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Bioenergy systems for the future 14 integration of microalgae into an existing biofuel industry Bioenergy systems for the future 14 integration of microalgae into an existing biofuel industry Bioenergy systems for the future 14 integration of microalgae into an existing biofuel industry Bioenergy systems for the future 14 integration of microalgae into an existing biofuel industry Bioenergy systems for the future 14 integration of microalgae into an existing biofuel industry
Integration of microalgae into an existing biofuel industry 14 M.R Rahimpour, P Biniaz, M.A Makarem Shiraz University, Shiraz, Iran Abbreviations MTOE TAG DO DOC UAE MAE IL FFA AD PEM SHE ABE HTL 14.1 million tonnes oil equivalent triacylglycerol dissolved oxygen dissolved oxygen concentration ultrasound-assisted extraction microwave-assisted extraction ionic liquid free fatty acid anaerobic digestion polymer electrolyte membrane sonication, heat, and enzymatic hydrolysis acetone-butanol-ethanol hydrothermal liquefaction Introduction Energy has always been one of the most challenging issues facing humanity In the year 2014, the total world energy consumption was equal to 12,928.4 million tonnes oil equivalent (MTOE), which was increased by about 1% compared with the previous year (plc, 2015) Generally, 70% of the needed energy is supplied by the fuels, especially for transportation, manufacturing, and domestic usages (Gouveia and Oliveira, 2009) Fossil fuels are one of the most common sources of energy due to their abundance However, they lead to serious environmental problems such as global warming (Cheng and Timilsina, 2011) Moreover, about 98% of carbon dioxide emissions are caused by fossil fuels (Najafi et al., 2011) On the other hand, these resources are considered nonrenewable and will end gradually Therefore, their supply and increasing cost can cause serious economic, political, and even social problems (Ribeiro et al., 2015) As a result, finding alternative sources of energy based on Bioenergy Systems for the Future http://dx.doi.org/10.1016/B978-0-08-101031-0.00014-4 © 2017 Elsevier Ltd All rights reserved 482 Bioenergy Systems for the Future renewable resources are considered vital (Mueller et al., 2011; Yusuf et al., 2011) This alternative fuels must be technically feasible, be easily available, and be able to compete economically with fossil fuels (Ayhan, 2009) In general, these conditions can be found in various sources of energy such as wind, solar, geothermal, hydroelectric, and biomass (Suganya et al., 2016) Among them, biomass, that is, vegetable materials, is the largest source of renewable energy that is produced by photosynthesis phenomenon (Wen et al., 2009) Biomass can be obtained from various sources such as waste materials (agricultural wastes, crop residues, urban wastes, and wood wastes), forest products (wood, logging residues, shrubs, and trees), energy crops (starch crops such as corn, wheat, barley, sugar crops, woody crops, grasses, vegetable oils, and hydrocarbon plants), or aquatic biomass (algae, water hyacinth, and water weed) (Huber and Corma, 2007) These resources can be turned into oil and used directly or with upgrading as fuel, which is named biofuel In the 1930s and 1940s, the vegetable oil was used as fuel in emergencies (Shay, 1993) Later, biomass was utilized as feedstock for the production of different chemicals and fuels including biomethanol (Chisti, 2007), bioethanol (Lee et al., 2015), biobutanol (Hansen and Kyritsis, 2010), biohydrogen (Hallenbeck and Benemann, 2002), bio-oil (Demirbas, 2011), and biogas (Harun et al., 2011) Generally, there are three main generations in developing biofuels (Adenle et al., 2013) At first, they were produced from food crops and oil seeds (Naik et al., 2010a) Limitations on food resources and its impact on food economy led to food-for-fuel debate (Gomez et al., 2008) Therefore, the second generation of biofuels was developed from nonfood biomass such as lignocellulosic feedstock materials (Sims et al., 2010) The low conversion rates of plant biomass to produce biofuels caused that researchers began to think about the third generation of biofuels such as microalgae (Milano et al., 2016) Microalgae, that is, microscopic algae, store solar energy in the form of carbon products, which leads to the accumulation of lipids such as triacylglycerol (TAG) TAGs then can be converted into biofuels (Maity et al., 2014) This causes microalgae to have the highest potential to produce biofuels (Suali and Sarbatly, 2012) Many developing countries have potentials to grow algae Therefore, oil imports can be reduced, and the rural economy can be improved (Adenle et al., 2013) The rapid growth of microalgae satisfies a great need for biofuels without shortage of biomass resources and makes it more cost-effective Most common algae (Chlorella, Crypthecodinium, Cylindrotheca, Dunaliella, etc.) have oil content in the range of 20%–50%; however, higher productivities can be reached (Mata et al., 2010) In addition, greenhouse gas emissions are reduced using microalgae as a biofuel source (Li et al., 2008c) Researchers believe that the producing biodiesel, plant- or animal-fat-based diesel fuel, from microalgae is the most effective method for making this kind of biofuels (Banerjee et al., 2002; Chisti, 2008; Demirbas and Demirbas, 2011) and can generally supersede the fossil fuels (Ghadiryanfar et al., 2016) Table 14.1 compares the advantages and disadvantages of different generations of biofuels with fossil fuels Table 14.1 Advantages and disadvantages of different generations of biofuels and fossil fuels Fuel Advantages Fossil fuels l Provided 88% of the primary energy consumption, potential reserves, and low cost (Brennan and Owende, 2010) Disadvantages l l Food crops l l Decreased CO2 emission Biodegradable, nontoxic, and essentially free of sulfur and aromatics (Ayhan, 2009) l l l l Nonfood biomass l l l l l Microalgae l l l l l l Decreased CO2 emission Do not need arable land (Chisti, 2007) Require less fertilizer, water, and pesticide inputs to low environmental impact (Carriquiry et al., 2011) Do not compete with food production (Havlı´k et al., 2011) Form of recycling wood ash (Stupak et al., 2007), residual agricultural biomass, and wastes (Nigam and Singh, 2011) Decreased nitrous oxide and CO2 emission, high growth rate, using limited land resources, less water (Li et al., 2008c) Large quantities of lipids adequate for biodiesel production (Demirbas and Demirbas, 2011) Wastewater treatment (Hammouda et al., 1995) Higher yield than most oil plants (Cheng and Timilsina, 2011) Potential to completely displaced liquid transport fuels derived from petroleum (Chisti, 2008) Coal power plants and hydrogen production plants can supply large amounts of CO2 for microalgal culture at a low cost (Takeshita, 2011) l l l l l l Changes in global climate because of greenhouse gas emission (Ugarte, 2000) Increased atmospheric CO2 And environmental degradation (M€ ollersten et al., 2003) Competition between food and fuel and use of agricultural land (Rathmann et al., 2010) High production and processing costs (Sims et al., 2010) More fertilizers, more irrigation, and more pesticides (Odling-Smee, 2007) Increase demand for food and related commodity prices (Mueller et al., 2011) Low conversion rates (Milano et al., 2016) Lower energy density compared with coal (McKendry, 2002b) Increase net deforestation drastically (Havlı´k et al., 2011) Technical hurdles(Gomez et al., 2008) Increased leaching after stump harvesting due to increased decomposition and high costs of waste deposits if waste cannot be recycled (Stupak et al., 2007) Low biomass concentration, energy-consuming process, higher capital costs, large-scale production necessary to be economical (Li et al., 2008c) 484 14.2 Bioenergy Systems for the Future An introduction to microalgae Microalgae (algae with 1–50 μ m in diameter) are alternative resource for producing energy They are group of microorganisms, such as prokaryotic and eukaryotic photosynthetic microorganisms (Singh et al., 2011), with great variety, which are adapted to different weather conditions (Hu et al., 2008) They are one of the fastest growing plants in the universe (Demirbas, 2010) that can also be grown on seawater, freshwater, or even on wastewater or sewage and not require food crops and fertile land (Wang et al., 2008; Demirbas and Demirbas, 2011) Although microalgae generally live in the waters, they can grow on the surface of different types of soils (Richmond, 2008) 14.2.1 Various types of microalgae Generally, alga (consist of microalgae and macroalgae) can be divided into various groups based on their color, such as green (Chlorophyceae), blue-green (Cyanobacteria or Cyanophyceae), diatoms (Bacillariophyceae), golden-brown (Chrysophyceae), yellow-green (Xanthophyceae), brown (Phaeophyceae), red (Rhodophyceae), dinoflagellates (Dinophyceae), and picoplankton (Prasinophyceae and Eustigmatophyceae) (Hu et al., 2008; Ghasemi et al., 2012) Some properties of different algae are summarized in Table 14.2 According to Maity’s investigation (Maity et al., 2014), the lipid content order for various algae (percent in dry mass) based on their colors are green > yellow-green > red > blood-red > blue-green Macroalgae, as a renewable resource of energy, can be used for biofuel production in an economically impressive and environmentally sustainable manner (Li et al., 2008c) However, many researchers reported that microalgae might be better for producing higher biofuels (Hossain et al., 2008; Li et al., 2008c) Based on the cell, microalgae can be divided into three general categories as shown in Fig 14.1: colonial, unicellular, and filamentous (Richmond, 2008) The unicellular microalgae are made from only one cell and most of them are nonmotile; however, motile cells sometimes can take place (Stanier et al., 1971) By comparison with most vascular plants, unicellular microalgae, because of the behavioral, structural, physiological, and biochemical reasons, have ability to survive at low flux densities of photons (Richardson et al., 1983) Colonial microalgae are made from one to several cell clusters unified by a hydrocarbon-rich colonial matrix When the light is sufficient for photosynthesis, the colony size is increased with light intensity (Banerjee et al., 2002) They appear as a green to orange, brown, or red floating scum on the calm water surface (Wolf, 1983) The green colonial microalgae have very high level of hydrocarbons (70%–90% of the dry mass), making it potentially suitable for biofuel production (Tsukahara and Sawayama, 2005; Tran et al., 2010) Filamentous microalgae have single cells that form long chains or filaments at microscopic dimension (Olson, 1950) They can be considered as a potential raw material for producing biodiesel; however, it is rarely investigated (Wang et al., 2013) One of the most advantages of filamentous species is that they can be cultivated in wastewaters They use organic and inorganic load of wastes for their growth and reduce the harmful substances contained in them (Markou and Georgakakis, 2011) Integration of microalgae into an existing biofuel industry Table 14.2 485 Properties of different algae Algae Properties Blue-green (Cyanobacteria) l l l l l Diatoms (Bacillariophyceae) l l l l Green (Chlorophyceae) l l l They are prokaryotes without membrane-bond organelles Could be unicellular, colonial, and filamentous forms with or without branching or differentiation of specialized cells Transformed with autonomously replicating plasmids High extraction rate Having low lipid content (% dry weight biomass) They are ubiquitous in marine, freshwater, and terrestrial environments and include the greatest number of extant species (up to 10 million) of any group of microalgae Diatoms are mostly unicellular, although filamentous species are abundant Cell walls (frustules) composed of silicon made of two identical halves that fit together Use the triacylglycerol lipid molecules (TAGs) as energy storage molecules that can be easily transesterified to biodiesel One of the largest number of species, most widely distributed morphologically diverse groups unicellular, colonial, filamentous, and pseudoparenchymatous Uni or multinucleate forms Having high lipid content (% dry weight biomass) Having eukaryotes characterized by chlorophylls a and b as the major photosynthetic pigment Reference Metting Jr (1996), Kanda and Li (2011), Maity et al (2014), Wehr et al (2015), and Suganya et al (2016) Round et al (1990), Metting Jr (1996), Singh et al (2011), and Wehr et al (2015) Metting Jr (1996), Maity et al (2014), and Wehr et al (2015) Continued 486 Bioenergy Systems for the Future Table 14.2 Continued Algae Properties Yellow-green (Xanthophyceae) l l Golden-brown (Chrysophyceae) l l l Red (Rhodophyceae) l l Reference Living on fresh water and moist soil Their color is not always easy to distinguish from true green microalgae taxa Macroalgae living in marine and freshwater and have not been reported on soil Having a diverse class of taxa as brown one And are from filamentous Including seaweeds and microalgae and lacking of any flagellate stages, red microalgae occur in fresh water and on soil Metting Jr (1996) and Wehr et al (2015) Metting Jr (1996) and Wehr et al (2015) Metting Jr (1996), and Wehr et al (2015) Having eukaryotic cells Microalgae Unicellular Nonflagellate Motile Flagellate Colonial Flagellate Nonflagellate Filamentous Branched Unbranched Nonmotile Fig 14.1 Different types of cell organization of microalgae (Richmond, 2008) 14.2.2 Microalgae potential for biofuel production Green microalgae, with high content of lipid, are used to produce different types of biofuels such as biodiesel, hydrogen, ethanol, and methanol as shown in Table 14.3 Researchers also use blue-green microalgae for producing biogas purification (Converti et al., 2009) and methane production (Costa and De Morais, 2011; Maity et al., 2014) In the case of biodiesel production, red marine microalgae can be used as well (Wu and Merchuk, 2004) One important factor for the production of biofuel from microalgae is the amount of oil exists inside it Table 14.4 compares oil content of different microalgae Based on Integration of microalgae into an existing biofuel industry 487 Various products derived from different green microalgae Table 14.3 Green microalgae Biofuel Reference Arthrospira maxima Chlorella biomass Chlorella minutissima Chlorella protothecoides Chlorococcum sp Chlorella fusca Chlorella protothecoides Chlorella reinhardtii Chlorella regularis Chlorella vulgaris Chlorococcum humicola Haematococcus pluvialis Neochloris oleoabundans Scenedesmus obliquus Spirulina platensis Spirogyra Hydrogen, biodiesel Ethanol Methanol Dismukes et al (2008) Zhou et al (2011) Kotzabasis et al (1999) Biodiesel Bioethanol Hydrogen Bio-oil Li et al (2007) and Chen and Walker (2011) Harun et al (2010) Ghirardi et al (2000) Miao and Wu (2004) Hydrogen Ethanol Ethanol Bioethanol Ghirardi et al (2000) Endo et al (1977) Hirano et al (1997) Harun and Danquah (2011) Biodiesel Damiani et al (2010) Biodiesel Gouveia and Oliveira (2009) Hydrogen Ghirardi et al (2000) Hydrogen gas, ethanol Ethanol Aoyama et al (1997) Sulfahri et al (2011) the reported data, oil content of microalgae can exceed up to 80% by weight of dry biomass (Metting Jr, 1996) Table 14.5 compares oil content and biofuel productivity of microalgae with other biofuel feedstocks As illustrated in this table, microalgae with high oil content and with the least usage of land (0.1 m2 year/kg biodiesel) can produce the largest amount of biodiesel (121,104 kg biodiesel/ha year) 14.2.3 Effects of nutrients on the growth rate The main factors that affect the growth and oil content of microalgae are CO2 supply, pH, light intensity, temperature, nutrients (carbon, nitrogen, sulfur iron, phosphate, and in some cases silicon), salinity, and dissolved oxygen (DO) (Hu et al., 2008; Kumar et al., 2010a) High dissolved oxygen concentration (DOC) levels can cause photooxidative damage on microalgal cells (Suh and Lee, 2003) Moreover, some toxic element compounds, such as synthetic organics or heavy metals, and some 488 Bioenergy Systems for the Future Table 14.4 Oil content of various microalgae (Becker, 1994; Chisti, 2007; Li et al., 2008a,b; Deng et al., 2009; Mata et al., 2010; Verma et al., 2010; Ghasemi et al., 2012) Microalgae Anabaena cylindrica Ankistrodesmus species Botryococcus braunii Chaetoceros calcitrans Chaetoceros muelleri Chlamydomonas reinhardtii Chlamydomonas species Chlorella Chlorella emersonii Chlorella minutissima Chlorella protothecoides Chlorella pyrenoidosa Chlorella sorokiniana Chlorella species Chlorella vulgaris Chlorococcum species Crypthecodinium cohnii Cyclotella species Cylindrotheca species Dunaliella Dunaliella bioculata Dunaliella primolecta Dunaliella salina Oil content (% dry wt.) Microalgae Oil content (% dry wt.) 22–29.7 33 Nannochloropsis oculata Nannochloropsis species Neochloris oleoabundans Nitzschia closterium Nitzschia frustulum 21 Nitzschia species 16–47 23 Nitzschia laevis 69.1 18–57 25–63 57 Oocystis pusilla Pavlova salina Pavlova lutheri 10.5 30 35 14–57.8 Parietochloris incisa Phaeodactylum tricornutum Porphyridium cruentum Prostanthera incisa Prymnesium parvum Pyrrosia laevis 62 4–7 24–40 25–86 14.6–39.8 19–22 10–48 5–58 19.3 23 Schizochytrium species Scenedesmus obliquus Scenedesmus quadricauda Selenastrum species Skeletonema costatum Skeletonema sp 6–28.1 Spirulina maxima 20–51 42 16–37 67 12–68 29–65 27.8 25.9 18–57 9–18.8/60.7 62 22–39 69.1 50–77 11–55 1.9–19.9 19.6–21.7 13–51 13.3–31.8 4–9 Integration of microalgae into an existing biofuel industry Table 14.4 489 Continued Microalgae Oil content (% dry wt.) Dunaliella species Dunaliella tertiolecta Ellipsoidion sp 17–67 16–71 Euglena gracilis Haematococcus pluvialis Hantzschia species 14–20 25 Isochrysis galbana Isochrysis species Monallantus salina Monodus subterraneus Nannochloris species 7–40 7–33 20–72 16–39.3 27.4 66 Microalgae Oil content (% dry wt.) Spirulina platensis Stichococcus species Tetraselmis maculata Tetraselmis sp Tetraselmis suecica 16.6 33 Thalassiosira pseudonana Nitzschia sp 20.6 12.6–14.7 8.5–23 4547 20–56 biological factors such as viruses, predation, competition, and growth of epiphytes may confine microalgae growth rates (Carlsson and Bowles, 2007) Approximate molecular formula of the microalgal biomass should be CO0.48H1.83N0.11P0.01 (Grobbelaar, 2004) The main sources of carbon dioxide required for microalgae growth are atmospheric CO2, industrial exhaust gases (e.g., flue gas and flaring gas), and CO2 produced from soluble carbonates (e.g., NaHCO3 and Na2CO3) (Becker, 1994) Since the atmospheric CO2 level (0.0387% (v/v)) is not sufficient for high microalgal growth rates (Kumar et al., 2010a), coal power plants and hydrogen production plants can supply large amounts of CO2 for this purpose at a low cost (Takeshita, 2011) Carbon (generally derived from carbon dioxide) and nitrogen are the most important nutrients required for growing microalgae (Becker, 1994) Ammonium and nitrates, which are primary nitrogen sources, are suitable for fast and medium growing rates (Green and Durnford, 1996; Jin et al., 2006) After carbon and nitrogen, phosphor is the third most important nutrient, which can be obtained from wastewater and seawater (Green and Durnford, 1996; Kumar et al., 2010b) On the other hand, microalgae, by adsorbing and accumulating organic nutrients and heavy metals, can enhance purifying process of domestic wastewater and changes the adsorbed species to interesting raw materials for producing biofuels (Munoz and Guieysse, 2006) However, it should be noted that microalgae are sensitive to toxic pollutants such as phenolic compounds (e.g., chlorophenols) and volatile organic component (Mun˜oz et al., 2003; Chen and Lin, 2006) 490 Bioenergy Systems for the Future Comparison of microalgae with other biofuel feedstocks (Mata et al., 2010) Table 14.5 Plant source Corn/maize (Zea mays L.) Hemp (Cannabis sativa L.) Soybean (Glycine max L.) Jatropha (Jatropha curcas L.) Camelina (Camelina sativa L.) Canola/rapeseed (Brassica napus L.) Sunflower (Helianthus annuus L.) Castor (Ricinus communis) Palm oil (Elaeis guineensis) Microalgae (low oil content) Microalgae (medium oil content) Microalgae (high oil content) Seed oil content (% oil by wt in biomass) Oil yield (L oil/ year) Land use (m2 year/kg biofuel) Biofuel productivity (kg biofuel/ year) 44 33 172 363 66 31 152 321 18 28 636 741 18 15 562 656 42 915 12 809 41 974 12 862 40 1070 11 946 48 1307 1156 36 5366 4747 30 58,700 0.2 51,927 50 97,800 0.1 86,515 70 136,900 0.1 121,104 14.2.4 Effects of environmental conditions on the growth rate Microalgae usually utilize light energy for growing, and sunlight is the most common source A phototrophic organism uses the energy of light to perform various cellular metabolic processes, while heterotrophic ones uses organic carbon for the plant growth Many microalgae species are generally mixotrophic, that is, they can switch from the phototrophic to the heterotrophic growth They can use photosynthesis for energy production and, alternatively, carbon compounds for biosynthesis (Carlsson and Bowles, 2007; Kumar et al., 2010a) Such a mixotrophic structure leads to higher biomass concentration and growth rate (Wang et al., 2014) In the existence of light, microalgae convert CO2 and nutrients to biomass; by increasing the light density, microalgae photosynthesis is increased up to an optimum point (i.e., 200–400 μEmÀ2sÀ1) By further increasing the intensity, photosynthesis rate will be decreased (Sorokin and Krauss, 1958; Ogbonna and Tanaka, 2000) On the other hand, low light intensity causes the formation Integration of microalgae into an existing biofuel industry 505 (Huber et al., 2006) Chaiwong et al., 2013 found that the suitable temperature to obtain biochar is $500°C Generally, slow pyrolysis produces larger amount of char than fast and flash pyrolysis Different operational conditions (e.g., temperature, pressure, type of reactor, and catalysts) and the type of feedstock for producing various biofuels including bioethanol, biomethanol, biobutanol, biohydrogen, bio-oil, biochar, and biogas (hydrogen and methane) via various upgrading methods such as transesterification, fermentation, liquefaction, pyrolysis, and anaerobic digestion are shown in Table 14.9 14.5 Conclusion Microalgae (algae with 1–50 μ m in diameter) are considered as sustainable alternative energy source of fossil fuels They are technically feasible, easily available, and able to compete economically with fossil fuels Being one of the fastest growing plants in the world with great variety of colors (green, yellow-green, blue-green, goldenbrown, red, and diatoms), microalgae are well adapted to different habitats such as marine, freshwater, moist soil, terrestrial environments, or even on wastewater and sewage Microalgae, with high content of lipid and the least land usage, are used to produce different types of biofuels such as biodiesel, biosyngas, biohydrogen, bioethanol, biobutanol, biomethanol, bio-oil, and biochar Based on the reported data, their oil content can exceed up to 80% by weight of dry biomass Sunlight, CO2 supply, pH, light intensity, temperature, nutrients (carbon, nitrogen, sulfur iron, phosphate, and in some cases silicon), salinity, and dissolved oxygen are the main factors affecting the growth and oil content of microalgae Before producing some kind of biofuels, it is necessary to extract the oil content At first, two applicable methods (open systems and closed systems) are used to cultivate microalgae Then, several processes including filtration, sedimentation, flocculation, ultrasound flotation, and centrifugation are applied to harvest the microalgae After performing dehydration process, microalgae cells are disrupted by physical, mechanical, chemical, and biological techniques Finally, to extract the oil content, physical techniques, solvent extraction, or supercritical fluids are utilized Finally, by transesterification or alcoholysis processes, biodiesel is produced Besides, syngas can be produced during gasification, anaerobic digestion, or fermentation processes Pyrolysis and hydrothermal liquefaction are two major processes for bio-oil production from microalgae biomass Pyrolysis requires a dry biomass, while hydrothermal liquefaction is suitable for a wet feedstock Moreover, biochar can be produced via pyrolysis process during bio-oil production and converted into H2 or syngas by steam reforming or gasification Producing hydrogen gas is also achievable in the green microalgae cells through photosynthetic metabolism With this huge amount of products gained from microalgae, it seems that they will play an important role in future biofuel industries 506 Table 14.9 Various approaches for biofuel production from microalgae T°C Catalyst Yield% Reactor Feedstock Product References Transesterification (1 atm) 60–80 $100 CSTR, plug flow 350–700 Up to 80 Fluidized-bed, circulating fluid beds Triglycerides and a second alcohol (methanol) Dry biomass Biodiesel Pyrolysis (1–5 atm) Alkali, nonionic base, acid, enzyme, heterogeneous Co/al2o3, ni/al2o3, γ-al2o3, Zsm-5, Hzsm-5, nickel phosphide Pyrolysisand char gasification $500 Silica particles Up to 35 Fluidized-bed gasifier Biomass, airsteam or oxygen Biochar Hydrothermal liquefaction (50–200 atm) 200–450 Alkali, metals, Ni and Ru heterogeneous Na2CO3, CH3COOH, HCOOH, NiO, Ca3 (PO4)2, H2SO4 50–90 Slurry reactor Solid biomass feed in a solvent Bio-oil Schuchardt et al (1998) and Meher et al (2006) Bridgwater and Peacocke (2000), Huber et al (2006), Le et al (2014), and Liu et al (2014) McKendry (2002a) and Huber et al (2006) Huber et al (2006), Zou et al (2009), Ross et al (2010), Jena et al (2012), and Xiu and Shahbazi (2012) Bio-oil Bioenergy Systems for the Future Process 200–800 Ni, Fe-Cr, Cu-Zn-Al Fluidized-bed, gasification reactor Biomass, air Hydrogen Gasification (50–100 bar) 220–300 Cu/ZnO, Zn/Cr2O3 Gasification reactor Syngas (CO and H2) Methanol Fermentation 20–30 – 30–40 Photobioreactor Hydrogen 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