, Ca + Mg) inert additives may be mixed with the oil during the seed processing, but these additives can lower the oxidation stability of the oil, so a stabilizer also needs to be added. Moreover these steps complicate the technological process and lower the commercial value of the oil, clearly demonstrating the advantage of producing oil with low concentration of P, Ca + Mg and K + Na in the first place.