A techno-economic study of Polybutylene adipate terephthalate (PBAT) production from molasses in an integrated sugarcane biorefinery

Abstract

The feasibility of producing biobased Polybutylene adipate terephthalate (PBAT) or 1,4-butanediol (BDO) as a way for diversification of sugar production facilities, was investigated in this study. Two scenarios for biorefineries integrated into an existing sugarcane mill, were investigated: In scenario 1, the feedstock (A-molasses) was diverted to produce three different monomers, i.e., terephthalic acid (TPA), adipic acid (AA) and 1,4-butanediol (BDO) in stoichiometric ratios required for PBAT production. Scenario 2 investigated using all the feedstock to produce BDO as a final product, based on substantial market potential. The processes were simulated in Aspen Plus® to obtain mass and energy balances for equipment sizing and costing. Then a discounted cash flow method was used to calculate the internal rate of return (IRR). The results indicated that scenario 1 had higher energy usage (47.3 MJ/kg of PBAT) compared to scenario 2 (42.1 MJ/kg of BDO) as PBAT synthesis required TPA and AA monomers, produced in energy-intensive processes. Scenario 2 with an IRR of 34.4% had a better economic performance than Scenario 1 with 19.1% IRR, partly due to Scenario 1 having smaller production scales for monomers, suffering the negative effects of economies-of-scale. Although both scenarios were profitable, the sensitivity analysis indicated that Scenario 1 would remain profitable with either a 30% increase in total capital investment or a 30% decrease in operation time, while Scenario 2 would become unprofitable. The study has demonstrated that bio-based PBAT can be produced from molasses in a manner that is cost-competitive with current fossil-based market prices.