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Table 3 Mass balance and assumptions for reference-case enzymatic and dilute acid conversion processes.

From: The greenhouse gas emissions performance of cellulosic ethanol supply chains in Europe

Feedstock/co-product (units) Mass balance
   Enzymatic processb Dilute acid processb
   Input (unit.odt-1) Output (unit.odt-1) Input (unit.odt-1) Output (unit.odt-1)
    Ethanol CO2 Solid fuel Waste (solid + liquid)   Ethanol CO2 Solid fuel Waste (solid + liquid)
Biomass            
Hexose kg 620 219 245   156 620 173 190   257
Pentose   60     60 60     60
Lignin   280    252 28 280    273 7
Other   40     40 40     40
Chemicals            
SO2 Kg 15.48     15.48 0.00     
H2SO4   0.00      63.20     63.20
NaOH (50%)   28.96     28.96 28.96     28.96
NH3 (25%)   2.36     2.36 1.68     1.68
H3PO4 (50%)   0.52     0.52 0.36     0.36
Defoamer   0.56     0.56 0.44     0.44
(NH4)2PO4   2.76     2.76 2.60     2.60
MgSO4.7 H2O   0.12     0.12 0.12     0.12
Enzymes 106 FPUa 9.36     9.36 0.00     
Electricity-buy MWh 0.18      0.18     
Cooling water m3 72.48      65.44     
Process water m3 3.36     3.36 3.20     3.20
  1. aFilter paper unit. bThe reference processes were adapted to include pentose fermentation using the following assumptions: the ethanol and CO2 yield from pentose sugars was assumed to be 50%, reflecting the fact that the recovery of pentoses after pre-treatment is lower than for hexoses [17]; the solid fuel yield and process heat requirement was unaffected; the flow of chemicals was the same as the respective softwood enzymatic or dilute acid process. The reference processes were adapted to use straw as a feedstock using similar assumptions: the ethanol and CO2 yield from hexose sugars was assumed to be the same as for the respective softwood enzymatic, or dilute acid, reference process; the solid fuel yield and process heat requirement was unaffected; the flow of chemicals was unaffected [5].