Biobased propylene glycol production in a sugarcane biorefinery through lactic acid, glycerol, or sorbitol: A techno-economic and environmental evaluation of intermediates and downstream processing methods

Abstract

Propylene glycol (PG) is a versatile chemical which can be produced by direct fermentation of sugars or through intermediates like lactic acid (LA), glycerol and sorbitol. Few studies have examined producing PG from different intermediates in terms of economic feasibility. In this study, seven process scenarios were assessed in a biorefinery annexed to an existing sugar mill. Aspen simulations were developed for each scenario as the basis for mass and energy balances, techno-economic, and environmental evaluations. Scenario 1 (LA intermediate) had the lowest minimum selling price (MSP) of 1,991 US$t-1 and greenhouse gas (GHG) emissions of 1.24 kgCO2/kgPG which was the best intermediate investigated. Scenario 2a-2d (glycerol intermediate) was used to offer insights on the economic benefits of different design changes to the process. Scenario 2a investigates the use of reactive distillation as opposed to normal distillation in the other scenarios. Scenario 2c and 2d offer insights on the purchasing of green hydrogen as an alternative to producing onsite and effect of increased hydrogen ratios respectively. The MSP for the scenarios ranged from 2,121-2,863 US$.t-1 and GHG emissions of 0.8-2.2 kgCO2/kgPG. Scenario 3 (sorbitol intermediate) had the poorest performance with an MSP of 2,751 US$t-1 and GHG emissions of 2.22 kgCO2/kgPG. Scenario 4 (combined first and second-generation feed) had an MSP of 2,065 US$t-1 and 1.04 kgCO2/kgPG for GHG.