(455c) Improving Economics of Cellulosic Biofuels: An Integrated Strategy for Co?Producing 1,5?Pentanediol and Bioethanol

Lignocellulosic biomass is an abundant and sustainable
feedstock that can be used to produce biofuels and biobased commodity chemicals. However, the
low oil price and the challenges in applying biorefinery technologies at scale
hamper the commercial production of biofuels. In this presentation we will
discuss a strategy to integrate the production of a high-value coproduct, 1,5-pentanediol (1,5-PDO), along with a typical bioethanol production
process.  

1,5-PDO and two other conventional α,ω-diols
(e.g. 1,6-hexandiol and 1,4-butanediol), are building blocks for polyurethane
and polyester plastics. These α,ω-diols are
currently derived from petroleum and, as a group, represent an annual market
over $6 billion. An economically viable approach of producing 1,5-PDO from biomass-derived furfural has been developed
recently (Brentzel et al., 2017; Huang et al., 2017), which offers the potential
to coproduce 1,5-PDO as a high value co-product of bioethanol manufacturing
process to improve cellulosic biorefinery economics. 

In
this work, we propose a novel strategy that integrates lignocellulosic biomass
fractionation with simultaneous conversion of cellulose and hemicellulose into
ethanol and 1,5-PDO, respectively. First, we
fractionate biomass into its three primary constituents— hemicellulose, cellulose, and lignin—using
γ-valerolactone (GVL) as a solvent (Alonso et
al., 2017), which also enables excellent yields of furfural by dehydration of
xylose. The purified furfural is then used to produce 1,5-PDO
(Huang et al., 2017), and the cellulose portion is converted to ethanol via enzymatic
hydrolysis and fermentation (Humbird et al.,
2011), while the lignin is combusted to generate steam and
electricity. We have developed an experimentally based process simulation model
(mass and energy balances) to determine the economic potential of the
integrated strategy. If we consider a plant processing to 1,000 dry metric
tonne per day white birch feedstock and producing 38,520 ton per year 1,5-PDO
and 19.3 MMgal per year ethanol, the integrated
strategy leads to a minimum ethanol selling price of $1.52 per gallon when
1,5-PDO is sold at $3,100 per ton (Figure 1). It is shown that this strategy
could lower the cost of ethanol produced from biomass by more than two dollars
per gallon. Finally, we perform sensitivity analysis to identify the major
economic drivers of the process and suggest future research directions.

Figure 1. Minimum ethanol selling price as a
function of 1,5-PDO selling price. The “green” region (1,5-PDO
selling price > $2,775 per ton) indicates that the integrated strategy has
favorable economics for ethanol production compared with the biochemical
conversion process used in NREL 2011 report (Humbird
et al., 2011).

References

1.     
Alonso,
D. M.; Hakim, S.; Zhou, S.; Won, W.; Hosseinaei, O.; Tao J.; Garcia-Negron, V.;
Motagamwala, A. H.; Mellmer, M. A., Huang, K.; Houtman
C. J.; Labbé, N.; Harper, D. P.; Maravelias, C. T.;
Runge T.; Dumesic, J. A. Increasing the revenue from lignocellulosic biomass:
Maximizing feedstock utilization. Science
Advances 2017.

2.     
Brentzel,
Z. J.; Barnett, K. J.; Huang, K.; Maravelias, C. T.; George, W.; Dumesic,
J. A.; Huber, G. W. Chemicals from Biomass: Combining
Ring-opening Tautomerization and Hydrogenation
Reactions to Produce 1,5-Pentanediol from Furfural. ChemSusChem 2017, 133, 12689.

3.     
Huang,
K.; Brentzel, Z. J.; Barnett, K. J.; George, W.; Dumesic, J. A.; Huber, G. W.;
Maravelias, C. T. Conversion of Furfural to 1,5-Pentanediol:
Process Synthesis and Analysis. ACS
Sustainable Chemistry & Engineering 2017.

4.     
Humbird, D.; Davis R.; Tao L.; Kinchin C.; Hsu D.; Aden A. Process Design and Economics
for Biochemical Conversion of Lignocellulosic Biomass to Ethanol: Dilute-Acid
Pretreatment and Enzymatic Hydrolysis of Corn Stover. NREL/TP-5100-47764. Golden, CO: National Renewable Energy
Laboratory, 2011.