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Development of hydrothermal liquefaction and upgrading technologies for lipid-extracted algae conversion to liquid fuels
... Furthermore, in spite of being an energy dense liquid (~35 MJ/kg), the boiling point of the major part of the biocrude (>80 wt.%) is above 250 ˚C; thereby, their application to the transport sector is hardly achievable. The use of the upgrading technologies increases significantly the cost of biofuel production (Zhu et al. 2013). ...
... Although the lipids from microalgae contribute to improve the yield and properties of the biocrude, and are themselves a source of biofuel, in the case of strains with a lipid content lower than 33 wt.% db, the amount of bio-oil produced from the lipid-extracted algae (LEA)generated mainly from proteins and carbohydratesis higher than the hydrocarbons obtained from the hydrotreated lipids ( Figure 5 from (Zhu et al. 2013)). This could be the case of Nannochloropsis sp., which present less than 33 db% of lipids and the simple extraction of its oil for biofuel production, lead to waste the other microalgae components, which in this case would contribute more to the biocrude than the lipids. ...
... Generally, the ultimate analysis of the biomass is given in dry basis (Zhu et al. 2013). In this way, the values directly obtained from the elemental analyser (Table 28) were converted to dry basis (Table 14) by discounting the amount of moisture in the biomass. ...
The depletion of the reserves of fossil fuel promotes the search for sustainable renewable sources of energy. Due to their similarities with the petroleum products, the biofuels represent a better alternative than other clean energies. The conversion process greatly depends on the biomass composition, which is a topic of debate, especially when it increases the price of the food. Therefore, third generation biofuels, derived from algae, are better accepted by society than using other raw materials. Due to the way of cultivating and the high moisture content of microalgae, hydrothermal liquefaction (HTL) is the transformation technology most suitable for this type of feedstock. Even when the application of HTL to microalgae is quite recent, a lot of research is being done because of the good expectations for biofuel production. In this way, the best operating conditions have already been determined, they are the critical point of water (374 ˚C and 221 bar), and the research is focussing now in the improvement of the quality of the products and the upscaling to a continuous process. The most important product is the biocrude, which has a high content of oxygen and nitrogen. The use of hydrogen for the removal of these heteroatoms is one of the most investigated techniques. Especially important is the presence of nitrogen, as the large production of NOx upon combustion is banned. The use of ultrasound as a pretreatment technology before the HTL of the microalgae slurry is intended to increase the yield of the biocrude while reducing the severity of the operating conditions. Also, milder conditions result in lower nitrogen content of the biocrude. This thesis shows the results of the use of a sonication bath to disrupt the microalgae cells before being liquefied. Three different microalgae species were considered: Nannochloropsis gaditana (N. gad.), Scenedesmus almeriensis (S. alm.), and Tetraselmis suecica (T. suec.). The experiments were carried out in a tubular batch reactor without stirrer and with an electric heater.
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It was found that the ultrasonic pretreatment does not affect the performance of the HTL of microalgae. The lack of influence of the pretreatment on the quantity and quality of the liquefaction products could be related to the fact that the microalgae samples were already disrupted during the drying process to prepare the powder biomass. Moreover, the poor performance of the sonication bath, in terms of achieving the microalgae cell breakage, is also considered as explanation. Therefore, the analysis of the ultrasonic equipment was done to understand the reason for its poor operation. The characteristics of the sonication equipment (configuration, ultrasonic power output, and energy frequency) were defined for future experiments.
... Biocrude from the HTL of lipid-extracted residues is mainly composed of cyclic nitrogenates and cyclic oxygenates, which should be upgraded prior to being used as transport fuels. Zhu et al. [126] proposed a system combining the HTL of lipid-extracted residues and further upgrading of fuels, as illustrated in Fig. 3. Briefly, the lipid-extracted residue slurry is introduced into a reactor for HTL, generating biocrude, gas, and solid residue as the products. The organic fraction is extracted from the biocrude for further upgrading, such as hydrocracking and hydrotreating; while the gas product from the HTL process and upgrading process is recycled for organic upgrading. ...
... Furthermore, catalysts for the upgrading process are conducive to improve the upgrading efficiency. Nevertheless, the results from the techno-economic analysis of this process reveal that the minimum fuel selling price may range from $2.07 to $7.11/gal gasoline-equivalent [126]. ...
... The Table 4 Yield and fatty acid profile of crude lipid extracted from algal biomass using different methods. Fig. 3. Block flow diagram of hydrothermal liquefaction and upgrading of lipidextracted algal residues [126]. LAR: Lipid-extracted algal residues, are the residue materials of algal biomass after lipid extraction. ...
Thermochemical processes, including gasification, liquefaction, and pyrolysis, are promising technologies for algal conversion. Gasification is effective to convert algal biomass into fuel gases while liquefaction and pyrolysis are favorable for the production of bio-oil with low molecular weight and biocrude with high energy density, respectively. To understand the role of algal components (proteins, lipids, and carbohydrates) on thermochemical conversion processes, this paper reviews the properties of biofuels from the thermochemical conversion of algal components and their model compounds. The characteristic fingerprints of algal components differ from one another. Consequently, the thermochemical conversion of the total algal biomass results in heterogeneity of the biofuels. The unfavorable nitrogenous compound production also leads to resource and energy losses, which are the critical bottleneck of algal biorefinery. As such, this review tackles some combined processes. The combination of the hydrothermal liquefaction of algal biomass and the hydrothermal gasification of an aqueous fraction shows potential for applications that improve fuel gas production. Lipid extraction combined with thermochemical residue conversion contributes to an increase in total oil yield. Protein extraction combined with thermochemical residue conversion decreases the risk of nitrogenous compound contamination in bio-oil and increases the recovery of value-added protein-derived products. Protein and lipid extraction before thermochemical conversion should be further explored to maximize the exploitation of multiple value-added products from algal biomass.
... Few studies used the component additivity model in their economic assessment [33][34][35]. Although most studies have used experimental results for HTL product yield estimation [36][37][38][39][40][41], it has not been reported the application of the kinetic model in economic analysis. ...
... According to the literature related to the economic analysis and viability of algal-derived biofuels, the cost of algal feedstock is one of the most important variables for overall economics. The cost of microalgae for different papers varies in the range from $30 to $3711 per dry ash-free metric ton [37,40,41,[54][55][56]. In this study, the feedstock price was assumed $50/dry metric ton. ...
In this work, a global kinetic model of hydrothermal liquefaction (HTL) is proposed for Aurantiochytrium sp., C. protothecoides, Scenedesmus sp., Chlorella vulgaris, and Tetraselmis sp. algae. Proteins, lipids, and carbohydrates were first decomposed to the aqueous phase and biocrude, followed by further decomposition to the gas phase. MATLAB optimization function was used to optimize the kinetic parameters of different algae. Furthermore, economic analysis was evaluated by using global kinetic modeling to estimate HTL product yields in Aspen Plus. The results showed that the calculated optimum values of activation energies were 31–50, 32–52, and 46–90 kJ/mol for the conversion of proteins, lipids, and carbohydrates to biocrude. Also, the global kinetic model had a great predictive ability with a reduced chi-square of 0.717 and R-squared of 0.987. Moreover, the application of the global kinetic model for different biomass such as Chlorella vulgaris, sewage sludge, green waste, food waste, grease residue, and their 50:50 mixtures with Chlorella was evaluated. The yields of Chlorella vulgaris, green waste, food waste, and their mixture with Chlorella could be predicted by the kinetic parameters of Scenedesmus sp., while kinetic parameters of Aurantiochytrium sp. were more appropriate for yield predicting of grease residue. Moreover, HTL techno-economic analysis of Aurantiochytrium sp. showed that the various ranges of the minimum fuel selling price (MFSP) were estimated to be $2.11 to $7.52/GGE by the effect of biomass price.
Graphical abstract
... Nitrogen, sulphur and oxygen are unfavorable regarding energy and environmental concerns. Thus, it is vital to know the presence of such elements for the deoxygenation and denitrogenation of fuels for upgrading (Ramirez et al., 2015;Zhu et al., 2013). Van Krevelen diagrams can be effectively used for the same (Tian Saral and P. Ranganathan et al., 2015). ...
... At the same time, the case of the N/C ratio is shown to be increased while blending. Hence the biocrude produced either from the single feedstock or the co-HTL process contains a high amount of heteroatoms should be removed; hence upgradation is required (Zhu et al., 2013). ...
Hydrothermal liquefaction (HTL) is a thermochemical conversion process to produce biofuel from biomass. In this work, co-HTL of spirulina platensis (SP) with rice husk (RH), coconut shell (CS) and high-density polyethylene (HDPE) is performed which are not reported in the literature. The maximum biocrude yield for SP and RH mixture is 20.1wt.% at blend ratio of 50:50, temperature of 300°C, reaction time of 30mins and solid loading of 20wt.% whereas for SP and CS mixture, the maximum biocrude yield of 12.2wt.% is obtained under same operating conditions. It is found that biocrude yield enhances with increasing blending ratio of SP to lignocellulosic biomass. For co-HTL of SP and HDPE, the maximum biocrude yield of 28.8wt.% is obtained at blend ratio of 50:50, 350°C, 30mins and 20wt.% solid concentrations. In this case, the biocrude yield decreases with increasing SP/HDPE ratios. Furthermore, various characterisation methods are used to analyse the quality of biocrude.
... Microalgae harbour the potential of producing biofuels which can be used to meet the growing energy requirements. The cellular composition of microalgae makes these tiny microbes suitable for multiple applications, such as for the production of biodiesel, syngas, biogas and bioethanol (Piechota, 2021a(Piechota, , 2021bKoley et al., 2018;Raheem et al., 2018;Zhu et al., 2013).Despite many advantages, the primary difficulty lies in the cost-effective biomass production/microalgae cultivation process. ...
... Hydrothermal liquefaction (HTL) is a technique to convert algal feedstocks (~90% moisture content) into crude oil at elevated temperature and pressure of ~250-600 • C and 10-25 MPa, respectively in the presence/absence of catalysts with a typical processing time of 20-100 min (Biller and Ross, 2011;Koley et al., 2018;Zhu et al., 2013). Feedstock for hydrothermal liquefaction can be based on both freshly harvested microalgae as well as defatted microalgae. ...
Microalgal biodiesel production experiences hurdles in every step, beginning from cultivation of microalgal strains for biomass generation followed by harvesting, drying, oil extraction, and transesterification, leading to higher cost of production. In this study, an approach was adopted to minimize the cost of biomass production by utilizing the locally available agricultural fertilizers, viz. urea, NPK 10 26 26, diammonium phosphate, potash, superphosphate, etc. for cultivation of the green microalga Tetradesmusobliquus that can be subsequently used for biodiesel and bio-crude production. For this, an optimized urea medium (OUr) was developed, which reduced the cost of production by 47-fold as compared to the commonly used N 11 medium, formulated with the analytical grade inorganic salts. This optimized medium further enhanced the biomass yield by 32% while reducing the requirements of the major nutrients like potash, magnesium sulfate and superphosphate by 29, 25 and 25%, respectively. Urea requirement was, however, increased by 20%. Raceway pond cultivation of T. obliquus in the newly formulated medium depicted a biomass productivity of 12.6 g m⁻² day⁻¹ during winter season followed by 10. 9 g m⁻² day⁻¹ in summer and 4.8 g m⁻² day⁻¹ in rainy season at a culture depth of 30 cm, thus leading to an estimated biomass productivity of 30.04 ton hectare⁻¹ year⁻¹,and a biodiesel productivity of 2.07 ton hectare⁻¹ year⁻¹. The fuel characteristics of the biodiesel produced showed comparable characteristics with petro-diesel, and were also within the limits specified by the national and international standards. Bio-crude productivity of 10 ton hectare⁻¹ year⁻¹ was projected from the de-fatted biomass. This study was thus successful in utilizing >40% of the biomass for simultaneous production of biodiesel and bio-crude from the same biomass, eventually paving a path for the development of a microalgal refinery by exploring the spent biomass for further applications.
... The results of the sensitivity analysis done by Zhu et al. (2013) also showed that the feedstock cost, the final product yield and the upgrading equipment cost were the main factors affecting MFSP. Zhu et al. (2013) investigated TEA for conversion of lipid-extracted microalgae (LEA) to liquid hydrocarbon fuels through HTL and the hydrotreating process based on the optimum experimental data. ...
... The results of the sensitivity analysis done by Zhu et al. (2013) also showed that the feedstock cost, the final product yield and the upgrading equipment cost were the main factors affecting MFSP. Zhu et al. (2013) investigated TEA for conversion of lipid-extracted microalgae (LEA) to liquid hydrocarbon fuels through HTL and the hydrotreating process based on the optimum experimental data. The LEA feedstock with a moisture content of 83 wt.% contained 19.9 ± 3 wt.% ...
... By exploring different ways of utilizing residual algal biomass, it may be possible to further improve the efficiency and profitability of the algal biorefinery process Zhu et al., 2013). Studies have also shown that the preservation of biomass and the cell disruption method can affect the targeted energy product. ...
... Ultimate analysis showed that Haematococcus have satisfactory limit of N and S, which will cause the formation of environmentally favorable NO x and SO x (Haque et al. 2017), which is comparable to rice husk, a popular biomass used to power generation commercially. The ratio of hydrogen and carbon of Haematococcus is similar to Chlorella, Nannochloropsis and Spirulina species (Chow et al. 2013;Phukan et al. 2011;Zhu et al. 2013), these species are being widely investigated for energy applications. Haematococcus is well known for algal research on food and medicine ingredients. ...
Covers recent topics of algae from bionanopesticides to genetic engineering
Presents algal biotechnology, updated food processing techniques and Biochemistry of Haematococcus
Offers information on the less explored areas of in silico therapeutic and clinical applications
... Ultimate analysis showed that Haematococcus have satisfactory limit of N and S, which will cause the formation of environmentally favorable NO x and SO x (Haque et al. 2017), which is comparable to rice husk, a popular biomass used to power generation commercially. The ratio of hydrogen and carbon of Haematococcus is similar to Chlorella, Nannochloropsis and Spirulina species (Chow et al. 2013;Phukan et al. 2011;Zhu et al. 2013), these species are being widely investigated for energy applications. Haematococcus is well known for algal research on food and medicine ingredients. ...
Haematococcus is a genus of green microalgae widely distributed in freshwater and seawater and well known for their ability to produce astaxanthin, a powerful antioxidant with diverse applications. Eight species have been assigned to this genus based on a recent genetic classification and among them Haematococcus lacustris (previously named Haematococcus pluvialis) is the most studied. This species is regarded as the most promising microalgae for the production of natural astaxanthin. It is also known for its ability to synthesize other interesting bioactive compounds with a wide range of biological activities. The present work highlights the diverse therapeutic applications of Haematococcus bioactive molecules such as antioxidant, anti-inflammation, antimicrobial, skin protection, treatment and prevention of cancer, treatment of eye and neurodegenerative diseases, and immune stimulation.KeywordsAstaxanthinAntioxidantAnti-inflammationCancer preventionNeurodegenerative diseases
... [32,33] The results are much better compared to the autoclave and steam explosion pretreatment methods (Table 1), owing to higher temperature and longer treatment time of HTL. According to Zhu et al., [75] lipid-extracted algae (LEA) undergo HTL treatment for the production of bio-oil. At the end of the process, dry microalgae biomass after oil extraction will be discarded as solid waste. ...
Microalgal lipids are promising and sustainable sources for the production of third-generation biofuels, foods, and medicines. A high lipid yield during the extraction process in microalgae could be influenced by the suitable pretreatment and lipid extraction methods. The extraction method itself could be attributed to the economic and environmental impacts on the industry. This review summarizes the pretreatment methods including mechanical and non-mechanical techniques for cell lysis strategy before lipid extraction in microalgae biomass. The multiple strategies to achieve high lipid yields via cell disruption techniques are discussed. These strategies include mechanical (shear forces, pulse electric forces, waves, and temperature shock) and non-mechanical (chemicals, osmotic pressure, and biological) methods. At present, two techniques of the pretreatment method can be combined to increase lipid extraction from microalgae. Therefore, the extraction strategy for a large-scale application could be further strengthened to optimize lipid recovery by microalgae.
... In the treatment of the waste were considered the purged fraction of the currents waste wet scrubber 1 (321), waste wet scrubber 2 (328) and waste fermentation (517), plus the disposal of the calcium sulfide (314). For streams 321, 328 and 517 was calculated the chemical oxygen demand (COD) and was considered a cost of 0.07 $/kg COD for the wastewater treatment [45]. For the waste treatment of stream 414, a price of 200 $/t was assumed [37]. ...
... In order to carry out its design, technical parameters based on commercial plants were used, and the catalyst was assumed to have a 5-years life [46]. The followed methodoloy, i.e., designing an on-site hydrogen generation plant rather than considering hydrogen as an operative cost, is commonly performed in literature for similar systems [51][52][53][54]. In fact, it takes into account the decentralized nature of biorefineries, which would lead to high costs for transportation and delivery if hydrogen derives from a centralized plant. ...
Hydrothermal liquefaction is a promising technology for producing renewable advanced biofuels. However, some weaknesses could undermine its large-scale application, such as the significant carbon loss in the aqueous phase (AP) and the necessity of biocrude upgrading. In order to deal with these challenges, in this work the techno-economic feasibility of coupling hydrothermal liquefaction (HTL) with aqueous phase reforming (APR) was evaluated. APR is a catalytic process able to convert water-dissolved oxygenates into a hydrogen-rich gas that can be used for biocrude upgrading. Two cases were proposed, based on different lignocellulosic feedstocks: corn stover (CS) and lignin-rich stream (LRS) from cellulosic ethanol production. HTL-APR plants operating with the same mass flow (3.6 t/h) at 10 wt.% solid loading were herein evaluated, resulting in an input size of 20 MW (LRS) and 16.5 MW (CS). Based on experimental and literature data, the mass and energy balances were performed; subsequently, the main equipment was designed; finally, the capital and operating costs were evaluated. The analysis showed that the minimum selling prices for the biofuel (0% internal rate of return) were 1.23 (LRS) and 1.27 €/kg (CS). The heat exchangers accounted for most of the fixed capital investment, while electricity and feedstock had the highest impact on the operating costs. The implementation of APR was particularly profitable with CS, as it produced 107% of the hydrogen required for biocrude upgrading. In this case, APR was able to significantly reduce the H2 production cost (1.5 €/kg) making it a competitive technology compared to conventional electrolysis.
... The hydrotreatment cost of bio-crude is also important to be considered as it impacts immensely on the product price. Zhu et al. [198] studied the upgradation of biocrude from lipid-extracted algae in a bench-scale operation and simulated the same for a larger scale plant operating at 608 dry metric tons per day capacity. The economic analysis revealed that the capital expenditure for the hydrotreatment process constituted 40% of the total installed cost. ...
The growing concerns on climate change, energy demand and depleting fossil fuel reserves have diverted the focus of the 21st century toward renewables. A wide range of technologies such as transesterification, gasification, pyrolysis, aqueous phase catalytic reforming and hydrothermal liquefaction (HTL) are used for producing biofuels and chemicals from a wide range of feedstocks. Due to its immense flexibility in handling a wide variety of organic substrates, ranging from dry to wet residual biomass, algae, sewage sludge, plastics and municipal solid wastes, HTL is regarded as a “feedstock agnostic technique.” The bio-crude obtained from HTL is a dark viscous liquid, which is immiscible with water and has a better calorific value with lower oxygen content than the bio-oil obtained from pyrolysis. Various organic compounds such as aromatics, aldehydes, ketones, alcohols, carboxylic acids, esters, and straight and cyclic hydrocarbons make up a major portion of the bio-crude, with its composition strongly dependent on the type of feedstock. The products from HTL can be considered as a renewable source of biofuels, bio-based specialty chemicals, and bio-products in a circular bioeconomy. This critical review will assess the possibilities of deriving chemicals, fuel molecules and bio-products from a range of feedstocks via HTL technology with special emphasis given to (a) characteristics and applications of different products from HTL, (b) possibilities of tailoring the selectivity to specific chemicals by using catalysts, (c) challenges and opportunities in integrating the HTL products in the existing refinery infrastructure and (d) industrial potential and economics of the process.
... However, addition of aqueous phase "micronutrient (compounds) such as Mg results in almost identical growth to standard media", indicating that recycle of the aqueous phase could have economic impacts by reducing operating costs. 62 Both lignocellulosic and algal HTL processes produce a significant aqueous phase with dissolved carbon ranging from 10 to 40 wt % of input. The effect on the process carbon conversion efficiency is undeniable, and a recycle and reuse method is needed. ...
... The presence of esters compounds would be very desirable to enhance the bio-crude properties such as its stability, acidity, and viscosity (Chen et al., 2018). Other studies employing organic solvents (other than ethanol) have also stated this enhancement in the properties and yields of the bio-crude (Baloch et al., 2018;Chumpoo and Prasassarakich, 2010;Zhu et al., 2013). However, the utilization of organic solvents would lead to higher costs, which would off-set the greater yields obtained with them. ...
Hydrothermal liquefaction (HTL) has been identified as one of the most promising thermochemical technologies to produce liquid biofuels. Although the production cost of HTL biofuels has not yet reached a competitive price, Brazil is recognized worldwide by its mature and well-developed biomass chain, along with a very market-competitive sugarcane industry, which could be used to deploy HTL technologies in a large-scale. The present study carried out a techno-economic analysis to understand the economic performance of HTL in the Brazilian context and considered sugarcane bagasse as the feedstock in two main configurations: a HTL stand-alone facility and a HTL plant integrated with the Brazilian sugarcane industry. The integration of the HTL with a sugarcane ethanol distillery has significantly increased the internal rate of return (IRR) compared with the stand-alone, moving from 8.1%–12.6% per year, thus indicating that HTL have the potential of being economically feasible if integrated to a sugarcane mill. Moreover, the minimum fuel selling prices of biofuels (MFSP) produced in the best integrated scenario showed a very high market-competitiveness, estimated as 0.44, 0.48, 0.51 and 0.37 US$/L for gasoline, diesel, jet fuel, and marine fuel, which were slightly lower than fossil counterparts. This study has also demonstrated that the selection of liquefaction solvents is a highly sensitive parameter to the economic feasibility of HTL; water has showed the highest economic feasibility, suggesting that the utilization of ethanol as solvent may not be feasible at industrial scale.
... Carbon (C), N, P, Cu, Fe, etc., can be utilized as a nutrient source in agriculture (Patterson and Gatlin, 2013). Zhu et al. (2013) reported that lipid extracted algae biomass was rich in nutrients such as C (49%), H (6.96%), N (5.76%), and O (26.30%), which can be explored as a nutrient source in agriculture. Recently, green algae have been investigated as fertilizers in agriculture due to their nutrient-rich biomass, which provides nutrients mainly through the mineralization process (Garcia-Gonzalez and Sommerfeld, 2016;Gatamaneni Loganathan et al., 2020). ...
Microalgae are recognized as potential candidates for resource recovery from wastewater and projected for biorefinery models. This study was undertaken to evaluate the potential of poultry litter and municipal wastewater as nutrient and water sources, for the cultivation of Acutodesmus obliquus for lipids production for biodiesel application. The efficacy of lipid extracted biomass (LEA) as fertilizer for mung bean crops was also assessed in microcosm. A. obliquus cultivation in acid pre-treated poultry litter extract (PPLE) showed maximum biomass production of 1.90 g L⁻¹, which was 74.67% and 12.61% higher than the raw poultry litter extract (RPPE) and BG11 respectively. Higher NO3-N, NH3-N, and PO4-P removal of 79.51%, 81.82%, and 80.52% respectively were observed in PPLE as compared to RPLE treatment. The highest biomass (140.36 mg L⁻¹ d⁻¹), lipids (38.49 mg L⁻¹ d⁻¹), and carbohydrates (49.55 mg L⁻¹ d⁻¹) productivities were observed in the PPLE medium. The application of LEA as a fertilizer for mung bean crops showed improvement in plant growth and soil microbial activity. A maximum increase in organic carbon (59.5%) and dehydrogenase activity (130.8%) was observed in LEA amended soil which was significantly higher than chemical fertilizer (CF) control in 30 days. Whilst plant fresh weight and leaf chlorophyll in the LEA amended soil was comparable to whole algal biomass (WA) and CF control. The strategy developed could be a basis for sustainable biorefinery for the valorization of wastewater for the production of microalgae-derived biofuel and byproducts for agricultural application.
... The most important product in algae HTL is a hydrophobic liquid called biocrude, which consists of various aliphatic and aromatic hydrocarbons, as well as oxygen and nitrogen-containing compounds (Raikova et al., 2019). Like crude oil, biocrude has the potential to be refined in existing refineries to generate fuels and chemicals (Zhu et al., 2013). However, while crude oil mainly consists of hydrocarbons, biocrude contains substantial levels of heteroatoms (O, N and S), leading to detrimental properties such as low energy content, poor stability, corrosiveness, NO x emission, and hydrotreating catalyst poisoning (Huber et al., 2006). ...
Fast hydrothermal liquefaction of acid-washed Cladophora socialis macroalgae has been studied over homogeneous (KOH, K2CO3, H3PO4, HCOOH) and heterogeneous (H-ZSM-5, Raney Ni, Ru/C, Fe metal) catalysts in a batch reactor at 350 oC. Biocrude with maximum yield (36.2%) and energy density (37.1 MJ kg⁻¹) and minimum heteroatom contents (3.8% N and 10.1% O) were achieved with metallic Fe. GC-MS indicates reduction in content of carbonyls, acids and N-containing substances and increase in levels of phenols and hydrocarbons in biocrude while ¹H NMR suggests the enhanced formation of oxygenated/nitrogenous compounds in aqueous phase over Fe catalyst compared to non-catalytic test. Such carbonyls and acids removal was proposed to occur via hydride reduction and decarboxylation pathways, respectively. GPC and TAN confirm vast improvement in stability and corrosiveness properties of Fe-catalyzed biocrude. Regeneration of used catalyst has been conducted and the regenerated catalyst exhibited slight deactivation, likely due to sintering of Fe particles.
... The biological oil of brown algae obtained by using HTL may contain such useful products as phenols, carboxylic acids, CO, ammonia, and organic bases [22]. Oil obtained by HTL from brown algae usually has a lower oxygen content and a higher energy density than oils obtained as a result of rapid pyrolysis [21], however, significant amounts of oxygen, nitrogen and sulfur due to the high content in raw materials must undergo further processing. ...
The study is devoted to the life cycle assessment and perspectives of the kelp seaweed of the Russian Federation northern seas water areas usage for the biogas, bioethanol and biodiesel production. The article presents the stages of seaweed growth, its harvesting (including environmental impact of different types), transportation, dewatering and three types of biofuel processing. Conclusions are made on the potential use of kelp seaweed as a feedstock for biofuel production for the northern regions of Russia (on the example of Arkhangelsk region). A diagram of the biofuel production from kelp seaweed life cycle is also presented.
... In fact, how to get the cost-effective algal biomass is still the main bottleneck in its large-scale utilization [12][13][14]. Previous results indicated that expense in algal harvesting step could take up to 30% of the entire expenditure of bioenergy production [15][16][17]. Thus, an economical technique with a high biomass harvesting efficiency has always been the focus of industries and scientific studies. ...
Improvements in the microalgal harvesting efficiency and separation processes will accelerate cost-effective biomass utilization. Magnetic harvesting is known as a low-cost and environmentally friendly downstream processing technology, but information on optimization of the harvesting procedures is rare. Here, we present optimized harvesting factors for Microcystis aeruginosa 1343 (M1) and 905 (M9) based on polyethylenimine (PEI)-coated iron oxide nanoparticles (IONPs) and response surface methodology. Four important factors including mass ratio (PEI-coated IONPs to dried cell biomass, g/g), stirring speed (rpm), stirring time (s), and adsorption time (min) were evaluated to obtain the optimal operational parameters for different types of cyanobacteria under natural environmental conditions. The maximum harvesting efficiencies for M1 and M9 were 93.3% and 97.5%, respectively; the optimal mass ratio, stirring speed, stirring time, and adsorption time were 0.14–0.18, 85–120 rpm, 70–95 s, and 5.5–7 min, respectively. Our results indicated that the mass ratio was the leading factor in algal harvesting. Changes in the number of cells bound with PEI-coated IONPs were closely related to the mass ratio, and this was confirmed via scanning electron microscopy results. Moreover, the PEI-coated IONPs were able to remove extracellular organic matter (EOM) synchronously via charge neutralization. Variations in fluorescence excitation emission spectra demonstrated an effective EOM removal. Quantitatively, over 34.97% and 45.35% of EOM in M1 and M9 were reduced, respectively, based on total organic carbon analysis. This study provides new insights into algal harvesting operations using magnetic separation technologies and provides practical guidance for performing magnetic separation under environmental conditions.
... Insbesondere algenbasierte Kraftstoffe sind häufig Gegenstand der Untersuchung (z. B.Collet et al. 2014;Gnansounou/Raman 2016;Kendall/Yuan 2013;Kröger et al. 2013;Lardon et al. 2009;Quinn et al. 2014;Rocca et al. 2015;Sander/Murthy 2010;Zhu et al. 2013). Dabei zeigt sich eine große Bandbreite für die Ergebnisse einzelner Umweltwirkungskategorien wie THG-Emissionen, Primärenergieverbrauch etc. für die verschiedenen Technologiepfade. ...
**** URL: https://www.tab-beim-bundestag.de/de/untersuchungen/u20600.html ****
Der Deutsche Bundestag hat das Büro für Technikfolgen-Abschätzung beim
Deutschen Bundestag (TAB) beauftragt, eine Untersuchung mit dem Titel
»Nachhaltige Potenziale der Bioökonomie – Biokraftstoffe der 3. Generation«
durchzuführen. Der Fokus der Studie liegt auf der Produktion von Biokraftstoffen
aus Algen und ihrer möglichen Rolle für den Lkw-Fernverkehr. Durch diesen
Fokus soll eine Lücke geschlossen werden, die das Umweltbundesamt (UBA
2015) in seiner Studie zur postfossilen Energieversorgung im Verkehr aufgezeigt
hat. Laut UBA bleibt die Frage nach einer klaren Option einer postfossilen
Energieversorgung für den Lkw-Fernverkehr bislang offen. Ungeachtet der Fokussierung
auf Algenkraftstoffe werden im vorliegenden Bericht bis zu einem
gewissen Grad auch andere Kraftstoffe und ihre jeweiligen Antriebssysteme angesprochen.
Das ist notwendig, um die potenzielle Rolle von Algenkraftstoffen
für Lkw im Hinblick auf die THG-Verminderungen im Verkehr in Relation zu
diesen anderen Technologiepfaden besser abwägen zu können.
Hierzu wird eruiert, ob bzw. welche Menge algenbasierten Biokraftstoffs
umweltverträglich zur Verfügung gestellt werden könnte. Zudem wird dargelegt, ob forschungs- und wirtschaftspolitische Strategien und Instrumente zur
Verfügung stehen oder ggf. notwendig wären, um dieses Potenzial zu heben und
algenbasierte Biokraftstoffe in absehbarer Zeit marktreif zu machen.
Zur Beantwortung dieser Fragen wurde vorhandenes Wissen systematisch
zusammengetragen und aufgearbeitet sowie Wissenslücken identifiziert, um
darauf aufbauend mögliche Handlungsoptionen identifizieren zu können.
Durchgeführt wurde eine Analyse der technischen, ökologischen und ökonomischen
Vor- und Nachteile bzw. Stärken und Schwächen spezifischer Algenproduktions-
und Kraftstofferzeugungsverfahren, insbesondere auch im Hinblick
auf Zielkonflikte zu Belangen des Umwelt- und Naturschutzes. Daneben
wurden für die Kraftstoffversorgung im Lkw-Verkehr exemplarisch der Zusammenhang
von Antriebstechnik und Mobilität behandelt, um besser die zukünftige
Bedeutung von Biokraftstoffen der 3. Generation für einen THG-neutralen
Verkehr abschätzen zu können.
... Cost analyzes are a valuable instrument to measure both the total costs and method elements that gives the best output and therefore help to guide potential research and growth. The drawbacks of the cost of algae development are close to those faced with life cycle evaluations which involve data restrictions and the emphasis on criteria extrapolated from laboratory analyzes [40,41,42]. It is also not possible to capture the current state of the art for microalgae culture. ...
There is a high demand for clean, affordable and sustainable source of energy due to the limitation in fossil fuel supplies. The algae industrial revolutions have proved to be a significant step to realize the growing need for energy and achieving the sustainable development goals (SDGs). In this review, the production and processing of algae from an industry point of view and the algae processing in Industry 4.0 as well as a paradigmatic shift from Industry 4.0 to Industry 5.0 were well-delineated. Moreover, numerous aspects in the algae industry have been discussed, including economic and environmental analysis of algae bioenergy production, customization of the algae-derived bioenergy, algae cultivation and modifications in the cultivating approach. Genetic engineering tools implemented in the algae culture for bioenergy and by-products generation was also studied, and area of focusing such as the desired algae strain and its detection through automated genetic manipulation and genetic modification. Furthermore, the impacts of the Industry 5.0 on the new market opportunities and environment aspect as well as the possibility of applying SDGs were significantly studied.
... Microalgae biomass is an attractive source due macromolecules production, such as protein, carbohydrate, and lipid [4]. Carbohydrate and lipid need to be extracted from microalgae biomass for biofuels production. ...
Magnetic field (MF) can interact with the metabolism of microalgae and has an effect (positive or negative) on the synthesis of molecules. In addition to MF, the use of pentose as a carbon source for cultivating microalgae is an alternative to increase carbohydrate yield. This study aimed at evaluating the MF application on the mixotrophic culture of Chlorella minutissima in order to produce carbohydrates. MF of 30 mT was generated by ferrite magnets and applied diurnally for 12 days. The addition of 5% pentose, MF application of 30 mT, and nitrogen concentration reduced (1.25 mM of KNO3) was the best conditions to obtain higher carbohydrate concentrations. MF application of 30 mT increased biomass and carbohydrate contents in 30% and 163.1%, respectively, when compared with the assay without MF application. The carbohydrate produced can be used for bioethanol production.
... The main alternatives investigated in the literature for the valorization of defatted biomass concern the production of other biofuels: by hydrolysis (chemical or enzymatic) to produce substrates for microbial fermentations for bioethanol or biogas production [58,59] and by thermal and hydrothermal treatments for biochar, gas, and liquid fuels production [60,61]. Other investigated applications include biosorption, by which the defatted biomass was used as biosorbent for heavy metal removal in contaminated water [62]. ...
Global warming and climate change have driven us to change our perceptions over our day-to-day lifestyle, practices, and habits. All the fields considered major contributor to climate change are being investigated to adapt new approaches to reduce or eliminate greenhouse gas. Call for changes have been made on all the fields and sectors responsible as major greenhouse gas emitters. The production and usage of energy is the largest source of greenhouse gas emission from human activities. Replacing fossil fuels with renewable resources can take us ahead a lot to combat climate change. Lack of commercially viable mature renewable energy technology is a major barrier of implementing renewable energy widescale. But this barrier also encouraged the researchers to investigate unexplored fields of renewable resources. Researchers are looking for bio-resources that can produce energy. Microalgae is one such bioresource that has drawn attention worldwide because of its unique features—variety of species, fast growth, capability to grow at any place, a potential source of CO2 sequestration, and a feedstock of biofuel and biochemicals. In this chapter, we will discuss about the bioenergy potential of one such algal strain Haematococcus. Haematococcus, well known as a source of astaxanthin, a raw material of medicines and food supplements. But recent studies showed that it also can be used to produce renewable bioenergy. We have studied the biomass to energy conversion approaches for Haematococcus through anaerobic digestion, pyrolysis, gasification, hydrothermal liquefaction, and esterification processes. Because of the cellular structure, residual biomass showed better potential than fresh biomass. This feature has also opened the potential of biorefinery approach for Haematococcus biomass.
Globally, nations are trying to address environmental issues such as global warming and climate change, along with the burden of declining fossil fuel reserves. Furthermore, countries aim to reach zero carbon emissions within the existing and rising global energy crisis. Therefore, bio-based alternative sustainable feedstocks are being explored for producing bioenergy. One such renewable energy resource is microalgae; these are photosynthetic microorganisms that grow on non-arable land, in extreme climatic conditions, and have the ability to thrive even in sea and wastewater. Microalgae have high photosynthetic efficiencies and biomass productivity compared to other terrestrial plants. Whole microalgae biomass or their extracted metabolites can be converted to various biofuels such as bioethanol, biodiesel, biocrude oil, pyrolytic bio-oil, biomethane, biohydrogen, and bio jet fuel. However, several challenges still exist before faster and broader commercial application of microalgae as a sustainable bioenergy feedstock for biofuel production. Selection of appropriate microalgal strains, development of biomass pre-concentrating techniques, and utilization of wet microalgal biomass for biofuel production, coupled with an integrated biorefinery approach for producing value-added products, could improve the environmental sustainability and economic viability of microalgal biofuel. This article will review the current status of research on microalgal biofuels and their future perspective.
The rising demand to settle a sustainable energy source is guiding researchers in the production of biofuels. The liquefaction process is an alternative to obtaining biocrude from different types of renewable biomass and can mitigate environmental impacts. All papers published since 2000, which are related to the hydrothermal liquefaction process that aims to obtain biocrude are analyzed in the present study using the bibliometric approach to provide the selected database. Furthermore, the use of algae biomass in the liquefaction was also a discussed topic considering its high relevance in the process. The focus of the present study was to evaluate the evolution of the current state of the art in these topics and also to indicate trends and courses that it might be taken in the future. The database used in the bibliometric analysis was taken from the Web of Science (WoS) and the papers were selected by two different search equations. With the selected data, the use of BibExcel, VOSviewer, and PowerBi software was useful to guide the discussion and to create graphics and visual networks. As shown in the results, it was noticeable the influence of China and the USA on the field, considering the high number of publications from these countries. Moreover, the main authors were indicated considering their citation numbers, publications, and local h-index factor. Based on the author’s keywords, the most significant and recent topics on liquefaction were listed. Among them, technical-economic analysis, nutrient, and energy recovery, response surface methodology, and kinetic model are highlighted. This may indicate a new direction being taken by researchers besides the operational parameters’ studies.
Graphical Abstract
Jet biofuel (JBF) is identified as an essential solution to mitigate the carbon footprint of the aviation sector. Since aeroplanes rely solely on liquid fuels, the development of pathways that generates JBF as a major product has become crucial. Thus far, seven pathways to produce JBF have been developed and certified over the past decade. Each of these pathways accommodates a specific type of biomass. However, the availability, sustainability and feasibility of feedstocks to fulfil the growing demand on jet fuel remains an issue. As such, this study presents a holistic approach for the design of a state-of-the-art hybrid biorefinery that accommodates multiple biomass feedstocks across different categories including energy crops (i.e., Jatropha energy crop), dry biomass (i.e., municipal solid waste) and wet biomass (i.e., livestock manure). A Qatar-based industrial scale biorefinery was modelled in Aspen Plus® considering a pre-defined geospatial distribution of biomass and the optimal biorefinery site in the country. The hybrid system integrated advanced technologies such as hydroprocessing, Fischer-Tropsch, gasification, dry-reforming and hydrothermal liquefaction. While biomass optimal insertion streams were evaluated using a prediction model. Besides, intensive materials, heat, water and power integrations were performed to maximise JBF production, mitigate its environmental impact and control its cost. The system generated 328, 94 and 44 million litres of JBF, gasoline and diesel, respectively. Produced JBF was characterised and found to comply with all international standards. The generated JBF can substitute 15.3 % of Qatar’s jet fuel needs, while it can power around one third of its fleet considering a maximum allowable jet biofuel blend of 50 %. The proposed model achieved a minimum selling price of JBF at 0.43 $/kg, which is 22 % lower than the market price of conventional Jet-A fuel (2019). In addition, the environmental analysis of the model indicated a 41 % mitigation in greenhouse gas emissions achieved by JBF throughout its lifecycle, relative to Jet-A fuel.
Carbon dioxide (CO2) emissions from fossil fuel burning are recognized as one of the major causes of climate change, particularly global warming. Thus, to reduce fossil fuels and CO2 emissions, it is essential to take preventative steps and investigate more tolerable energy options. Effective combining microalgae cultivation and hydrothermal liquefaction (HTL) technology can reduce CO2 emissions and the energy cost of algal biofuel production, making it more environmentally friendly. However, the carbon migration in processes must be considered prior to industry production. Therefore, this paper reviews the transformation of carbon, including the CO2 sequestration in microalgae cultivation, the carbon conversion in HTL and the CO2 emissions of algae-derived biofuel. Including a summary of the conversion path and recovery of carbon, which are noticeably affected by parameters such as cultivation system, algae species, HTL reaction conditions (temperature, time and pretreatment methods) and upgrading catalyst. In addition, techno-economic assessments and environmental impact considerations on microalgae biofuel are reported.
A novel approach for modelling hydrothermal liquefaction (HTL) biocrude is presented, using a combination of fractional distillation data of biocrude and multi-objective optimisation to simulate the biocrude various properties using the non-dominated sorting genetic algorithm (NSGA-II). The complex composition of biocrude has made it challenging to analyse and simulate in process models. Most HTL simulation studies use a simple basis for biocrude using limited GC-MS data, which may not be reliably accurate. Applying multi-objective optimisation reduced the density and TBP curve error by ten times compared to single-objective optimisation. In addition,the results were further improved by combining distillation experimental data into multi-objective optimisation, in contrast with previous studies which used only the biocrude data. Separating complicated HTL biocrude into five fractions and analysing the obtained results increased the number of candidate databank compounds from 72 to 216, which led to a noticeable improvement in the accuracy of the model.
Biofuels derived from biomass are receiving increasing attention for their great potential of replacing fossil fuels and reducing CO2 emissions. Thermochemical conversion technologies have been commonly used to produce biofuels and are experiencing fast development in recent years. This chapter provides a review of the techno-economic analysis of the biofuel production via liquefaction, gasification, and pyrolysis technologies. The biofuel production costs of the technologies are compared across different countries and regions. Existing challenges and gaps are identified, and future development is recommended.
Biorefinery explores the conversion of different biomass into a variety of bio-based products. The bioeconomy is an important aspect of biorefinery. Among various biorefinery concepts, hydrocarbon biorefinery is extremely important and provides hydrocarbon biofuels, which are compatible with the existing petroleum facilities. The techno-economic assessment is useful tool to optimize and improve various biomass conversion processes for the sustainability of hydrocarbon biorefinery. This chapter thus discusses the technical and economic aspects to produce hydrocarbon biofuels using thermochemical conversion pathways of pyrolysis and hydrothermal liquefaction. These pathways produce renewable liquid hydrocarbon biofuels with a minimum selling price in the range of $0.5–3.5/L which is higher in comparison to fossil fuel-based transportation fuels. Thus, to compete with fossil fuels, further improvement in the area of process integration and intensification in hydrocarbon biorefinery is required.
Livestock manures significantly contribute to greenhouse gas emissions and soil contamination if not valorised or disposed properly. Meanwhile, hydrothermal liquefaction has emerged as a promising technology for the conversion of wet wastes into value-added products. As such, this study investigates the potential of hydrothermal liquefaction of camel manure and subsequent upgrading into drop-in fuels in Qatar. Experimental characterisation of manure samples is conducted, while a small-scale plant is simulated and evaluated using Aspen Plus®. Excess treated wastewater of Qatar is utilised as an alternative to fresh water in the process, while power is completely generated on-site. The demonstrated results are promising; whereby, a biocrude yield of 37.9% (on dry and ash-free basis) is achieved, while the biocrude is upgraded into a high-quality bio-gasoline. The produced bio-gasoline contributes to a 7% reduction in greenhouse gas emissions relative to conventional gasoline. The project capital investment is estimated to be 38 M$, while the bio-gasoline’s minimum selling price is at 0.87 $/kg, which is still above the market price of conventional gasoline in Qatar (∼0.6 $/kg). However, the conducted sensitivity analysis indicates that scaling-up the plant by 5-fold can shift the fuel’s minimum selling price below the average market price. As such, it has a high potential to be locally commercialised especially at times of petroleum price hikes.
Hydrothermal liquefaction is a promising conversion technology in algae biofuel research due to its ability to agnostically convert proteins, carbohydrates, and lipids to biocrude. The high-temperature conditions that define this conversion process require the material to maintain a subcritical liquid state, which complicates the assessment of accurate thermochemical properties due to the required pressure. To clarify this issue, this work compares the estimated performance of algal hydrothermal liquefaction between different thermodynamic models. A process model was developed in Aspen Plus from a robust assessment of current literature. Techno-economic assessment and life-cycle assessment metrics are derived from this model and used as key performance indicators. The baseline fuel price contribution of hydrothermal liquefaction is $0.45 per liter gasoline equivalent. Independently decreasing the temperature from 350 °C to 260 °C while maintaining yield reduces the conversion cost by 19%, illustrating the importance of understanding the high-temperature thermodynamics of the system. Different thermodynamic property models can vary fuel conversion cost results by $0.07 per liter gasoline equivalent. The baseline global warming potential is +23 g CO2 eq MJ⁻¹ and the net energy ratio is 0.30. Environmental metrics beyond global warming potential and net energy ratio are also discussed for the first time. Uncertainties in conversion performance are bounded through a scenario analysis that manipulates parameters such as product yield and nutrient recycle to produce a range of economic and environmental metrics. The work is supplemented with an open source model to support future hydrothermal liquefaction assessments and accelerate the development of commercial-scale systems.
The purpose of the present work is to investigate the feasibility of hydrothermal liquefaction (HTL) on food waste using a mobile pilot scale reactor and assess its techno-economic potential as a renewable energy technology that can be commercialized in the future. A 35 L pilot scale reactor (0.15 gal·min⁻¹, 300°C, and 60 min retention time) resulted in a higher biocrude oil yield than lab scale reactors (29.5 wt.% vs 21.9 wt.%). Biocrude oil qualities from pilot scale and lab scale HTL showed similar characteristics when comparing the elemental distribution, oil composition, and heating values. Further, techno-economic assessment (TEA) showed that the minimum selling price of the biocrude oil from a base case scenario was $3.48 per gallon gasoline equivalent (GGE). The transportation cost of the feedstock and oil product was compared between onsite and mobile scenarios of HTL reactor operation. The results demonstrated that the mobile HTL reactor was more profitable when the sources of food waste were widely distributed (more than 106 miles). Combined pilot reactor results and assessments in different scenarios could be used to assess the sustainability of the HTL process for future large-scale implementation.
The utilization of algal biomass residue after lipid extraction for other purposes can lead to maximum usage of algal biomass and economically beneficial microalgal biodiesel technology. In this study, the performance and economic potential of the conversion of Scenedesmus sp. lipids to biodiesel over lipid extracted algae (LEA) derived catalysts were investigated. The lipid extracted algae (LEA) derived catalysts (Ni/C and Ni/Fe3O4-C) were synthesized by impregnation technique and characterized using different analytical tools. The biodiesel conversion of 96.43%, 98.5% and 95.12% was achieved using biochar (C), Ni/C, and Ni/Fe3O4-C respectively under the following conditions: reaction time (4 h), temperature (60 °C), methanol to oil molar ratio (30:1) and catalyst dosage (15% w/w of oil). The findings from this study have shown that the use of lipid extracted algae derived catalysts reduced the unit production cost of microalgal biodiesel from 2.03 $/kg to (1.70–1.74 $/kg) when compared to homogeneous catalyst. Among the lipid extracted algae derived catalysts, the use of Ni/C catalyst gave the lowest unit production cost (1.70 $/kg) for biodiesel production from microalgae. The recyclability potential of the LEA derived catalysts could improve the economic viability of the process. The payback period in the range of 1.32 yr–5.57 yr obtained using LEA derived catalysts was below the lifespan of the project (10 years), suggesting that the proposed microalgal biodiesel production is economically feasible.
The production of ‘Jet Biofuel’ has been identified as a promising strategy to mitigate the carbon footprint of the aviation sector. During the past decade, the commercial production of Jet Biofuel has attracted the attention of airline companies and governments across the globe. However, achieving a competitive production cost and sustainable Jet Biofuel remains a challenge. In this regard, various feedstocks have been tested for this purpose, where the vast majority have not complied with sustainability and feasibility expectations. Although not fully utilised in the Jet Biofuel industry, Jatropha curcas has emerged as one of the most promising feedstocks for Jet Biofuel production, since it is non-edible and is able to grow in non-arable lands with minimal water and energy requirements. This study presents a novel integrated pathway that utilises all parts of Jatropha fruit to produce a cost-effective Jet Biofuel using conventional hydroprocess, gasification, Fischer-Tropsch and reforming technologies. Different integration techniques are employed, including waste valorisation, by-products incorporation, as well as water, heat and power integration. The effect of various operating parameters on the products’ characteristics and yields has been evaluated. The model is validated against literature experimental data and demonstrates promising results. Whereby, 49 wt% of Jatropha fruit is converted into liquid fuels, with a Jet Biofuel selectivity of 65%, which represents an increment of almost 88% of Jet Biofuel yield compared to processing Jatropha oil alone. Furthermore, the system developed is power and water self-sufficient. The proposed pathway significantly lowers the production cost of Jet Biofuel below the market price of conventional Jet-A fuel for the base year of analysis, achieving a minimum selling price of 0.445 $/kg.
The growing anthropogenic greenhouse gas (GHG) emissions combined with the rise of the demand on energy resources has expedited research into sustainable alternatives to fossil fuel. In this context, biomass has increased in popularity and acquired a significant share of the global energy mix in a relatively short time. However, several biomass resources have triggered wide criticism for compromising food resources, agricultural lands and fresh water to produce energy crops. Therefore, a second generation of non-edible biomass such as Jatropha curcas has become a major biofuel feedstock for several countries. Not only can its oil be converted into liquid fuels, but also the Jatropha fruit residues have high calorific value and are processed into several forms of energy. Several studies have investigated the different processing technologies to produce energy and food-related products, although no conclusions have been made on the most sustainable pathway for Jatropha utilisation considering its interlinkages to the energy, water and food resources, whilst considering its possible contributions to mitigating carbon emissions and the development of circular economies. As such, this study investigates 11 processing pathways for the major three components of Jatropha fruit from cradle to gate via a combination of three key tools including Energy-Water-Food (EWF) Nexus, Global Warming Potential (GWP) and Return on Investment (ROI). Aspen Plus software is used to simulate the production processes including transesterification, hydrotreatment, hydrocracking, gasification, pyrolysis, hydrothermal liquefaction, anaerobic digestion, saccharification and fermentation, incineration and detoxification. In addition, a mathematical model is developed to run a five-objective optimisation study using MATLAB. The model identifies an opportunity to process the Jatropha oil by transesterification (49%), hydrotreatment (28%) and hydrocracking (23%). while it is suggested that the seedcake is best utilised directly as fertilisers (35%) and processed for energy production by pyrolysis (30%) and anaerobic digestion (17%). Nevertheless, the shells of Jatropha are best utilised via SSF (32%), pyrolysis (28%), anaerobic digestion (22%) and incineration (11%).
Extensive uses of fossil fuels are posing several threats to the environment as well as human health. They have been used in such a way that in coming few decades, the finite sources of fossil fuels will be completely exhausted. Algae are one of the most primitive microorganisms on the Earth. They are small photosynthetic organisms that have an ability to completely replace the need of conventional fossil fuel for energy demand. They are robust microorganisms and can be grown in photo-bioreactors, open ponds, sewage or industrial waste without the need of arable land. Microalgal biomass can be converted to variety of biofuels via biochemical and thermochemical methods, they can also be used for the production of high value nutraceuticals at industrial scale. The present chapter deals with the various conversion technologies of algal biomass to biofuel, resource requirements, research gaps and operational costs associated with it.
A wide variety of biomass, from triglycerides to lignocellulosic‐based feedstock, are among promising candidates to possibly fulfill requirements as a substitute for crude oils as primary sources of chemical energy feedstock. During the feedstock processing carried out to increase the H:C ratio of the products, heteroatom‐containing compounds can promote corrosions, thus limiting and/or deactivating catalytic processes needed to transform the biomass into fuel. The use of advanced GC techniques, in particular multi‐dimensional GC, both heart‐cutting and comprehensive coupled to MS, has been widely exploited in the field of petroleomics over the last 30 years and has also been successfully applied to the characterization of volatile and semi‐volatile compounds during the processing of biomass feedstock. This review intends to describe advanced GC‐MS‐based techniques, mainly focusing in the period 2010‐ early 2020. Particular emphasis has been devoted to the multi‐dimensional GC‐MS techniques, for the isolation and characterization of the oxygen‐containing compounds in biomass feedstock. Within this context, the most recent advances to sample preparation, derivatization, as well as GC instrumentation, MS ionization, identification, and data handling in the biomass industry, are described. This article is protected by copyright. All rights reserved
Biomass materials are abundant, low-cost, non-hazardous, disposable, environmentally friendly, and renewable organic materials that are considered as an appropriate solution for environmental contamination. Algae are renewable living organisms that grow throughout the world. More than one million algae species are grown around the world. Algae have several important applications in materials science. One of the important applications of algae is preparing electrochemical energy storage (EES) devices. EES devices are considered as an appropriate solution for industries to reduce environmental pollution. EES device preparation from renewable organic materials is a significant issue which extensively examined by scientists in recent years. Tremendous efforts have been accomplished to prepare EES devices from algae as a renewable resource. The four main parts of the EES devices include electrode, binder, electrolyte, and membrane can be prepared from algae. The purpose of this review is to overview the progress in the preparation of EES devices from algae, examine algae-EES Electrochemical properties in the last few decades, and also present an appropriate perspective for future research on the algae-based EES devices.
Experimental work observed a synergetic effect of using microalgae/wood blended feedstocks for hydrothermal liquefaction (HTL) conversion with a yield advantage over using microalgae only or wood only as the feedstock. Experimental results for HTL and hydrotreating were used to develop the techno-economic analysis (TEA) for a blended feedstock HTL and biocrude upgrading system. For the blended feedstock system, wood is blended with algae feedstock during the lower algal productivity seasons (winter, fall, and spring) to match the maximum algal seasonal production rate. Adding woody biomass led to a 34% larger plant scale than the algae-only system with the same assumptions for algae seasonal productivity. In addition, low-cost woody biomass led to lower blended feedstock cost than the algae-only case. Blended feedstock also eliminated the need for drying a portion of the algae during summer and spring for winter and fall use, a requirement of the algae-only case, and thus reduced the related capital and operating costs. Economic analysis results indicated that, with feeding of microalgae/wood blended feedstock, the minimum fuel selling price (MFSP) to produce naphtha and diesel blendstock was reduced by 21% and the conversion-only cost (excluding cost for feedstock) was reduced by 13% compared to the algae-only case. Sensitivity analysis identified algae feedstock cost, algae blend ratios, and biocrude yields as key factors affecting the MFSP of the blended feedstock system.
Microalgal biomass is composed of different valuable metabolites that can satisfy the requirements of renewable biofuels, alternative proteins, carbohydrates, and food grade natural colorants. Production of a specific product from microalgae has been proved to be economically infeasible on the commercial scale except for the production of high-value products (e.g. carotenoids and phycobiliproteins). Therefore, the simultaneous extraction of multiple products is essential to bring pragmatism for the production of biofuels, proteins, and carbohydrate derived products from microalgal biomass. In order to obtain multiple products, various strategies have been implemented using potential techniques of cell disruption and biomass fractionation based on the priorities of products. Conventional approaches of downstream processing have often proved to be inefficient in the case of integrated fractionation systems. This is attributable to the divergent nature of the intracellular metabolites of microalgae and their vulnerability toward the different chemicals and conditions of those downstream processes. However, three phase partitioning (TPP), aqueous two-phase separation, membrane separation, supercritical fluid extraction (SFE), and pressurized liquid extraction (PLE) are some of the advanced techniques which have been proved to be useful in this regard. Choice of cell disruption mechanisms is critical for several purposes, such as the selective release of metabolites into a suitable solvent, preservation of bioactivity of molecules and cost-savings. Unfortunately, consolidated report for the fractionation of priority-based products from microalgal biomass using these techniques is lacking. Therefore, in this review, we have critically discussed the different strategies for the priority-based multiple products by implementation of the advanced techniques.
Bio-oil production from food waste, consisting of pineapple peel, banana peel, and watermelon peel, is investigated by a two-step process, namely, an alkaline pretreatment process with K2CO3 (10 wt% of the dry feedstock) followed by a hydrothermal liquefaction (HTL) process. Meanwhile, the Taguchi method is introduced to maximize the energy yield of the two-step process. Four parameters in the Taguchi approach are taken into account; they are the pretreatment temperature and time as well as the liquefaction temperature and holding time. The optimal combination of the four parameters gives the highest energy yield of 56.55%. The higher heating value of the bio-oil is 25.12 MJ/kg, yielding a 45.88% improvement when compared to the HHV of the dry-basis feedstock. A double analysis, namely, the Taguchi approach and analysis of variance (ANOVA), suggests that the liquefaction temperature plays the most influential role in the energy yield, and a strong linear relationship (R² ≈ 0.99) is exhibited between the effect in the Taguchi approach and the F value in ANOVA. The experiments of thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy indicate that the composition of the bio-oil from the optimal operation is more uniform.
In order to understand the effects of the major algal components-carbohydrates and proteins on the hydrothermal liquefaction (HTL) process of algae, the HTL of polysaccharides or proteins with lipids was performed at 220, 260, 300 °C, respectively. Bio-oil yields and qualities were investigated and compared with the individual liquefaction of the major algal components. Results show that the presence of polysaccharides or proteins has little effect on bio-oil yield but increased the HHV and significantly changed the boiling point distribution as compared with the HTL of lipids. The compositions of bio-oils from the HTL of binary mixtures were similar to that from the HTL of lipids. Heavy components in bio-oil were increased in the presence of polysaccharides or proteins, which was mainly caused by the hydrolysis product of polysaccharides/proteins being easily polymerized during the HTL process, forming macromolecular compounds into bio-oil.
Global energy demand is increasing due to global development initiatives and steady population growth. The US Energy Information Administration’s International Energy Outlook 2017 (IEO 2017) projects that the world energy consumption will raise from approximately 575 quadrillion Btu in 2015 to 736 Btu by 2040—an increase of 28% (IEO 2017). Fossil fuels, such as petroleum and natural gas, serve as the leading energy sources for various sectors, such as transportation. However, the International Energy Agency (IEA) forecasts that biofuel production will increase by 15% over the next 5 years to reach approximately 42.6 billion gallons (IEA 2018). Various types of renewable fuels or fossil fuel additives are being researched and developed as complements or supplements to fossil fuels. Ethanol, or ethyl alcohol, is one such additive, particularly for motor fuel in the United States and Brazil. Fuel ethanol has been proprosed to offset dependence on petroleum, thereby reducing greenhouse gas emissions by up to 43% relative to gasoline (Flugge et al. 2017). Additionally, as advanced ethanol production processes are less sensitive to the vagaries of geography, as will be discussed later in this chapter, countries can produce it domestically rather than having to rely on the geopolitics associated with the world petroleum market.
Experimental data reported in the literature for gross heating values of various types of biomass were correlated with heating values that were estimated using the Boie equation. This equation was originally developed to estimate the gross heating values of fossil fuels from their respective compositions of carbon, hydrogen, oxygen, nitrogen, and sulfur. The estimated heating values agreed within 50% of the experimental data for 47 types of plants and crop residues and within 8% for cattle feedlot manure of normal quality. This correlation makes it possible to accurately predict the gross heating values of most biomass fuels of known
ultimate composition and ash content.
As energy prices climb there is an increasing interest in alternative, renewable energy sources. One possible source of renewable bio-fuel is algae. This research uses a multi-year, Monte Carlo financial feasibility model to estimate the costs of production and chance of economic success for commercial size algal biofuel facilities in the Southwest. Capital and operating costs and productivity information from Davis et al. were used to develop parameters to define and simulate two types of algae production systems; open pond and photo-bioreactor (PBR).The financial feasibility of PBRs is substantially lower than for open ponds. In the base case, average total costs of production for lipids, including financial costs, were $12.73/gal and $31.61/gal for open ponds and PBRs, respectively. The chance of economic success for the base situation was zero for both open ponds and PBRs. The financial feasibility analysis showed that the only way to achieve a 95% probability of economic success in the PBR system was to reduce CAPEX by 80% or more and OPEX by 90% or more. For the open pond system there were several options that could return a 95% or greater chance of economic success, for example, reducing CAPEX by 60% and OPEX by 90%.
Following scrutiny of present biofuels, algae are seriously considered as feedstocks for next-generation biofuels production. Their high productivity and the associated high lipid yields make them attractive options. In this review, we analyse a number aspects of large-scale lipid and overall algal biomass production from a biochemical and energetic standpoint. We illustrate that the maximum conversion efficiency of total solar energy into primary photosynthetic organic products falls in the region of 10%. Biomass biochemical composition further conditions this yield: 30 and 50% of the primary product mass is lost on producing cellprotein and lipid. Obtained yields are one third to one tenth of the theoretical ones. Wasted energy from captured photons is a major loss term and a major challenge in maximising mass algal production. Using irradiance data and kinetic parameters derived from reported field studies, we produce a simple model of algal biomass production and its variation with latitude and lipid content. An economic analysis of algal biomass production considers a number of scenarios and the effect of changing individual parameters. Our main conclusions are that: (i) the biochemical composition of the biomass influences the economics, in particular, increased lipid content reduces other valuable compounds in the biomass; (ii) the “biofuel only” option is unlikely to be economically viable; and (iii) among the hardest problems in assessing the economics are the cost of the CO2 supply and uncertain nature of downstream processing. We conclude by considering the pressing research and development needs.
We determined the influence of a Pt/C catalyst, high-pressure H2, and pH on the upgrading of a crude algal bio-oil in supercritical water (SCW). The SCW treatment led to a product oil with a higher heating value (∼42MJ/kg) and lower acid number than the crude bio-oil. The product oil was also lower in O and N and essentially free of sulfur. Including the Pt/C catalyst in the reactor led to a freely flowing liquid product oil with a high abundance of hydrocarbons. Overall, many of the properties of the upgraded oil obtained from catalytic treatment in SCW are similar to those of hydrocarbon fuels derived from fossil fuel resources. Thus, this work shows that the crude bio-oil from hydrothermal liquefaction of a microalga can be effectively upgraded in supercritical water in the presence of a Pt/C catalyst.
This report describes one potential biochemical ethanol conversion process, conceptually based upon core conversion and process integration research at NREL. The overarching process design converts corn stover to ethanol by dilute-acid pretreatment, enzymatic saccharification, and co-fermentation. Building on design reports published in 2002 and 1999, NREL, together with the subcontractor Harris Group Inc., performed a complete review of the process design and economic model for the biomass-to-ethanol process. This update reflects NREL's current vision of the biochemical ethanol process and includes the latest research in the conversion areas (pretreatment, conditioning, saccharification, and fermentation), optimizations in product recovery, and our latest understanding of the ethanol plant's back end (wastewater and utilities). The conceptual design presented here reports ethanol production economics as determined by 2012 conversion targets and 'nth-plant' project costs and financing. For the biorefinery described here, processing 2,205 dry ton/day at 76% theoretical ethanol yield (79 gal/dry ton), the ethanol selling price is $2.15/gal in 2007$.
This chapter introduces techno-economic analysis (TEA) methodology. Case studies of pulverized coal (PC), natural gas combined cycle (NGCC) and integrated gasification combined cycle (IGCC) systems without and with the impacts of CO2 capture are presented, illustrating the application of TEA methods and comparing performance, emissions and costs of these power generation alternatives. The advantage and disadvantage of different process simulation methods for TEA are described. IGCC systems are estimated to have less relative decrease in efficiency and increase in capital and levelized costs than the other technology options. Given uncertainties in the costs of CO2 capture, and that IGCC technologies are at an earlier stage of commercial deployment than PC and NGCC technologies, the potential cost advantage of IGCC with CO2 capture is promising but requires ongoing evaluation.
Wet algae slurries can be converted into an upgradeable biocrude by hydrothermal liquefaction (HTL). High levels of carbon conversion to gravity separable biocrude product were accomplished at relatively low temperature (350 °C) in a continuous-flow, pressurized (sub-critical liquid water) environment (20 MPa). As opposed to earlier work in batch reactors reported by others, direct oil recovery was achieved without the use of a solvent and biomass trace components were removed by processing steps so that they did not cause process difficulties. High conversions were obtained even with high slurry concentrations of up to 35 wt.% of dry solids. Catalytic hydrotreating was effectively applied for hydrodeoxygenation, hydrodenitrogenation, and hydrodesulfurization of the biocrude to form liquid hydrocarbon fuel. Catalytic hydrothermal gasification was effectively applied for HTL byproduct water cleanup and fuel gas production from water soluble organics, allowing the water to be considered for recycle of nutrients to the algae growth ponds. As a result, high conversion of algae to liquid hydrocarbon and gas products was found with low levels of organic contamination in the byproduct water. All three process steps were accomplished in bench-scale, continuous-flow reactor systems such that design data for process scale-up was generated.
This paper develops a hedonic pricing model for post-extracted algae residue (PEAR), which can be used for assessing the economic feasibility of an algal production enterprise. Prices and nutritional characteristics of commonly employed livestock feed ingredients are used to estimate the value of PEAR based on its composition. We find that PEAR would have a value lower than that of soybean meal in recent years. The value of PEAR will vary substantially based on its characteristics. PEAR could have generated algal fuel co-product credits that in recent years would have ranged between $0.95 and $2.43 per gallon of fuel produced.
A method for lactic acid production and lipid extraction from microalgae (Nannochloropsis salina) biomass was investigated. Microalgae biomass was acid (5% H2SO4) hydrolyzed at 120 °C for 1 h, and subsequently treated with hexane at 40 °C and 200 rpm to separate lipid from the hydrolysate. The sugar (glucose plus xylose) yield reached 64.3% and remained the same until the biomass loading of 15% (w/v) after which, it dropped. Lipid free hydrolysate was neutralized and used as fermentation medium for Lactobacillus pentosus for lactic acid production. Lactic acid yield reached 92.8% at sugar 3–25 g/l, 30 °C and shaking speed 150 rpm under anaerobic condition. The acid hydrolysis facilitated lipid extraction from microalgae biomass, and lipid yields with and without acid hydrolysis were 85.6% and 48.7%, respectively. Results suggest that the developed method can be successfully applied in lipid extraction and lactic acid production from microalgae biomass.
In the present study, fast pyrolysis tests of microalgae were performed in the fluid bed reactor. The experiments were completed at temperature of 500 °C with a heating rate of 600 °C s−1 and a sweep gas (N2) flow rate of 0.4 m3 h−1 and a vapour residence time of 2–3 s. In comparison with the previous studies on slow pyrolysis from microalgae in an autoclave, a greater amount of high quality bio-oil can be directly produced from continuously processing microalgae feeds at a rate of 4 g min−1 in the present work, which has a potential for commercial application of large-scale production of liquid fuels. The liquid product yields of 18 and 24% from fast pyrolysis of Chllorella protothecoides and Microcystis aeruginosa were obtained. The saturated and polar fractions account for 1.14 and 31.17% of the bio-oils of microalgae on average, which are higher than those of bio-oil from wood. The H/C and O/C molar ratios of microalgae bio-oil are 1.7 and 0.3, respectively. The gas chromatograph analyses showed that the distribution of straight-chain alkanes of the saturated fractions from microalgae bio-oils were similar to diesel fuel. Bio-oil product from fast pyrolysis microalgae is characterized by low oxygen content with a higher heating value of 29 MJ/kg, a density of 1.16 kg l−1 and a viscosity of 0.10 Pa s. These properties of bio-oil of microalgae make it more suitable for fuel oil use than fast pyrolysis oils from lignocellulosic materials.
The hydrocracking behavior of a C44–C70 mixture of n-paraffins on a platinum/amorphous silica–alumina catalyst has been analyzed. The influence on the system behavior of operating conditions, i.e. pressure, temperature, H2/feed ratio and stream velocity, has been investigated by means of experimental data from a bench scale reactor, the last aim being the derivation of a proper model for the reaction system. Because of the high number of species involved, a model which takes into account pseudocomponents (lumped model) corresponding to the cuts of interest for the refinery has been considered. The obtained results show good agreement with experimental data.
This design report describes an up-to-date benchmark thermochemical conversion process that incorporates the latest research from NREL and other sources. Building on a design report published in 2007, NREL and its subcontractor Harris Group Inc. performed a complete review of the process design and economic model for a biomass-to-ethanol process via indirect gasification. The conceptual design presented herein considers the economics of ethanol production, assuming the achievement of internal research targets for 2012 and nth-plant costs and financing. The design features a processing capacity of 2,205 U.S. tons (2,000 metric tonnes) of dry biomass per day and an ethanol yield of 83.8 gallons per dry U.S. ton of feedstock. The ethanol selling price corresponding to this design is $2.05 per gallon in 2007 dollars, assuming a 30-year plant life and 40% equity financing with a 10% internal rate of return and the remaining 60% debt financed at 8% interest. This ethanol selling price corresponds to a gasoline equivalent price of $3.11 per gallon based on the relative volumetric energy contents of ethanol and gasoline.
This report describes the results of the work performed by PNNL using feedstock materials provided by the National Renewable Energy Laboratory, KL Energy and Lignol lignocellulosic ethanol pilot plants. Test results with algae feedstocks provided by Genifuel, which provided in-kind cost share to the project, are also included. The work conducted during this project involved developing and demonstrating on the bench-scale process technology at PNNL for catalytic hydrothermal gasification of lignin-rich biorefinery residues and algae. A technoeconomic assessment evaluated the use of the technology for energy recovery in a lignocellulosic ethanol plant.
This techno-economic study investigates the production of ethanol and a higher alcohols coproduct by conversion of lignocelluosic biomass to syngas via indirect gasification followed by gas-to-liquids synthesis over a precommercial heterogeneous catalyst. The design specifies a processing capacity of 2,205 dry U.S. tons (2,000 dry metric tonnes) of woody biomass per day and incorporates 2012 research targets from NREL and other sources for technologies that will facilitate the future commercial production of cost-competitive ethanol. Major processes include indirect steam gasification, syngas cleanup, and catalytic synthesis of mixed alcohols, and ancillary processes include feed handling and drying, alcohol separation, steam and power generation, cooling water, and other operations support utilities. The design and analysis is based on research at NREL, other national laboratories, and The Dow Chemical Company, and it incorporates commercial technologies, process modeling using Aspen Plus software, equipment cost estimation, and discounted cash flow analysis. The design considers the economics of ethanol production assuming successful achievement of internal research targets and nth-plant costs and financing. The design yields 83.8 gallons of ethanol and 10.1 gallons of higher-molecular-weight alcohols per U.S. ton of biomass feedstock. A rigorous sensitivity analysis captures uncertainties in costs and plant performance.
It is well-established that microalgal-derived biofuels have the potential to make a significant contribution to the US fuel market, due to several unique characteristics inherent to algae. Namely, autotrophic microalgae are capable of achieving very high efficiencies in converting solar energy into biomass and oil relative to terrestrial oilseed crops, while at the same time exhibiting great flexibility in the quality of land and water required for algal cultivation. These characteristics allow for the possibility to produce appreciable amounts of algal biofuels relative to today’s petroleum fuel market, while greatly mitigating “food-versus-fuel” concerns. However, there is a wide lack of public agreement on the near-term economic viability of algal biofuels, due to uncertainties and speculation on process scale-up associated with the nascent stage of the algal biofuel industry.
The purpose of this study is to evaluate a processing pathway for converting biomass into infrastructure-compatible hydrocarbon biofuels. This design case investigates production of fast pyrolysis oil from biomass and the upgrading of that bio-oil as a means for generating infrastructure-ready renewable gasoline and diesel fuels. This study has been conducted using similar methodology and underlying basis assumptions as the previous design cases for ethanol. The overall concept and specific processing steps were selected because significant data on this approach exists in the public literature. The analysis evaluates technology that has been demonstrated at the laboratory scale or is in early stages of commercialization. The fast pyrolysis of biomass is already at an early stage of commercialization, while upgrading bio-oil to transportation fuels has only been demonstrated in the laboratory and at small engineering development scale. Advanced methods of pyrolysis, which are under development, are not evaluated in this study. These may be the subject of subsequent analysis by OBP. The plant is designed to use 2000 dry metric tons/day of hybrid poplar wood chips to produce 76 million gallons/year of gasoline and diesel. The processing steps include: 1.Feed drying and size reduction 2.Fast pyrolysis to a highly oxygenated liquid product 3.Hydrotreating of the fast pyrolysis oil to a stable hydrocarbon oil with less than 2% oxygen 4.Hydrocracking of the heavy portion of the stable hydrocarbon oil 5.Distillation of the hydrotreated and hydrocracked oil into gasoline and diesel fuel blendstocks 6. Hydrogen production to support the hydrotreater reactors. The "as received" feedstock to the pyrolysis plant will be "reactor ready". This development will likely further decrease the cost of producing the fuel. An important sensitivity is the possibility of co-locating the plant with an existing refinery. In this case, the plant consists only of the first three steps: feed prep, fast pyrolysis, and upgrading. Stabilized, upgraded pyrolysis oil is transferred to the refinery for separation and finishing into motor fuels. The off-gas from the hydrotreaters is also transferred to the refinery, and in return the refinery provides lower-cost hydrogen for the hydrotreaters. This reduces the capital investment. Production costs near $2/gal (in 2007 dollars) and petroleum industry infrastructure-ready products make the production and upgrading of pyrolysis oil to hydrocarbon fuels an economically attractive source of renewable fuels. The study also identifies technical areas where additional research can potentially lead to further cost improvements.
As a result of algae's promise as a renewable energy feedstock, numerous studies have used Life Cycle Assessment (LCA) to quantify the environmental performance of algal biofuels, yet there is no consensus of results among them. Our work, motivated by the lack of comprehensive uncertainty analysis in previous studies, uses a Monte Carlo approach to estimate ranges of expected values of LCA metrics, such as Energy Return on (Energy) Invested (EROI), by incorporating parameter variability with empirically specified distribution functions. Results show that large uncertainties exist at virtually all steps of the biofuel production process. Although our findings agree with a number of earlier studies on matters such as the need for wet lipid extraction, nutrients recovered from waste streams, and high energy co-products, the ranges of reported values of LCA metrics help explain the high variability in EROI values from earlier studies. Reporting results from LCA models as ranges, and not single values, are necessary to reliably inform industry and policy makers on expected energetic and environmental performance of biofuels produced from microalgae.
Direct liquefaction of a woody biomass (Jack pine sawdust) in sub/near-critical water without and with catalysts (alkaline earth and iron ions) has been investigated at temperatures of 280–380 °C. Heavy oils with a high caloric value of 30–35 MJ/kg (much greater than that of the crude wood sample used) were obtained, along with water soluble oils with a caloric value of 19–25 MJ/kg. The yields of heavy oil and total oil products tended to maximize in the temperature range of 280–340 °C for all the liquefaction operations regardless of the presence of a catalyst or the type of catalyst. All the catalysts tested, i.e., Ca(OH)2, Ba(OH)2, and FeSO4, were found effective for enhancing the formation of heavy oil products at 280–340 °C, while they significantly promoted the formation of gas and water at >340 °C. The yield of heavy oil in the operation at 300 °C for 30 min was improved significantly from around 30% without catalyst to greater than 45% by Ba(OH)2. The maximum yield of total oil products reached 51% in the operation without catalyst, while it increased to about 65% with Ca(OH)2 at 300 °C. The GC/MS measurements for the heavy oil products revealed that the oils contain mainly carboxylic acids, phenolic compounds and derivatives, and long-chain alkanes.
The hydrothermal treatment (HTT) technology is evaluated for its potential as a process to convert algae and algal debris into a liquid fuel, within a sustainable algae biorefinery concept in which, next to fuels (gaseous and liquid), high value products are coproduced, nutrients and water are recycled, and the use of fossil energy is minimized. In this work, the freshwater microalgae Desmodesmus sp. was used as feedstock. HTT was investigated over a very wide range of temperatures (175–450 °C) and reaction times (up to 60 min), using a batch reactor system. The different product phases were quantified and analyzed. The maximum oil yield (49 wt %) was obtained at 375 °C and 5 min reaction time, recovering 75% of the algal calorific value into the oil and an energy densification from 22 to 36 MJ/kg. At increasing temperature, both the oil yield and the nitrogen content in the oil increased, necessitating further investigation on the molecular composition of the oil. This was performed in the adjacent collaborative paper with special attention to the nitrogen-containing compounds and to gain insight in the liquefaction mechanism. A pioneering visual inspection of the cells after HTT showed that a large step increase in the HTT oil yield, when going from 225 to 250 °C at 5 min reaction time, coincided with a major cell wall rupture under these conditions. Additionally, it was found that the oil composition, by extractive recovery after HTT below 250 °C, did change with temperature, even though the algal cells were visually still unbroken. Finally, the possibilities of recycling growth nutrients became evident by analyzing the aqueous fractions obtained after HTT. From the results obtained, we concluded that HTT is most suited as post-treatment technology in an algae biorefinery system, after the wet extraction of high value products, such as protein-rich food/feed ingredients and lipids.
We converted the marine microalga Nannochloropsis sp. into a crude bio-oil product and a gaseous product via hydrothermal processing from 200 to 500 °C and a batch holding time of 60 min. A moderate temperature of 350 °C led to the highest bio-oil yield of 43 wt %. We estimate the heating value of the bio-oil to be about 39 MJ kg−1, which is comparable to that of a petroleum crude oil. The H/C and O/C ratios for the bio-oil decreased from 1.73 and 0.12, respectively, for the 200 °C product to 1.04 and 0.05, respectively, for the 500 °C product. Major bio-oil constituents include phenol and its alkylated derivatives, heterocyclic N-containing compounds, long-chain fatty acids, alkanes and alkenes, and derivatives of phytol and cholesterol. CO2 was always the most abundant gas product. H2 was the second most abundant gas at all temperatures other than 500 °C, where its yield was surpassed by that of CH4. The activation energies for gas formation suggest the presence of gas-forming reactions other than steam reforming. Nearly 80% of the carbon and up to 90% of the chemical energy originally present in the microalga can be recovered as either bio-oil or gas products.
We produced crude bio-oils from the microalga Nannochloropsis sp. via reactions in liquid water at 350 °C
in the presence of six different heterogeneous catalysts (Pd/C, Pt/C, Ru/C, Ni/SiO2-Al2O3, CoMo/γ-Al2O3
(sulfided), and zeolite) under inert (helium) and high-pressure reducing (hydrogen) conditions. To our
knowledge, this is the first application of common hydrocarbon processing catalysts to microalgae liquefaction
in water. In the absence of added H2, all of the catalysts tested produced higher yields of crude bio-oil from
the liquefaction of Nannochloropsis sp., but the elemental compositions and heating values of the crude oil
(about 38 MJ/kg) were largely insensitive to the catalyst used. The gaseous products were mainly H2, CO2,
and CH4, with lesser amounts of C2H4 and C2H6. The Ru and Ni catalysts produced the highest methane
yields. Only the zeolite catalyst produced significant amounts of N2. Typical H/C and O/C atomic ratios for
the crude bio-oil are 1.7 and 0.09, respectively. In the presence of high-pressure H2, the crude bio-oil yield
and heating value were largely insensitive to the presence or identity of the catalyst. The presence of either
the hydrogen or the higher pressure in the reaction system did suppress the formation of gas, however. The
total gas yield was always lower in H2 than it was in analogous experiments without H2 and at lower pressure.
In both the presence and absence of H2, the supported Ni catalyst produced a crude bio-oil with a sulfur
content below the detection limits. This apparent desulfurization activity for the Ni catalyst was unique to
this material.
Through the use of a metal catalyst, gasification of wet biomass can be accomplished with high levels of carbon conversion to gas at relatively low temperature (350 °C). In a pressurized-water environment (20 MPa), near-total conversion of the organic structure of biomass to gases has been achieved in the presence of a ruthenium metal catalyst. The process is essentially steam reforming, as there is no added oxidizer or reagent other than water. In addition, the gas produced is a medium heating value gas due to the synthesis of high levels of methane, as dictated by thermodynamic equilibrium. While good gas production was demonstrated, biomass trace components caused some processing difficulties in the fixed catalyst bed tubular reactor system used for the catalytic gasification process. Results are described for tests using both bench-scale and scaled-up reactor systems.
A technoeconomic analysis of a 2000 tonne/day lignocellulosic biomass conversion process to make mixed alcohols via gasification and catalytic synthesis was completed. The process, modeled using ASPEN Plus process modeling software for mass and energy calculations, included all major process steps to convert biomass into liquid fuels, including gasification, gas cleanup and conditioning, synthesis conversion to mixed alcohols, and product separation. The gas cleanup area features a catalytic fluidized-bed steam reformer to convert tars and hydrocarbons into syngas. Conversions for both the reformer and the synthesis catalysts were based on research targets expected to be achieved by 2012 through ongoing research. The mass and energy calculations were used to estimate capital and operating costs that were used in a discounted cash flow rate of return analysis for the process to calculate a minimum ethanol selling price of $0.267/L ($1.01/gal) ethanol (U.S.$2005).
The purpose of the work presented here is the production of liquid biofuels from wet organic waste matter in a continuous one-step catalytic process under hydrothermal conditions. The catalytic reaction of wet organic matter at near-critical water conditions (T > 300 °C, p > 22.1 MPa) is used to produce a mixture of combustible organics which can be used as liquid biofuel. In order to achieve a good product quality in a continuous one-step process, two catalysts were applied, a homogeneous potassium carbonate catalyst and a heterogeneous ZrO2 catalyst. In addition, the reaction mixture was recirculated. The continuous flow of concentrated waste biomass feed at low flow rates and recirculation of the hot reaction mixture were the most challenging obstacles to overcome. The scale of the plant (0.1 l reactor volume) allowed for a variation of the feed, reaction temperature, and recirculation rate in order to optimise the process conditions. Still, the product quantity obtained was sufficient to perform a analytical characterisation. The experimental results confirmed the feasibility of the process. Hydrothermal treatment of waste biomass, after dewatering, resulted in a biocrude oil of high calorific value.
The production of hydrogen by steam reforming of bio-oils obtained from the fast pyrolysis of biomass requires the development of efficient catalysts able to cope with the complex chemical nature of the reactant. The present work focuses on the use of noble metal-based catalysts for the steam reforming of a few model compounds and that of an actual bio-oil. The steam reforming of the model compounds was investigated in the temperature range 650–950 °C over Pt, Pd and Rh supported on alumina and a ceria–zirconia sample. The model compounds used were acetic acid, phenol, acetone and ethanol. The nature of the support appeared to play a significant role in the activity of these catalysts. The use of ceria–zirconia, a redox mixed oxide, lead to higher H2 yields as compared to the case of the alumina-supported catalysts. The supported Rh and Pt catalysts were the most active for the steam reforming of these compounds, while Pd-based catalysts poorly performed. The activity of the promising Pt and Rh catalysts was also investigated for the steam reforming of a bio-oil obtained from beech wood fast pyrolysis. Temperatures close to, or higher than, 800 °C were required to achieve significant conversions to COx and H2 (e.g., H2 yields around 70%). The ceria–zirconia materials showed a higher activity than the corresponding alumina samples. A Pt/ceria–zirconia sample used for over 9 h showed essentially constant activity, while extensive carbonaceous deposits were observed on the quartz reactor walls from early time on stream. In the present case, no benefit was observed by adding a small amount of O2 to the steam/bio-oil feed (auto-thermal reforming, ATR), probably partly due to the already high concentration of oxygen in the bio-oil composition.
The aim of this study is to investigate the algae production technologies such as open, closed and hybrid systems, production costs, and algal energy conversions. Liquid biofuels are alternative fuels promoted with potential to reduce dependence on fossil fuel imports. Biofuels production costs can vary widely by feedstock, conversion process, scale of production and region. Algae will become the most important biofuel source in the near future. Microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels. Microalgae can be converted to bio-oil, bioethanol, bio-hydrogen and bimethane via thermochemical and biochemical methods. Microalgae are theoretically very promising source of biodiesel.
Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world's forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Therefore, based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO2, N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products.
Eighteen kinds of biomass residues in Indonesia were liquefied to heavy oil in hot-compressed water with sodium carbonate as the catalyst at 300°C and around 10 MPa. The oil was obtained in the range of the yields between 21–36 wt% on an organic basis. Typically the oils had almost the same properties; carbon, around 70 wt%, hydrogen, 7 wt%, nitrogen, <1 wt%, calorific value, around 30 kJ/g, and viscosity, >105 mPa.s. The result of the simple energy balance estimation shows that this liquefaction process might become a net energy producer.
Fischer–Tropsch (FT) diesel derived from biomass via gasification is an attractive clean and carbon neutral transportation fuel, directly usable in the present transport sector. System components necessary for FT diesel production from biomass are analysed and combined to a limited set of promising conversion concepts. The main variations are in gasification pressure, the oxygen or air medium, and in optimisation towards liquid fuels only, or towards the product mix of liquid fuels and electricity. The technical and economic performance is analysed. For this purpose, a dynamic model was built in Aspen Plus®, allowing for direct evaluation of the influence of each parameter or device, on investment costs, FT and electricity efficiency and resulting FT diesel costs. FT diesel produced by conventional systems on the short term and at moderate scale would probably cost 16 €/GJ. In the longer term (large scale, technological learning, and selective catalyst), this could decrease to 9 €/GJ. Biomass integrated gasification FT plants can only become economically viable when crude oil price levels rise substantially, or when the environmental benefits of green FT diesel are valued. Green FT diesel also seems 40–50% more expensive than biomass derived methanol or hydrogen, but has clear advantages with respect to applicability to the existing infrastructure and car technology.