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Table 6 Hydrogen production from microalgae pretreated by combined methods

From: Fermentative hydrogen production using pretreated microalgal biomass as feedstock

Treatment methods

Substrate

Substrate concentration (g/L TS)

Inoculum

Operational conditions

Hydrogen yield (mL H2/g VS)

Comments

References

Acid: HCl 2.0%, 12 h;

Heat: 121 °C, 20 min

Chlorella sorokiniana

10

Enterobacter cloacae IIT-BT 08

pH = 7.0, 37 °C; batch

201.6c

Algal biomass of C. sorokiniana was produced by CO2 sequestration in continuous mode, and then used as substrate for anaerobic hydrogen production. Substrate concentration was optimized to enhance the hydrogen yield from C. sorokiniana

[32]

Acid-heat: HCl 5%, 121 °C, 20 min

Chlorella sorokiniana

14

Anaerobic sludge

pH = 6.5, 60 °C; batch

760

Better hydrogen production was achieved from microalgae biomass treated by combined treatment than single treatment method including autoclave, sonication and H2O2 treatment

[25]

Acid-heat: HCl 20%, 121 °C, 20 min

Chlorella sorokiniana

14

Anaerobic sludge

pH = 6.5, 60 °C; batch

958

Hydrogen yield was increased from 760 to 958 mL/g VS when HCl concentration was increased from 5 to 20%

[25]

Acid-heat: H2SO4 0.1 mM, 108 °C, 30 min

Chlorella vulgaris

20

Clostridium acetobutylicum B-1787

pH = 6.8, 37 °C; batch

2.24d

Immobilized Clostridium acetobutylicum cells were used for hydrogen production from various microalgae species

[33]

Acid-heat: H2SO4 0.1 mM, 108 °C, 30 min

Nannochloropsis sp. rsemsu-N-1

20

Clostridium acetobutylicum B-1787

pH = 6.8, 37 °C; batch

0.90–9.52d

Different microalgae species were used as substrate, and highest hydrogen yield was obtained from wet Nannochloropsis sp. biomass

[33]

Acid-heat: H2SO4 0.1 mM, 108 °C, 30 min

Arthrospira platensis

20

Clostridium acetobutylicum B-1787

pH = 6.8, 37 °C; batch

2.24–8.06d

Heating temperature range of 100–121 °C, with and without acid addition were applied in treating microalgae biomass, most efficient treatment condition was determined to be 108 °C, 30 min with 0.1 mmol/L H2SO4

[33]

Acid-heat: H2SO4 0.1 mM, 108 °C, 30 min

Dunaliella tertiolecta

20

Clostridium acetobutylicum B-1787

pH = 6.8, 37 °C; batch

0.22–1.46d

Immobilized Clostridium acetobutylicum cells were used for hydrogen production from various microalgae species

[33]

Acid-heat: H2SO4 0.5 mol/L, 100 °C, 30 min

Scenedesmus obliquus

Clostridium butyricum

pH = 7.0, 37 °C; batch

2.9e

Potential of H2 production from microalgae biomass and the respective energy consumption and CO2 emissions in the bioconversion process were evaluated. Energy consumption of 7270 MJ/MJH2 and 670 kg CO2/MJH2 were achieved, 98% of which owed to microalgae culture process due to the use of artificial lighting

[34]

Acid-heat: H2SO4 0.5%, 121 °C, 60 min

Spirulina platensis

10

Bacillus firmus NMBL-03

pH = 6.5, 38 °C; batch

0.38e

A wide variety of substrates (glucose, xylose, arabinose, lactose, sucrose, and starch) and carbohydrate rich waste products (bagasse hydrolysate, molasses, potato peel and cyanobacterial mass) were used for dark fermentative hydrogen production. Abundant VFA were present in spent medium of hydrogen production from cyanobacterial mass, which can be further used as substrate for photo fermentative hydrogen production

[35]

Acid-heat: H2SO4 1%, 135 °C, 15 min

Chlorella pyrenoidosa

20

Clostridium butyricum

pH = 6.0, 35 °C; batch

81.2

Heat and acid treated Chlorella pyrenoidosa biomass was used as substrate for hydrogen production. Energy was further removed through following photo hydrogen production and methane fermentation

[36]

Acid-heat: H2SO4 1%, 135 °C, 15 min

Chlorella pyrenoidosa

10 (additional cassava starch 10 g/L)

Clostridium butyricum

pH = 6.0, 35 °C; batch

276.2

Hydrogen production from microalgae biomass was significantly increased from 81.2 to 276.2 mL/g VS by the addition of cassava starch to get an optimum C/N ratio

[36]

Acid-heat: H2SO4 3%, 121 °C, 60 min

Lipid extracted algae cake (collected from a lake)

5b

Anaerobic sludge

pH = 6.0, 29 °C; batch

122d

Comparison of hydrogen production from algae untreated, liquid fraction of treated algae, solid fraction of treated algae and treated algae mixture was examined. Best hydrogen and VFA generation was achieved from liquid fraction of treated algae

[37]

Acid-microwave: H2SO4 0–2.0%, 80–180 °C, 5–25 min

Nannochloropsis oceanica

50

Anaerobic sludge

pH = 6.0, 35 °C; batch

39

Hydrogen production from microalgae biomass was significantly increased by combined acid and microwave treatment

[21]

Base-heat: NaOH, 8 g/L, 100 °C, 8 h

Scenedesmus (lipid extracted)

18a

Anaerobic sludge

pH = 6.3, 37 °C; batch

45.54

For the combined treatment, lower temperature and longer treating time was preferred than higher temperature and shorter time

[15]

Base-heat: NaOH, 8 g/L, 121 °C, 4 h

Scenedesmus (lipid extracted)

18a

Anaerobic sludge

pH = 6.3, 37 °C; batch

37.42

Better hydrogen production was achieved from microalgae biomass treated by combined treatment than single treatment method

[16]

Acid-heat: pH 1.4, 140 °C, 15 min; biological: cellulase 0.05 g/g TVS, 48 h; glucoamylase 0.05 g/g VS, 24 h

Mixed algae (collected from algae bloom in Taihu Lake)

25

Anaerobic sludge

pH = 6.0, 35 °C; batch

33.56–43.84

Steam with acid treatment showed better reducing sugar release than steam with alkaline treatment. The energy conversion efficiency was significantly increased through 3-stage process: dark-fermentation, photo-fermentation, and methanogenesis

[30]

Acid-microwave: pH 1.4, 140 °C, 15 min; biological: cellulase 0.05 g/g TVS, 48 h; glucoamylase 0.05 g/g TVS, 24 h

Mixed algae (collected from algae bloom in Taihu Lake)

25

Anaerobic sludge

pH = 6.0, 35 °C; batch

42.4–47.07

Microwave with diluted acid treatment degraded algal cells into smaller fragments (< 5 mm), and resulted in higher saccharification efficiency of microalgae

[30]

Acid-microwave: H2SO4 0.2 mL, 140 °C, 15 min; biological: glucoamylase 0.2%

Arthrospira platensis

10–40

Anaerobic sludge

pH = 6.5, 35 °C; batch

86.5–96.6d

Hydrogen yield was significantly enhanced from 96.6 to 337.0 mL H2/g DW using a combination of dark- and photo-fermentation. Removal of harmful byproducts from hydrolysis pretreatment and dark fermentation can further enhance the overall hydrogen yield

[38]

  1. ag/L VS
  2. bg/L COD
  3. cmL H2/g COD
  4. dmL H2/g TS
  5. emol H2/mol sugar