Cost evaluation of large-scale membrane capacitive deionization for biomass hydrolysate desalination

Abstract

The bio-based industry is striving to replace refined sugars by much cheaper secondary feedstocks for the
production of bio-fuels and chemicals. However, due to their higher complexity, a number of technological
challenges need to be overcome. One example are the high concentrations of sodium and potassium
present in the biomass hydrolysates that inhibit fermentation and hence need to be reduced. Previous
research demonstrated the technical feasibility of membrane capacitive deionization (MCDI) for biomass
hydrolysate desalination as a chemical/waste free alternative compared to the commonly used ion-exchange
process (IEX). In this paper, the economic viability of MCDI was investigated for a production
capacity of 500 ton sugar day 1 and a target Na removal from 3 to 0.1 g kg 1 hydrolysate. Although capital
costs were higher for MCDI than for IEX due to the expensive MCDI cells and power supplies, operating
costs were lower because less water and chemicals are used and less wastewater is generated. Cost
calculations for different initial feed concentrations indicated that IEX was only preferential over MCDI
when the feed Na+ concentration was below 0.4 g kg 1 hydrolysate. Then the higher chemical, water
and wastewater treatment costs for IEX no longer outweighed the higher cost of MCDI cells compared
to IEX resins.