Castor oil biodiesel and its blends as alternative fuel

Intensive production and commercialization of biodiesel from edible-grade sources have raised some critical environmental concerns. In order to mitigate these environmental consequences, alternative oilseeds are being investigated as biodiesel feedstocks. Castor (Ricinus communis L.) is one of the most promising non-edible oil crops, due to its high annual seed production and yield, and since it can be grown on marginal land and in semi-arid climate. Still, few studies are available regarding its fuel-related properties in its pure form or as a blend with petrodiesel, many of which are due to its extremely high content of ricinoleic acid. In this study, the specifications in ASTM D6751 and D7467 which are related to the fatty acid composition of pure castor methyl esters (B100) and its blend with petrodiesel in a 10% vol ratio (B10) were investigated. Kinematic viscosity and distillation temperature of B100 (15.17 mm² s^-1 and 398.7 °C respectively) were the only two properties which did not meet the appropriate standard limits. In contrast, B10 met all the specifications. Still, ASTM D7467 requires that the pure biodiesel meets the requirements of ASTM D6751. This can limit the use of a wide range of feedstocks, including castor, as alternative fuel, especially due to the fact that in practice vehicles normally use low level blends of biodiesel and petrodiesel. These issues are discussed in depth in the present study.