Table 2 Comparison of integration of hydrothermal treatment and gas biofuels production in the literature and this study

Algae

Methane

Batch (stainless steel cylinder), 100 °mL

0–1.5 h, 260–320 °C

Batch, 37 °C, Liquid products

62

–

44–61

Tommaso et al. [35]

Swine manure

Methane

–

–

Batch, 37 °C, Liquid products

65

~150–175 mL/g COD

45–55

Zhou et al. [58]

Sunflower stalks

Methane

Batch

30 min, 160 °C H₂SO₄

Batch, 37 °C, Mixture

45

278 mL/g VS

Hesami et al. [19]

Sugar beet pulp

Methane

Batch (thermostatic reactor), 600 mL

20 min, 160 °C

Batch, 37 °C, Mixture

25

502.5 mL/g VS

Ziemin´ski et al. [17]

Wheat straw

Methane

Batch (cylindrical steel tank), 6.2 L

1 h, 160 °C, NaOH

Batch, 35 °C, Mixture

31

224 mL/g TS

Sambusiti et al. [15]

Rice straw

Methane

Batch (hydrothermal

reactor), 131 mL

10 min, 200 °C,

Batch, 35 °C, Mixture

60

132.7 mL/g VS

Chandra et al. [18]

Beech wood

Methane

Batch (Inconel-625 vessel), 5 mL

7–240 s, 380 °C

Batch, 50 °C, Liquid products

35

–

–

Yoshida et al. [28]

Laminaria japonica

Hydrogen

Batch (stainless steel vessel), 5 L

20 min, 170 °C

Batch, 35 °C, Mixture

3.5

109.6 mL/g COD

Jung et al. [38]

Wheat straw

Hydrogen

–

15 min, 180 °C

Continuous (CSTR, UASB AF), 70 °C, Liquid products

1–3

212 mL/g sugar

Kongjan et al. [39]

Sunflower stalks

Hydrogen

Batch (Stainless autoclave), 1 L

1 h, 170 °C, HCl

Batch, 35 °C, Liquid products

30

–

Monlau et al. [33]

Gelidium amansii

Hydrogen

Batch (high-pressure reactor) 30 L

15 min, 150 °C H₂SO₄

Batch, 35 °C, Liquid products

1.25

–

Parka et al. [36]

Switchgrass

Hydrogen

Batch (steam explosion

reactor), 4 L

10 min, 190 °C

Continuous (UASB), 37 °C, Liquid products

0.42

288 mL/g COD

–

Veeravalli et al. [37]

Cornstalk

Hythane

Batch (High-pressure reactor), 1.8 L

0 min, 260 °C

Continuous(UASB, PBR), 37 °C, Liquid products

Hydrogen, 0.5

Methane, 0.5

H₂, 0–146 mL/g COD CH₄, 158–302 

mL/g COD

H₂, 19 − 2

CH₄, 93 − 67

This study