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Life cycle assessment of green diesel production from microalgae
Abstract
Many LCA based viability studies have already been done for the production of green diesel from
microalgae, still a comprehensive LCA, has not yet been undertaken. Current study aims to find out if the Net Energy Balance(NEB) can further be increased by using a combination of many available agronomical practices & the techniques of production of green diesel from microalgae. The results show that neither open raceway pond nor Photobioreactor routes (Wet and dry routes) yield positive energy balance. The production of green diesel via open raceway pond, both in dry as well as wet route, have less negative NEB and comparatively higher NER than the photobioreactors. Comparison says that open raceway pond dry route has slightly higher value for NER than the wet route. Even with the best possible route (open raceway pond dry route), the total energy use is almost 5 times more than the energy produced, with a negative NEB of 4.07 MJ & very low NER value of 0.20. Study concludes that R & D in the area of green diesel production from microalgae has yet to go a long way & has a huge scope to further lower its input energy demand for biofuel production.
... Flashpoint is the measure of flammability of the fuel. It is the lowest possible temperature at which the vapor will be formed near the liquid fuel surface and will ignite on exposure to flame [88]. ...
... Pragya et al. studied the LCA for producing green diesel from Chlorella Vulgaris microalgae. In this study, greenhouse gas emissions from the production process and the net energy balance were calculated [88]. ...
... Both dry route (pyrolysis) and wet route (hydrothermal liquefaction) are studied for the conversion of algae culture (after lipid extraction) to bio-oil, which is further upgraded through hydrotreatment. Reproduced with permission from [88]. ...
First, second, and third-generation green diesel are being considered as promising alternatives to petrodiesel in terms of renewable energy demand, process economic, and environmental concerns. Green diesel is an advanced biofuel that can be produced from different cellulosic biomass such as crop residue, forestry waste or woody biomass. As green diesel has identical chemical properties to petrodiesel, it could be used in its pure form or blended with petrodiesel. This chapter covers the literature related to the different feedstocks (First, second, and third-generation) used for green diesel production, hydroprocessing technology, catalytic materials for such processes, characterization of green diesel, comparison between petro-diesel and green diesel in terms of physicochemical properties, techno-economic analysis, and life cycle assessment. Besides, this chapter covered the current status of the green diesel industry from various commercial plants such as Neste, Honeywell, and ExxonMobil. This chapter discusses several commercial plants that are proposed, under construction or expansion stage, for the production of green diesel.
... Proc. R [19,85,97,113,141,167,[190][191][192][193][194][195][196][197][198][199][200][201][202][203][204][205][206][207][208][209]. The negative values are due to the credits for co-products and avoided processes, such as wastewater treatment. ...
... However, a majority of the studies conclude that, at present state of development, algal biodiesel has higher life cycle GHG emissions than that of fossil diesel. The main reasons for higher emissions include lower algal yield [19,190] and high energy use in the cultivation, harvesting and drying stages [191][192][193]. ...
... Various indicators have been used in LCA studies to quantify energy use in the life cycle of biofuels, including fossil energy consumption, primary, secondary or cumulative energy demand and net energy ratio [218]. However, many focused on fossil energy consumption, given that [17][18][19]40,47,48,54,55,57,58,60,68,76,77,80,85,89,92,93,95,96,98,108,[113][114][115]120,121,129,132,133,136,138,139,143,144,147,[152][153][154]156,159,161,162,[164][165][166][167][169][170][171]175,176,[179][180][181]187,[190][191][192][195][196][197][198][199]204,206,208,[219][220][221][222][223]. For the box plot legend, see electronic supplementary material, figure S1 and for the data used to plot this graph, see electronic supplementary material, figure S7. ...
Biofuels are being promoted as a low-carbon alternative to fossil fuels as they could help to reduce greenhouse gas (GHG) emissions and the related climate change impact from transport. However, there are also concerns that their wider deployment could lead to unintended environmental consequences. Numerous life cycle assessment (LCA) studies have considered the climate change and other environmental impacts of biofuels. However, their findings are often conflicting, with a wide variation in the estimates. Thus, the aim of this paper is to review and analyse the latest available evidence to provide a greater clarity and understanding of the environmental impacts of different liquid biofuels. It is evident from the review that the outcomes of LCA studies are highly situational and dependent on many factors, including the type of feedstock, production routes, data variations and methodological choices. Despite this, the existing evidence suggests that, if no land-use change (LUC) is involved, first-generation biofuels can—on average—have lower GHG emissions than fossil fuels, but the reductions for most feedstocks are insufficient to meet the GHG savings required by the EU Renewable Energy Directive (RED). However, second-generation biofuels have, in general, a greater potential to reduce the emissions, provided there is no LUC. Third-generation biofuels do not represent a feasible option at present state of development as their GHG emissions are higher than those from fossil fuels. As also discussed in the paper, several studies show that reductions in GHG emissions from biofuels are achieved at the expense of other impacts, such as acidification, eutrophication, water footprint and biodiversity loss. The paper also investigates the key methodological aspects and sources of uncertainty in the LCA of biofuels and provides recommendations to address these issues.
... Ben [35]: LCA for biodiesel production from microalgae comparing two different thermochemical processes on a system level (hydrothermal liquefaction and pyrolysis). 22. Pra [36]: LCA for two harvesting techniques (gravitational settling and microfiltration) for biodiesel and biogas production and their uses in internal combustion engine for transportation. 23. ...
... Finally, among the studies dedicated to the biodiesel production, four are well-to-gate studies, which means that the transport to pumps or combustion is not included in the perimeter [34,[42][43][44]. Eight are well-to-pump studies, which means that the use of the fuel is not included [17,18,21,23,[28][29][30]35], and ten are well-towheel studies, where the use of the fuel is included [16,19,22,24,25,27,31,[36][37][38]40]. In the case of the three studies focused on jet fuel, the limits of the system are defined as well-to-wake, which include the processes, such as feedstock production, fuel production, and pump-to-wheels for a plane [32,33,41]. ...
... The nitrogen and phosphorus quota can strongly vary during a starvation period [47]. The hypotheses on required fertilizers strongly vary according to the species, and between the publications for a same species [16,22,[29][30][31]36,37]. Needs in nitrogen vary from 10.9 g/kg DM [16] to 70.7 g/kg DM [36] in limiting conditions, and from 9.41 g/kg DM [15] to 180 g/ kg DM [ 35] without stress. ...
Fossil fuel depletion and attempts of global warming mitigation have motivated the development of biofuels. Several feedstock and transformation pathways into biofuel have been proposed as an alternative to usual fuels. Recently, microalgae have attracted a lot of attention because of the promise of reduced competition with food crop and lowered environmental impacts. Over the last years, several Life Cycle Assessments have been realised to evaluate the energetic benefit and Global Warming Potential reduction of biofuel and bioenergy produced from microalgae. This chapter presents a bibliographic review of fifteen LCA of microalgae production and/or transformation into biofuel. These studies differ often by the perimeter of the study, the functional unit and the production technologies or characteristics. Methods for the environmental impacts assessment and the energy balance computation also diverge. This review aims at identifying the main options and variations between LCAs and concludes by some recommendations and guidelines to improve the contribution of an LCA and to facilitate the comparison between studies.
... Ben [35]: LCA for biodiesel production from microalgae comparing two different thermochemical processes on a system level (hydrothermal liquefaction and pyrolysis). 22. Pra [36]: LCA for two harvesting techniques (gravitational settling and microfiltration) for biodiesel and biogas production and their uses in internal combustion engine for transportation. 23. ...
... Finally, among the studies dedicated to the biodiesel production, four are well-to-gate studies, which means that the transport to pumps or combustion is not included in the perimeter [34,[42][43][44]. Eight are well-to-pump studies, which means that the use of the fuel is not included [17,18,21,23,[28][29][30]35], and ten are well-towheel studies, where the use of the fuel is included [16,19,22,24,25,27,31,[36][37][38]40]. In the case of the three studies focused on jet fuel, the limits of the system are defined as well-to-wake, which include the processes, such as feedstock production, fuel production, and pump-to-wheels for a plane [32,33,41]. ...
... The nitrogen and phosphorus quota can strongly vary during a starvation period [47]. The hypotheses on required fertilizers strongly vary according to the species, and between the publications for a same species [16,22,[29][30][31]36,37]. Needs in nitrogen vary from 10.9 g/kg DM [16] to 70.7 g/kg DM [36] in limiting conditions, and from 9.41 g/kg DM [15] to 180 g/ kg DM [ 35] without stress. ...
... Ben [35]: LCA for biodiesel production from microalgae comparing two different thermochemical processes on a system level (hydrothermal liquefaction and pyrolysis). 22. Pra [36]: LCA for two harvesting techniques (gravitational settling and microfiltration) for biodiesel and biogas production and their uses in internal combustion engine for transportation. 23. ...
... Finally, among the studies dedicated to the biodiesel production, four are well-to-gate studies, which means that the transport to pumps or combustion is not included in the perimeter [34,[42][43][44]. Eight are well-to-pump studies, which means that the use of the fuel is not included [17,18,21,23,[28][29][30]35], and ten are well-towheel studies, where the use of the fuel is included [16,19,22,24,25,27,31,[36][37][38]40]. In the case of the three studies focused on jet fuel, the limits of the system are defined as well-to-wake, which include the processes, such as feedstock production, fuel production, and pump-to-wheels for a plane [32,33,41]. ...
... The nitrogen and phosphorus quota can strongly vary during a starvation period [47]. The hypotheses on required fertilizers strongly vary according to the species, and between the publications for a same species [16,22,[29][30][31]36,37]. Needs in nitrogen vary from 10.9 g/kg DM [16] to 70.7 g/kg DM [36] in limiting conditions, and from 9.41 g/kg DM [15] to 180 g/ kg DM [ 35] without stress. ...
... The study performed by Pragya et al. [131] aimed to find out whether the net energy balance (NEB) could be optimized for green diesel production from microalgae. They studied two technologies for microalgae cultivation: (i) open pond pathway; (ii) photobioreactor. ...
... The microalgae culture, electricity use during harvesting, and drying of the microalgae were the most energy-consuming activities. Pragya et al. [131] concluded that, although microalgae have enormous potential as an alternative source of RE, research and development in green diesel production from microalgae has a long way to go. Handler et al. [294] carried out an LCA study concerning green diesel from algae to investigate the specific impacts of the combination of different algae cultivation techniques. ...
The environmental impact of traditional fuels and related greenhouse gas emissions (GHGE) has promoted policies driven towards renewable fuels. This review deals with green diesel, a biofuel obtained by catalytic deoxygenation of edible and non-edible biomasses. Green diesel, biodiesel, and petrodiesel are compared, with green diesel being the best option in terms of physical–chemical properties and reduction in GHGE. The deoxygenation process and the related types of catalysts, feedstocks, and operating conditions are presented. Reactor configurations are also discussed, summarizing the experimental studies. Several process simulations and environmental economic analyses—up to larger scales—are gathered from the literature that analyze the potential of green diesel as a substitute for petrodiesel. In addition, current industrial processes for green diesel production are introduced. Future research and development efforts should concern catalysts and the use of waste biomasses as feedstock, as well as the arrangement of national and international policies.
... Most studies have indicated that, currently, microalgae-based biodiesel results in higher greenhouse gas emissions than fossil diesel. This is due to the small microalgal harvest [118] and high energy utilization required for cultivating, harvesting, and drying microalgae [119,120]. Several studies have indicated that microalgae-based biofuels require abundant energy for several processes, including pumping, lipid extraction, dewatering, and thermal drying [119,121]. Nevertheless, the energy requirements for cultivating microalgae in raceway ponds are lower than 1 MJ MJ −1 , which is much lower than the energy requirements for photobioreactors [122]. ...
... This is due to the small microalgal harvest [118] and high energy utilization required for cultivating, harvesting, and drying microalgae [119,120]. Several studies have indicated that microalgae-based biofuels require abundant energy for several processes, including pumping, lipid extraction, dewatering, and thermal drying [119,121]. Nevertheless, the energy requirements for cultivating microalgae in raceway ponds are lower than 1 MJ MJ −1 , which is much lower than the energy requirements for photobioreactors [122]. In addition to greenhouse gas emissions, microalgae emit methane gas, nitrogen gas, biogenic halogenated, biogenic sulphur, isoprene, and volatile organic carbon [123]. ...
The world has heavily relied on fossil fuels for decades to supply energy demands. However, the usage of fossil fuels has been strongly correlated with impactful problems, which lead to global warming. Moreover, the excessive use of fossil fuels has led to their rapid depletion. Hence, exploring other renewable and sustainable alternatives to fossil fuels is imperative. One of the most sustainable fossil fuel alternatives is biofuel. Microalgae-based biofuels are receiving the attention of researchers due to their numerous advantages compared with those obtained from other types of feedstocks. Hence, it is essential to explore the recent technologies for biofuel produced from microalgae species and define the possible challenges that might be faced during this process. Therefore, this work presents the recent advancements in biofuel production from microalgae, focusing on emerging technologies such as those using nanomaterials and genetic engineering. This review focuses on the impact of nanoparticles on the harvesting efficiency of various microalgae species and the influence of nanoparticles on biofuel production. The genetic screening performed by genome-scale mutant libraries and their high-throughput screening may assist in developing effective strategies for enhancing microalgal strains and oil production through the modification of enzymes. Furthermore, the barriers that limit the production of biofuels from microalgae are introduced. Even though microalgae-based biofuels are perceived to engage with low negative impacts on the environment, this review paper touches on several environmental issues associated with the cultivation and harvesting of microalgae species. Moreover, the economic and technical feasibility limits the production of microalgae-based biofuels.
... Note that microalgae are cultivated in water. Thus, the management of habitat conditions, harvesting and drying of microalgae, and lipid extraction from wet feedstocks necessitate energy input into the multiple processes [280,282,286]. In contrast, BD production from edible crops does not require the additional energy input ( Table 8). ...
... To make microalgal BD production process more environmentally benign, it is necessary to improve the process efficiency of drying microalgae and lipid extraction from them because these processes contributed to more than 70 % of GWP [280,282,286]. As suggested in Section 3.4, direct transesterification of microalgae into BD without lipid extraction could be considered a useful solution, because it can cost down drying and lipid extraction processes. ...
High lipid content and excellent CO 2 fixation capability of microalgae by photosynthesis have made microalgal biodiesel (BD) a promising carbon-neutral fuel. Nonetheless, the commercialization of BD has not yet been realized because of expensive and energy-intensive cultivation, pretreatment, and BD conversion processes in reference to 1 st generation BD production. To resolve the issues, this study comprehensively reviewed the current technical developments of microalgal BD production process and suggested promising future studies. Current microalgal BD production processes highly rely on the processes developed from 1 st generation BD process, namely base-catalyzed transesterifications. However, the base-catalyzed suffers from saponification reaction and low production yield due to high water and free fatty acid contents in microalgae. Vigorous pretreatments such as dewatering, drying, esterification of free fatty acid, and purification are required for high yield of microalgal BD production, making this process economically not attractive. As efforts to construct new transesterification platform, novel approaches tolerant to impurities such as thermally induced non-catalytic transesterifications were suggested. The thermally induced reactions allowed in situ conversion of microalgal lipid into BD (≥ 95 wt. % yield) within 1 min of reaction at ≥ 350 C. This process resists to presence of water and free fatty acids and does not require lipid extraction process. To make this process more promising, it was suggested lowering reaction temperature for thermally induced transesterifications. In addition, pilot study, in-depth life cycle assessment, and economic analysis were suggested to assess economic viability and environmental impacts.
... In a study of pennycress oil, which is less intensively cultivated in the agricultural sector, the life-cycle GHG emission was estimated as 30.1 g CO 2 eq/MJ of biofuel [271]. The life-cycle GHG emission could be as low as 370 g CO 2 eq/MJ of green diesel when microalgae are grown naturally in an open pond, whereas an intensively cultivated scenario could have emissions as high as 2.47 kg CO 2 eq/MJ of biofuel [272]. If the microalgae cultivation is used to substitute traditional biological nutrient removal unit operations in a municipal wastewater treatment plant as a beneficial service, a much lower GHG emission (12.2 g CO 2 eq/MJ of green diesel) is obtained [273]. ...
... In the New EC database, the difference was not obvious. When waste cooking oil and algal oil were considered as feedstocks, the life-cycle GHG emissions were as high as 81.59 g [275] and 3.27 kg CO 2 eq/MJ [272] of green diesel, respectively. ...
Investigations and applications of renewable and sustainable energy have become central for addressing the issue of emissions of greenhouse gases from the use of fossil transportation fuels. Triglyceride-based liquid fuels have great potential as substitutes for petroleum and its derivatives. To date, the proven technologies for converting triglycerides into biofuels include transesterification, thermal cracking conversion, and hydrogenation. This paper presents an overview of recent research on these conversion technologies, employing homogeneous, heterogeneous, enzymatic, and photocatalytic catalysts. We focus on technical aspects critical to triglyceride conversion, including feedstock analysis, mechanism research, analysis of technological advantages and disadvantages, and catalyst development and selection. Biodiesel produced by the transesterification process must be blended with diesel before use due to its higher oxide content. The resultant “green diesel” has a broader range of applications, especially when its structure has been upgraded. Life cycle assessment (LCA) and greenhouse gas (GHG) emissions are reviewed to assess the renewability and sustainability of biofuels. We discuss the typical biodiesel production technologies with their development status, as well as the relevant policies and prospects for biofuels, mainly concerning biodiesel and aviation biofuel. It is hoped that our work will be of guiding significance for future biofuel research.
... On the other hand, supercritical CO 2 extraction (SC-CO 2 ) approach also presented relatively high NER value of 3.07 (Quinn et al., 2014) as compared to extraction methods. HTL is another promising wet extraction technique with NER value of 0.2 to 2.5 (Delrue et al., 2013;Pragya and Pandey, 2016;Vasudevan et al., 2012) and GHG emission of −0.01 to 0.36 kg CO 2-eq/MJ (Bennion et al., 2015;Delrue et al., 2013;Fortier et al., 2014;Vasudevan et al., 2012). However, in general, all these nonconventional wet extraction techniques are facing high capital and operating cost (Halim et al., 2011). ...
... Dry extraction studies are primarily focused on pyrolysis and combustion techniques (Pragya and Pandey, 2016;Xu et al., 2011), which demonstrates much lower energy recovery (NER less than 1) and environmental feasibility compared to wet extraction technique. A comparison study between wet (HTL) and dry (pyrolysis) extraction routes performed by Bennion et al. (2015) showed that dewatering of microalgae to 84% of solid content prior to pyrolysis step and also heating during the pyrolysis reaction increase substantially the requirement of fossil energy. ...
Algae biomass comprises variety of biochemicals components such as carbohydrates, lipids and protein, which make them a feasible feedstock for biofuel production. However, high production cost mainly due to algae cultivation remains the main challenge in commercializing algae biofuels. Hence, extraction of other high value-added bioproducts from algae biomass is necessary to enhance the economic feasibility of algae biofuel production. This paper is aims to deliberate the recent developments of conventional technologies for algae biofuels production, such as biochemical and chemical conversion pathways, and extraction of a variety of bioproducts from algae biomass for various potential applications. Besides, life cycle evaluation studies on microalgae biorefinery are presented, focusing on case studies for various cultivation techniques, culture medium, harvesting, and dewatering techniques along with biofuel and bioenergy production pathways. Overall, the algae biorefinery provides new opportunities for valorisation of algae biomass for multiple products synthesis.
... NER is the functional unit used in LCA (Quinn et al., 2014). Pragya and Pandey (2016) conducted an LCA using wet and dry biomass by cultivating the algal cells using open-raceway ponds and flat-plate reactors. The NER obtained by both the pathways was negative and also reported that the harvesting and drying were the highest energy-consuming activities (Pragya and Pandey, 2016). ...
... Pragya and Pandey (2016) conducted an LCA using wet and dry biomass by cultivating the algal cells using open-raceway ponds and flat-plate reactors. The NER obtained by both the pathways was negative and also reported that the harvesting and drying were the highest energy-consuming activities (Pragya and Pandey, 2016). Another study performed by Bennion et al. (2015) compared the NER from pyrolysis and hydrothermal liquefaction (HTL) at both laboratory and industrial scale. ...
Depleting petroleum reserves and increasing rate of consumption have necessitated the search for alternative environmentally friendly CO2-neutral fuels. Many crops and nonfood plants were used for the production of biofuel, but microalgal biomass has shown added advantages over crop-based biodiesel. This article investigates and comprehends each production process for biodiesel production from microalgae in detail and also identifies the existing challenges. The major challenge for biofuel production is translating laboratory-scale findings to full-scale application. Large-scale microalgae cultivation for the production of biofuels has been a challenge in the past two decades. Many of the techniques developed are species dependent and also consume large amount of energy. The article also provides the advantages and disadvantages of each of the techniques developed for a particular stage of the production process. There are still a number of challenges in the production process of biofuel from microalgae and hence, requires further investigation to develop an optimized process.
... Even if algae are considered a fast-growing biomass and studied as a potential optimal biofuels source for the future, the environmental analysis still points out many issues to be solved: in Ref. [26] final results show that algal biodiesel produced through current conventional technologies has higher energy demand and greenhouse gas emissions than fossil diesel. From an energy point of view, as stated in Ref. [27], neither open raceway pond nor PBR wet and dry routes yields positive energy balance. Even with the best possible route (open raceway pond dry route), the total energy use is almost 5 times more than the energy produced [27,28]. ...
... From an energy point of view, as stated in Ref. [27], neither open raceway pond nor PBR wet and dry routes yields positive energy balance. Even with the best possible route (open raceway pond dry route), the total energy use is almost 5 times more than the energy produced [27,28]. ...
The Life Cycle Assessment (LCA) of biogas-fed Solid Oxide Fuel Cell (SOFC) integrated with a CO2 recovery system is presented in this work. The goal of the work is to evaluate the environmental performance of an SOFC fueled with sewage biogas and to compare it with traditional technologies (internal combustion engines and microturbines) using the same fuel. CO2 recovery is performed through a tubular photobioreactor, fixing the recovered carbon in the form of a micro-algae. The analysis takes into account both the biogas production line (anaerobic digester) and its exploitation into the fuel cell (i.e., the power generator). Results show that the SOFC manufacturing activity is highly intensive since it requires a large amount of use of electricity. During operation, instead, the highest burden is associated with the fuel production. We analyzed two scenarios for biogas operation underlining the benefits of introducing sludge pre-thickening before the anaerobic digestion process. The use of a sludge pre-thickening system can reduce the inlet flow of natural gas into the plant, thus affecting the fuel chain contribution and reducing the overall impact. The photobioreactor results in consuming more energy than what it produces (looking at the operation phase only; the manufacturing phase was not even included) and being responsible for more carbon emissions than the amount fixed in algae. On the other side, data for the photobioreactor system were based on a real system at the proof-of-concept level. Therefore significant improvements are expected for an industrial-size system. Finally, the SOFC environmental burdens have been compared with main competitors in the same field (internal combustion engines and microturbines), showing the superior environmental performance. The proposed energy system is thus an interesting choice for cleaner energy production.
... Most studies on dry extraction use pyrolysis and combustion techniques (Pragya andPandey, 2016, Xu et al, 2011). These methods yield lower energy recovery and lower environmental feasibility than wet extraction techniques. ...
Biomass from algae, which is rich in proteins, carbohydrates, and lipids, could be used for the production of biofuels and chemicals. Because algal cultivation and harvesting require high energy and costs, algae-based fuel production is a challenging commercial application. At the pilot scale, this is a common bottleneck problem in algae processing for fuels or chemicals. By implementing an integrated algae biorefinery concept, the need for energy and costs can be reduced. Biopolymers, biochemicals, biofuels, and biofertilizers can all be recovered with higher economic efficiency than conventional methods. A green economy based on algae will also be more viable by reducing production costs. The purpose of this mini-review is to give information about the development of integrated biorefineries for the recovery of algal-based bioproducts and their potential applications. The authors discuss the lifecycle assessment and the economic aspects of an integrated algal biorefinery. A discussion of the challenges and future directions of integrated algal biorefinery is concluded.
... An eco-friendly generous yeast residue-based strong corrosive (YSA) catalyst can be delivered from yeast residue waste by sulfonation and therefore might be used for the transesterification of non-eatable WCO and yeast oil to create biodiesel (Deeba et al. 2017). Green diesel through yeast buildup may also be delivered by using various techniques yet the most widely recognized mode for the change of oil to biodiesel is trans-esterification process which takes place Pragya and Pandey 2016) in the presence of a catalyst to accomplish sensible transformation rates alongside glycerol as a by-product (Atapour and Kariminia 2011;Kumar et al. 2018). Henceforth, creating reactant procedure of gainfulness is likewise foreseen for biodiesel creation for example simple and modest impetus produced using waste biomass (Atapour and Kariminia 2011;Karavalakis et al. 2011). ...
Global warming and the greenhouse gases are alarming issues concern for humans worldwide. It is not only causing harm to the environment but also are a threat for the survival of all living species. As the population has increased due to wide growth, the threat has escalated to an alarming level. The uncontrolled population increase has amplified the use of resources and production of domestic, industrial, and biological waste causing inappropriate reliance and exploitation of fossil fuels bringing its closer to exhaustion. The biological waste has potential to be used in producing the green diesel which has great potency as fuel in the place of fossil-based and toxic gas releasing fuels. The use of green diesel can contribute in controlling increasing of different pollution viz. air, water, and soil which can help in managing the problems of waste disposal. Green diesel production through the process of hydrogenation/hydro-deoxygenation using catalyst may also be explored for potential evaluation which has led to involvement of catalyst as a measure for fuel production as a new avenue for research. The manuscript provides a detailed insight about the applications and future aspects for the utilization of green diesel.
... The costeffectiveness of 3G biofuel is increased by coupling microalgae cultivation with wastewater remediation [24], taking advantage of the ability of microalgae to uptake inorganic nitrogen and phosphorous [25][26][27]. However, at the current developmental stage, algal biofuel is not a feasible option, because the biomass yield does not meet industrial requirements for profitability [28,29], particularly taking into consideration the elevated energetic input required by algal cultivation, harvesting, and processing [30][31][32]. By comparison, the fourth generation of biofuels (4G) involves the application of genetic engineering of microalgae, yeasts, fungi, and cyanobacteria to improve the overall biomass yield and reduce the carbon footprint of the conversion process [33] (Figure 1). ...
To mitigate the current global energy and the environmental crisis, biofuels such as bioethanol have progressively gained attention from both scientific and industrial perspectives. However, at present, commercialized bioethanol is mainly derived from edible crops, thus raising serious concerns given its competition with feed production. For this reason, lignocellulosic biomasses (LCBs) have been recognized as important alternatives for bioethanol production. Because LCBs supply is sustainable, abundant, widespread, and cheap, LCBs-derived bioethanol currently represents one of the most viable solutions to meet the global demand for liquid fuel. However, the cost-effective conversion of LCBs into ethanol remains a challenge and its implementation has been hampered by several bottlenecks that must still be tackled. Among other factors related to the challenging and variable nature of LCBs, we highlight: (i) energy-demanding pretreatments, (ii) expensive hydrolytic enzyme blends, and (iii) the need for microorganisms that can ferment mixed sugars. In this regard, thermophiles represent valuable tools to overcome some of these limitations. Thus, the aim of this review is to provide an overview of the state-of-the-art technologies involved, such as the use of thermophilic enzymes and microorganisms in industrial-relevant conditions, and to propose possible means to implement thermophiles into second-generation ethanol biorefineries that are already in operation.
... However, the energy and emissions performances of torrefaction processes need to be evaluated given the lack of studies in this area. While there are several life cycle assessment (LCA) studies of various biomass conversion processes, such as pyrolysis and hydrothermal liquefaction [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32], there are very few LCAs of electricity produced from bio-coal via DT and especially novel WT. WT is in the early development stage and many aspects of the process require more research [9]. ...
This study compares the life cycle energy consumption and greenhouse gas (GHG) emissions of electricity generation from bio-coals produced from various biomass feedstocks via dry torrefaction (DT) and wet torrefaction (WT) processes. Wheat straw, pine woodchips, grape pomace, manure and algae are the main feedstocks evaluated. The energy consumption and the associated GHG emissions at each life cycle stage were calculated. The main stages included are in-field preparation, feedstocks transportation to torrefaction plant, torrefaction process, bio-coal transportation to power plant, and power plant operations. The results show that all pathways are competitive with coal-based electricity in terms of GHG emissions except pathways with algae as feedstock and manure biochar-based electricity generation. Among the pathways, electricity generation from pine woodchips biochar appears to be the best option, with an 88% GHG emissions reduction compared to coal-derived electricity, followed by grape pomace hydrochar with an 85% emission reduction. Electricity generation from wheat straw biochar, grape pomace hydrochar, and pine woodchips biochar lead to the highest net energy ratios (NERs) of 4.19, 4.08, and 3.58, respectively. The developed information is novel and can be used for investment decisions and policy formulation around the world.
... The rapeseed oil methyl ester and wheat ethanol marginally enhanced performance in terms of global warming and eutrophication, but the same was true of potential photochemical ozone production and energy consumption. The greenhouse gas emissions and a wide range of environmental impacts with a combination of biofuels (methyl ester, ethanol, biogas, dimethyl ether, etc.) have been studied [118]. Methyl ester from waste cooking oil had low greenhouse gas emissions, but no analysis on acidification and eutrophication have been studied [119]. ...
First, second, third, and fourth-generation biofuels are continuously evolving as a promising substitute to petrodiesel catalyzed by energy depletion, economic and environmental considerations. Bio-diesel can be synthesized from various biomass sources, which are commonly divided into FAME and renewable biodiesel. FAME biodiesel is generally produced by the transesterification of vegetable oils and fats while renewable diesel is produced by hydro-deoxygenation of vegetable and waste oils and fats. The different generation, processing technologies and standards for FAME and renewable biodiesel are reviewed. Finally, the life cycle analysis and production cost of conventional and renewable biodiesel are described.
... A sustainable biofuel needs to be one that results in a net decrease in greenhouse gas emissions, does not have any hindering effect to the local environment in its implementation, is priced competitively with existing fuel resources, able to provide for employment opportunities locally and does not compete land usage with food crops [78][79][80][81][82][83][84][85][86]. An experimental study on biodiesel from microalgae presented that Chlorella species contained very high content of fatty acid and 34.53-230.38 mg L − 1 d − 1 biodiesel was produced from these Chlorella strains in Malaysia [87]. ...
Biodiesel is an attractive fuel replacement for diesel engine in Malaysia. The application of biodiesel as fuel-blend has been implemented commercially in transport sector in the country. Among various potential feedstock for biodiesel production, microalgae have been appeared as a promising source since a decade due to its' high biomass productivity, rapid growth rate, large amount of lipid content, capability of high CO 2 capture and sequestration as well as suitable geographical location to be harvested. The main objective of this study was to determine the feasibility of microalgae harvesting in Malaysia to produce biodiesel and potential to implement microalgae-biodiesel as commercial transportation fuel. This study demonstrated the current scenario of overall biodiesel production and application in Malaysia. Since Malaysia is the world's second-largest oil palm producer, exploitation of edible palm oil for the making of biodiesel is to be blamed as the cause of soaring food price; therefore, the country is currently looking for 3rd generation biofuel sources and microalgae has been preferred for this purpose. Therefore, insight of the significance of microalgae cultivation for this purpose, suitable microalgae candidates and possible feasibility of microalgae biodiesel have been delineated in this review study. Prospects and challenges to implement microalgae biodiesel have also been emphasized in this study. Therefore, the advantages and limitations of this biodiesel can be transparent to government and non-government sectors. Thus, this study can redirect both sectors in future. Consequently, it may contribute setting an appropriate government policy to encourage microalgae for biodiesel production to sustain the local biofuel and secure economic growth, energy security and improve environmental conditions in near future.
... • Soil inappropriate usage. Massive financial supports to energy crops growth to biofuels production is the second source of concerns because it can force indirect land and output use, loss of natural habitats and extensive adoption of fertilizers and pesticides to boost crops growth and, indeed, their production (see, e.g., References [27][28][29][30][31][32]). • Environmental issues. ...
Despite biogas renewability, it is mandatory to experimentally assess its combustion products in order to measure their pollutants content. To this purpose, the Authors selected six in-operation biogas plants fed by different substrates and perform an on-site experimental campaign for measuring both biogas and engines exhausts composition. Firstly, biogas measured compositions are compared among them and with data available in literature. Then, biogas engines’ exhaust compositions are compared among them, with data available in literature and with measurements obtained from an engine characterised by the same design power but fuelled with natural gas. Finally, the Health Impact Assessment analysis is used to estimate the damage on human health caused by both biogas and natural gas engines emissions. Results show that biogas causes a damage on human health three times higher than the natural gas one. But, this approach does not consider biogas renewability. So, to include this important aspect, also an analysis which considers Global Warming categories is carried out. Results highlight that natural gas is twice harmful than biogas.
... Transesterification remains to be the most commonly adopted strategy for the purpose [10,11]. Hydroprocessing of oleaginous matter to renewable diesel (also termed as green diesel or hydroprocessed vegetable oil) is emerging as an attractive approach, but its overall feasibility is yet to be clearly understood [12,13]. Biodiesel is an attractive alternative fuel for climate change mitigation commitments and for meeting the ever-increasing demand for fuel [14,15]. ...
Poor stability and low-temperature operability are among the major hurdles in the commercialization of biodiesel. The presence of polyunsaturated fatty acid esters renders the fuel susceptible to oxidative attack while the long-chain saturated components limit its utility under low-temperature conditions. In this study, an attempt was made to improve these properties of Karanja biodiesel. Karanja biodiesel synthesized via a two-step alkali-catalyzed process exhibited poor stability and cold-flow properties. Karanja biodiesel was winterized to limit the content of long-chain saturates, and it had a favorable effect on the cloud and pour point of the fuel. Removal of long-chain saturated components led to an enrichment of the fuel in unsaturated fractions, and as a result, the stability of the fuel further deteriorated. For improving, the stability of the fuel T. cordifolia stem extract rich in phenolic constituents was added to winterized biodiesel. The combined treatment of winterization and phenolic-rich extract (1000 ppm) had a pronounced effect on fuel quality as it led to a reduction in the cloud (by 7 °C) and pour point (by 6 °C) and substantially improved the stability of the fuel under accelerated oxidative test conditions. The ASTM D6751, IS 15607, and EN 14214 specifications for the minimum induction period for blendstock biodiesel were satisfied. Thus, coupling the use of winterization and natural antioxidants offers novel opportunities in improving the fuel properties and acceptability of biodiesel in an efficient, economical, and environment-friendly manner.
... For this, life cycle assessment (LCA) is a promising tool to guide decision-making in ecologically sound processes. It contributes to quantification, identification, and comparison of energy, water and materials use, as well as waste emissions, analyzing their potential impacts on the environment, and enabling opportunities for improvement throughout the life cycle (Pragya and Pandey, 2016). Therefore, the chapter aims to present aspects related to biologically-assisted combustion with an approach in waste-to- ...
The objective of this chapter is to address aspects related to biologically-assisted combustion focusing on waste-to-energy. Divided into six different sections, the chapter reports issues that outline the combustion science and technology, the oxygen and fuel requirements in combustion systems, the biologically-assisted combustion, the photobioreactors, the mass and energy integration, the environmental performance evaluation and the bioeconomy of the process, summarizing a series of sustainable approaches for the industrial combustion processes.
... -hydrotreatment (HT) [26,32] [ 37.17 [16] 43.00 [31] 38.30 [32] 44.00 [57] 40.62 Mean value ...
With their fast growth rate and ability to accumulate a high percentage of their weight as lipid and carbohydrate, microalgae potentially represent an ideal feedstock for the production of biodiesel and bioethanol. In addition, microalgae offer several environmental benefits, and do not compete with food production for land, fresh water, and nutrients.
Therefore, the main goal of this work is to provide a quantitative, systematic and harmonized assessment of current bio-energy potential. The analysis is conducted by considering all the main steps in detail, from cultivation to biodiesel production, and by deriving an overall estimation of energy consumption for biodiesel production. Energy consumption uncertainty is also quantified and discussed. A systematic review of all the main technologies available for all the main processing steps towards the production of biodiesel from microalgae is presented, focusing on the derivation of the Net Energy Ratio (NER) of each combination of technologies, complemented by an uncertainty analysis of the data used and those obtained in the present work.
A wide scatter in the data available in the literature has been identified, highlighting the need for an uncertainty analysis. If the average overall energy consumption per unit of biodiesel mass is considered, all the routes adopting a raceway pond have a lower energy consumption, but if the uncertainty on the overall energy consumption is also considered, the minimum value of the range of NER values for some of the routes adopting a photobioreactor is comparable to the NER value obtainable by using raceway ponds.
Thus, the present framework proposes a harmonized and comprehensive methodology to compare and contrast technologies for the production of biodiesel from microalgae, and is applied in this paper to identify, with an appreciation of the uncertainty, the most promising combinations of technologies.
... A large amount of biomass is required for the commercialization of microalgal products. However, a major obstacle for algal based product development is the harvesting of microalgal biomass, which involves separation of the microalgal biomass from the culture media [7]. Development of economical and environmentally friendly methods for biomass harvesting of microalgae is a subject for extensive research. ...
Flocculation is an effective technique for harvesting microalgae due to low energy input and being scalable up to industrial algaculture. In this study, four different flocculants at various concentration, and pH levels were employed for the harvesting of Chlorella sp. HS2. Among the tested flocculants, chitosan showed the highest flocculation efficiency of 99.6% ± 0.25 at 10 mg L⁻¹ dosage, pH 8.0 and 30 min of sedimentation. It turned out that the choice of flocculants had minimum impact on the fatty acids methyl ester (FAME) yield and composition. When the reusability of the spent medium for each flocculant was investigated, the culture supernatant obtained from chitosan-based harvesting method had lower growth inhibitory effects in comparison to those harvested using the other flocculants. The cost analysis also favored chitosan-based flocculation, because it returned the highest flocculant efficiency while the flocculant dosage was the lowest. Due to its high harvest efficiency and low impact on the water footprint, it was concluded that the chitosan offer promising advantages over other flocculants.
... The scenarios 2a and 2b (WSE route) and 12a and 12b (pyrolysis route) showed high NER and GHG emissions, as in both belt drying was used. 102 The effect of drying is also observed by comparing the results in scenarios 1a-1b (for WSE only dewatering required) compared to scenarios 10a−10d (dewatering + thermal drying required for intake in pyrolysis unit). Another example of the impact from drying activities is shown in the scenarios 7a and 7b (HTL, minimal dewatering) and scenarios 11a and 11b (pyrolysis, dewatering + thermal drying). ...
Sustainability, at present, is a prominent aspect in the development of any production system that aims to provide the energy resources of the future. Developing sustainable bioenergy production technologies is no mean task. Microalgae appear to be a promising feedstock, however, the sustainability of algae based production systems is still on debate. Commercial market volumes of algae derived products are still narrow. The extraction and conversion of primary metabolites to biofuels requires cultivation at large scales; cost-effective methods are therefore highly desirable. This review sets the attention on sustainability analysis of microalgae production systems, focusing majorly on techno-economic constrains and challenges, life cycle analysis and socio-environmental impacts, both in medium-scale cultivars intended for the production of high added value secondary metabolites and/or in large-scale plants for biofuel production derived from primary metabolites.
... However, all the activity involved in the production of biofuels from microalgae is energy intensive, and the production-related parameters usually refer to biomass productivity, lipid content, and energy efficiency downstream. Given this scenario, any proposed biofuels process should have a positive net energy ratio (NER > 1), i.e., to produce more energy than is consumed [190,118]. ...
Biorefineries are commercial facilities that transform raw materials into commodities of considerable interest to the world bioeconomy. In addition, biorefineries have the potential to achieve favorable environmental characteristics, such as minimal greenhouse gas (GHG) emissions and a lower water footprint, compared to homologous fossil fuels. However, for this concept to become efficient and viable, the use of potentially abundant and specific renewable biological feedstocks should be considered, such as microalgae biomass and other generated products. However, there is an emerging need to consolidate industrial plants that are not only affected by market fluctuations but also aim to transform biological materials into industrially usable products. Thus, for a microalgae biorefinery to compete with the resilient oil refineries in the future, process integration in the supply chain is a promising engineering approach, associating all the components from the cultivation to obtain multiple products that are economically and environmentally sustainable. Therefore, the objective of this review is to compile issues related to microalgal biorefineries applied to bioenergy and biofuel production.
... They do not compete with food or feed crops and can be produced in various, often polluted, water systems offering at the same time relatively high oil/lipid yield, thus making them an ideal source for biodiesel or HVO production (Chisti 2007;Lu et al. 2015;Luque 2010;Yang et al. 2016;Zhao et al. 2013). Still, a sustainable microalgae biorefinery concept would require the efficient utilization of the whole microalgae biomass via selective fractionation and conversion/use of its main components, i.e., lipids/oil for biodiesel/HVO, proteins, and other high-value compounds, i.e., carotenoids for food and health applications, and remaining carbohydrate-rich biomass for the production of additional valuable chemicals/fuels, i.e., H 2 , ethanol, methane, bio-oil, etc. (Dibenedetto et al. 2016;Ho et al. 2011;Mata et al. 2010;Pragya and Pandey 2016;Singh et al. 2011). ...
A systematic study of the effect of nitrogen levels in the cultivation medium of Chlorella vulgaris microalgae grown in photobioreactor (PBR) on biomass productivity, biochemical and elemental composition, fatty acid profile, heating value (HHV), and composition of the algae-derived fast pyrolysis (bio-oil) is presented in this work. A relatively high biomass productivity and cell concentration (1.5 g of dry biomass per liter of cultivation medium and 120 × 10⁶ cells/ml, respectively) were achieved after 30 h of cultivation under N-rich medium. On the other hand, the highest lipid content (ca. 36 wt.% on dry biomass) was obtained under N-depletion cultivation conditions. The medium and low N levels favored also the increased concentration of the saturated and mono-unsaturated C16:0 and C18:1(n-9) fatty acids (FA) in the lipid/oil fraction, thus providing a raw lipid feedstock that can be more efficiently converted to high-quality biodiesel or green diesel (via hydrotreatment). In terms of overall lipid productivity, taking in consideration both the biomass concentration in the medium and the content of lipids on dry biomass, the most effective system was the N-rich one. The thermal (non-catalytic) pyrolysis of Chlorella vulgaris microalgae produced a highly complex bio-oil composition, including fatty acids, phenolics, ethers, ketones, etc., as well as aromatics, alkanes, and nitrogen compounds (pyrroles and amides), originating from the lipid, protein, and carbohydrate fractions of the microalgae. However, the catalytic fast pyrolysis using a highly acidic ZSM-5 zeolite, afforded a bio-oil enriched in mono-aromatics (BTX), reducing at the same time significantly oxygenated compounds such as phenolics, acids, ethers, and ketones. These effects were even more pronounced in the catalytic fast pyrolysis of Chlorella vulgaris residual biomass (after extraction of lipids), thus showing for the first time the potential of transforming this low value by-product towards high added value platform chemicals.
... Jayakumar et al. [60] claimed that total biodiesel cost would reduce by 7.3% by nutrient elimination using wastewater cultivation. High biomass yield can be obtained using indoor cultivation, however it is always compensated by exceedingly high electricity consumption [61]. Lam and Lee [62] supported outdoor cultivation as more economically feasible though lower yield obtained compared to indoor cultivation. ...
... The ideal source for production of biofuels mainly depends on its availability and cost. Thus, a need arises to address the current energy and environmental issues to produce biofuels [1,2]. ...
... Microalgae are one of the most promising green energy re- sources ( Pragya and Pandey, 2016). The utilization of flue gas by microalgae is a growing area of research ( Sun et al., 2015;Tas¸tanTas¸Tas¸tan et al., 2013;Doucha et al., 2005). ...
Current techniques for cleaning flue gas produced by coal-fired thermal power plants have high capital and operational costs and are not effective enough. Ongoing research focuses on increasing efficiency of power plants by using coal additives and biological treatment methods especially microalgae for flue gas treatment. Here, we propose use of a resistant microalgae for flue gas treatment and using its biomass as a novel coal additive.
Utilization of CO2 from thermal power plant coal samples by bio-stimulated _Scenedesmus_ sp. was investigated for producing a novel coal additive material for use in thermal power plants. _Scenedesmus_ sp. biomass was stimulated by IAA (3-Indoleacetic acid) and VO (_Viburnum opulus_) promoters. A novel coal additive material with 8.7% lower amounts of ash and 26.17% higher calorific value, termed as “green coal” was produced in this system. The maximum biomass was produced with lowest culture media consumption, minimum time, highest temperature and highest flow rate. The XRF analyses were performed, fatty acid methyl ester levels were determined and morphology of _Scenedesmus_ sp. were observed. The growth of _Scenedesmus_ sp. in open pond system by bubbling with 9.6 vvm of flue gas resulted in volumetric biomass productivity (_P__max_) of 0.033 g/L/d and CO2 fixation rate of 1512.22 mg CO2/day. This system has the potential to replace other conventional coal additive and cleaning methods since it needs lower energy expenditure and lower use of chemicals.
Biomass, widespread and carbon-neutral energy, can provide electric energy and replace fossil fuel-derived production. Pyrolysis is the main way of converting biomass to different bioenergy products with the consumption of material and energy, which will cause environmental impacts. To confirm the actual environmental impact of biomass conversion, life cycle assessment (LCA) is used for analyzing the process. Due to choosing different LCA methods, the results for the same thing in different reports will show obvious fluctuation. This review is devoted to providing recommendations on how to handle methodological issues when analyzing LCA study, by which researchers can better realize the similarities and differences in biomass conversion system. In this review, multiple clarifications and methodological recommendations on the four steps of the LCA process (including goal and scope definition, life cycle inventory, life cycle impact assessment, and interpretation) are provided. Furthermore, the LCA results are discussed systematically, in which the global warming potential got extra attention. Meanwhile, different biomass feedstocks are divided into agricultural residues, forest residues, and microalgae carefully. Finally, the current challenges and future framework of biomass conversion are expounded in detail from the perspective of LCA.
Depletion of fossil fuels and the need for an eco-friendly substitute has resulted in utilizing biological materials for producing biofuels. Algae is one of the biological species that act as beneficial biomass for producing biodiesel, a toxic-free alternative to commercial transportation fuels. Algae seem to be the most promising species for biodiesel production with merits such as easy cultivation, large biomass production, adaptability, etc. The main concern is the production cost and environmental conditions. This review focuses on the production of biodiesel production using algal species. The parameters affecting the algal growth such as pH, temperature, light source, and nutrient availability are discussed in detail. In addition, the factor that influences biodiesel production like oil to alcohol ratio, secretion of lipid content, nature, and catalyst type is analyzed in detail. Lifecycle assessments (LCA) on cultivation system, mode of algal growth like heterotrophic and autotrophic, and nutrient availability in the medium have been discussed in detail. The economic concerns and ecological impacts have been elaborated that resolve the challenges in algal biodiesel production. The algal community proves to be safe, non-toxic, and effective in producing biodiesel. There still exists a challenge limiting its development to large-scale commercialization.
Green diesel is a kind of next-generation diesel that can be derived from renewable feedstocks. A large range of feedstock is available for the production of green diesel. Various generations of feedstock such as 1st generation (Edible oil—sunflower, palm, corn, rapeseed, and soybean), 2nd generation (Non-edible oil—Jatropha and castor bean, plant waste biomass, and animal fat), 3rd generation (Microalgae) are being used for green diesel production. The chapter sheds light on the different feedstocks used in the production of green diesel along with their chemistry and classification.
There is a continuous depletion of fossil resources recorded in 20th century for the production of diesel that resulted in significant climatic change. The current study focuses on the challenges faced due to energy crisis and climate change followed by biodiesel production from various feedstock sources such as Soybean, Jatropha, Calophyllum inophyllum, and Microalgae. The pivotal aim of the study is to analyze the life cycle balance of biodiesel produced from three generation feedstocks. These sources were selected based on energy balance and Greenhouse Gas (GHG) emissions, specifically on the aspect of Well-to-Pump module. The results infer that GHG emission was stringent in the production of soybean biodiesel i.e., 32.53 gCO2Eq/MJ whereas other sustainable measures such as net energy value, net renewable energy value, and energy ratio were low in the life cycle of microalgae-based biodiesel. This phenomenon indicates its efficiency in obtaining the maximal energy output. On the contrary, about 49.44 gCO2Eq/MJ was produced during all the stages of biodiesel production from microalgae. In terms of sensitivity, the output dependency over input value was also estimated since it showcases the significant influence of cultivation, transportation, oil extraction and biodiesel production upon biodiesel Life Cycle Analysis (LCA). After taking the entire LCA values, sensitivity analyses of selected feedstocks and the importance of food crops into account, the biodiesels produced from Jatropha and Calophyllum inophyllum feedstocks were found to be viable and possess the ability to overcome GHG emission challenges without compromising the energy balance.
Algal biofuels have the potential to effectively replace conventional crude-based fossil fuels. The fact that the algae growth process sequestrates a considerable amount of carbon dioxide can lead to substantial greenhouse gas (GHG) emission reduction. In the recent past, several life cycle assessment (LCA) studies have been conducted to demonstrate the benefits of algal biofuels. However, considerable differences are observed in the predicted environmental benefits from these studies. These differences arise from a variety of factors such as choice of the functional unit, system boundary, algae species, and conversion processes. Furthermore, most studies focus only on GHG emissions, thus neglecting other potential environmental impacts of algal biofuel production. This chapter aims to provide a review of the LCA studies for algal biofuels, which have been conducted in the recent past. The basics of algal biofuels and life cycle assessment have been thoroughly discussed. The differences in the assumptions, and their possible effects on the final results, have been highlighted. Some of the recent advances, as well as future directions in LCA of algal biofuels, have also been discussed. The chapter aims to underline the state-of-the-art practices to enable the decision makers to make informed choices related to the sustainability of algal biofuels.KeywordsAlgal biofuelsGreenhouse gas emissionsLife cycle assessmentSustainability
The utilization of microalgae-derived fuel is very important for our sustainability. Here, adsorptive denitrogenation of model green-diesel (with considerable nitrogen-containing compounds, NCCs) was investigated to check the feasibility of adsorptive purification of fuel, derived from microalgae that is composed of NCCs. A highly porous MIL-101(Cr) (named M101) metal–organic framework was firstly modified to introduce protonated amino groups on both the linker and metallic sites of the MOF. The functionalized MOFs including P-M101-NH2-ED (P and ED mean ‘protonated’ and ethylenediamine, respectively), M101-NH2-ED, and M101-NH2 were applied (together with pristine M101 and a conventional activated carbon) in the adsorptive removal of N-containing compounds like benzonitrile (BENZ) and carbazole (CARB) from model green-diesel. The prepared P-M101-NH2-ED showed the most effective performances in the adsorption, compared with any other adsorbents known thus far. For instance, P-M101-NH2-ED adsorbed 15.6 and 3.6 times of BENZ and CARB, respectively, that of the activated carbon. The observed remarkable performances of P-M101-NH2-ED (Q0 values for BENZ and CARB are 500 and 455 mg/g, respectively), although with lower porosity than other M101s, for BENZ and CARB adsorption could be explained mainly with hydrogen bonding and hydrogen bonding/cation-π interactions, respectively. Moreover, P-M101-NH2-ED was recyclable in several cycles after simple ethanol washing. Therefore, P-M101-NH2-ED could be suggested as a plausible adsorbent to remove NCCs from green-diesel, based on remarkable performances and facile reusability.
Microalgae-derived biodiesel has been extensively researched as a promising substitute for petroleum diesel since it releases fewer greenhouse gas (GHG) emissions, has reduced eutrophication potential, and is fully compatible with the current fuel infrastructure. Numerous Life Cycle Assessment (LCA) studies have been conducted to date to evaluate the environmental sustainability of algal-based biofuels. These studies are essential for identifying the bottlenecks in the algal biomass to biodiesel conversion pathways, which can then be improved to increase the economic and environmental viability of the entire value chain. This chapter discusses the basics of LCA, provides a comprehensive review of numerous algae-to-biodiesel LCA studies, and compares them based on Net Energy Ratio (NER) and life cycle-GHG emissions. The analysis indicates that significant improvements are required in algae production and conversion to achieve sustainability and cost-competitiveness. Integrating algal biodiesel production with value-added coproducts, such as animal feed, and nutraceuticals can help the commercialization prospects of the algae industry.
The harmful effect of carbon pollution leads to depletion of the ozone layer, which is one of the main challenges confronting the world. Although progress is made in developing different carbon dioxide (CO2) capturing methods, these methods are still expensive and face several technical challenges. Fuel cells (FCs) are efficient energy converting devices that produce energy via an electrochemical process. Recently varying kinds of fuel cells are considered as an effective method for CO2 capturing and/or conversion. Among the different types of fuel cells, solid oxide fuel cells (SOFCs), molten carbonate fuel cells (MCFCs), and microbial fuel cells (MFCs) demonstrated promising results in this regard. High-temperature fuel cells such as SOFCs and MCFCs are effectively used for CO2 capturing through their electrolyte and have shown promising results in combination with power plants or industrial effluents. An algae-based microbial fuel cell is an electrochemical device used to capture and convert carbon dioxide through the photosynthesis process using algae strains to organic matters and simultaneously power generation. This review present a brief background about carbon capture and storage techniques and the technological advancement related to carbon dioxide captured by different fuel cells, including molten carbonate fuel cells, solid oxide fuel cells, and algae-based fuel cells.
Although fossil fuels remain the main source of energy, the volume of renewable sources of energy is constantly increasing. Biodiesel is a promising alternative fuel due to the number of advantages compared to fossil fuel and other types of biofuel. The specific objective of this study was to identify the difference between conventional and novel technologies applied during the whole life cycle of biodiesel production and consumption. The study offers some important insights into the recent advances in the biodiesel industry including biodiesel production from microalgal lipids, advanced homogenous and enzymatic transesterification, non-catalytic supercritical transesterification, application of microwave and ultrasound assisting technologies. Considering all the factors affecting the efficiency and safety of the biodiesel production process, here we reviewed the main principals and recent achievements in the environmental life cycle assessment of biodiesel production and consumption.
Two locally isolated oleaginous microalgae from Songkhla Lake in Thailand were identified as Micractinium reisseri SIT04 and Scenedesmus obliquus SIT06. The effects of nutrient starvations on the responses of these two strains were intensively investigated in order to increase their lipid contents and manipulate their fatty acid compositions for suitable use as biodiesel feedstocks. Starvation of either phosphorus or ferrous less affected cell growth but did stimulate lipid accumulation of both strains by 1.2 folds. While nitrogen starvation severely limited cell growth but most effectively increased lipid content of both strains by 1.54 folds for M. reisseri SIT04 (up to 36.6%) and by 1.6 folds for S. obliquus SIT06 (up to 56.8%). The lipid accumulated during nitrogen starvation contained higher saturated fatty acids which could make biodiesel with better fuel properties and higher oxidative stability. The harvesting process through bioflocculation was optimized by Response Surface Methodology. The maximum flocculation efficiency greater than 99.5% was achieved using minimum dosage of chitosan as bioflocculant. This study has revealed the strategies to increase the potential use of oleaginous microalgae as biodiesel feedstocks and the cost-effective process for the harvesting of microalgal biomass.
Microalgae has gained substantial attention as a promising feedstock for producing biodiesel. In situ transesterification using a heterogeneous catalyst renders the conversion process more advantageous as lipid extraction and transesterification occurs simultaneously. In this study, LiOH-pumice catalyst was prepared via acid treatment and wet impregnation. X-ray diffraction analysis validated the successful LiOH impregnation to the pumice material while scanning electron microscopy and Brunauer–Emmett–Teller surface area analyses revealed that the LiOH-pumice catalyst had a spherical and porous morphology and a high surface area. Moreover, the applicability of the LiOH-pumice catalyst for the in situ transesterification of Chlorella sp. was investigated by evaluating the effects of catalyst dosage, reaction temperature and time, and methanol-to-biomass ratio on the % fatty acid methyl ester (FAME) yield. The highest % FAME yield of 47% was obtained at 20 wt.% catalyst, 80 °C reaction temperature, 3 h reaction time, and 12 mL g−1 methanol-to-biomass ratio. Overall, the results of this study shows that LiOH-pumice is a promising catalyst for the production of microalgae-based biodiesel via in situ transesterification.
In the pursuit of renewable sources of energy, biomass is emerging as a promising resource because of its abundance and carbon neutral nature. Pyrolysis is a prevailing technology for biomass conversion into the valuable hydrocarbon and alternative fuels. In this review, pyrolysis of lignocellulosic biomass has been addressed, focusing primarily on the ideal feedstock, technologies, reactors, and properties of the end product. Technical problems in using biofuel from pyrolysis, as transport fuel have also been discussed, along with solutions to address these challenges, and comments on the future scope of the pyrolysis process.
A microalgae-based energy system, which is a combination of different microalgae-to-biodiesel chains and an integrated cogasification combined cycle (ICGCC) system, is presented. To address the low environmental impacts, the electricity is generated from ICGCC to meet the load demand from the microalgae-to-biodiesel chains and the flue gas exits from ICGCC to meet the demand of growing algal culture. To achieve the microalgae-based energy system with minimum life cycle greenhouse gas (GHG) emissions, the first step is to develop the superstructure model based on GAMS, the second step is to use the optimal heat exchanger network to maximize the heat recovery of ICGCC, and the third step is to find the optimal combination of the microalgae-to-biodiesel chain and optimal operating conditions of ICGCC by solving the global optimization of nonconvex mixed-integer nonlinear programming (MINLP) problem. For the scope of well-to-tank (WTT), the optimal microalgae-based energy system reduces 16.80% greenhouse gas (GHG) emissions compared to the other reported microalgae-to-biodiesel chains. For the scope of well-to-wheel (WTW), the optimal microalgae-based energy system reduces 45.77% GHG emissions compared to the conventional diesel process.
Algae are capable of switching their metabolism that is integrated with photosynthesis under certain conditions to produce H2 gas and substrates for fuels such as biodiesel. H2 is produced by microalgae under anaerobic conditions induced by sulfur deprivation as the most commonly applied treatment. Under these conditions, the demand for reducing electrons by the CO2 fixation process is decreased making them available for H2 production by algal O2-senstive hydrogenase enzymes. The electrons are generated from water oxidation by the photosynthetic linear electron transfer and the oxidation of stored organic compounds such as starch. Biodiesel as fatty acid methyl esters can be produced from algal triacylglycerides by a transesterification process. The triacylglyceride synthesis in microalgae can be induced under stress conditions such as nitrogen (N) deprivation. Proteomic studies have shown that N stress can cause a shift in metabolism in favor of directing carbon skeletons toward fatty acid biosynthesis for triacylglyceride production. Several important factors limiting the potential of microalgae for biofuel production and their possible solutions, including the production of other fuels such as bioethanol and biomethane from algal biomass are also presented.
The aim of this work is to compare the life cycle assessments of low-N and normal culture conditions for a balance between the lipid content and specific productivity. In order to achieve the potential contribution of lipid content to the life cycle assessment, this study established relationships between lipid content (nitrogen effect) and specific productivity based on three microalgae strains including Chlorella, Isochrysis and Nannochloropsis. For microalgae-based aviation fuel, the effects of the lipid content on fossil fuel consumption and greenhouse gas (GHG) emissions are similar. The fossil fuel consumption (0.32-0.68 MJ·MJ⁻¹ MBAF) and GHG emissions (17.23-51.04 g CO2e·MJ⁻¹ MBAF) increase (59.70-192.22%) with the increased lipid content. The total energy input decreases (2.13-3.08 MJ·MJ⁻¹ MBAF, 14.91-27.95%) with the increased lipid content. The LCA indicators increased (0-47.10%) with the decreased nitrogen recovery efficiency (75-50%).
Algae biomass is an attractive biofuel feedstock when grown with high productivity on marginal land. Hydrothermal liquefaction (HTL) produces more oil from algae than lipid extraction (LE) does because protein and carbohydrates are converted, in part, to oil. Since nitrogen in the algae biomass is incorporated into the HTL oil, and since lipid extracted algae for generating heat and electricity are not co-produced by HTL, there are questions regarding implications for emissions and energy use. We studied the HTL and LE pathways for renewable diesel (RD) production by modeling all essential operations from nutrient manufacturing through fuel use. Our objective was to identify the key relationships affecting HTL energy consumption and emissions. LE, with identical upstream growth model and consistent hydroprocessing model, served as reference. HTL used 1.8 fold less algae than did LE but required 5.2 times more ammonia when nitrogen incorporated in the HTL oil was treated as lost. HTL RD had life cycle emissions of 31,000 gCO2 equivalent (gCO2e) compared to 21,500 gCO2e for LE based RD per million BTU of RD produced. Greenhouse gas (GHG) emissions increased when yields exceeded 0.4 g HTL oil/g algae because insufficient carbon was left for biogas generation. Key variables in the analysis were the HTL oil yield, the hydrogen demand during upgrading, and the nitrogen content of the HTL oil. Future work requires better data for upgrading renewable oils to RD and requires consideration of nitrogen recycling during upgrading.
In this study, we present the activities of Al2O3 supported CaO and MgO catalysts in the transesterification of lipid of yellow green microalgae, Nannochloropsis oculata, as a function of methanol amount and the CaO and MgO loadings at 50°C. We found that pure CaO and MgO were not active and CaO/Al2O3 catalyst among all the mixed oxide catalysts showed the highest activity. Not only the basic site density but also the basic strength is important to achieve the high biodiesel yield. Biodiesel yield over 80wt.% CaO/Al2O3 catalyst increased to 97.5% from 23% when methanol/lipid molar ratio was 30.
Effects of nitrogen source and concentration as well as lipid extraction method on the lipid yield of autotrophic Scenedesmus dimorphus and heterotrophic Chlorella protothecoides were studied. Three concentration levels of nitrate, urea and glycine/yeast extract as the nitrogen source were investigated. The highest lipid yield of S. dimorphus in the 17-d autotrophic culture was 0.40 g/L from the 1.8 g/L urea medium, and the maximum lipid yield of C. protothecoides in the nine-day heterotrophic culture was 5.89 g/L from the 2.4 g/L nitrate medium. Four different cell disruption methods— bead-beater, French press, sonication and wet milling— were studied for their effectiveness in solvent extraction of algal lipids from S. dimorphus and C. protothecoides. Wet milling followed by hexane extraction was most effective for S. dimorphus lipid extraction, whereas bead-beater disruption followed by hexane extraction was best for C. protothecoides.. Effect of nitrogen and extraction method on algae lipid yield. Int J Agric & Biol Eng, 2009; 2(1): 51－57.
Twelve salts were tested for their ability to coagulate microalgae cells in cultures of Chlorella minutissima. The final aim was to develop an easy and efficient approach for harvesting microalgae biomass in dense cultures. Aluminum,
ferric, and zinc salts coagulated C. minutissima cultures, while optimum concentration was 0.75 and 0.5gL−1 for sulfate and chloride salts, respectively. Aluminum salts were most efficient, but caused some cell lysis, which may render
this approach inappropriate in some cases. Ferric and zinc salts were ranked second and third, respectively, according to
their culture cell-coagulation efficiency. Ferric salts caused a change in the color of the cells, mainly at concentrations
higher than 1gL−1. Zinc salts were less harmful for the microalgal cells, but an additional problem was observed with cell aggregates adhering
to the walls of the glass test tubes. Selection of the appropriate coagulant is related to the purpose of the coagulation
process.
KeywordsAluminum salts-Ferric salts-Flocculation-Microalgae-Zinc salts
The purpose of this study was to explore efficient methods of harvesting the microalga Phaeodactylum tricornutum. Natural sedimentation experiments, performed at different light and temperature conditions, did not yield significant improvements in efficiency even after 1 week. When alkalinity-induced flocculation was performed, both the flocculation efficiency and the concentration factor dramatically improved at pH = 9.75 (0.5–0.7 units over the original pH of the culture) after 10 min settling time. Sedimentation rates are documented at pH ranging between pH 9.75 and 11.0. The results of the application of two conventional flocculants used in wastewater treatment, polyaluminium chloride and aluminium sulphate, are also presented. Chitosan was also used as a natural flocculating agent to improve possible contamination problems in the downstream process. pH was adjusted in order to determine optimum flocculation efficiency of chitosan in combination with a high concentration factor. Satisfactory results were found with chitosan at an adjusted pH of 9.9 using concentrations as low as 20 mg L−1, after testing a flocculant range of 5–200 mg L−1.
In the present study, the use of immobilization technology to cultivate microalgae in entrapped matrix gel beads was demonstrated. Since the gel beads are denser in water, the beads can be easily collected through simple filtration method and hence, simplifying the overall separation process. Various parameters were investigated to optimize the growth rate of immobilized microalgae and the optimum conditions were obtained as: alginate to microalgae volume ratio of 0.3, Ca2+ concentration of 2%, organic nutrients concentration of 50 mL (equivalent to 13.09 mg/L nitrate), initial culture pH of 4 and photoperiod of 24 h. Using this optimum culture condition, 0.50 mg biomass/bead was attained on the 10th day of cultivation. Apart from that, this study also attempted to co-immobilize nutrients into microalgae beads in order to minimize free cell culture (microalgae cells that are released into the culture medium due to rupturing of beads) and to reduce water consumption. Through this approach, it was found that microalgae biomass yield increased to 0.67 mg/bead within a shorter culturing time (5 days) with insignificant amount of free cell culture detected. Furthermore, lipid extracted from immobilized microalgae biomass has high potential for biodiesel production due to the similarity of fatty acid profile with other oil bearing crops.
The term ''fast pyrolysis'' has been used to describe a pyrolysis regime in which vapor production is enhanced and char minimized by rapid heating. It has been found in the last decade that high yields of primary pyrolysis oil can be achieved using fast pyrolysis. More recently it has been found that the pyrolysis vapors can be converted to high grade fuels using a catalyst. This makes fast pyrolysis of biomass desirable for synthetic fuel manufacture. The authors present results derived from the Diebold Integrated Kinetic Model (DKM) that predict the time, the temperature, and the products of pyrolysis and the heat for pyrolysis of cellulose as a function of heating rates between 0.01 and 10âµC/min. This range covers very slow pyrolysis requiring days to fast pyrolysis occurring in fractions of a second. The predictions are in good qualitative agreement with experimental measurements. They then compare the heat flux required for slow and fast pyrolysis for particles with that which can be obtained with practical heating devices. The comparison shows that convective and radiative heat transfer is adequate for fast pyrolysis of small particles, but not for large particles, due to conduction to the interior.
Renewable energy sources and technologies have potential to provide solutions to the longstanding energy problems being faced by the developing countries like India. Solar energy can be an important part of India's plan not only to add new capacity but also to increase energy security, address environmental concerns, and lead the massive market for renewable energy. Solar thermal electricity (STE) also known as concentrating solar power (CSP) are emerging renewable energy technologies and can be developed as future potential option for electricity generation in India. In this paper, efforts have been made to summarize the availability, current status, strategies, perspectives, promotion policies, major achievements and future potential of solar energy options in India.
In this study different methods were applied for lipids extraction from the dry biomass of Chlorella pyrenoidosa. The survey was carried under different conditions seeking comparative assessment of extraction methods. The method using chloroform:methanol (2:1 v/v) showed the highest lipid extraction followed by methanol, chloroform, ethanol, and hexane. Afterward, we also assessed the relative influence of the solvent extractor selectivity on the overall FAMEs (Fatty Acids Methyl Esters) yield. The application of the transesterification process on the several lipidic extracts was compared with direct transesterification process from dry biomass. In the extraction using chloroform:methanol system a larger amount of lipids was obtained but the conversion to FAMEs using transesterification process was the lowest from lipids. However, despite the amount of extracted lipids with methanol being smaller, its conversion to FAMEs was higher from lipids. In addition, the extraction with methanol followed by transesterification process also resulted in a higher FAMEs yield from biomass than direct transesterification process using methanol.
Microalgae have been proposed as possible alternative feedstocks for the production of biodiesel because of their high photosynthetic efficiency. The high energy input required for microalgal culture and oil extraction may negate this advantage, however. There is a need to determine whether microalgal biodiesel can deliver more energy than is required to produce it. In this work, net energy analysis was done on systems to produce biodiesel and biogas from two microalgae: Haematococcus pluvialis and Nannochloropsis. Even with very optimistic assumptions regarding the performance of processing units, the results show a large energy deficit for both systems, due mainly to the energy required to culture and dry the microalgae or to disrupt the cell. Some energy savings may be realized from eliminating the fertilizer by the use of wastewater or, in the case of H. pluvialis, recycling some of the algal biomass to eliminate the need for a photobioreactor, but these are insufficient to completely eliminate the deficit. Recommendations are made to develop wet extraction and transesterification technology to make microalgal biodiesel systems viable from an energy standpoint.
The combination of microalga-based biodiesel production and wastewater treatment is a promising approach to solve problems related to the energy crisis as well as eutrophication in bodies of water. A freshwater microalga, Chlorella ellipsoidea YJ1, with a high capacity for biomass production and lipid accumulation in secondary effluent was isolated. C. ellipsoidea YJ1 could achieve a biomass of 425mgL−1 (dry weight) in domestic secondary effluent treated with activated sludge technology; and the lipid content per unit of algal biomass was as high as 43% (w/w) in this condition. The lipid growth rate of C. ellipsoidea YJ1 in domestic secondary effluents could attain 11.4mg/L. Furthermore, after the cultivation of C. ellipsoidea YJ1, the removal efficiencies of nitrogen and phosphorus from the secondary effluent studied in this paper were more than 99% and 90%, respectively. Logistic and Monod models were used successfully to simulate the growth of C. ellipsoidea YJ1, and its maximum biomass and maximum population growth rate under different initial concentrations of nitrogen and phosphorus could be simulated and predicted using the models. .
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.
Microalgae are photosynthetic microorganisms that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and useful chemicals. Two algae samples (Cladophora fracta and Chlorella protothecoid) were studied for biofuel production. 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 biodiesel, bioethanol, bio-oil, biohydrogen and biomethane via thermochemical and biochemical methods. Industrial reactors for algal culture are open ponds, photobioreactors and closed systems. Algae can be grown almost anywhere, even on sewage or salt water, and does not require fertile land or food crops, and processing requires less energy than the algae provides. Microalgae have much faster growth-rates than terrestrial crops. the per unit area yield of oil from algae is estimated to be from 20,000 to 80,000liters per acre, per year; this is 7–31 times greater than the next best crop, palm oil. Algal oil can be used to make biodiesel for cars, trucks, and airplanes. The lipid and fatty acid contents of microalgae vary in accordance with culture conditions. The effect of temperature on the yield of hydrogen from two algae (C. fracta and C. protothecoid) by pyrolysis and steam gasification were investigated in this study. In each run, the main components of the gas phase were CO2, CO, H2, and CH4.The yields of hydrogen by pyrolysis and steam gasification processes of the samples increased with temperature. The yields of gaseous products from the samples of C. fracta and C. protothecoides increased from 8.2% to 39.2% and 9.5% to 40.6% by volume, respectively, while the final pyrolysis temperature was increased from 575 to 925K. The percent of hydrogen in gaseous products from the samples of C. fracta and C. protothecoides increased from 25.8% to 44.4% and 27.6% to 48.7% by volume, respectively, while the final pyrolysis temperature was increased from 650 to 925K. The percent of hydrogen in gaseous products from the samples of C. fracta and C. protothecoides increased from 26.3% to 54.7% and 28.1% to 57.6% by volume, respectively, while the final gasification temperature was increased from 825 to 1225K. In general, algae gaseous products are higher quality than gaseous products from mosses.
With rapid economic development, energy consumption in China has tripled in the past 20years, exceeding 2.8 billion tons of standard coal in 2008. The search for new green energy as substitutes for nonrenewable energy resources has become an urgent task. Biodiesel is one of the most important bioenergy sources. According to the Mid- and Long-term Development Plan for Renewable Energy in China, the consumption of biodiesel in China will reach 0.2 million tons in 2010 and 2.0million tons in 2020. However, large-scale production of biodiesel is restricted by the limited sources of raw materials. Microalgal oil is a prospective raw material for biodiesel production. Development of technology for the production and commercialization of biodiesel from microalgae has become a hot topic in the field of bioenergy and CO2 emission mitigation. Biodiesel from microalgae can be produced at laboratory-scale, but the cost is too high. Few studies on the commercialization of the technology of producing biodiesel from microalgae have been reported. In this review, recent progress on the research and development of biodiesel from microalgae that have resulted in scientific breakthroughs and innovation in engineering in China are introduced. The existing challenges are also discussed. Based on a detailed analysis, several novel strategies on commercial biodiesel production from microalgae are proposed.
The objective of this paper is to study marine macroalgae as an alternative raw material for the biodiesel production. The obtained results show that biodiesel production from oil extracted from marine algae is feasible by transesterification. Oil extraction can be carried out simultaneously with the transesterification. To investigate the optimum reaction conditions, the reaction was carried out at various methanol to oil molar ratios, catalyst concentrations and reaction temperatures. The process yields 1.6–11.5% depending on the reaction conditions. Moreover, the properties of macroalgae transesterification residue after transesterification were analyzed, concluding that it is a suitable material for fuel pellets manufacturing.
For the extraction of oil from microalgae, which are recognised as an important renewable source of bioactive lipids, supercritical CO2 is regarded with interest being safer than hexane and offering a negligible environmental impact, short extraction time and petroleum-free final product. A mathematical model, able to describe the kinetics of a supercritical fluid extraction (SFE) process, was applied to the recovery of oil from the cyanobacterium Spirulina (Arthrospira) platensis, characterised by a particularly high content in γ-linolenic acid (C18:3ω-6). In this paper, we examine the kinetics of the SFE and the effect of operating conditions on extraction yield and fatty acid composition of lipid extracts.
Recent au fost cercetate mai multe tipuri de biomasă, care pot produce
energie în vederea înlocuirii combustibililor fosili. Această lucrare prezintă o
abordare în vederea optimizării producţiei de bio-cocs din piroliza prin modificarea
parametrilor de proces. Materialul analizat a fost rumeguşul de cireş.
Experimentele s-au efectuat prin piroliza la temperaturi între 450 ºC şi 800 ºC.
Studiul experimental s-a bazat pe influenţa temeraturii, timpului de staţionare şi a
ratei de încălzire asupra producţiei de bio-cocs şi asupra determinării puterii
calorifice superioare a cocsului.
Recently much research has been investigated on identifying suitable
biomass species, which can provide high-energy outputs, to replace conventional
fossil fuels. This paper reports an approach for increasing the yield of bio-char
production from pyrolysis with respect to process conditions. The analyzed material
was cherry sawdust. The experiments were conducted for pyrolysis temperature
between 450ºC and 800ºC. The experimental study focused on the influence of
pyrolysis temperature, residence time or heating rate on the bio-char yield and on
determination of the HHV of the pyrolysis char.
The applicability of ionic liquid-polar covalent molecule co-solvent systems to extract bio-oils from biomass is evaluated. In our approach the extracted lipids are auto-partitioned to a separate immiscible phase for ease of harvesting. We propose that the action of the polar covalent molecule is largely to disrupt the cell wall and to improve the efficiency at which the lipid is extracted from the biomass. As ionic liquid solutions are both amphiphilic and characterized by strong “self-associating” ionic bonding between the cations and anions, we propose that the action of the ionic liquid is to facilitate the transfer of the lipids to the surface interface where they auto partition into a self-associating and separate phase. The potential of the co-solvent system to co-extract protein is also noted.
Dewatering of microalgal culture is a major bottleneck towards the industrial-scale processing of microalgae for bio-diesel production. The dilute nature of harvested microalgal cultures poses a huge operation cost to dewater; thereby rendering microalgae-based fuels less economically attractive. This study explores the influence of microalgal growth phases and intercellular interactions during cultivation on dewatering efficiency of microalgae cultures. Experimental results show that microalgal cultures harvested during a low growth rate phase (LGRP) of 0.03 d−1 allowed a higher rate of settling than those harvested during a high growth rate phase (HGRP) of 0.11 d−1, even though the latter displayed a higher average differential biomass concentration of 0.2gL−1d−1. Zeta potential profile during the cultivation process showed a maximum electronegative value of −43.2±0.7mV during the HGRP which declined to stabilization at −34.5±0.4mV in the LGRP. The lower settling rate observed for HGRP microalgae is hence attributed to the high stability of the microalgal cells which electrostatically repel each other during this growth phase. Tangential flow filtration of 20L HGRP culture concentrated 23 times by consuming 0.51kWh/m3 of supernatant removed whilst 0.38kWh/m3 was consumed to concentrate 20L of LGRP by 48 times.
A product's environmental life cycle progresses from raw material extraction through production, use and finally to waste management. Life Cycle Assessment (LCA) concerns the impact of a product on the environment. LCA's holistic perspective of products' environmental performance makes it a key concept for environmental management in industry as well as for environmental policy-making in government.
This book for environmental engineers and managers, ecodesigners and students presents a broad repertoire of LCA methological alternatives, their implications and their usefulness in many different applications such as product development, marketing, production and waste management.
Here environmental professionals can learn to interpret LCA methodology and results. The text also provides indepth coverage of LCA applications and offers many useful exercises to help prepare for the 10 major LCA exercise projects that are also included.
One of the future-generation biofuel options that has recently recieved increased attention is the production of biofuels from microalgae. Besides the use of algae oil for physicochemical biodiesel production, biochemical and thermochemical pathways are possible. Although there is still a need to research algae production systems, downstream processing (e.g., biofuel production) needs to be researched in parallel. As there are several methods to produce biofuel from algae, different possible production processes are reviewed. By investigating the different steps of each of the processes and highlighting the challenges and risks that can occur, it is possible to make a decision regarding which pathway might be feasible for algal resources in the future.
Microalgae for carbon dioxide mitigation was applied to the production of acetic acid under hydrothermal conditions with H2O2 oxidant. Results showed that acetic acid was obtained with a good yield of 14.9% based on a carbon base at 300 °C for 80 s with 100% H2O2 supply. This result should be helpful to facilitate studies for developing a new green and sustainable process in order to produce acetic acid from microalgae, which are the fastest growing sunlight-driven cell factories. These results show that it is possible to develop a process for conversion of microalgae biomass into acetic acid.
Nannochloropsis sp., one kind of green microalgae cultivated autotrophically and axenically in laboratory, is used as raw material to produce biodiesel by one-step method in an amended reactor. The effects of several reaction parameters on transesterification over Mg–Zr solid base catalyst were investigated through both conventional method and one-step method. One-step method could give a higher yield of methyl ester than conventional two-step method, which demonstrates that the present one-step method is suitable for biodiesel production from the microalgae Nannochloropsis sp. Moreover, the present one-step method realizes the convenient in situ separation of catalyst from microalgae residue which can be easily used consequently, reducing the procedure units as well as the overall costs.
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.
Global threats of fuel shortages in the near future and climate change due to green-house gas emissions
are posing serious challenges and hence and it is imperative to explore means for sustainable ways of
averting the consequences. The dual application of microalgae for phycoremediation and biomass production
for sustainable biofuels production is a feasible option. The use of high rate algal ponds (HRAPs)
for nutrient removal has been in existence for some decades though the technology has not been fully
harnessed for wastewater treatment. Therefore this paper discusses current knowledge regarding wastewater
treatment using HRAPs and microalgal biomass production techniques using wastewater streams.
The biomass harvesting methods and lipid extraction protocols are discussed in detail. Finally the paper
discusses biodiesel production via transesterification of the lipids and other biofuels such as biomethane
and bioethanol which are described using the biorefinery approach.
A process for isolation of three products (fatty acids, chars and nutrient-rich aqueous phases) from the hydrothermal carbonization of microalgae is described. Fatty acid products derived from hydrolysis of fatty acid ester groups in the microalgae were obtained in high yield and were found to be principally adsorbed onto the char also created in the process. With the highest lipid-containing microalga investigated, 92% of the fatty acids isolated were obtained by solvent extraction of the char product, with the remaining 8% obtained by extraction of the acidified filtrate. Obtaining the fatty acids principally by a solid–liquid extraction eliminates potential emulsification and phase separation problems commonly encountered in liquid–liquid extractions. The aqueous phase was investigated as a nutrient amendment to algal growth media, and a 20-fold dilution of the concentrate supported algal growth to a level of about half that of the optimal nutrient growth medium. Uses for the extracted char other than as a solid fuel are also discussed. Results of these studies indicate that fatty acids derived from hydrothermal carbonization of microalgae hold great promise for the production of liquid biofuels.
Due to increasing oil prices and climate change concerns, biodiesel has gained attention as an alternative energy source. Biodiesel derived from microalgae is a potentially renewable and carbon–neutral alternative to petroleum fuels. One of the most important decisions in obtaining oil from microalgae is the choice of algal species to use. Eight microalgae from a total of 33 isolated cultures were selected based on their morphology and ease of cultivation. Five cultures were isolated from river and identified as strains of Scenedesmus obliquus YSR01, Nitzschia cf. pusilla YSR02, Chlorella ellipsoidea YSR03, S. obliquus YSR04, and S. obliquus YSR05, and three were isolated from wastewater and identified as S. obliquus YSW06, Micractinium pusillum YSW07, and Ourococcus multisporus YSW08, based on LSU rDNA (D1-D2) and ITS sequence analyses. S. obliquus YSR01 reached a growth rate of 1.68 ± 0.28 day−1 at 680nm and a biomass concentration of 1.57 ± 0.67 g dwt L−1, with a high lipid content of 58 ± 1.5%. Under similar environmental conditions, M. pusillum reached a growth rate of 2.3 ± 0.55 day−1 and a biomass concentration of 2.28 ± 0.16 g dwt L−1, with a relatively low lipid content of 24 ± 0.5% w/w. The fatty acid compositions of the studied species were mainly myristic, palmitic, palmitoleic, oleic, linoleic, g-linolenic, and linolenic acids. Our results suggest that S. obliquus YSR01 can be a possible candidate species for producing oils for biodiesel, based on its high lipid and oleic acid contents.
The conversion of lipid-extracted microalgal biomass residues (LMBRs) into hydrogen plays the dual role in renewable energy production and sustainable development of microalgal biodiesel industry. An anaerobic fermentation process to covert LMBRs into hydrogen was investigated in this work. Using batch experiments, the effects of pretreatment of inoculum (by acid, base, heat, and chloroform, respectively), initial pH (5.0–7.0), inoculum concentrations at 0.59–2.94 g VSS/l (volatile suspended solids, VSS) and substrate concentrations at 4.5–45 g VS/l (volatile solids, VS) were investigated, respectively. The results showed that the most effective hydrogen production was obtained from fermentation of LMBRs with a concentration of 36 g VS/l at the initial pH 6.0–6.5 using the heat-treated anaerobic digested sludge as inoculum. Acetate, propionate and butyrate were the main fermentation byproducts in the conversion of LMBRs into hydrogen.
a b s t r a c t Carbon-neutral renewable liquid biofuels are needed to displace petroleum-derived transport fuels in the near future – which contribute to global warming and are of a limited availability. A promising alterna-tive is conveyed by microalgae, the oil content of which may exceed 80% (w/w DW) – as compared with 5% of the best agricultural oil crops. However, current implementation of microalga-based systems has been economically constrained by their still poor volumetric efficiencies – which lead to excessively high costs, as compared with petrofuel prices. Technological improvements of such processes are thus critical – and this will require a multiple approach, both on the biocatalyst and bioreactor levels. Several bottlenecks indeed exist at present that preclude the full industrial exploitation of microalgal cells: the number of species that have been subjected to successful genetic transformation is scarce, which hampers a global understanding (and thus a rational design) of novel blue-biotechnological processes; the mechanisms that control regulation of gene expression are not fully elucidated, as required before effective biopro-cesses based on microalgae can be scaled-up; and new molecular biology tools are needed to standardize genetic modifications in microalgae – including efficient nuclear transformation, availability of promoter or selectable marker genes, and stable expression of transgenes. On the other hand, a number of pending technological issues are also present: the relatively low microalga intrinsic lipid productivity; the max-imum cell concentration attainable; the efficiency of harvest and sequential recovery of bulk lipids; and the possibility of by-product upgrade. This review briefly covers the state of the art regarding mic-roalgae toward production of biofuels, both from the point of view of the microalgal cell itself and of the supporting bioreactor; and discusses, in a critical manner, current limitations and promising perspectives in this field.
and BTG Biomass Technology Group B.V., Josink Esweg 34, 7545 PN Enschede, The Netherlands Fast pyrolysis oils from lignocellulosic biomass are promising second-generation biofuels. Unfortunately, the application range for such oils is limited because of the high acidity (pH∼2.5) and the presence of oxygen in a variety of chemical functionalities, and upgrading of the oils is required for most applications. Herein, we report an experimental study on the upgrading of fast pyrolysis oil by catalytic hydrotreatment. A variety of heterogeneous noble-metal catalysts were tested for this purpose (Ru/C, Ru/TiO 2 , Ru/Al 2 O 3 , Pt/C, and Pd/C), and the results were compared to those obtained with typical hydrotreatment catalysts (sulfided NiMo/ Al 2 O 3 and CoMo/Al 2 O 3). The reactions were carried out at temperatures of 250 and 350 °C and pressures of 100 and 200 bar. The Ru/C catalyst was found to be superior to the classical hydrotreating catalysts with respect to oil yield (up to 60 wt %) and deoxygenation level (up to 90 wt %). The upgraded products were less acidic and contained less water than the original fast pyrolysis oil. The HHV was about 40 MJ/kg, which is about twice the value of pyrolysis oil. Analyses of the products by 1 H NMR spectroscopy and 2D GC showed that the upgraded pyrolysis oil had lower contents of organic acids, aldehydes, ketones, and ethers than the feed, whereas the amounts of phenolics, aromatics, and alkanes were considerably higher.
a b s t r a c t The biodiesel production from a naturally isolated strain of Chlorella in 2 L bubble-column photobioreac-tor was studied. The microalgal strain was isolated from the rice paddy-field soil samples during a screen-ing program. After 17 days, at the end of exponential phase of growth, the total content of the lipids was extracted. The extracted fatty acids were first esterified and then identified using GC/MS analysis. Several types of fatty acid methyl esters (FAMEs) were identified in the isolated microalga and the presence of saturated fatty acids in Chlorella sp. MCCS 040 was approved. The composition of fatty acids in the studied species of microalga was mainly palmitic acid methyl ester, myristic acid methyl ester, stearic acid methyl ester and undecanoic acid methyl ester. This strain because of its highly saturated fatty acids con-tent can be an ideal candidate for biodiesel production.
In the current scenario of depleting energy resources, increasing food insecurity and global warming, Jatropha has emerged as a promising energy crop for India. The aim of this study is to examine the life cycle energy balance for Jatropha biodiesel production and greenhouse gas emissions from post-energy use and end combustion of biodiesel, over a period of 5 years. It’s a case specific study for a small scale, high input Jatropha biodiesel system. Most of the existing studies have considered low input Jatropha biodiesel system and have used NEB (Net energy balance i.e. difference of energy output and energy input) and NER (Net energy ratio i.e. ratio of energy output to energy input) as indicators for estimating the viability of the systems. Although, many of them have shown these indicators to be positive, yet the values are very less. The results of this study, when compared with two previous studies of Jatropha, show that the values for these indicators can be increased to a much greater extent, if we use a high input Jatropha biodiesel system. Further, when compared to a study done on palm oil and Coconut oil, it was found even if the NEB and NER of biodiesel from Jatropha were lesser in comparison to those of Palm oil and Coconut oil, yet, when energy content of the co-products were also considered, Jatropha had the highest value for both the indicators in comparison to the rest two.
a b s t r a c t This article reports the results of the screening of microalgae capable of removing nitrogen and phospho-rus while accumulating lipids in effluents from secondary domestic wastewater treatment. Twenty strains were tested for their growth capacity; the growth parameters of 13 strains were determined, and the following three strains were selected and cultivated in photobioreactors: the isolated and unknown LEM-IM 11, Botryococcus braunii and Chlorella vulgaris. The capacity of each strain to remove nitrogen and phosphorus as well its growth rate and biomass composition was determined. B. braunii LEM 14 showed the best combined results and is a good candidate for the development of a large-scale process. From the treated domestic wastewater, 79.63% of the nitrogen and phosphorus was removed after 14 days of culture at 25 °C. Biomass composition indicated an oil accumulation (36% dry weight) and high carbon uptake (144.91 mg CO 2 g À1 biomass L À1 day À1). Fatty acid methyl ester analysis showed a pre-dominance of palmitic (C16:0) and oleic (C18:1) acids, with considerable amounts of stearic (C18:0), lin-oleic (C18:2) and alpha-linolenic (C18:3) acids.
Marine microalgae are recognised as an important renewable source of bioactive lipids with a high proportion of polyunsaturated fatty acids (PUFA), which have been shown to be effective in preventing or treating several diseases. For the extraction of oil from microalgae, supercritical CO2 (ScCO2) is regarded with interest, being safer than hexane and offering a negligible environmental impact, a short extraction time and a high-quality final product. Whilst some experimental papers are available on the supercritical fluid extraction (SFE) of oil from microalgae, only limited information exists on the kinetics of the process. In such a contest, a mathematical model able to describe the kinetics of the SFE was applied to the recovery with ScCO2 of lipids from Nannochloropsis sp., a marine microalga commonly used in aquaculture and characterised by a lipid fraction with a high PUFA content. The aim of this paper was to examine the effect of operating conditions on the kinetics of the SFE, on process yields and on the fatty acid composition of lipid extracts.