*2.3. Process Simulation and Economic Calculations*

The main processes of the biorefineries are simulated by Aspen Plus to obtain the composition and properties of streams. The physical properties databank of NREL (National Renewable Energy Laboratory, Golden, CO, USA) is used for the definition of lignocellulosic components [34]. The sizing and cost of all equipment are estimated by Aspen PEA. The assumptions are: plant capacity, 120,000 tons/year castor plant (dry basis); plant location, Asia (Iran); costs index, 2019; depreciation, straight-line for 7 years with zero salvage value; contingency factor, 18%; construction period, two years with a 6-month start-up; working capital, 5% of the total investment cost; project life, 30 years; tax rate, 0% based on Iran regulation for biofuel production.

The sensitivity analysis to identify the factors affecting the profitability and final price of biodiesel is carried out.
