Biodiesel is renewable, nontoxic, biodegradable, and essentially free of sulfur and aromatics, hence it may be one of the most suitable candidates for future biofuel. Besides, US Department of Energy life cycle analysis on biodiesel shows that it produces 78.5% less net carbon dioxide emissions compared to petroleum diesel [1]. In 2011, the United States produced approximately 1.1 bil- lion gallons of biodiesel and the production is expected to increase to 1.9 billion gallons in 2015 [2]. The major drawbacks of biodiesel production using vegetable oil are the high costs of manufacturing and the feedstock oil, which competes with food. Currently, biodiesel produc- tion plants depend on government subsidies in order to keep their plants in operation [2]. Thus, seeking for a more economic biodiesel production process to reduce the dependency of government subsidies and promote expansion of biodiesel industry is desirable. Recently, a conventional biodiesel production plant was retrofitted using thermodynamic analysis, which em- ploys process heat integration, column grand composite curves, and exergy loss profiles to assess the existing operation and suggest modifications [3]. The retrofit de- sign operates with less thermodynamic imperfections, hence it requires less energy. With a suitable reaction rate, a type of catalyst, relative volatilities of the compo- nents, and the reaction and separation temperature range,
reaction and separation can be combined into a reac- tive distillation (RD) [4-6]. RD reduces operational and equipment costs by decreasing waste energy and over- coming thermodynamic and chemical equilibrium limita- tions. Further reduction of energy and equipment cost of the biodiesel production plant is possible by using ther- mally coupled distillation column sequences as they al- low interconnecting vapor and liquid flows between the two columns to eliminate the reboiler or condenser or both [7]. About 1 kg of glycerol is formed for every 10 kg of biodiesel produced [8]. The production cost of biodiesel increases by $0.021/liter for every $0.22/kg reduction in glycerol selling price [9,10]. As a result, economical utilization schemes of bioglycerol can lead to a more economical biodiesel production plant. A recent study suggests that addition of glycerol carbonate production by direct carboxylation route may be more economical than the conventional biodiesel production plant [11]. However, recently, Li and Wang (2011) [12] have sug- gested that direct carboxylation of glycerol and CO2 is thermodynamically limited and the yield is very low (less than 35%) [13]. Low yield requires high energy for the separation of products and the recovery of reactants lead- ing to high cost of manufacturing. Thus, in this study synthesis of glycerol carbonate by glycerolysis route is developed and economics of the biodiesel-glycerol car- bonate production by direct carboxylation and glyceroly- sis plants are compared. Economic analyses based on