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www.uni-due.de/zwu/iwatec

Methods

Scenedesmus sp. cultures (Figure 1) have been pretreated before digestion with the seeding material in different ways to investigate the best performance for hydrogen production. The seeding material was sludge from a wastewater treatment plant. The pretreatments included microwave digestion (Figure 2), ultrasonic, acid pretreatment and a combination between acid pretreatment and microwave digestion. For control purposes experiments without pretreatment have been performed as well (Table 1). With and without pretreatments the Scenedesmus sp. cultures have been digested in batch experiments (Figure 3 & 4) under mesophilic conditions with different pH-values in order to produce hydrogen. The experiment was performed in triplicates while the seeding material in duplicates for about 8 days. The quality and quantity of gas has been monitored during the experiments by an eudiometer for measuring the quantity of gas produced and infrared gas analyzer to determine the composition of produced gas.

Conclusions and outlook The quantity and quality of gas volume produced differed between the various pretreatments. Hydrogen gas was produced but not in large quantities. It varied from 8% to 16% and 5% to 15.5% in pH 5.0 and pH 6.0 respectively. We couldn´t obtain clear results. One reason for this could be that the seeding sludge contained vast types of microorganisms instead of pure hydrogen producing ones. The other microorganisms could be hydrogen utilizing microorganism which consumed parts of the produced hydrogen. The solution could be to use pure hydrogen producing strains in order to increase the hydrogen quantity in the produced gas. This has to be investigated in future experiments.

Contact: Bahieeldin E. A. Abdelhalim, 9 Gamma Street, Faculty of Agriculture – Cairo University 12613, +2012-2620-7548, bahieeldin@staff.cu.edu.eg

References 1. Das, D. and T. Veziroglu, Advances in biological hydrogen production processes. International Journal of Hydrogen Energy, 2008. 33(21): p. 6046-6057. 2. Levin, D., Biohydrogen production: prospects and limitations to practical application. International Journal of Hydrogen Energy, 2004. 29(2): p. 173-185. 3. Chong, M.-L., et al., Biohydrogen production from biomass and industrial wastes by dark fermentation. International Journal of Hydrogen Energy, 2009. 34(8): p. 3277-3287. 4. Hawkes, F., et al., Continuous dark fermentative hydrogen production by mesophilic microflora: Principles and progress. International Journal of Hydrogen Energy, 2007. 32(2): p. 172-184.

Introduction Biohydrogen is one of the most promising solutions to energy scarcity as it is renewable and could have high potential to replace fossil fuel in the future beside that it is environmental friendly[1-3]. Most of hydrogen produced nowadays is produced by chemical means[3]. Biohydrogen can be produced from vast arrays of substrate[3]. In this study the biohydrogen is produced from microalgae by dark fermentation[4]. The microalgae have been chosen because of the autotrophicity. They can grow easily and do not compete with cultivated lands.

The gas production from Scenedesmus sp. is monitored for 7.75 days in 35 C° and different pH conditions, the pH conditions is adjusted to 5.00 and 6.00 for each pretreatment. Figure five and sex shows the amount of produced gas as normal state milliliter per gram volatile solids (Nml/gVS) in different pH 5.0 (Figure 5) and 6.0 (Figure 6) respectively. Glucose is used as a control and the sludge as a base line of the experiment, changing the pH condition have an impact on gas production either quantity or quality. The gas volume dramatically decreased in the state of pH 6.0 than pH 5.0 as well as the hydrogen percentage within the gas. Glucose treatment produced about 460 ml of gas in pH 5.0 while in pH 6.0 produced 305 ml. Table two and three shows the gas quality measurements of the produced gas in pH 5.0 and 6.0 respectively, the highest percent of hydrogen production from algae achieved from no pretreatment in pH 5 was 16.2% then the MWA 100 was 14.94%, while pH 6.0 shows less hydrogen percent.

Biohydrogen Production from Scenedesmus sp. using Dark Fermentation Bahieeldin E. A. Abdelhalim1,2

Dr.-Ing. Ruth Brunstermann2; Dr. rer. nat. Mohammad. H. A. Ibrahim3; Prof. Dr.-Ing. Renatus Widmann2

1: Microbiology Department, Faculty of Agriculture - Cairo University. 2: Municipal Water- and Waste Management Department, Faculty of Engineering - University of Duisburg Essen.

3: Natural and Microbial Products Chemistry Dept., Pharmaceutical and Drug Industries Research Division, National Research Center.

Results

Table 3 :

Sample O2 % CO2 % CH4 % H2 % N2 % H2 % CO2 % CH4 %

Glu 2.90 21.00 0.33 13.11 62.66 38.07 60.98 0.96

NP 3.20 6.74 0.31 1.30 88.45 15.57 80.72 3.71

MW 70 2.77 7.34 0.41 1.20 88.28 13.41 82.01 4.58

MWA 70 1.81 7.58 0.45 1.10 89.06 12.05 83.02 4.93

MW 100 2.31 6.65 0.48 0.70 89.86 8.94 84.93 6.13

MWA 100 1.65 8.99 0.40 0.68 88.28 6.75 89.28 3.97

MWP 1.00 7.77 0.33 0.45 90.45 5.26 90.88 3.86

US 2.16 8.90 0.29 1.20 87.45 11.55 85.66 2.79

Acid 1% 2.11 9.90 0.31 1.10 86.58 9.73 87.53 2.74

Acid 5% 2.50 7.90 0.44 1.00 88.16 10.71 84.58 4.71

Gas quality measurements for the samples for the pH 6.

Measured Values Calculated Values

Table 2 :

Sample O2 % CO2 % CH4 % H2 % N2 % H2 % CO2 % CH4 %

Glu 2.30 17.50 0.22 18.90 61.08 51.61 47.79 0.60

NP 2.30 9.50 0.33 1.90 85.97 16.20 80.99 2.81

MW 70 2.19 9.58 0.29 1.21 86.73 10.92 86.46 2.62

MWA 70 1.93 10.10 0.31 1.40 86.26 11.85 85.52 2.62

MW 100 0.70 10.00 0.33 1.20 87.77 10.41 86.73 2.86

MWA 100 2.00 7.80 0.17 1.40 88.63 14.94 83.24 1.81

MWP 0.90 10.00 0.20 0.90 88.00 8.11 90.09 1.80

US 2.10 14.00 0.21 1.20 82.49 7.79 90.85 1.36

Acid 1% 1.00 10.10 0.30 1.10 87.50 9.57 87.83 2.61

Acid 5% 1.87 8.90 0.29 0.98 87.96 9.64 87.51 2.85

Gas quality measurements for the samples for the pH 5.

Measured Values Calculated Values

Figure 5: Total gas production from treatments in pH 5.0.

Figure 6: Total gas production from treatments in pH 6.0.

Figure 7: Comparison between volume of produced gas (Nml) for each treatment in the different pH conditions

Figure 1: Scenedesmus sp. total magni-fication 1000x

Figure 2: Microwave treatment effect, cell wall and plasma membrane destruction.

Figure 3: Schematic diagram of batch experiment according to DIN 38414 S8.

Figure 4: Digestion process, pretreated algae with sludge particles.

Table 1:

Probe Pretreatment Specification pH

pH 5

pH 6

pH 5

pH 6

pH 5

pH 6

pH 5

pH 6

pH 5

pH 6

pH 5

pH 6

pH 5

pH 6

pH 5

pH 6

pH 5

pH 6

pH 5

pH 6

Glucose

Algae

No Pretreatment (NP)

Microwave Digestion 100 C° for 10 min. heat up + 5 min. hold (MW 100)

70 C° for 10 min. heat up + 5 min. hold (MW 70)

Pressure 2 bar for 10 min. heat up + 5 min. hold (MWP)

100 C° for 10 min. heat up + 5 min. hold + 1% HCl (MWA 100)

70 C° for 10 min. heat up + 5 min. hold + 1% HCl (MWA 70)

Ultrasonic (US)

A summary of the probes used and the pretreatments done in biohydrogen production batch

batch test by dark fermentation in mesophilic conditions.

Power 4 kW, Duty cycle 50% for 5 min.

HCl 1%

HCl 5%

Figure seven compares all treatments in terms of produced gas volume (Nml) in the different pH conditions. The volume of gas produced reaches its maximum after 4 days then start to be stationary then declining phase .