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Table 4 Comparison of hydrothermal/chemical pretreatment followed by mechanical refining and hydrothermal/chemical pretreatment alone or mechanical refining alone

From: Promise of combined hydrothermal/chemical and mechanical refining for pretreatment of woody and herbaceous biomass

Sample Pretreatmenta Milling energy (kWh/ton)b, c Sugar yield (%)d Reference
Hardwood chips Sodium carbonate NAe 42.11 (total sugar) [53]
Sodium carbonate + PFI milling 360–1800 46.90–53.12 (total sugar)
Sodium carbonate + disk milling (12 inch diameter) 698 69.51 (total sugar)
Sodium carbonate + disk milling (42 inch diameter) 67–147 62.48–66.51 (total sugar)
Japanese cedar Ozonolysis NA 28–68 (glucose) [54]
Disk milling 4167–26,389 29–44 (xylose)
Ozonolysis + disk milling 8333–22,222 38–75 (glucose)
   26–45 (xylose)
71–94 (glucose)
44–59 (xylose)
Lodgepole pine trees Disk milling 615.9 11.3 (glucose) [52]
Hot water (initial pH 5.0) + disk milling 537.0 33.1 (glucose)
Acid (initial pH 1.1) + disk milling 335.6 39.6 (glucose)
SPORL (initial pH 4.2) + disk milling 499.3 84.1 (glucose)
SPORL (initial pH 1.9) + disk milling 134.5 92.2 (glucose)
Eucalypt chips Disk milling 990 72.94 (total sugar) [65]
Sodium hydroxide impregnation + disk milling 630 80.77 (total sugar)
Magnesium hydroxide impregnation + disk milling 430 91.53 (total sugar)
Hinoki cypress eucalyptus chips Disk milling 853 50 (glucose) [73]
Steam treatment + disk milling 744–1489 96.8 (glucose)
Eucalyptus chips Disk milling 408 45 (glucose)
Steam treatment + disk milling 192–458 98.4 (glucose)
Eucalyptus chips Hot water NA 50 (glucose) [55]
Hot water + disk milling 167 101.7 (glucose)
Eucalyptus chips Hot water NA 3.1–65.2 (total sugar) [37]
Hot water + ball milling 1436 45.6–66.7 (total sugar)
Rice straw Hot water NA 97.5 (glucose) [62]
Hot water + mechanical refining 250–583 97.3–99.5 (glucose)
Oil palm mesocarp fiber Disk milling 5250 30.2 (glucose) [56]
Superheated steam + disk milling 1417–3028 30.6 (xylose)
Hot water + disk milling 4083–4972 26.0–47.8 (glucose)
   24.1–42.1 (xylose)
46.3–91.1 (glucose)
10.1–54.3 (xylose)
Corn stover Alkali deacetylation + disk milling (36 inch diameter) 128–468 85.9–91.7 (glucose) [42]
81.1–86.2 (xylose)
Sugarcane bagasse Alkaline + disk milling 11,111 77 (glucose) [63]
67 (xylose)
Sugarcane bagasse Hot water NA 72.1–78.7 (total sugar) [75]
Hot water + PFI refining   82.1–87.2 (total sugar)
Wheat straw Hot water NA 28.1–72.4 (total sugar) [59]
Hot water + PFI refining   28.3–75.5 (total sugar)
Oil palm mesocarp fiber Ball milling NRf 7.3–10.3 (glucose) [38]
Alkaline   12.2–14.9 (xylose)
Alkaline + ball milling   39.6–63.9 (glucose)
   21.1–46.5 (xylose)
97.3 (glucose)  
63.2 (xylose)
Corn stover Acid impregnation + dilute acid NA 69–73 (glucose) [58]
Alkali deacetylation + acid impregnation + dilute acid   55–58 (xylose)
Acid impregnation + dilute acid + PFI refining   80–83 (glucose)
Alkali deacetylation + acid impregnation + dilute acid + PFI refining   76–80 (xylose)
   85 (glucose)
75 (xylose)
90 (glucose)
92 (xylose)
Corn stover Alkali deacetylation + acid impregnation + steam explosion + PFI refining NR 79–83 (glucose) [49]
Alkali deacetylation + acid impregnation + steam explosion + extruder   50–55 (xylose)
Alkali deacetylation + acid impregnation + steam explosion + food processor/blending   82–83 (glucose)
Alkali deacetylation + acid impregnation + steam explosion + disk milling (12 inch)   56–58 (xylose)
Alkali deacetylation + acid impregnation + dilute acid (pilot-scale)   71–75 (glucose)
Alkali deacetylation + acid impregnation + dilute acid pretreatment (pilot-scale) + Szego milling   49–51 (xylose)
   75–78 (glucose)
52–54 (xylose)
82 (glucose)
80 (xylose)
90–95 (glucose)
85–90 (xylose)
Eucalyptus chips Hot water NA 73.19 (glucose) [72]
Hot water + disk milling   90.45 (xylose)
   91.62 (glucose)
88.12 (xylose)
Rice straw Disk milling NR 86 (glucose) [60]
Hot water + disk milling   40 (xylose)
   110 (glucose)
84 (xylose)
  1. aHot compressed water, hydrothermal and autohydrolysis are named as hot water
  2. bWhen energy consumption was presented as kJ/ton, it was converted into kWh/ton
  3. cEnergy consumption is only from mechanical refining
  4. dIf the exact sugar yields were not indicated in the reports, sugar yields were estimated or calculated as the ratio of the amount of monosaccharides produced during hydrolysis to the corresponding carbohydrate concentrations in the original samples
  5. eNA means not applicable
  6. fNR means not reported