Feedstock Feedstock availability

Composition, % w/w

Pretreatment

Hydrolysis and fermentation

Ethanol

Reference

Corn stover (agricultural by-product 80 - 100 million dry tonnes annum⁻¹ [40]

Glucan-41.0% Xylan-25.3% Arabinan-6.1% Galactan-3.0% Lignin-21.0%

Steam pretreatment of SO₂ impregnated corn stover at 200˚C for 5 min

SSF at 10% WIS using cellulase and β-glucosidase mixture and S. cerevisiae (Baker’s yeast); fermentation at 30˚C, pH 5, 72 h and inoculum 2 g yeast∙L⁻¹

74% of the theoretical ethanol yield, ethanol 25 g∙L⁻¹

[41]

Corn stover

Glucan-42.2%

Xylan-19.6%

Arabinan-2.9%

Galactan-1.1%

Lignin-20.8%

Steam pretreatment as described in [41]

Pre enzymatic hydrolysis using Thermo-active enzyme mixture followed by SSF using S. cerevisiae (Baker’s yeast) at 11.50% WIS; fermentation at 35˚C, pH 5, 96 h and inoculum 1.8 g yeast 100 mL⁻¹

Ethanol 33.8 g∙L⁻¹, 80.2% overall ethanol yield

[42]

Corn stover

Steam pretreatment as described in [41] Ohgren et al., 2006

8% WIS and 10 FPU/g WIS SSF Vs. SHF; S. cerevisiae in fermentation at 35˚C, pH 5, 144 h and inoculum 1 g dry yeast L⁻¹

Theoretical ethanol yield in SSF-72.4 % and in SHF-59.1 %

[43]

Japanese cedar (Cryptomeria japonica) 7.6 million tonnes annum⁻¹ forest residues

Crushed to 20 micron of particle size using Cogwheel mill

SSF using commercial cellulase and S. cerevisiae after 24 h. Fermentation conditions not available

270 L ethanol tonne⁻¹ of Japanese cedar, 0.2 g ethanol g⁻¹ of Japanese cedar

[44]

Wheat straw 84.5 million dry tonnes of wheat straw annum⁻¹ at residue to wheat grain ratio of 1.3 - 1.7:1 [45]

Cellulose 33.5%,

Hemicellulose 22.4%, Klason lignin 16.4%, Ash 5.8%, Residual 21.8%

A three step pretreatment: Presoaking at 80˚C for 20 min followed by thermal treatment at 170˚C - 180˚C for 7.5 - 15 min then steam treatment at 195˚C for 3 min

Enzymatic hydrolysis of the solid residue using Cellubrix L enzyme

203 - 205 kg ethanol tonne⁻¹ of straw from cellulose fraction; 350.5 kg tonne⁻¹ from both cellulose and hemicelluloses fractions (calculated based on sugars obtained in hydrolysis step)

[46]

Cassava stems and peelings Cassava stems and peelings: 403 tonnes∙ha⁻¹

Cellulose 28.9%, 9.7% Hemicellulose 21.1%, 32.3% Klason lignin 30.6%, 16.9% Proteins 1.4%, 3.7% Ash 7.3%, 11.3% Lipids 0.7%, 1.7% others 9.9%, 24.2% in stems, peelings, respectively

Thermohydrolysis at 225˚C for 50 min

Enzymatic hydrolysis using Cellulase followed by fermentation using S. cerevisiae or Rhyzopus spp. at 1 g dry biomass inoculum per 100 mL hydrolyzate and other fermentation conditions not available

Stems: 5.2 g ethanol 100 g⁻¹ stems Peelings: 2.6 g ethanol 100 g⁻¹ peelings

[47]

Cassava cellulosic wastes from starch processing Liquid waste (1% total solids): 8.9 - 10.6 tonnes and Wet cassava bagasse: 0.9 - 1.1 tonnes from 1 tonne of dry cassava processed [48]

Carbohydrate 76.6% Starch 60.8% Fibre 15.8% Protein 0.8%

Hydrolysis using α-amylase for 1 h at 97˚C - 100˚C followed by Dilute HCl hydrolysis

Saccharification of hydrolyzed starch using amyloglucosidase at 50˚C - 60˚C followed by fermentation using S. cerevisiae at 40˚C - 50˚C, pH 4.6 - 5.5, 8 h and inoculum 0.2 g dry biomass per 100 mL hydrolyzate

2.7 g ethanol 15 g⁻¹ cassava cellulosic waste, 32.4% w/w ethanol concentration

[49]

Sugar cane bagasse

276 kg bagasse∙tonne⁻¹ of sugarcane; Sugarcane harvest in South Central Brazil 516 million tonnes in 2011/2012 [50]

Cellulose 52% Hemicellulose 20% Lignin 24% [51]

Delignification using NaOH (1N) at reflux temperature for 2 h

SSF using cellulase and S. cerevisiae using 1 g de-lignified bagasse per 20 mL medium; fermentation 5 days and other conditions not available

11.8 g ethanol∙L⁻¹

[52]