Response surface methodology (RSM) based on central composite design (CCD) was used to optimize biodiesel production process from corn oil. The process variables, temperature and catalyst concentration were found to have significant influence on biodiesel yield. The optimum combination derived via RSM for high corn oil methyl ester yield (99.48%) was found to be 1.18%？wt catalyst concentration at a reaction temperature of C. To determine how long biodiesel can safely be stored, it is desirable to have a measurement for the stability of the biodiesel against such oxidation. Storage time and oxygen availability have been considered as possible factors influencing oxidative instability. Biodiesel from corn oil was stored for a period of 30 months, and the physico-chemical parameters of samples were measured at regular interval of time. Results show that the acid value (AV), peroxide value (PV), and viscosity ( ) increased while the iodine value (IV) decreased. These parameters changed very significantly when the sample was stored under normal oxygen atmosphere. However, the , AV, and IV of the biodiesel sample which was stored under argon atmosphere were within the limit by the European specifications (EN 14214). 1. Introduction In the last few years, the world’s energy demand is increasing due to the needs from the global economic development and population growth. However, the most important part of this energy currently used is the fossil energy sources. The problem is fossil fuels are nonrenewable. They are limited in supply and will one day be depleted. There is an increased interest in alternative renewable fuels. As biodiesel is an environmentally friendly fuel, it is the best candidate to replace fossil-diesel, which has lower emissions than that of fossil-diesel, it is biodegradable, nontoxic, and essentially free of sulphur and aromatics [1]. However, only nitrogen oxides increase using biodiesel as fuels [2, 3]. Renewable feedstocks such as vegetable oils and animal fats have been used as raw materials for biodiesel production [4]. The general way to produce biodiesel fuels is transesterification of fat or oil triacylglycerols with short-chain alcohol such as methanol or ethanol in presence of alkaline or acid catalysts [5–7]. Vegetable oils are promising feedstocks for biodiesel production since they are renewable origin and can be produced on a large scale. More than 95% of biodiesel production feedstocks come from edible oils since they are varying considerably with location according to climate and availability. In the United States, soybean
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