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The research in this project looks forward to the large-scale production of algal biodiesel which requires both higher productivity and lower cultivation costs. The first generation of large-scale processes is likely to use natural algal species that have already been cultivated at an industrial scale (such as Dunaliella). Manipulation of environmental factors (media, biodiversity) provides an effective way to optimize lipid production and this thesis presents several studies in this direction. We investigated the effect of nitrogen deprivation on overall lipid productivity. Fourier transform infrared spectroscopy (FTIR) was applied to determine the accumulation of lipids over time. Our results suggest that the FTIR signal at 2926 cm-1 (rather than 1740 cm-1) is better for measuring lipids, and the principal component analysis (PCA) of the full spectrum showed a clear separation between the nitrogen replete and nitrogen depleted cells. The only stress condition that gave significantly higher total lipid production was the treatment with highest cell density inoculum. We also investigated low cost, ammonia and urea containing medium. We found considerably higher growth rate for Nannochloropsis salina in an inexpensive medium of seawater and agricultural fertiliser as compared to that in standard f/2 medium. We have found that Nannochloropsis prefers ammonia to nitrate as a nitrogen source and we found that biomass productivity reached 0. 352 g L-1 day-1 after 10 days in the low-cost medium compared to 0.106 g L-1 day-1 in the f/2 medium. The lipid productivity of algae grown in the low-cost medium was also higher than that in the f/2 medium (0.082 g L-1 day-1 versus 0.033 g L-1 day-1). The lipid productivity was higher than the highest published value for the Nannochloropsis species (0.076 g L-1 day-1). Another important contribution of this work was to investigate the performance of polycultures. We showed that a polyculture of two species, Dunaliella salina and Nannochloropsis gaditana, produces an average of 2.2 times more biomass than the corresponding monocultures. Moreover, the lipid productivity of the polyculture is 8.3 times the highest values of recently published work for Nannochloropsis and Dunaliella. The optimization of nutrient supply to benefit the coexistence of Dunaliella salina and Nannochloropsis gaditana was performed by the response surface method (RSM). We also investigated the interaction between the media and more diverse polycultures consisting of two species of Dunaliella salina (Dunaliella salina 30/18 and 19/18) and three species of Nannochloropsis spp. (Nannochloropsis oculata, Nannochloropsis salina and Nannochloropsis gaditana). This polyculture produced an average of 6-fold more biomass when grown on the low cost media as compared to the defined lab media (f/2). The most diverse polyculture had the highest value of growth rate, biomass and lipid productivity (1.0111 day-1, 1.2 g L-1 day-1 and 0.3104 g L-1 day-1, respectively). The biomass concentration reached 1.19 g L-1 for the polyculture in 10 days starting from 0.0026 g L-1. Moreover, the lipid productivity is around seven times the highest values of recently published work for Nannochloropsis and Dunaliella. The new medium is more than 1000 times cheaper than the f/2 medium (Sigma price). In conclusion, we have demonstrated, for an industrially important species, that growth rate is more important than lipid content for overall lipid productivity. This suggests that complex stressing strategies (e.g. by nitrogen deprivation) may not be economically advantageous. Given the importance of biomass productivity, therefore, we have investigated two environmental factors that affect growth rates and which are relevant to large-scale production. Firstly, we have shown that new low cost medium can actually lead to superior growth to that achievable on expensive standard media. Secondly, we have shown that diverse cultures can be more productive than monocultures. This suggests that huge problems of limiting contamination in large-scale processes (in order to maintain pure cultures) can be avoided.
Biofuels made from algae are gaining attention as a domestic source of renewable fuel. However, with current technologies, scaling up production of algal biofuels to meet even 5 percent of U.S. transportation fuel needs could create unsustainable demands for energy, water, and nutrient resources. Continued research and development could yield innovations to address these challenges, but determining if algal biofuel is a viable fuel alternative will involve comparing the environmental, economic and social impacts of algal biofuel production and use to those associated with petroleum-based fuels and other fuel sources. Sustainable Development of Algal Biofuels was produced at the request of the U.S. Department of Energy.
This edited volume focuses on comprehensive state-of-the-art information about the practical aspects of cultivation, harvesting, biomass processing and biofuel production from algae. Chapters cover topics such as synthetic ecological engineering approaches towards sustainable production of biofuel feedstock, and algal biofuel production processes using wastewater. Readers will also discover more about the role of biotechnological engineering in improving ecophysiology, biomass and lipid yields. Particular attention is given to opportunities of commercialization of algal biofuels that provides a realistic assessment of various techno-economical aspects of pilot scale algal biofuel production. The authors also explore the pre-treatment of biomass, catalytic conversion of algal lipids and hydrothermal liquefaction with the biorefinery approach in detail. In a nut shell, this volume will provide a wealth of information based on a realistic evaluation of contemporary developments in algal biofuel research with an emphasis on pilot scale studies. Researchers studying and working in the areas of environmental science, biotechnology, genetic engineering and biochemistry will find this work instructive and informative.
Extensive effort is being made globally to develop various biofuels as an inexhaustible and renewable energy source. Biofuels are viewed as promising alternatives to conventional fossil fuels because they have the potential to eliminate major environmental problems such as global warming and climate change created by fossil fuels. Among the still-developing biofuel technologies, biodiesel production from algae offers a good prospect for large-scale practical use, considering the fact that algae are capable of producing much more yield than other biofuels such as corn and soybean crops. Although research on algae-based biofuel is still in its developing stage, extensive work on laboratory- and pilot-scale algae-harvesting systems with promising prospects has been reported. This chapter presents a discussion of the literature review of recent advances in algal biomass harvesting. The chapter focuses on stability and separability of algae and algae-harvesting methods. Challenges and prospects of algae harvesting are also outlined. The review aims to provide useful information for future development of efficient and commercially viable algal biodiesel production.
The edited book presents sustainable adopting options in basic research for improving algal biofuels production. This book is probably first book on algal biofuels which is focused on improving the primary basic research to enhance mass scale technological production of algal biofuels. The book explores significance of basic bench top research to increase pilot scale production of algal biofuels. The books also targeting the most sustainable and economical algal biofuels option with in depth details. Further, it highlights the existing roadblock, their analysis and eco-friendly solution to control them in most greenery way. This book is highly useful for academician, researchers and industries professionals and of high interest for students of bioenergy, sustainable practices and renewable energy.
Biofuels produced from agricultural starch, sugar and oil crops such as corn, sugarcane, and palm, or first-generation biofuels, are produced at commercial scales worldwide. Though most biofuels are produced with the intent to reduce greenhouse gas (GHG) emissions and fossil fuel dependency, these first-generation biofuels have increasingly been shown to be problematic; achieving little to no reduction in GHG emissions compared to their fossil fuel counterparts, competing with food and feed crops, and causing direct and indirect land use change. Second generation biofuel feedstocks, such as microalgae, are hoped to reduce or eliminate the drawbacks of first-generation feedstocks. This dissertation investigates the environmental impacts of biodiesel production from microalgae, with the main focus on primary energy requirements and life cycle GHG emissions. The dissertation includes a critical review of existing studies; a mass balance model of a simulated microalgae biodiesel production system; a detailed life cycle assessment (LCA) of the production system with a variety of technology options for each step of the production process; and a scenario analysis with alternative utilization scenarios for the primary co-product from the system, lipid-extracted algal biomass residual. In addition to assessing and informing technology choices and strategies for environmentally preferable pathways among current algal biodiesel technologies, this research also addresses an important methodological issue in LCA, co-product allocation, and proposes some possible solutions to reduce the uncertainty caused by this issue. Results of the critical review show that significant variation exists among existing LCA studies of algal biodiesel production, which arises from inconsistency in both parameter assumptions and methodological choices. Even after a meta-analysis was conducted, which corrected for some differences in scope and key assumptions, the reviewed studies show a large range in life cycle primary energy and GHG emissions; 0.2 to 8.6 MJ per MJ of algal biodiesel, and -30 to 320 g of CO2e per MJ of algal biodiesel. This range is so large that very little can be concluded regarding the potential for algal biodiesel to meet the goals of second-generation biofuels, and provides the motivation for development an independent and original model for algal biodiesel production. A mass balance model for an integrated algal oil and biogas system was developed to understand nutrient, water and carbon flows and identify recycling opportunities. The model showed that recycling growth media and recovering nutrients from residual algal biomass through anaerobic digestion can reduce the total demand for nitrogen (N) and phosphorus (P) by 66% and 35%, respectively. Freshwater and carbon dioxide requirements can also be reduced significantly under these conditions. The mass balance model provided the basis for developing a LCA model capable of incorporating multiple technology options and identifying preferable pathways. The LCA found the best performing scenario consists of normal nitrogen cultivation conditions (as opposed to nitrogen deficient conditions which can increase algal lipid content, but decrease overall productivity), a combination of bioflocculation and dissolved air flotation for harvesting algal cells from cultivation media, centrifugation for dewatering of separated algae, oil extraction from wet biomass using hexane solvent, transesterification of algal oil to biodiesel, and anaerobic digestion of biomass residual with the liquid digestate returning to cultivation ponds. This pathway results in a life cycle energy requirement and GHG emissions of 1.08 MJ and 73 g CO2-equivalent per MJ of biodiesel, with cultivation and oil extraction dominating energy use and emissions. This result suggests that current technologies can neither achieve a positive net energy return for algal biodiesel, nor achieve substantial reductions in CO2e emissions compared to petroleum diesel. A comparison between different scenarios for using the major co-product from algae biodiesel production, lipid-extracted algal biomass residual, suggests that utilizing the co-product within the production system for nutrient and energy recovery is preferable than utilizing it outside as animal feed from a life cycle perspective. A number of possible ways to allocate the environmental burdens between co-products were tested. Among them, system expansion and economic allocation return favorable results compared value-based allocation methods; however, there are still unsolved issues when applying system expansion, for example, current practices do not consider future market values in the context of a consequential LCA. This dissertation shows that the near-term performance of biodiesel derived from microalgae does not achieve the significant reductions in fossil energy dependence and GHG emissions hoped for from second-generation feedstocks. Furthermore, there is substantial uncertainty in technology performance and other key modeling parameters that could influence these findings. However, some promising, but still uncertain technologies, such as hydrothermal gasification, have the potential to achieve greater reduction in life cycle GHG emissions and energy consumption.
This book critically discusses different aspects of algal production systems and several of the drawbacks related to microalgal biomass production, namely, low biomass yield, and energy-consuming harvesting, dewatering, drying and extraction processes. These provide a background to the state-of-the-art technologies for algal cultivation, CO2 sequestration, and large-scale application of these systems. In order to tap the commercial potential of algae, a biorefinery concept has been proposed that could help to extract maximum benefits from algal biomass. This refinery concept promotes the harvesting of multiple products from the feedstock so as to make the process economically attractive. For the last few decades, algal biomass has been explored for use in various products such as fuel, agricultural crops, pigments and pharmaceuticals, as well as in bioremediation. To meet the huge demand, there has been a focus on large-scale production of algal biomass in closed or open photobioreactors. Different nutritional conditions for algal growth have been explored, such as photoautotrophic, heterotrophic, mixotrophic and oleaginous. This book is aimed at a wide audience, including undergraduates, postgraduates, academics, energy researchers, scientists in industry, energy specialists, policy makers and others who wish to understand algal biorefineries and also keep abreast of the latest developments.
This volume, The Science of Algal Fuels (volume 25 of COLE), contains 26 chapters dealing with biofuels contributed by experts from numerous countries and covers several aspects of algal products, one being “oilgae from algae,” mainly oils and fuels for engines. Among the prominent algal groups that participate in this process are the diatoms and green algae (Chlorophyceae). Their metabolism and breeding play an important role in biomass and extraction of crude oil and algal fuel. There is a strong relation between solar energy influencing algal culture and the photobiology of lipid metabolism. Currently, many international meetings and conferences on biofuel are taking place in many countries, and several new books and proceedings of conferences have appeared on this topic. All this indicates that this field is “hot” and in the forefront of applied bioscience.
Microalgae Cultivation for Biofuels Production explores the technological opportunities and challenges involved in producing economically competitive algal-derived biofuel. The book discusses efficient methods for cultivation, improvement of harvesting and lipid extraction techniques, optimization of conversion/production processes of fuels and co-products, the integration of microalgae biorefineries to several industries, environmental resilience by microalgae, and a techno-economic and lifecycle analysis of the production chain to gain maximum benefits from microalgae biorefineries. Provides an overview of the whole production chain of microalgal biofuels and other bioproducts Presents an analysis of the economic and sustainability aspects of the production chain Examines the integration of microalgae biorefineries into several industries