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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].