Table 1 Various pretreatment methods used in biorefineries and their results

Physical

Ball milling

Oil palm biomass

15.9% glucose yield

67.5% glucose yield

CI reduced from 56.1% (untreated) to 9.3%

(Zakaria et al. 2014)

5.4% Xylose yield

80.1% xylose yield

Twin-screw extrusion

Corn stover

25 g/L glucose yield

45 g/L glucose yield

Increase in cellulose content, decrease in hemicellulose content, and CI

(Wang et al. 2020)

19 g/L Xylose yield

40 g/L Xylose yield

Microwave pretreatment

Wheat straw

Ethanol yield of 26.78 g/kg

Ethanol yield of 148.93 g/kg

–

(Xu et al. 2011)

–

Cellulose recovery > 93%

80% Hemicellulose recovery

Chemical pretreatment

Alkaline pretreatment

Corn stover

–

glucose and xylose yield 0.48 g/g of the original biomass

78.2% sugar yield

(Li et al. 2012b)

92% lignin removal

Corn stover

–

95.1% glucose yield

Glucose yields were two to fourfold compared to untreated, with less than 5% cellulose removal

(Mirmohamadsadeghi et al. 2016)

Fivefold xylose yield

40–45% lignin removal

Miscanthus

–

62.3% glucose yield

20-fold xylose yield

40–45% lignin removal

Switchgrass

–

81.3% glucose yield

40–45% lignin removal

Acid pretreatment

Sunflower stalks

100 g raw material

33 g glucose recovery

Recovery of 65% of the glucose and xylose present in the raw material

(Ruiz et al. 2013)

33 g xylose recovery

Organosolv pretreatment

Sugarcane bagasse

–

91% glucose yields

99% glucan enzyme digestibility, 90% lignin purity

(Hassanpour et al. 2020)

67% xylose yields

63% lignin yield

Physio-chemical pretreatment

AFEX

Corn stover

~ 32% glucan conversion

Higher severity AFEX gave rise to higher glucan conversion (~ 85%)

The total pore volume of the biomass decreased

(Chaudhari et al. 2022)

~ 23% Xylan conversion

~ 85% maximum xylan conversion

Hot-water pretreatment

Napier grass

–

73% of inhibitor-free glucose yield

Higher temperatures may lead to inhibitor production

(Wells et al. 2020)

Energycane

–

65% of inhibitor-free glucose yield

Steam explosion

Spruce wood chips

Very recalcitrant

Up to 90% cellulose digestibility

The particle size of the biomass is decreased

(Pielhop et al. 2016)

Biological pretreatment

White rot fungi (Pleurotus ostreatus)

Eucalyptus grandis sawdust

2.8% hydrolysable cellulose recovery

16.7% of total cellulose generation for hydrolysis

–

(Castoldi et al. 2014)

White rot fungi (Ceriporiopsis subvermispora)

Sugarcane bagasse

–

47% of the potential glucose of untreated biomass was recovered after pretreatment followed by enzymatic hydrolysis

Increased cellulose digestibility of the biomass

(Machado and Ferraz 2017)

Mixed microbes/bacteria

Corn straw

–

Cellulose, hemicellulose, and lignin degradation rates were 34.9%, 44.4%, and 39.2%, respectively

Strong ability to degrade lignin, could accelerate the hemicellulose degradation rate, increased methane content, and shortened the fermentation period

(Li et al. 2020)