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Technical and economic aspects of furfural and ethanol co-production from sugarcane bagasse and harvest residues, annexed to a sugar mill
ENGLISH ABSTRACT: Lignocellulose biomass has potential to reduce the consumption of fossil resources. Furfural and ethanol are some of the most promising bioproducts that can be produced from lignocellulose biomass, with the potential to replace fossil-based products. Commercial furfural producti...
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2021
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| Summary: | ENGLISH ABSTRACT: Lignocellulose biomass has potential to reduce the consumption of fossil resources.
Furfural and ethanol are some of the most promising bioproducts that can be produced from
lignocellulose biomass, with the potential to replace fossil-based products. Commercial
furfural production is performed in a one-stage process, where furfural is recovered in the
vapour phase leaving the reactor. Furfural may also be produced using a two-stage process,
whereby lignocelluloses are fractionated into hemicellulose-rich hydrolysate and cellu-lignin
solid residues, followed by conversion of the solubilised hemicelluloses into furfural in a
subsequent process unit. Conditions of the one-stage furfural process reduce biomass
recalcitrance but tend to degrade cellulose components and produce yeast inhibitors. In
contrast, conditions in the two-stage furfural process minimise cellulose degradation, while
increasing enzymatic susceptibility of residual biomass.
Most studies that consider ethanol production from the cellu-lignin residues from the
one-stage furfural process include washing and/or chemical pretreatments prior to
fermentation, which increases processing costs. Conversely, residual solids from steam
explosion applied in the first stage of the two-stage process, do not require further
pretreatment prior to fermentation, in cases where inhibitor resistant yeast strains are used.
However, furfural produced from the hemicellulose hydrolysate in the second stage of this
process is often recovered and purified using organic solvents that will negatively affect the
environment.
Therefore, this study compared the technical and economic differences between the
one-stage and two-stage methods of co-producing furfural and ethanol from sugarcane
lignocelluloses. One-stage furfural production was achieved in the temperature range of 170-
200ºC and acid doses of 0-2 wt.% H2SO4 using sugarcane bagasse, with unwashed solid esidues used for ethanol production. Pretreated lignocelluloses from the two-stage furfural
production process were similarly assessed for ethanol production. Mass and energy balances
for alternative biorefinery scenarios co-producing furfural and ethanol in the one-stage or
two-stage configurations, were obtained with Aspen Plus® V8.8 process simulations, using
experimental data either collected in this study or published. The internal rate of return (IRR)
of the most promising one-stage furfural and ethanol co-production biorefinery was 12.78%,
while the equivalent two-stage biorefinery obtained an IRR of 13.59%. The lowest minimum
ethanol selling prices (MESPs) achieved by the one-stage furfural and ethanol co-production
biorefineries were 1.14 US$/L and 2.54 US$/L at a desired IRR of 15 and 20%, respectively.
The two-stage furfural and ethanol co-production biorefinery achieved economic indicators
that were improved by 36-51%, as demonstrated by the lowest MESPs 0.73 US$/L and 1.25
US$/L (at IRRs of 15 and 20%, respectively), in comparison to the one-stage furfural and
ethanol co-production biorefinery. One-stage furfural production resulted in significant
degradation of cellu-lignin residues, which negatively affected ethanol yield, and the
profitability. Improvements in ethanol production due to preservation of cellu-lignin residues
in the two-stage furfural production process provided economic benefits. However, the
economic potential of furfural and ethanol co-production remained significantly hindered by
process energy demands, in the context of energy self-sufficient biorefinery reliant on available feedstock for energy supply. These energy demands decrease the financial viability
of furfural production compared to alternative potential co-products. |
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