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One-stage and two-stage anaerobic digestion of lipid-extracted algae

One-stage and two-stage anaerobic digestion of lipid-extracted algae Ann Microbiol (2015) 65:1465–1471 DOI 10.1007/s13213-014-0985-x ORIGINAL ARTICLE One-stage and two-stage anaerobic digestion of lipid-extracted algae Yan Li & Mintian Gao & Dongliang Hua & Jie Zhang & Yuxiao Zhao & Hui Mu & Haipeng Xu & Xiaohui Liang & Fuqiang Jin & Xiaodong Zhang Received: 3 July 2014 /Accepted: 14 September 2014 /Published online: 8 October 2014 Springer-Verlag Berlin Heidelberg and the University of Milan 2014 Abstract Waste-grown microalgae are a potentially impor- Introduction tant biomass for wastewater treatment. The lipid accumulated in microalgae could be utilized as feedstocks for biodiesel The potential of microalgae as a source of biofuels is subject to production. The algal residues, as major by-products derived increasing academic and industrial research (Brennan and from lipid extraction, mainly consist of carbohydrate and Owende 2010; Ahmad et al. 2011). Therefore, the cultivation protein, making anaerobic digestion an efficient way to recov- of microalgae and subsequent product refinery such as lipid er energy. The conversion of lipid-extracted algal residues into extraction have gained much more attention by many re- methane plays dual role in renewable energy production and searchers (Bellou and Aggelis 2012). As a result of microalgae sustainable development of microalgal biodiesel industry. technology development, lipid-extracted algal residues Therefore, an anaerobic fermentation process for investigation (LARs) are the residual biomass from biodiesel production of the methane production potential of algal residues was processes that are rich in carbohydrate and protein. LARs conducted in this paper. The effect of inoculum to substrate could be used as a high-protein animal feed, a source of small ratios (ISRs) on the methane production by anaerobic diges- amounts of other high-value microalgal products (Chisti tion of Chlorella sp. residue in a single stage was evaluated. 2007), and possibly to produce bioactive compounds and The maximum methane yield of 195.6 ml CH /g volatile solid hydrogen (Singh et al. 2005;Yangetal. 2010). The compo- (VS) was obtained at an ISR of 1:1. The stability and progress sitions of LARs make anaerobic digestion an efficient way to of the reaction from algal residues to methane were monitored recover energy, which will also reduce the cost of microalgal- by measuring the pH, volatile fatty acids (VFAs), total ammo- biodiesel production (Sialve et al. 2009). niacal nitrogen (TAN), and methane volume. Based on the The technology for anaerobic digestion is well developed. results of one-stage experiments, two-stage technology was The effects of fermentation conditions such as feedstocks, proposed and was found to be more suitable for high organic controlled parameters, inoculum and substrate concentrations load. The optimum conditions for acidogenesis and on biogas production have been studied (Chae et al. 2008; methanogenesis are indicated in this paper. Forster-Carneiro et al. 2008;Kaparajuet al. 2009). The inves- tigation of algal biomass as feedstock for biogas production has also been reported (Marcin et al. 2013). Considering the . . . . Keywords Biogas Methane Algal residues One stage substrates relevant to this paper, there is some research on Two stage algal species such as Spirulina maxima (Samson and Leduy : : : : : : : 1982), Chlorella vulgaris (Sánchez Hernández and Córdoba Y. Li (*) M. Gao D. Hua J. Zhang Y. Zhao H. Mu H. Xu : : X. Liang F. Jin X. Zhang (*) 1993), Scenedesmus obliquus and Phaeodactylum Key Laboratory for Biomass Gasification Technology of Shandong tricornutum (Zamalloa et al. 2012). In those investigations Province, Jinan 250014, China for methane production, intact algae were used; as a result, the e-mail: liy@sderi.cn resistance of the cell wall limited the hydrolysis step and the e-mail: xd_zhang77@yahoo.com.cn fermentation period was prolonged. In addition, the C/N ratio : : : : : : : Y. Li M. Gao D. Hua J. Zhang Y. Zhao H. Mu H. Xu of algal biomass was lower than the empirical value; thus, co- : : X. Liang F. Jin X. Zhang digestion was commonly adopted for nutrient adjustment to Energy Research Institute of Shandong Academy of Sciences, enhance the biogas productivity (Zhong et al. 2012). The Jinan 250014, China 1466 Ann Microbiol (2015) 65:1465–1471 Table 1 Characteristics number of studies assessing the biochemical methane poten- Parameter Value of lipid-extracted algal tial of lipid-extracted microalgae is limited (Chisti 2008; residue Ehimen et al. 2009;Ehimenetal. 2011;Alzateetal. 2014; Total solid (TS, %) 94.6 Zhao et al. 2014). Volatile solid (VS, %-TS) 89.3 To find out the best conditions for the digestion of LARs Total carbon (%) 43.04 and to obtain dependable data, the methane potential of the Total nitrogen (%) 8.07 digestion process was investigated in this article. The experi- Protein (%) 50.4 ments were performed in one-stage and two-stage set-ups. The Lipid (%) 3.1 effect of inoculum to substrate ratios on methane production in a one-stage reactor was studied in an appropriate load range. The operation of a two-stage digestion system was not. The acidogenesis protocol was identical to that described for one-stage digestion, but the ISR was adjusted to 1:3 and carried out in terms of a high organic load at which failure would occur during the process of one-stage digestion. the pH was controlled at 8. Acidogenesis efficiency (AE) was calculated by the equation: Materials and methods AE ¼ VFA OutputðÞ g =VS InputðÞ g Substrate and inoculum characteristics An Up-flow Anaerobic Sludge Blanket (UASB), made of Dried and disrupted Chlorella vulgaris (Tianjian Co., organic glass, was used as methanogenic reactor with a work- Binzhou, China) after lipid extraction was used as substrate. ing volume of 2.5 l. During the start-up, UASB reactors were The main parameters were listed in Table 1. The C/N ratio of inoculated with granular sludge and acclimated with glucose lipid-extracted Chlorella vulgaris was 5.3. Anaerobic digested solution (1.5 g/l) at an organic loading rate (OLR) of 1.0 g sludge collected from a digester operating at 35 °C in COD/l·d for 1 month. Xiangchi Corporation was used as inoculum. The total solid Due tothe largedemandofacidicliquidwithlong-term (TS) and volatile solid (VS) contents of sludge were 7.85 and operation of UASB, the component of influent that flew into 86.33 %, respectively. UASB simulated genuine volatile fatty acids (VFAs) compo- sitions and content. The UASB reactors were continuously fed One-stage experiments with synthetic medium at an initial OLR of 2.0 g COD/l·d for 10 days, and then increased to 3, 4, 6, 8, 10, and 12 g COD /l·d Batch anaerobic digestion of algal residue was performed in at 10 days intervals. To achieve different OLRs, the hydraulic 1 l bottles. The mixture of sludge and algal residues were retention time (HRT) varied with the control of influent vol- added to reach final volume of 0.8 l with fresh water supple- ume. The chemical composition of the synthetic medium was ment. The outlet of the reactor gap was connected to the as follows (g/l): acetic acid 0.9, propionic acid 0.225, butyric airbag. Then, the set-up was placed in water bath at 35 °C acid 0.178, valeric acid 0.0225, iso-butyric acid 0.102, iso- and shaken at intervals. Headspace was purged with nitrogen valeric acid 0.068. Sodium nitrate and potassium dihydrogen every time the cap was opened. Tests were run as duplicates to phosphate were supplemented to maintain the COD:N:P at the test statistical reliability. Inoculum without substrate was used level of 100:4:1. Experiments were run for a total of 60 days as control. under controlled room temperature (35 °C). The three different ISRs in the test were 2:1, 1:1 and 1:2. They were achieved by keeping a constant inoculum concen- tration (20 g VS/l, an empirical value for seed concentration) Analytical methods and varying the substrate concentrations according to the ISRs. For the investigated ISRs, the TS concentrations didn’t The composition of biogas was measured using a double- exceed the maximum empirical value of 10 %. Anaerobic channel infrared technique with a biogas analyzer (GA2000, digestion of algal residues was operated for 15 days. Geotech), which showed the desired methane content. pH values were measured with a pH meter. Total ammoniacal Two-stage experiments nitrogen (TAN, NH and NH ) was analyzed according to 3 4 Nessler’s colorimetry with 5B-2(N) ammoniacal nitrogen The preliminary data obtained from one-stage anaerobic di- analysis meter (Lianhua Technology Company, China). gestion indicated that there was hardly methane produced at COD was measured by a COD analyzer (Lianhua Technology ISR of 1:3. Thus, two-stage technology was applied to inves- Company, China). The free ammonia concentrations (i.e., tigate whether the methane production could be improved or unionized NH ) are a function of the total ammoniacal 3 Ann Microbiol (2015) 65:1465–1471 1467 nitrogen concentration, pH, and dissociation constant, and The methane yield was calculated for each ISR by dividing formulae for the calculation of free ammonia concentrations the final methane volume by the VS weight of substrate are available in the literature (Kayhanian 1999). TS and VS added. Table 2 indicates that the methane yield after 15 days were determined according to APHA (2005). of digestion reached high levels of 195.6 ml CH /g VS and The VFA (acetic, propionic, butyric, valeric, iso-butyric 191.6 ml CH /g VS as the ISRs were 2:1 and 1:1 (initial and iso-valeric acids) concentrations were determined using substrate VS loads of 8 g VS and 5.3 g VS), respectively, an Agilent 7890 series gas chromatograph (GC) system. The but decreased when the substrate load (32 g VS for ISR of 1:2) column of HP-FFAP (50 m×320 μm×0.5 μm) was selected. was further increased. The result gave a methane yield higher Flame ionization detector (FID) was adjusted to 300 °C as the than that found in batch experiments with Microcystis spp. operating temperature. Nitrogen was used as the carrier gas, carried out by Zeng, who obtained a yield of 132.44 ml CH /g with a constant flow rate of 30 ml/min, and the inlet temper- VS at an ISR of 1:1 (Zeng et al. 2010). However, compared to ature was kept at 250 °C. Oven temperature was initially set to the methane yields of 300 ml/g VS (Alzate et al. 2014)and 60 °C and then increased to 100 °C with 10 °C/min ramping. 380 ml/g VS (Zhao et al. 2014), it was lower mainly because After a 2 min holding time at 100 °C, the oven temperature of different composition of algae and digestion conditions. As was gradually increased to 250 °C at the rate of 10 °C/min, can be seen in Table 2, the methane yield decreased from with 2 min holdings. 195.6 ml/g VS to 26.6 ml/g VS with the ISR varying from 2:1 to 1:2. The same conclusion was previously achieved by other researchers using different substrates (Raposo et al. 2006; Medina and Neis 2007). With an ISR of less than 1:1, methane Results and discussion yields significantly decreased and reached the lowest level of 26.6 ml CH /g VS at an ISR of 1:2, with yields approximately One-stage anaerobic digestion one-tenth of those obtained at other ISRs (Table 2). Combined with Fig. 2, though, the pH value for the whole process at an Biogas and methane production ISR of 1:2 was in an appropriate range, which was the contri- bution of the coexistence of VFA and ammonium. The yield Figure 1 shows the cumulative methane production, as a decrease was perhaps due to the weak methanogenic activity function of time with different ISRs used, corrected taking in the digesters, resulting from the inhibition caused by am- the control production into account. As indicated in Fig. 1, monia (Sawayama et al. 2004). methane production started immediately on the first day of It was observed that the operating time of 15 days was a digestion. Methane production almost reached a maximum on little long for the digestion. The methane production was day 7 and leveled off thereafter at all ISRs, because the almost finished in 10 days. The practical period for digestion substrate was almost completely consumed by the bacteria could be shortened from the perspective of methane produc- consortium. The methane production was proportional to the tion and energy conservation. Taking the methane yield and VS load applied. As can be seen from Fig. 1, the cumulative appropriate organic load into consideration, an ISR of 1:1 was methane volumes after 15 days of digestion for the ISRs of the optimum for anaerobic digestion with algae alone, the 1:2, 1:1 and 2:1 were 850, 3,066 and 1,565 ml, respectively. organic loading of which was 2 g VS/(l·d). pH variation The variation of pH over the period of digestion is shown in Fig. 2 and ranges from 6.7 to 7.7. When measured at days per unit, the pH climbed and gradually reached a relatively steady ISR=1:2 ISR=1:1 state with increasing time. It was obtained (not listed in Fig. 2) ISR=2:1 Table 2 Performances of reactors at ISRs of 1:2, 1:1 and 2:1 1000 ISR TS loaded VS loaded Methane yield substrate (g/l) substrate (g/l) (ml CH /g VS-add) 1:2 72.4 40 26.6 0 2 4 6 8 10121416 1:1 45.6 20 191.6 Time (d) 2:1 35.5 10 195.6 Fig. 1 The cumulative methane production for different ISRs Cumulative methane volume (ml) 1468 Ann Microbiol (2015) 65:1465–1471 8000 40000 8.0 ISR=1:2 ISR=1:1 7.8 ISR=2:1 7.6 7.4 30000 7.2 7.0 6.8 ISR=1:2 ISR=1:1 6.6 ISR=2:1 6.4 6.2 02468 0 2 4 6 8 1100112211441166 6.0 Time (d) Time (d) 0 2 4 6 8 10121416 Time (d) Fig. 3 VFA variation for different ISRs Fig. 2 pH variation for different ISRs during anaerobic digestion (Hashimoto 1983). As the ISRs were 2:1 and 1:1, the observed TAN concentrations in this study appeared not to directly affect the process. This suggested that the initial and final ammonia that the pH decreased during the first few hours of day 1. Organic acid production was generally initiated from the onset of the were too little to inhibit anaerobic digestion. When the ISR was 1:2, an accumulation of TAN of 4,300 mg/ reactor operations and resulted in these expected pH drops. The short-chain fatty acids as important intermediates were then l at day 2 was far above the threshold concentration (4,000 mg/l) reported in literature (Hashimoto 1983); therefore, the relatively quickly converted to methane by methanogens. Ammonium was simultaneously produced and drove the pH upwards. lower methane yield at an ISR of 1:2 was ascribed to the presence of a large amount of NH -N. Ammonia exerts negative effects Poor performance of methane production was obtained at on microbial cells and the concentration must be monitored in an ISR of 1:2. At this ISR, the pH stayed in the narrow range order to prevent toxic amounts from being reached. between 6.7 and 7.2, which was compatible with the normal Methanogens have been proven to be particularly sensitive to growth of anaerobic microorganisms. However, as can be seen from Fig. 3, VFAs were accumulated to a high level, but pH ammonia (Sasaki et al. 2011; Procházka et al. 2012). In terms of anaerobic digestion, a low C/N ratio can compromise the effi- didn’t drop accordingly, due to the simultaneous presence of a high level of ammonium (Fig. 4). The stability in pH can be ciency of the process, especially when high input and/or long retention times are applied. attributed to the high buffering capacity of the reactor. For ISRs of 1:1 and 2:1, the maximum free ammonia was about 148 and 102 mg/l, respectively. The TAN concentration TAN production reached 13,200 mg/l at the ISR of 1:2, corresponding to 240 mg/l free ammonia. It was found from Fig. 3 that VFAs Total produced ammoniums of different ISRs are indicated in were accumulated to a high level at ISR of 1:2, which was Fig. 4. An increment on TAN was observed at the experimen- possibly due to the poor methanogenesis, inhibited by tal ISRs. This fact was predictable, since it is widely known that some organic nitrogen (mainly protein) is converted to ammonium during anaerobic digestion (Koster and Lettinga 1988). The final ammoniacal nitrogen concentrations in- creased from 2,115 to 13,200 mg/l as the ISR values decreased from 2:1 to 1:2. ISR=1:2 Ammonia, known as one of the inhibitors of methanogens, ISR=1:1 ISR=2:1 may be thought of as a problem in anaerobic digestion, espe- cially those digestions using protein-rich feedstocks as sub- strates (Nielsen and Angelidaki 2008). Ammonia could mainly influence the anaerobic digestion by affecting acetate-utilizing methanogenic archaea, hydrogen-utilizing methanogens and syntrophic bacteria. Though the inhibitory concentrations of 02468 10 12 14 16 ammonia varied due to different experiments, a TAN of 1.7– Time (d) 5 g/l, corresponding to 0.4–1 g/l free ammonia, is the most Fig. 4 NH -N variation for different ISRs during anaerobic digestion acceptable concentration inhibiting anaerobic digestion pH Volatile fatty acids (VFAs) concentration (mg/l) Ammoniacal nitrogen concentration (mg/l) Ann Microbiol (2015) 65:1465–1471 1469 Fig. 5 VFA distribution and total VFAs concentration at pH 8 ammonia. Because the inhibitory effect of ammonia is asso- that methanogenic activity was significantly affected due to ciated with many factors such as pH, temperature and accli- the inhibition of free ammonia, despite the pH being relatively mation of microorganisms, the free ammonia concentration stable and appropriate for anaerobic digestion. for inhibition couldn’t bedeterminedinthisstudy. Two-stage anaerobic digestion VFA production Bad performance of biogas production occurred during the VFAs, as one of the most important parameters for the accu- above-mentioned results in one-stage operation, and was rate control of anaerobic digestion, have a direct correlation mainly due to system overload with an ISR of 1:2. Accumu- with digester performance. The variations in VFA concentra- lation of high concentrations of VFAs and ammonia during tion during the course of the digestion at different ISRs are the initial stage of anaerobic digestion subsequently affects the shown in Fig. 3. The initial values of VFAs increased with the methanogenic stage in single-stage anaerobic reactors. To amount of algae added. As indicated in Fig. 3, the VFA overcome these problems, a two-phase anaerobic digestion system at ISR of 1:3 was adopted to permit different bacterial concentrations showed a declining tendency at ISRs of 1:1 and 2:1, and low levels of VFAs were detected after 10 days of enrichment in two different reactors, by providing optimal growth conditions for initial acidogens and later methanogens digestion, which means that the conversion of VFAs into methane was proceeding and gradually terminated. The de- (Cirne et al. 2007). The inhibition caused by the accumulation of intermediates could be eliminated through stage separation. crease of VFA concentrations also indicated that the produc- tion of VFAs was relatively slower than consumption by methanogenesis, which corresponded to the high output of Acidogenesis methane. For the ISR of 1:2, unstable operation occurred as indicated in Fig. 3. VFAs weren’t completely consumed, but The strong pH dependency of VFA production during accumulated to a level as high as 36,240 mg/l with a small acidogenesis was investigated in our previous research (Li amount of methane produced. Combined with the pH value et al. 2013). It was found that at a pH of 8, acidogenesis could and ammoniacal nitrogen concentration, it could be explained occur better than at other pH values. The VFA yield was Table 3 Performance of UASB OLR (g/l·d) HRT (h) COD of COD of COD removal Methane yield reactors under different OLRs influent (g/l) efluent(g/l) efficiency (%) (ml CH /g COD) 2 24 2 0.041 97.9 336 3 16 2 0.051 97.4 332 4 12 2 0.11 94.5 330 6 8 2 0.17 91.5 323 8 6 2 0.24 88.0 324 * 2 g/l of COD for influent was 10 4.8 2 0.29 85.5 318 adopted in all the experiments 12 4 2 0.33 83.5 319 with various OLRs 1470 Ann Microbiol (2015) 65:1465–1471 calculated to be 0.6 g VFAs/g VS-added, according to the concerning the system set-up, microbial consortium in both equation described in experiment. the hydrolyser and the methanizer, etc., in order to optimize As indicated in Fig. 5b, the total VFA concentration conditions in both reactors. However, if the two-stage system reached 37,200 mg/l when the pH of the acidogenic reactor is operated in a straightforward manner, like the one-phase was controlled at a value of 8. This was mainly attributed to system, the latter would be the best choice. the dissolution of protein to different extents under alkaline Acknowledgments This study was funded by National High Technol- conditions, which was beneficial for protein degradation to ogy Research and Development Program of China (863 Program) under fatty acids. However, according to the study by Liu et al., the Grant No. 2012AA101803, Key Projects in the National Science & output of VFAs produced at pH 10 was higher than at other Technology Pillar Program during the twelfth 5-year Plan Period pHs (Liu et al. 2009). The discrepancy was caused by the (No.2014BAD02B04), and the Natural Science Foundation of Shandong province (ZR2012BL16, ZR2012CL04). presence of a different microbial consortium, which changed with the variation of substances and environment. As shown in Fig. 5a, acetate accounts for 56.8 % of total VFAs. The next References important VFAs were propionic acid and butyric acid. Valeric acid, iso-valeric acid and iso-butyric acid were found at lower percentages. The maximum total VFA concentration and in- Ahmad AL, Yasin NHM, Derek CJC, Lim JK (2011) Microalgae as a sustainable energy source for biodiesel production: a review. Renew dividual VFA concentration leveled off after 108 h. Sust Energ Rev 15(1):584–593 Alzate ME, Muñoz R, Rogalla F, Fdz-Polanco F, Pérez-Elvira SI (2014) Methanogenesis Biochemical methane potential of microalgae biomass after lipid extraction. Chem Eng J 243:405–410 APHA (2005) Total and volatile suspended solids. Standard operating Of the several intermediate steps in LARs based anaerobic procedure, Revision 2. American Public Health Association, digestion, methane formation from VFAs is often the critical Baltimore, Maryland, USA pathway that limits the overall reaction rate, because the Bellou S, Aggelis G (2012) Biochemical activities in Chlorella sp. and substrate could be readily degraded. The efficient conversion Nannochloropsis salina during lipid and sugar synthesis in a lab- scale open pond simulating reactor. J Biotechnol 164:318–329 of VFAs was closely correlated with the enrichment and Brennan L, Owende P (2010) Biofuels from microalgae—areview of diversity of methanogens; therefore, methanogenesis was a technologies for production, processing, and extractions of biofuels rate-limiting step during the whole process. In this study, the and co-products. Renew Sust Energ Rev 14:557–577 authors operated UASB reactors at different organic loading Chae KJ, Am J, Yim SK, Kim IS (2008) The effects of digestion temperature and temperature shock on the biogas yields from the rates using an artificial medium containing acetic acid, mesophilic anaerobic digestion of swine manure. Bioresour Technol propionic acid, butyric acid, valeric acid, iso-butyric acid 99:1–6 and iso-valeric acid. Chisti Y (2007) Biodiesel from microalgae. Biotechnol Adv 25:294–306 A quite stable performance of UASB reactors under fluc- Chisti Y (2008) Biodiesel from microalgae beats bioethanol. Trends Biotechnol 26:126–131 tuating organic loads was observed (Table 3). Parawira et al. Cirne DG, Lehtomäki A, Björnsson L, Blackall LL (2007) Hydrolysis (2006) reported that the UASB can provide a stable process and microbial community analyses in two-stage anaerobic digestion conversion rate up to an OLR of 6.1 g COD/l·d. In the present of energy crops. J Appl Microbiol 103(3):516–527 study, the OLR reached 12 g COD/l·d with specific VFAs Ehimen EA, Connaughton S, Sun ZF, Carrington CG (2009) Energy recovery from lipid extracted transesterified and glycerol co- compositions, which provided a high COD removal efficiency digested microalgae biomass. GCB Bioenergy 1:371–381 (>80 %) throughout the operational periods. Based on the Ehimen EA, Sun ZF, Carrington CG, Birch EJ, Eaton-Rye JJ influent COD of UASB, the methane yield for the test was (2011) Anaerobic digestion of microalgae residues resulting 319 ml CH /g COD. 4 from the biodiesel production process. Appl Energy 88:3454– Forster-Carneiro T, Pérez M, Romero LI (2008) Influence of total solid and inoculum contents on performance of anaerobic reactors treating food waste. Bioresour Technol 99:6994–7002 Conclusion Hashimoto AG (1983) Thermophilic and mesophilic anaerobic fermen- tation of swine manure. Agric Wastes 6:175–191 Kaparaju P, Ellegaard L, Angelidaki I (2009) Optimisation of biogas In this study, anaerobic digestion of LARs was carried out production from manure through serial digestion: lab-scale and using one-phase and two-phase systems. The maximum meth- pilot-scale studies. Bioresour Technol 100:701–709 ane yield was obtained at an ISR of 1:1 in a one-stage reactor. Kayhanian M (1999) Ammonia inhibition in high-solids biogasification: an overview and practical solutions. Environ Technol 20:355–365 The methane production decreased or even failed when the Koster IW, Lettinga G (1988) Anaerobic digestion at extreme ammonia organic load was 2:1 and 1:2. At a high organic load of ISR concentrations. Biol Wastes 25:51–59 1:3, the two-stage system seems to be very effective for the Li Y, Hua D, Zhang J, Zhao Y, Xu H, Liang X, Zhang X (2013) Volatile improvement of methane production. To upgrade yields in a fatty acids distribution during acidogenesis of algal residues with pH control. World J Microbiol Biotechnol 29:1067–1073 two-stage system, more investigations would be needed Ann Microbiol (2015) 65:1465–1471 1471 Liu H, Liu X, Zhang J, Che J (2009) Acetate accumulation and shift of Sasaki K, Morita M, S-i H, Ohmura N, Igarashi Y (2011) Decreasing ammonia inhibition in thermophilic methanogenic bioreactors using bacterial community during anaerobic sewage sludge fermentation by pH adjustment. Acta Microbiol Sin 49:1643–1649 carbon fiber textiles. Appl Microbiol Biotechnol 90:1555–1561 Marcin D, Marcin Z, Anna G, Magda D (2013) Algae biomass as an Sawayama S, Tada C, Tsukahara K, Yagishita T (2004) Effect of ammo- alternative substrate in biogas production technologies—review. nium addition on methanogenic community in a fluidized bed Renew Sust Energ Rev 27:596–604 anaerobic digestion. J Biosci Bioeng 97(1):65–70 Medina M, Neis U (2007) Symbiotic algal bacterial wastewater treat- Sialve B, Bernet N, Bernard O (2009) Anaerobic digestion of microalgae ment: effect of food to microorganism ratio and hydraulic retention as a necessary step to make microalgal biodiesel sustainable. time on the process performance. Water Sci Technol 55:165–171 Biotechnol Adv 27:409–416 Nielsen HB, Angelidaki I (2008) Strategies for optimizing recovery of the Singh S, Kate BN, Banerjee UC (2005) Bioactive compounds from biogas process following ammonia inhibition. Bioresour Technol cyanobacteria and microalgae: an overview. Crit Rev Biotechnol 99:7995–8001 25(3):73–95 Parawira W, Murto M, Zvauya R, Mattiasson B (2006) Comparative Yang Z, Guo R, Xu X, Fan X, Li X (2010) Enhanced hydrogen produc- performance of a UASB reactor and an anaerobic packed-bed tion from lipid-extracted microalgal biomass residues through pre- reactor when treating potato waste leachate. Renew Energy treatment. Int J Hydrogen Energy 35(18):9618–9623 31:893–903 Zamalloa C, Boon N, Verstraete W (2012) Anaerobic digestibility of Procházka J, Dolejš P, Máca J, Dohányos M (2012) Stability and inhibi- Scenedesmus obliquus and Phaeodactylum tricornutum under tion of anaerobic processes caused by insufficiency or excess of mesophilic and thermophilic conditions. Appl Energy 92:733–738 ammonia nitrogen. Appl Microbiol Biotechnol 93:439–447 Zeng S, Yuan X, Shi X, Qiu Y (2010) Effect of inoculum/substrate ratio Raposo F, Banks CJ, Siegert I, Heaven S, Borja R (2006) Influence of on methane yield and orthophosphate release from anaerobic diges- inoculum to substrate ratio on the biochemical methane potential of tion of Microcystis spp. J Hazard Mater 178:89–93 maize in batch tests. Process Biochem 41:1444–1450 Zhao B, Ma J, Zhao Q, Laurens L, Jarvis E, Chen S, Frear C (2014) Samson R, Leduy A (1982) Biogas production from anaerobic digestion Efficient anaerobic digestion of whole microalgae and lipid- of Spirulina maxima algal biomass. Biotechnol Bioeng 24(8):1919– extracted microalgae residues for methane energy production. 1924 Bioresour Technol 161:423–430 Sánchez Hernández EP, Córdoba LT (1993) Anaerobic digestion of Zhong W, Zhang Z, Luo Y, Qiao W, Xiao M, Zhang M (2012) Biogas Chlorella vulgaris for energy production. Resour Conserv Recycl productivity by co-digesting Taihu blue algae with corn straw as an 9:127–132 external carbon source. Bioresour Technol 114:281–286 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Annals of Microbiology Springer Journals

One-stage and two-stage anaerobic digestion of lipid-extracted algae

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Springer Journals
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Copyright © 2014 by Springer-Verlag Berlin Heidelberg and the University of Milan
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Life Sciences; Microbiology; Microbial Genetics and Genomics; Microbial Ecology; Mycology; Medical Microbiology; Applied Microbiology
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10.1007/s13213-014-0985-x
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Abstract

Ann Microbiol (2015) 65:1465–1471 DOI 10.1007/s13213-014-0985-x ORIGINAL ARTICLE One-stage and two-stage anaerobic digestion of lipid-extracted algae Yan Li & Mintian Gao & Dongliang Hua & Jie Zhang & Yuxiao Zhao & Hui Mu & Haipeng Xu & Xiaohui Liang & Fuqiang Jin & Xiaodong Zhang Received: 3 July 2014 /Accepted: 14 September 2014 /Published online: 8 October 2014 Springer-Verlag Berlin Heidelberg and the University of Milan 2014 Abstract Waste-grown microalgae are a potentially impor- Introduction tant biomass for wastewater treatment. The lipid accumulated in microalgae could be utilized as feedstocks for biodiesel The potential of microalgae as a source of biofuels is subject to production. The algal residues, as major by-products derived increasing academic and industrial research (Brennan and from lipid extraction, mainly consist of carbohydrate and Owende 2010; Ahmad et al. 2011). Therefore, the cultivation protein, making anaerobic digestion an efficient way to recov- of microalgae and subsequent product refinery such as lipid er energy. The conversion of lipid-extracted algal residues into extraction have gained much more attention by many re- methane plays dual role in renewable energy production and searchers (Bellou and Aggelis 2012). As a result of microalgae sustainable development of microalgal biodiesel industry. technology development, lipid-extracted algal residues Therefore, an anaerobic fermentation process for investigation (LARs) are the residual biomass from biodiesel production of the methane production potential of algal residues was processes that are rich in carbohydrate and protein. LARs conducted in this paper. The effect of inoculum to substrate could be used as a high-protein animal feed, a source of small ratios (ISRs) on the methane production by anaerobic diges- amounts of other high-value microalgal products (Chisti tion of Chlorella sp. residue in a single stage was evaluated. 2007), and possibly to produce bioactive compounds and The maximum methane yield of 195.6 ml CH /g volatile solid hydrogen (Singh et al. 2005;Yangetal. 2010). The compo- (VS) was obtained at an ISR of 1:1. The stability and progress sitions of LARs make anaerobic digestion an efficient way to of the reaction from algal residues to methane were monitored recover energy, which will also reduce the cost of microalgal- by measuring the pH, volatile fatty acids (VFAs), total ammo- biodiesel production (Sialve et al. 2009). niacal nitrogen (TAN), and methane volume. Based on the The technology for anaerobic digestion is well developed. results of one-stage experiments, two-stage technology was The effects of fermentation conditions such as feedstocks, proposed and was found to be more suitable for high organic controlled parameters, inoculum and substrate concentrations load. The optimum conditions for acidogenesis and on biogas production have been studied (Chae et al. 2008; methanogenesis are indicated in this paper. Forster-Carneiro et al. 2008;Kaparajuet al. 2009). The inves- tigation of algal biomass as feedstock for biogas production has also been reported (Marcin et al. 2013). Considering the . . . . Keywords Biogas Methane Algal residues One stage substrates relevant to this paper, there is some research on Two stage algal species such as Spirulina maxima (Samson and Leduy : : : : : : : 1982), Chlorella vulgaris (Sánchez Hernández and Córdoba Y. Li (*) M. Gao D. Hua J. Zhang Y. Zhao H. Mu H. Xu : : X. Liang F. Jin X. Zhang (*) 1993), Scenedesmus obliquus and Phaeodactylum Key Laboratory for Biomass Gasification Technology of Shandong tricornutum (Zamalloa et al. 2012). In those investigations Province, Jinan 250014, China for methane production, intact algae were used; as a result, the e-mail: liy@sderi.cn resistance of the cell wall limited the hydrolysis step and the e-mail: xd_zhang77@yahoo.com.cn fermentation period was prolonged. In addition, the C/N ratio : : : : : : : Y. Li M. Gao D. Hua J. Zhang Y. Zhao H. Mu H. Xu of algal biomass was lower than the empirical value; thus, co- : : X. Liang F. Jin X. Zhang digestion was commonly adopted for nutrient adjustment to Energy Research Institute of Shandong Academy of Sciences, enhance the biogas productivity (Zhong et al. 2012). The Jinan 250014, China 1466 Ann Microbiol (2015) 65:1465–1471 Table 1 Characteristics number of studies assessing the biochemical methane poten- Parameter Value of lipid-extracted algal tial of lipid-extracted microalgae is limited (Chisti 2008; residue Ehimen et al. 2009;Ehimenetal. 2011;Alzateetal. 2014; Total solid (TS, %) 94.6 Zhao et al. 2014). Volatile solid (VS, %-TS) 89.3 To find out the best conditions for the digestion of LARs Total carbon (%) 43.04 and to obtain dependable data, the methane potential of the Total nitrogen (%) 8.07 digestion process was investigated in this article. The experi- Protein (%) 50.4 ments were performed in one-stage and two-stage set-ups. The Lipid (%) 3.1 effect of inoculum to substrate ratios on methane production in a one-stage reactor was studied in an appropriate load range. The operation of a two-stage digestion system was not. The acidogenesis protocol was identical to that described for one-stage digestion, but the ISR was adjusted to 1:3 and carried out in terms of a high organic load at which failure would occur during the process of one-stage digestion. the pH was controlled at 8. Acidogenesis efficiency (AE) was calculated by the equation: Materials and methods AE ¼ VFA OutputðÞ g =VS InputðÞ g Substrate and inoculum characteristics An Up-flow Anaerobic Sludge Blanket (UASB), made of Dried and disrupted Chlorella vulgaris (Tianjian Co., organic glass, was used as methanogenic reactor with a work- Binzhou, China) after lipid extraction was used as substrate. ing volume of 2.5 l. During the start-up, UASB reactors were The main parameters were listed in Table 1. The C/N ratio of inoculated with granular sludge and acclimated with glucose lipid-extracted Chlorella vulgaris was 5.3. Anaerobic digested solution (1.5 g/l) at an organic loading rate (OLR) of 1.0 g sludge collected from a digester operating at 35 °C in COD/l·d for 1 month. Xiangchi Corporation was used as inoculum. The total solid Due tothe largedemandofacidicliquidwithlong-term (TS) and volatile solid (VS) contents of sludge were 7.85 and operation of UASB, the component of influent that flew into 86.33 %, respectively. UASB simulated genuine volatile fatty acids (VFAs) compo- sitions and content. The UASB reactors were continuously fed One-stage experiments with synthetic medium at an initial OLR of 2.0 g COD/l·d for 10 days, and then increased to 3, 4, 6, 8, 10, and 12 g COD /l·d Batch anaerobic digestion of algal residue was performed in at 10 days intervals. To achieve different OLRs, the hydraulic 1 l bottles. The mixture of sludge and algal residues were retention time (HRT) varied with the control of influent vol- added to reach final volume of 0.8 l with fresh water supple- ume. The chemical composition of the synthetic medium was ment. The outlet of the reactor gap was connected to the as follows (g/l): acetic acid 0.9, propionic acid 0.225, butyric airbag. Then, the set-up was placed in water bath at 35 °C acid 0.178, valeric acid 0.0225, iso-butyric acid 0.102, iso- and shaken at intervals. Headspace was purged with nitrogen valeric acid 0.068. Sodium nitrate and potassium dihydrogen every time the cap was opened. Tests were run as duplicates to phosphate were supplemented to maintain the COD:N:P at the test statistical reliability. Inoculum without substrate was used level of 100:4:1. Experiments were run for a total of 60 days as control. under controlled room temperature (35 °C). The three different ISRs in the test were 2:1, 1:1 and 1:2. They were achieved by keeping a constant inoculum concen- tration (20 g VS/l, an empirical value for seed concentration) Analytical methods and varying the substrate concentrations according to the ISRs. For the investigated ISRs, the TS concentrations didn’t The composition of biogas was measured using a double- exceed the maximum empirical value of 10 %. Anaerobic channel infrared technique with a biogas analyzer (GA2000, digestion of algal residues was operated for 15 days. Geotech), which showed the desired methane content. pH values were measured with a pH meter. Total ammoniacal Two-stage experiments nitrogen (TAN, NH and NH ) was analyzed according to 3 4 Nessler’s colorimetry with 5B-2(N) ammoniacal nitrogen The preliminary data obtained from one-stage anaerobic di- analysis meter (Lianhua Technology Company, China). gestion indicated that there was hardly methane produced at COD was measured by a COD analyzer (Lianhua Technology ISR of 1:3. Thus, two-stage technology was applied to inves- Company, China). The free ammonia concentrations (i.e., tigate whether the methane production could be improved or unionized NH ) are a function of the total ammoniacal 3 Ann Microbiol (2015) 65:1465–1471 1467 nitrogen concentration, pH, and dissociation constant, and The methane yield was calculated for each ISR by dividing formulae for the calculation of free ammonia concentrations the final methane volume by the VS weight of substrate are available in the literature (Kayhanian 1999). TS and VS added. Table 2 indicates that the methane yield after 15 days were determined according to APHA (2005). of digestion reached high levels of 195.6 ml CH /g VS and The VFA (acetic, propionic, butyric, valeric, iso-butyric 191.6 ml CH /g VS as the ISRs were 2:1 and 1:1 (initial and iso-valeric acids) concentrations were determined using substrate VS loads of 8 g VS and 5.3 g VS), respectively, an Agilent 7890 series gas chromatograph (GC) system. The but decreased when the substrate load (32 g VS for ISR of 1:2) column of HP-FFAP (50 m×320 μm×0.5 μm) was selected. was further increased. The result gave a methane yield higher Flame ionization detector (FID) was adjusted to 300 °C as the than that found in batch experiments with Microcystis spp. operating temperature. Nitrogen was used as the carrier gas, carried out by Zeng, who obtained a yield of 132.44 ml CH /g with a constant flow rate of 30 ml/min, and the inlet temper- VS at an ISR of 1:1 (Zeng et al. 2010). However, compared to ature was kept at 250 °C. Oven temperature was initially set to the methane yields of 300 ml/g VS (Alzate et al. 2014)and 60 °C and then increased to 100 °C with 10 °C/min ramping. 380 ml/g VS (Zhao et al. 2014), it was lower mainly because After a 2 min holding time at 100 °C, the oven temperature of different composition of algae and digestion conditions. As was gradually increased to 250 °C at the rate of 10 °C/min, can be seen in Table 2, the methane yield decreased from with 2 min holdings. 195.6 ml/g VS to 26.6 ml/g VS with the ISR varying from 2:1 to 1:2. The same conclusion was previously achieved by other researchers using different substrates (Raposo et al. 2006; Medina and Neis 2007). With an ISR of less than 1:1, methane Results and discussion yields significantly decreased and reached the lowest level of 26.6 ml CH /g VS at an ISR of 1:2, with yields approximately One-stage anaerobic digestion one-tenth of those obtained at other ISRs (Table 2). Combined with Fig. 2, though, the pH value for the whole process at an Biogas and methane production ISR of 1:2 was in an appropriate range, which was the contri- bution of the coexistence of VFA and ammonium. The yield Figure 1 shows the cumulative methane production, as a decrease was perhaps due to the weak methanogenic activity function of time with different ISRs used, corrected taking in the digesters, resulting from the inhibition caused by am- the control production into account. As indicated in Fig. 1, monia (Sawayama et al. 2004). methane production started immediately on the first day of It was observed that the operating time of 15 days was a digestion. Methane production almost reached a maximum on little long for the digestion. The methane production was day 7 and leveled off thereafter at all ISRs, because the almost finished in 10 days. The practical period for digestion substrate was almost completely consumed by the bacteria could be shortened from the perspective of methane produc- consortium. The methane production was proportional to the tion and energy conservation. Taking the methane yield and VS load applied. As can be seen from Fig. 1, the cumulative appropriate organic load into consideration, an ISR of 1:1 was methane volumes after 15 days of digestion for the ISRs of the optimum for anaerobic digestion with algae alone, the 1:2, 1:1 and 2:1 were 850, 3,066 and 1,565 ml, respectively. organic loading of which was 2 g VS/(l·d). pH variation The variation of pH over the period of digestion is shown in Fig. 2 and ranges from 6.7 to 7.7. When measured at days per unit, the pH climbed and gradually reached a relatively steady ISR=1:2 ISR=1:1 state with increasing time. It was obtained (not listed in Fig. 2) ISR=2:1 Table 2 Performances of reactors at ISRs of 1:2, 1:1 and 2:1 1000 ISR TS loaded VS loaded Methane yield substrate (g/l) substrate (g/l) (ml CH /g VS-add) 1:2 72.4 40 26.6 0 2 4 6 8 10121416 1:1 45.6 20 191.6 Time (d) 2:1 35.5 10 195.6 Fig. 1 The cumulative methane production for different ISRs Cumulative methane volume (ml) 1468 Ann Microbiol (2015) 65:1465–1471 8000 40000 8.0 ISR=1:2 ISR=1:1 7.8 ISR=2:1 7.6 7.4 30000 7.2 7.0 6.8 ISR=1:2 ISR=1:1 6.6 ISR=2:1 6.4 6.2 02468 0 2 4 6 8 1100112211441166 6.0 Time (d) Time (d) 0 2 4 6 8 10121416 Time (d) Fig. 3 VFA variation for different ISRs Fig. 2 pH variation for different ISRs during anaerobic digestion (Hashimoto 1983). As the ISRs were 2:1 and 1:1, the observed TAN concentrations in this study appeared not to directly affect the process. This suggested that the initial and final ammonia that the pH decreased during the first few hours of day 1. Organic acid production was generally initiated from the onset of the were too little to inhibit anaerobic digestion. When the ISR was 1:2, an accumulation of TAN of 4,300 mg/ reactor operations and resulted in these expected pH drops. The short-chain fatty acids as important intermediates were then l at day 2 was far above the threshold concentration (4,000 mg/l) reported in literature (Hashimoto 1983); therefore, the relatively quickly converted to methane by methanogens. Ammonium was simultaneously produced and drove the pH upwards. lower methane yield at an ISR of 1:2 was ascribed to the presence of a large amount of NH -N. Ammonia exerts negative effects Poor performance of methane production was obtained at on microbial cells and the concentration must be monitored in an ISR of 1:2. At this ISR, the pH stayed in the narrow range order to prevent toxic amounts from being reached. between 6.7 and 7.2, which was compatible with the normal Methanogens have been proven to be particularly sensitive to growth of anaerobic microorganisms. However, as can be seen from Fig. 3, VFAs were accumulated to a high level, but pH ammonia (Sasaki et al. 2011; Procházka et al. 2012). In terms of anaerobic digestion, a low C/N ratio can compromise the effi- didn’t drop accordingly, due to the simultaneous presence of a high level of ammonium (Fig. 4). The stability in pH can be ciency of the process, especially when high input and/or long retention times are applied. attributed to the high buffering capacity of the reactor. For ISRs of 1:1 and 2:1, the maximum free ammonia was about 148 and 102 mg/l, respectively. The TAN concentration TAN production reached 13,200 mg/l at the ISR of 1:2, corresponding to 240 mg/l free ammonia. It was found from Fig. 3 that VFAs Total produced ammoniums of different ISRs are indicated in were accumulated to a high level at ISR of 1:2, which was Fig. 4. An increment on TAN was observed at the experimen- possibly due to the poor methanogenesis, inhibited by tal ISRs. This fact was predictable, since it is widely known that some organic nitrogen (mainly protein) is converted to ammonium during anaerobic digestion (Koster and Lettinga 1988). The final ammoniacal nitrogen concentrations in- creased from 2,115 to 13,200 mg/l as the ISR values decreased from 2:1 to 1:2. ISR=1:2 Ammonia, known as one of the inhibitors of methanogens, ISR=1:1 ISR=2:1 may be thought of as a problem in anaerobic digestion, espe- cially those digestions using protein-rich feedstocks as sub- strates (Nielsen and Angelidaki 2008). Ammonia could mainly influence the anaerobic digestion by affecting acetate-utilizing methanogenic archaea, hydrogen-utilizing methanogens and syntrophic bacteria. Though the inhibitory concentrations of 02468 10 12 14 16 ammonia varied due to different experiments, a TAN of 1.7– Time (d) 5 g/l, corresponding to 0.4–1 g/l free ammonia, is the most Fig. 4 NH -N variation for different ISRs during anaerobic digestion acceptable concentration inhibiting anaerobic digestion pH Volatile fatty acids (VFAs) concentration (mg/l) Ammoniacal nitrogen concentration (mg/l) Ann Microbiol (2015) 65:1465–1471 1469 Fig. 5 VFA distribution and total VFAs concentration at pH 8 ammonia. Because the inhibitory effect of ammonia is asso- that methanogenic activity was significantly affected due to ciated with many factors such as pH, temperature and accli- the inhibition of free ammonia, despite the pH being relatively mation of microorganisms, the free ammonia concentration stable and appropriate for anaerobic digestion. for inhibition couldn’t bedeterminedinthisstudy. Two-stage anaerobic digestion VFA production Bad performance of biogas production occurred during the VFAs, as one of the most important parameters for the accu- above-mentioned results in one-stage operation, and was rate control of anaerobic digestion, have a direct correlation mainly due to system overload with an ISR of 1:2. Accumu- with digester performance. The variations in VFA concentra- lation of high concentrations of VFAs and ammonia during tion during the course of the digestion at different ISRs are the initial stage of anaerobic digestion subsequently affects the shown in Fig. 3. The initial values of VFAs increased with the methanogenic stage in single-stage anaerobic reactors. To amount of algae added. As indicated in Fig. 3, the VFA overcome these problems, a two-phase anaerobic digestion system at ISR of 1:3 was adopted to permit different bacterial concentrations showed a declining tendency at ISRs of 1:1 and 2:1, and low levels of VFAs were detected after 10 days of enrichment in two different reactors, by providing optimal growth conditions for initial acidogens and later methanogens digestion, which means that the conversion of VFAs into methane was proceeding and gradually terminated. The de- (Cirne et al. 2007). The inhibition caused by the accumulation of intermediates could be eliminated through stage separation. crease of VFA concentrations also indicated that the produc- tion of VFAs was relatively slower than consumption by methanogenesis, which corresponded to the high output of Acidogenesis methane. For the ISR of 1:2, unstable operation occurred as indicated in Fig. 3. VFAs weren’t completely consumed, but The strong pH dependency of VFA production during accumulated to a level as high as 36,240 mg/l with a small acidogenesis was investigated in our previous research (Li amount of methane produced. Combined with the pH value et al. 2013). It was found that at a pH of 8, acidogenesis could and ammoniacal nitrogen concentration, it could be explained occur better than at other pH values. The VFA yield was Table 3 Performance of UASB OLR (g/l·d) HRT (h) COD of COD of COD removal Methane yield reactors under different OLRs influent (g/l) efluent(g/l) efficiency (%) (ml CH /g COD) 2 24 2 0.041 97.9 336 3 16 2 0.051 97.4 332 4 12 2 0.11 94.5 330 6 8 2 0.17 91.5 323 8 6 2 0.24 88.0 324 * 2 g/l of COD for influent was 10 4.8 2 0.29 85.5 318 adopted in all the experiments 12 4 2 0.33 83.5 319 with various OLRs 1470 Ann Microbiol (2015) 65:1465–1471 calculated to be 0.6 g VFAs/g VS-added, according to the concerning the system set-up, microbial consortium in both equation described in experiment. the hydrolyser and the methanizer, etc., in order to optimize As indicated in Fig. 5b, the total VFA concentration conditions in both reactors. However, if the two-stage system reached 37,200 mg/l when the pH of the acidogenic reactor is operated in a straightforward manner, like the one-phase was controlled at a value of 8. This was mainly attributed to system, the latter would be the best choice. the dissolution of protein to different extents under alkaline Acknowledgments This study was funded by National High Technol- conditions, which was beneficial for protein degradation to ogy Research and Development Program of China (863 Program) under fatty acids. However, according to the study by Liu et al., the Grant No. 2012AA101803, Key Projects in the National Science & output of VFAs produced at pH 10 was higher than at other Technology Pillar Program during the twelfth 5-year Plan Period pHs (Liu et al. 2009). The discrepancy was caused by the (No.2014BAD02B04), and the Natural Science Foundation of Shandong province (ZR2012BL16, ZR2012CL04). presence of a different microbial consortium, which changed with the variation of substances and environment. As shown in Fig. 5a, acetate accounts for 56.8 % of total VFAs. The next References important VFAs were propionic acid and butyric acid. Valeric acid, iso-valeric acid and iso-butyric acid were found at lower percentages. The maximum total VFA concentration and in- Ahmad AL, Yasin NHM, Derek CJC, Lim JK (2011) Microalgae as a sustainable energy source for biodiesel production: a review. Renew dividual VFA concentration leveled off after 108 h. Sust Energ Rev 15(1):584–593 Alzate ME, Muñoz R, Rogalla F, Fdz-Polanco F, Pérez-Elvira SI (2014) Methanogenesis Biochemical methane potential of microalgae biomass after lipid extraction. Chem Eng J 243:405–410 APHA (2005) Total and volatile suspended solids. Standard operating Of the several intermediate steps in LARs based anaerobic procedure, Revision 2. American Public Health Association, digestion, methane formation from VFAs is often the critical Baltimore, Maryland, USA pathway that limits the overall reaction rate, because the Bellou S, Aggelis G (2012) Biochemical activities in Chlorella sp. and substrate could be readily degraded. The efficient conversion Nannochloropsis salina during lipid and sugar synthesis in a lab- scale open pond simulating reactor. J Biotechnol 164:318–329 of VFAs was closely correlated with the enrichment and Brennan L, Owende P (2010) Biofuels from microalgae—areview of diversity of methanogens; therefore, methanogenesis was a technologies for production, processing, and extractions of biofuels rate-limiting step during the whole process. In this study, the and co-products. Renew Sust Energ Rev 14:557–577 authors operated UASB reactors at different organic loading Chae KJ, Am J, Yim SK, Kim IS (2008) The effects of digestion temperature and temperature shock on the biogas yields from the rates using an artificial medium containing acetic acid, mesophilic anaerobic digestion of swine manure. Bioresour Technol propionic acid, butyric acid, valeric acid, iso-butyric acid 99:1–6 and iso-valeric acid. Chisti Y (2007) Biodiesel from microalgae. Biotechnol Adv 25:294–306 A quite stable performance of UASB reactors under fluc- Chisti Y (2008) Biodiesel from microalgae beats bioethanol. Trends Biotechnol 26:126–131 tuating organic loads was observed (Table 3). Parawira et al. Cirne DG, Lehtomäki A, Björnsson L, Blackall LL (2007) Hydrolysis (2006) reported that the UASB can provide a stable process and microbial community analyses in two-stage anaerobic digestion conversion rate up to an OLR of 6.1 g COD/l·d. In the present of energy crops. J Appl Microbiol 103(3):516–527 study, the OLR reached 12 g COD/l·d with specific VFAs Ehimen EA, Connaughton S, Sun ZF, Carrington CG (2009) Energy recovery from lipid extracted transesterified and glycerol co- compositions, which provided a high COD removal efficiency digested microalgae biomass. GCB Bioenergy 1:371–381 (>80 %) throughout the operational periods. Based on the Ehimen EA, Sun ZF, Carrington CG, Birch EJ, Eaton-Rye JJ influent COD of UASB, the methane yield for the test was (2011) Anaerobic digestion of microalgae residues resulting 319 ml CH /g COD. 4 from the biodiesel production process. Appl Energy 88:3454– Forster-Carneiro T, Pérez M, Romero LI (2008) Influence of total solid and inoculum contents on performance of anaerobic reactors treating food waste. Bioresour Technol 99:6994–7002 Conclusion Hashimoto AG (1983) Thermophilic and mesophilic anaerobic fermen- tation of swine manure. Agric Wastes 6:175–191 Kaparaju P, Ellegaard L, Angelidaki I (2009) Optimisation of biogas In this study, anaerobic digestion of LARs was carried out production from manure through serial digestion: lab-scale and using one-phase and two-phase systems. The maximum meth- pilot-scale studies. Bioresour Technol 100:701–709 ane yield was obtained at an ISR of 1:1 in a one-stage reactor. Kayhanian M (1999) Ammonia inhibition in high-solids biogasification: an overview and practical solutions. Environ Technol 20:355–365 The methane production decreased or even failed when the Koster IW, Lettinga G (1988) Anaerobic digestion at extreme ammonia organic load was 2:1 and 1:2. At a high organic load of ISR concentrations. Biol Wastes 25:51–59 1:3, the two-stage system seems to be very effective for the Li Y, Hua D, Zhang J, Zhao Y, Xu H, Liang X, Zhang X (2013) Volatile improvement of methane production. To upgrade yields in a fatty acids distribution during acidogenesis of algal residues with pH control. World J Microbiol Biotechnol 29:1067–1073 two-stage system, more investigations would be needed Ann Microbiol (2015) 65:1465–1471 1471 Liu H, Liu X, Zhang J, Che J (2009) Acetate accumulation and shift of Sasaki K, Morita M, S-i H, Ohmura N, Igarashi Y (2011) Decreasing ammonia inhibition in thermophilic methanogenic bioreactors using bacterial community during anaerobic sewage sludge fermentation by pH adjustment. Acta Microbiol Sin 49:1643–1649 carbon fiber textiles. Appl Microbiol Biotechnol 90:1555–1561 Marcin D, Marcin Z, Anna G, Magda D (2013) Algae biomass as an Sawayama S, Tada C, Tsukahara K, Yagishita T (2004) Effect of ammo- alternative substrate in biogas production technologies—review. nium addition on methanogenic community in a fluidized bed Renew Sust Energ Rev 27:596–604 anaerobic digestion. J Biosci Bioeng 97(1):65–70 Medina M, Neis U (2007) Symbiotic algal bacterial wastewater treat- Sialve B, Bernet N, Bernard O (2009) Anaerobic digestion of microalgae ment: effect of food to microorganism ratio and hydraulic retention as a necessary step to make microalgal biodiesel sustainable. time on the process performance. Water Sci Technol 55:165–171 Biotechnol Adv 27:409–416 Nielsen HB, Angelidaki I (2008) Strategies for optimizing recovery of the Singh S, Kate BN, Banerjee UC (2005) Bioactive compounds from biogas process following ammonia inhibition. Bioresour Technol cyanobacteria and microalgae: an overview. Crit Rev Biotechnol 99:7995–8001 25(3):73–95 Parawira W, Murto M, Zvauya R, Mattiasson B (2006) Comparative Yang Z, Guo R, Xu X, Fan X, Li X (2010) Enhanced hydrogen produc- performance of a UASB reactor and an anaerobic packed-bed tion from lipid-extracted microalgal biomass residues through pre- reactor when treating potato waste leachate. Renew Energy treatment. Int J Hydrogen Energy 35(18):9618–9623 31:893–903 Zamalloa C, Boon N, Verstraete W (2012) Anaerobic digestibility of Procházka J, Dolejš P, Máca J, Dohányos M (2012) Stability and inhibi- Scenedesmus obliquus and Phaeodactylum tricornutum under tion of anaerobic processes caused by insufficiency or excess of mesophilic and thermophilic conditions. Appl Energy 92:733–738 ammonia nitrogen. Appl Microbiol Biotechnol 93:439–447 Zeng S, Yuan X, Shi X, Qiu Y (2010) Effect of inoculum/substrate ratio Raposo F, Banks CJ, Siegert I, Heaven S, Borja R (2006) Influence of on methane yield and orthophosphate release from anaerobic diges- inoculum to substrate ratio on the biochemical methane potential of tion of Microcystis spp. J Hazard Mater 178:89–93 maize in batch tests. Process Biochem 41:1444–1450 Zhao B, Ma J, Zhao Q, Laurens L, Jarvis E, Chen S, Frear C (2014) Samson R, Leduy A (1982) Biogas production from anaerobic digestion Efficient anaerobic digestion of whole microalgae and lipid- of Spirulina maxima algal biomass. Biotechnol Bioeng 24(8):1919– extracted microalgae residues for methane energy production. 1924 Bioresour Technol 161:423–430 Sánchez Hernández EP, Córdoba LT (1993) Anaerobic digestion of Zhong W, Zhang Z, Luo Y, Qiao W, Xiao M, Zhang M (2012) Biogas Chlorella vulgaris for energy production. Resour Conserv Recycl productivity by co-digesting Taihu blue algae with corn straw as an 9:127–132 external carbon source. Bioresour Technol 114:281–286

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Annals of Microbiology – Springer Journals

Published: Oct 8, 2014

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