Physicochemical exploration of castor seed oil for high-quality biodiesel production and its sustainable application in agricultural diesel engines

In Thailand, castor seeds often classified as weeds are locally distributed in every region of the country and not fully utilized. Therefore, this research aimed to study the physicochemical properties of castor seed oil as a raw material for the production of liquid biofuels. The study of extracting oil from castor seeds using various methods revealed that the Soxhlet extraction technique, a circulatory extraction method, yielded the highest amount of extracted oil at 52.45 wt%, compared to the dry weight of the castor seed. In the study of the physicochemical properties of castor seed oil, the results revealed that the major components were 89.71% ricinoleic acid, 3.96% linoleic acid, and 3.09% oleic acid, respectively. The kinematic viscosity of castor seed oil was as high as 164.68 cSt. However, when converted into castor seed oil biodiesel, the kinematic viscosity decreased to 10.36 cSt, still two times higher than that of the standard biodiesel oil. Therefore, blending castor seed oil biodiesel with petroleum diesel oil to obtain B30 and B40 revealed that the fuel properties met the qualifications of both ASTM D6751 and EN 14214 standards. The initial tests on agricultural diesel engines found that the gas emissions of CO2, CO, HC, and NO2 from biodiesel blends B30 and B40 tend to be lower than those from using only petroleum diesel oil and biodiesel oil derived from castor seeds. Therefore, blending biodiesel oils B30 and B40, derived from castor seed oil, not only results in good biofuel liquid qualities but also proves to be efficient for use in agricultural diesel engines. It is suitable to encourage the community to adopt it for agricultural purposes in the future.