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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.
Fossil-fuel depletion and attempts at global-warming mitigation have motivated the development of biofuels. Several feedstock and transformation pathways into biofuel have been proposed as an alternative to the usual fuels. Recently, microalgae have attracted a good deal of attention because of the promise of reduced competition with food crops and lowered environmental impacts. Over the last years, several life-cycle assessments (LCAs) have been realized to evaluate the energy benefit and potential global-warming reduction of biofuel and bioenergy produced from microalgae. This chapter presents a bibliographic review of 15 LCAs of microalgae production and/or transformation into biofuel. These studies often differ by the perimeter of the study, the functional unit, and the production technologies or characteristics. Methods for environmental impact assessment and the energy balance computation also diverge. This review aims to identify the main options and variations among LCAs and concludes with some recommendations and guidelines to improve the contribution of an LCA and to facilitate comparisons among studies.
This book presents an authoritative and comprehensive overview of the production and use of microalgal biomass and bioproducts for energy generation. It also offers extensive information on engineering approaches to energy production, such as process integration and process intensification in harnessing energy from microalgae. Issues related to the environment, food, chemicals and energy supply pose serious threats to nations’ success and stability. The challenge to provide for a rapidly growing global population has made it imperative to find new technological routes to increase the production of consumables while also bearing in mind the biosphere’s ability to regenerate resources. Microbial biomass is a bioresource that provides effective solutions to these challenges. Divided into eight parts, the book explores microalgal production systems, life cycle assessment and the bio-economy of biofuels from microalgae, process integration and process intensification applied to microalgal biofuels production. In addition, it discusses the main fuel products obtained from microalgae, summarizing a range of useful energy products derived from algae-based systems, and outlines future developments. Given the book’s breadth of coverage and extensive bibliography, it offers an essential resource for researchers and industry professionals working in renewable energy.
Biodiesel produced from microalgal lipids is being extensively researched as an alternative to petroleum-derived diesel. Literature reports of prior modeling to estimate the likely energy and carbon footprints and manufacturing cost of microalgal biodiesel are inconclusive, with wide ranges for performance measures such as Net Energy Return and manufacturing cost. The goals of this research are to develop an integrated techno-economic life cycle inventory model of microalgal biodiesel production, create a base case that simulates proven manufacturing processes, identify potential barriers to technical, financial, and/or environmental viability, perform sensitivity analyses that identify the input parameters and modeling assumptions that have significant influence on key biodiesel performance indicators (KPI's), and perform case studies involving alternative microalgal properties, manufacturing processes and operating conditions, modeling time-scales, and geographic locations. The model created to meet these objectives, called TELCIM, is the first publicly available, integrated techno-economic life cycle inventory model of microalgal biodiesel manufacture. It consists of a set of interlinked engineering, financial, and life cycle inventory models. It is implemented in Microsoft Excel®, and simulates a five-step manufacturing process consisting of microalgae cultivation, biomass harvesting, lipid extraction, lipid conversion to biodiesel, and anaerobic digestion of residual biomass. Material and energy flows are estimated using mass and energy balances and equipment performance equations. Operating and capital costs are estimated using standard accounting methods, and a cradle-to-gate life cycle inventory of energy and resource consumptions and pollutant releases is compiled. Detailed descriptions of TELCIM's component physical models, along with the derivation of their governing equations, are provided. TELCIM was initially populated with data representing conventional microalgae cultivation and harvesting and vegetable oil extraction and conversion technologies deployed in a southern California location. The Net Energy Return for this case is below 1.0, the minimum threshold for long-term sustainability; the carbon intensity is similar to that of petrodiesel; and the manufacturing cost is uncompetitive with current transportation fuels. Detailed breakdowns show the contributions of each major process step and use category to these performance metrics, allowing identification of the major barriers to viability. Among the biggest obstacles is the large amount of energy used to dry the biomass to the 10% residual moisture content required by the conventional oilseed extraction process. Two types of single-parameter sensitivity analyses are used to identify input parameters that have significant influence on the KPI's. Tornado plots reveal that biological properties including lipid fraction, intracellular water content, and growth rate are among the most influential with respect to one or more of the KPI's. Trend analyses of several of the anaerobic digester operating parameters show that factors affecting biogas production have much stronger influence on the KPI's than factors relating to nutrient recovery. Several variants to the base case were performed, including cases in which the microalga's growth rate and lipid content conform to R & D targets established by the National Alliance for Advanced Biofuels and Bioproducts; a hypothetical wet extraction process allows the drying step to be bypassed; and there is no anaerobic digestion step. The results from these cases suggest that one or more breakthroughs in cell biology and/or process engineering are necessary to make microalgal biodiesel a sustainable large-scale alternative to petroleum diesel. They also show that including anaerobic digestion in the manufacturing scheme improves the KPI's of greatest interest, and delivers an acceptable financial return on incremental investment. TELCIM is a steady-state model, and the climatological data used in the base case represents annual average conditions. The effects of monthly variations in sunlight intensity are simulated under several facility design bases and operating strategies; it appears that designing for maximum sunlight intensity is more cost and energy effective, but necessitates underutilization of available carbon dioxide and reduces the biodiesel production rate. Enhancing the correlation between sunlight intensity and microalgal growth rate to account for the effect of light saturation on photosynthetic efficiency significantly dampens seasonal variations in biomass productivity. Analysis of hourly average versus daily average sunlight intensity indicates that daily average data is sufficiently precise if the long-term average biomass productivity is known; otherwise substantial error can be introduced if biomass productivity is estimated directly from sunlight intensity data, and daily average data is used instead of hourly average data. Five alternative manufacturing locations along the southern rim of the continental United States are simulated using local climatological inputs, including sunlight intensity. The only performance measure that differs significantly among these sites is water intensity, which is predicted to be much lower east of the Rockies due to higher precipitation rates. Several supporting analyses are also presented in the dissertation, including a comparison of the composition of microalgal and soy lipids, which addresses the assumption that conventional oilseed extraction and conversion technologies will be effective with microalgal biomass as a substrate. The mechanisms of oil extraction, and the effects of residual water on extraction efficiency, are explored in an attempt to optimize evaporation energy load and oil yield. The impact of ambient temperature and relative humidity, dryer operating conditions, and dryer control strategies, on the energy burden imposed by biomass drying, are evaluated. And a multi-parameter sensitivity analysis explores the effect of potential interdependencies among biomass growth rate, intracellular water content, and lipid fraction on the KPI's. Additional findings from this research include that microalgal properties affect virtually every step of the manufacturing process; TELCIM can be used to identify optimal strain characteristics for a given processing scheme. The bulk of the energy use and carbon dioxide emissions attributable to the cradle-to-gate manufacturing process occur within the biodiesel plant, but offsite emissions resulting from energy and raw material supply and transportation activities are not negligible. The main driver of Net Energy Return, carbon intensity and unit manufacturing cost is electricity usage, primarily for pumping fluids over long distances. Replacing evaporation losses can impose an enormous water burden, perhaps overwhelming local supplies, especially in the western United States. TELCIM is a deterministic model; for a given set of input data it returns a set of numerical outputs without any measures of uncertainty or error. Recommendations for future work include an uncertainty analysis involving Monte Carlo simulations. They also include enhancing TELCIM to perform life cycle assessments, by assigning specific fates to byproducts and gauging the environmental impacts of resource usages and pollutant emissions. TELCIM can be modified to simulate alternative manufacturing schemes, such as feeding the biogas produced in the digesters to the central power unit, using the algae ponds for secondary wastewater treatment, and separate growth stages in which biomass production and lipid production are alternately promoted. Finally, the case studies simulating alternative manufacturing sites can be enhanced by using local operating and capital cost structures, especially for those sites in the southeastern United States that appear to have a more acceptable water intensity.
Microalgae can be future resource for industrial biotechnology In current energy crisis era, microalgae are under tremendous research focus for the production of biodiesel due to their high photosynthetic efficiency, growth rate and high lipid content compared to territorial plants. However, the large-scale production of algal biomass and downstream processing of harvested algae towards bio-fuels are facing several challenges from economic viability perspective. Apart from bio-fuels, the microalgae synthesize number of bio-molecules such as pigments (e.g., chlorophyll, carotenoid), protein (e.g., lectin, phycobiliprotein), and carbohydrates (e.g., agar, carrageenan, alginate, fucodian) which are available in the various forms of microalgal products. Therefore, developing a strategy for large-scale production and use of algal biomass for the co-production of these value-added macromolecules is thus imperative for the improvement of the economics of algal biorefinery. In the above context, this book covers three major areas (i) commercial-scale production of bio-molecules from microalgae, (ii) sustainable approach for industrial-scale operation, and (iii) optimization of downstream processes. Each of these sections is composed of several chapters written by the renowned academicians/industry experts. Furthermore, in this book, a significant weightage is given to the industry experts (around 50%) to enrich the industrial perspectives. We hope that amalgamate of fundamental knowledge from academicians and applied research information from industry experts will be useful for forthcoming implementation of a sustainable integrated microalgal biorefinery. This book highlights following. Explores biomolecules from microalgae and their applications Discusses microalgae cultivations and harvesting Examines downstream processing of biomolecules Explores sustainable integrated approaches for industrial scale operations Examines purification techniques specific for microalgal proteins, Omega 3 fatty Acids, carbohydrates, and pigments
Handbook of Algal Biofuels: Aspects of Cultivation, Conversion and Biorefinery comprehensively covers the cultivation, harvesting, conversion, and utilization of microalgae and seaweeds for different kinds of biofuels. The book addresses four main topics in the algal biofuel value-chain. First, it explores algal diversity and composition, covering micro- and macroalgal diversity, classification, and composition, their cultivation, biotechnological applications, current use within industry for biofuels and value-added products, and their application in CO2 sequestration, wastewater treatment, and water desalination. Next, the book addresses algal biofuel production, presenting detailed guidelines and protocols for different production routes of biodiesel, biogas, bioethanol, biobutanol, biohydrogen, jet fuel, and thermochemical conversation methods. Then, the authors discuss integrated approaches for enhanced biofuel production. This includes updates on the recent advances, breakthroughs, and challenges of algal biomass utilization as a feedstock for alternative biofuels, process intensification techniques, life cycle analysis, and integrated approaches such as wastewater treatment with CO2 sequestration using cost-effective and eco-friendly techniques. In addition, different routes for waste recycling for enhanced biofuel production are discussed alongside economic analyses. Finally, this book presents case studies for algal biomass and biofuel production including BIQ algae house, Renewable Energy Laboratory project, Aquatic Species Program, and the current status of algal industry for biofuel production. Handbook of Algal Biofuels offers an all-in-one resource for researchers, graduate students, and industry professionals working in the areas of biofuels and phycology and will be of interest to engineers working in renewable energy, bioenergy, alternative fuels, biotechnology, and chemical engineering. Furthermore, this book includes structured foundational content on algae and algal biofuels for undergraduate and graduate students working in biology and life sciences. Provides complete coverage of the biofuel production process, from cultivation to biorefinery Includes a detailed discussion of process intensification, lifecycle analysis and biofuel byproducts Describes key aspects of algal diversity and composition, including their cultivation, harvesting and advantages over conventional biomass
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.
Life-Cycle Assessment of Biorefineries, the sixth and last book in the series on biomass-biorefineries discusses the unprecedented growth and development in the emerging concept of a global bio-based economy in which biomass-based biorefineries have attained center stage for the production of fuels and chemicals. It is envisaged that by 2020 a majority of chemicals currently being produced through a chemical route will be produced via a bio-based route. Agro-industrial residues, municipal solid wastes, and forestry wastes have been considered as the most significant feedstocks for such bio-refineries. However, for the techno-economic success of such biorefineries, it is of prime and utmost importance to understand their lifecycle assessment for various aspects. Provides state-of-art information on the basics and fundamental principles of LCA for biorefineries Contains key features for the education and understanding of integrated biorefineries Presents models that are used to cope with land-use changes and their effects on biorefineries Includes relevant case studies that illustrate main points
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.
The cultivation of fish and shellfish larvae under controlled hatchery conditions requires not only the development of specific culture techniques, but in most cases also the production and use of live food organisms as feed for the developing larvae. The present manual describes the major production techniques currently employed for the cultivation of the major types of live food commonly used in larviculture, as well as their application potential in terms of their nutritional and physical properties and feeding methods. The manual is divided into different sections according to the major groups of live food organisms used in aquaculture, namely micro-algae, rotifers, Artemia, natural zooplankton, and copepods, nematodes and trochophores.