The biorefineries begin with identical pretreatment and hydrolysis steps, and then diverge to their respective fermentation
pathways and conversion processes to produce ethanol.
Process parameters for pretreatment and enzymatic hydrolysis are listed in Table 2.
The conversion process begins with dilute acid pretreatment of poplar chips.
This process is outlined by NREL and has been modified for a poplar feedstock.
Following pretreatment, cellulose in the poplar biomass is broken down to glucose using enzymatic hydrolysis.
In the Ethanologen Pathway (EP) (Fig. 1: Subsection 2a) glucose and xylose are fermented using Zymomonas mobilis.
Fermentation conditions and yields come from NREL.
Ethanol produced during fermentation is distilled to a purity of 99.5% ethanol by mass.
Lignin and unreacted carbohydrates are combusted in a boiler to provide process steam.
275,000 kg h 1 of 8.6 MPa steam is generated and sent to a turbine to produce 67 MW (MW) of power.
The biorefinery consumes 46 MW of this electricity sending 21 MW of electricity on to the grid to displace marginal electricity production.
EP biorefinery process parameters, major chemical demands, and emissions are listed inTable 3.
For a complete list of chemical demands see thesupplementary material.
In the acetogen pathway (AP) (Fig. 1: Subsection 2b) glucose and xylose are fermented to acetic acid using Moorella thermoacetica.
The acetic acid undergoes hydrogenation to be converted into ethanol.