Algal Biofuel Research Articles

Experimental Investigation for Determining an Ideal Algal Biodiesel-Diesel Blend to Improve the Performance and Mitigate Emissions Using a Response Surface Methodology.

The ongoing depletion of the world's fossil fuel sources and environmental damage has compelled the quest for alternative energy. Excellent characteristics of biodiesel include its renewable nature, safety, absence of sulfur, environmental advantages, and biodegradability, which can eradicate the above problems. In this study, algal oil was characterized to obtain the fatty acid profile, and the free fatty acid value of algal oil suggested a two-step process of esterification and transesterification for efficient biodiesel production. The performance and emission results of biodiesel and its blends (B10, B20, and B30) were investigated in a constant speed, single-cylinder, 4-stroke, 3.5 kW compression ignition engine at different loads for arriving at an appropriate fuel blend ratio. The response surface methodology technique is used to predict the ideal composition of microalgae-diesel using the experimental data with due weightage for the optimization criterion. The predicted blend ratio of B25 was tested on the engine and authenticated. The findings recorded an improvement in brake thermal efficiency to 31.42% and reduction in brake specific energy consumption to 9.82 MJ/kW h, unburned hydrocarbon to 85 ppm, carbon monoxide to 0.164% v/v, carbon dioxide to 4.115% v/v, nitrogen oxides to 691 ppm, and smoke opacity to 16.93%.

Conversion of Sugar Di-Ketals to Bio-Hydrocarbons through Catalytic Cracking over Beta Catalysts in Fixed and Fluidized Catalytic Beds

Second-generation biomass (BM) can be produced in amounts that meet worldwide fuel demands. However, BM favors parallel and undesirable reactions in its transformation chain. We circumvent this problem by first modifying BM by ketalization, giving a user-friendly liquid we named BP (bio-petroleum). This study converted a representative compound of BP, DX (1,2:3,5-di-O-isopropylidene-α-D-xylofuranose), mixed with n-hexane by beta zeolites and catalysts containing beta zeolite. Beta zeolite showed low coke and high liquid product yields in converting this mixture (having 30 wt. % DX) into hydrocarbons in a fixed-bed reactor at 500 °C with a space velocity of 16 h−1 (0.3 catalyst/feed). Its performance was further improved by steam treatment (lowering the coke yield by lowering the acid site density) or incorporation into a catalyst (improving DX participation due to the active sites in the matrix). Further, by changing the conversion process from a fixed bed to a fluidized cracking unit, a much larger amount of the deactivated catalyst could be used (catalyst/feed = 3), remarkably reducing oxygenates and fully converting DX. Additionally, the green hydrocarbon efficiency (olefin, aromatics, furans, and cyclo-alkanes) of DX was approximately 77%. Hence, beta catalysts were shown to have a great potential to provide green fuels for future bio-refineries.

Experimental investigation on performance and emission characteristics of algae oil biodiesel with methanol additive in CI engine

Due to the depletion of fossil fuels, the world is moving towards alternate fuels or resources. Algae is the most abundant and easily available food source in the world. This will be enough to meet the future fuel requirement. Though using pure algae biofuel is not feasible. Initially, the proper proportion of algae to diesel is to be fixed. The efficiency of mixing diesel and oil with algae and methanol in certain quantities is analyzed to improve the performance and pollution of diesel engines. An algae biodiesel with a methanol blend in three proportions, such as B10, B20 and B30 is taken. In this investigation, B10 (90% + Diesel + Algae oil 7.5% + Methanol 2.5%) and B20 (Diesel 80% + Algae Oil 15% + Methanol 5%) and B30 (70% Diesel + Algae 22.5% + Methanol 7.5%) are taken for the experimental tests and performed on a diesel engine. The blends of B10, B20, B30 is given as input to the CI engine and various performance parameters like brake power, torque, mean effective pressure and etc., are considered in this analysis. The effects of various pollutants like HC, CO, CO2 and NOx emissions were compared to diesel fuel emission. B20 biodiesel is very close to pure diesel fuel performance as compared with B10 and B30. There is slight increase in HC and CO emissions but NOx emission is reduced considerably for all blends.

Experimental Investigation on the PCCI Engine Fueled by Algal Biodiesel Blend with CuO Nanocatalyst Additive and Optimization of Fuel Combination for Improved Performance and Reduced Emissions at Various Load Conditions by RSM Technique.

Fossil fuel depletion and environmental pollution are paramount problems the world faces. Despite several measures, the transportation industry is still battling to manage these issues. A combined approach of fuel modification for low-temperature combustion with combustion enhancers could offer a breakthrough. Due to their properties and chemical structure, biodiesels have piqued the interest of scientists. Studies have asserted that microalgal biodiesel might be a viable alternative. Premixed charge compression ignition (PCCI) is an easily adoptable promising low-temperature combustion strategy in compression ignition engines. The objective of this study is to identify the optimal blend and catalyst measure for improved performance and reduced emissions. Microalgae biodiesel at various proportions (B10, B20, B30, and B40) was amalgamated with CuO nanocatalyst and tested to arrive at the right concoction of biodiesel with nanoparticles in a 5.2 kW CI engine for different load conditions. The PCCI function warrants that about 20% of the fuel supplied is vaporized for premixing. Finally, the interplay factors of the independent variables of the PCCI engine were then explored by response surface methodology (RSM) to determine the optimal level of desired dependent and independent variables. The RSM experiment findings suggest that the best biodiesel and nanoparticle concoctions at 20%, 40%, 60%, and 80% loads were B20CuO76, B20Cu60, B18CuO61, and B18CuO65, respectively. These findings were experimentally validated.

Using Algae for Biofuel Production: A Review

One of the greatest challenges of the 21st century is to obtain an ecological source of transport fuels. The production of biofuels based on feedstock obtained through the exploitation of arable land translates into an increase in food prices and progressive degradation of the environment. Unlike traditional agricultural raw materials, algae are a neutral alternative in many respects. They can even be obtained as waste from polluted water reservoirs. One of the manifestations of the deterioration of surface waters is the eutrophication of water reservoirs, which leads to an increase in the number of algae. Algae reaching the shores of water reservoirs can be used as a raw material for the production of biofuels, including biogas, bioethanol and biodiesel. However, it should be remembered that water blooms are a periodic phenomenon, appearing in the summer months. Therefore, in order to ensure the continuity of obtaining energy from biomass, it is necessary to conduct algae cultivation in artificial open tanks or photobioreactors. Accordingly, this review first briefly discusses the properties and possible applications of different species of algae in various industrial areas, and then describes the process of eutrophication and the presence of algae in eutrophicated reservoirs. Technologies of algal cultivation in various systems and technologies of algal biomass pretreatment were critically discussed. Various methods of obtaining biomass from algae were also reviewed, and the process conditions were summarized. Biofuels of various generations and raw materials from which they are obtained are presented in order to determine the possible future directions of development in this field. Parameters affecting the selection of algae species for the production of biofuels were also examined and presented. Overall, algal biofuels still face many challenges in replacing traditional fossil fuels. Future work should focus on maximizing the yield and quality of algae-derived biofuels while increasing their economic viability.

Impacts of Fungal Disease on Algal Biofuel Systems: Using Life Cycle Assessment to Compare Control Strategies.

While climate change has incentivized attention on sustainable fuel sources, algae has positioned itself as a both promising and problematic biofuel feedstock. Diseases such as fungal pathogens cause costly algal feedstock crashes, but the life cycle assessments (LCAs) used to analyze the viability of algal feedstocks for biofuel have yet to consider the impact of disease on life cycle metrics. Here, we incorporate a disease model into a well-documented LCA for algal biorefineries to compare two sustainability metrics, energy return on investment (EROI) and global warming potential (GWP). We begin by showing that failure to consider disease leads to overly optimistic LCA metric outputs. Then, we compare two leading control strategies of disease─chemical and biological. Our analyses show that biological engineering of a multispecies consortium of algae has a greater positive impact on LCA metrics than chemical control of the fungal pathogen using a fungicide. We expand how and when bi-cultures might advantageously exhibit the "dilution effect" whereby differentially susceptible species exhibit compensatory dynamics that stabilize feedstock production. Our results emphasize the impact of disease and suggest that multispecies consortia of algae can be biologically engineered to reduce greenhouse gas emissions and improve the economic viability of biofuel.

Outdoor annual algae productivity improvements at the pre-pilot scale through crop rotation and pond operational management strategies

The Development of Integrated Screening, Cultivar Optimization, and Verification Research (DISCOVR) collaborative consortium operated pre-pilot scale outdoor ponds to deliver much-needed multi-year, long-term and consistent, algae cultivation data relevant to understanding the current state of technology in terms of expected seasonal algae biomass productivity. Over the course of four years from 2018 to 2021, twelve identical 4.2 m2 mini-ponds were run in triplicate sets to test strains and operational strategies demonstrated in small-, indoor photobioreactors, in pursuit of increasing overall algae areal productivity and projected farm yield. Fourteen different cultivars derived from a strain screening pipeline were tested. Through deliberate seasonal crop rotation and improvements in operational strategies, annual biomass productivity increased from 11.6 to 17.6 g m−2 day−1, a > 50 % increase over the 2018 baseline. Both brackish and marine strains were included and four out of the fourteen strains consistently yielded high productivity across multiple years; brackish strains Monoraphidium minutum (26BAM) and Scenedesmus obliquus (UTEX393), and marine strains Tetraselmis striata (LANL1001) and Picochlorum celeri (TG2). These freely available datasets, which represent nearly complete annual daily coverage of cultivation metrics including weather, pond temperature and pH, nutrients, and productivity, are unique in the public domain and seek to fill agronomic and operational knowledge gaps to help in the eventual commercialization of algal biofuels and bioproducts.

An improved phenol-sulfuric acid method for the quantitative measurement of total carbohydrates in algal biomass

Total carbohydrate analysis with phenol‑sulfuric acid method is the simplest method among many colorimetric and modern instrument analytical methods. It has great potential to be used as a rapid screening method for characterization of algal biomass for algae-based biofuel research. The reproducibility and accuracy of the conventional phenol‑sulfuric method remain to be improved when applied directly to algal biomass. In the present study, several important factors that influenced the colorimetric determination were characterized and methods to eliminate the influences were further developed. Results indicated that system temperature and the addition mode of sulfuric acid and phenol were the key parameters which affected the color development and reproducibility of the conventional methods. A new design using the premixed reagent replacing the individual phenol and sulfuric acid solution solved this problem ideally. The color inferences caused by algal pigments including chlorophylls and carotenoids were quantitatively analyzed. Solutions for reducing overestimation of total carbohydrates were also addressed. In addition, hydrolysis conditions for algae biomass such as type of acids, temperature, and time were also investigated and optimized in this study. The new modified phenol‑sulfuric acid method has been shown to be more reproducible and reliable than the conventional methods for the analysis of total carbohydrates from algal biomass.

Biodiesel Production from Chlorella homosphaera by Two-Step Catalytic Conversion Using Waste Radish Leaves as a Source for Heterogeneous Catalyst.

The economic viability of algal biodiesel can be improved by enhancing the microalgal lipid accumulation and using agricultural waste as a cheap and sustainable source of catalysts. In the current study, the effect of various nitrogen concentrations on the growth and lipid of Chlorella homosphaera were investigated. Furthermore, two-step catalytic conversion was applied to convert the oil of C. homosphaera with high free fatty acids (FFA) to biodiesel using waste radish leaves as a source of a heterogeneous base catalyst. The result revealed that the maximum lipid productivity of 25.0mg L-1day-1 and lipid content of 30.83% were obtained under nitrogen-depleted and limited nitrogen conditions, respectively. The FFA was reduced from 18.79 to 0.76%, and the acid value was decreased from 37.4 to 1.52mg KOH g-1 using a 15:1 methanol to oil molar ratio (MTOR), 1.5 wt.% H2SO4, at 60°C for 150min. Under the optimized conditions, i.e., MTOR of 10:1, 3 wt.% of catalyst ratio for 120min at 60°C, the highest oil conversion of 96.61% was obtained. The physicochemical properties of the produced biodiesel were in the range of the standard specification norms for biodiesel. Hence, the proposed two-step catalytic conversion using calcined radish leaves as a heterogeneous catalyst has thus exhibited good potential for biodiesel production using algal oil with high FFA.

Nanotechnology for improved production of algal biofuels: a review

Nanotechnology for improved production of algal biofuels: a review

The role of microtubules in microalgae: promotion of lipid accumulation and extraction

BackgroundMicrotubules in cells are closely related to the growth and metabolism of microalgae. To date, the study of microalgal microtubules has mainly concentrated on revealing the relationship between microtubule depolymerization and synthesis of precursors for flagellar regeneration. While information on the link between microtubule depolymerization and biosynthesis of precursors for complex organic matter (such as lipid, carbohydrate and protein), is still lacking, a better understanding of this could help to achieve a breakthrough in lipid regulation. With the aim of testing the assumption that microtubule disruption could regulate carbon precursors and redirect carbon flow to promote lipid accumulation, Chlorella sorokiniana SDEC-18 was pretreated with different concentrations of oryzalin.ResultsStrikingly, microalgae that were pretreated with 1.5 mM oryzalin accumulated lipid contents of 41.06%, which was attributed to carbon redistribution induced by microtubule destruction. To promote the growth of microalgae, two-stage cultivation involving microtubule destruction was employed, which resulted in the lipid productivity being 1.44 times higher than that for microalgae with routine single-stage cultivation, as well as yielding a desirable biodiesel quality following from increases in monounsaturated fatty acid (MUFA) content. Furthermore, full extraction of lipid was achieved after only a single extraction step, because microtubule destruction caused removal of cellulose synthase and thereby blocked cellulose biosynthesis.ConclusionsThis study provides an important advance towards observation of microtubules in microalgae through immunocolloidal gold techniques combined with TEM. Moreover, the observation of efficient lipid accumulation and increased cell fragility engendered by microtubule destruction has expanded our knowledge of metabolic regulation by microtubules. Finally, two-stage cultivation involving microtubule destruction has established ideal growth, coupling enhanced lipid accumulation and efficient oil extraction; thus gaining advances in both applied and fundamental research in algal biodiesel production.

Neural-Network-Inspired Correlation (N2IC) Model for Estimating Biodiesel Conversion in Algal Biodiesel Units

Algal biodiesel is of growing interest in reducing carbon emissions to the atmosphere. The production of biodiesel is affected by many process parameters. Although many research works have been conducted, the influence of each parameter on biodiesel production is not well understood when considering a complete system. Therefore, the experimental data from literature sources related to types of algae, methanol-to-algal-oil ratio, temperature, and time on the biodiesel production rate were reviewed and introduced into a neural-network-inspired correlation (N2IC) model to study the rate of transesterification. The developed N2IC model optimized for biodiesel production is based on the studied variables, specifically reaction time, temperature, methanol-to-algal-oil ratio, and type of algae. It was found from ANN analysis that the reaction time is the most significant parameter with 87% importance, followed by temperature (85%), alcohol-to-oil-molar ratio (75%), and type of algae (62%). Using error analysis, the results from the proposed N2IC model show excellent agreement with the experimentally obtained values with an overall 5% error. The results show that the N2IC model can be utilized effectively to solve the problem of industrial biodiesel production when various operating data are readily available.

Effects of sulfur and phosphorus concentration on the lipid accumulation and fatty acid profile in Chlorella vulgaris (Chlorophyta).

Nutrient deficiency induces a variety of cellular responses, including an increase in lipid accumulation in microalgae. Nitrogen starvation is the most studied deprivation. Here, we determine the effects of phosphorus and sulfur limitation on lipid accumulation in Chlorella vulgaris. A set of 9 experiments were performed, varying the initial concentration of these nutrients (set to 0, 50, and 100% of their original composition in Bold's basal medium). According to our results, the variation of P and S modified the specific growth rate, lag phase, and cell generation time. The ratio of 50%P and 0%S significantly increased the total lipid concentration. The fatty acid profile was dominated by C16:0, C18:0, and C18:1; a considerable increase in C20:5 was observed with 0%P and 50%S and 0%P and 100%S. Regarding neutral lipids, the response surface methodology (RSM) indicates that the maximum was observed when S was between 40 and 60% and P was between 95 and 100%. Therefore, the enhanced production of lipids caused by P and S limitation may contribute to the efficient oil production useful for algal biofuels.

Effects of feast-famine nutrient regimes on wastewater algal biofuel communities.

Microalgae accumulate lipids in response to nutrient deprivation, and these lipids are a biodiesel fuel stock. Algal cultivation with secondary wastewater effluent is one proposed platform for biofuel production, which provides nutrients to algae while further polishing wastewater effluent. Algal bioreactors were tested using a feast-famine feeding regiment in simulated secondary wastewater effluent to evaluate the effects on lipid content and algal community structure. Algal polycultures were inoculated into reactors fed with synthetic secondary wastewater effluent at pH 7.5 and 9 and operated under a feast-famine nutrient (N, P, and BOD) supply regime in sequencing batch reactors. Fatty acid methyl ester contents of the reactors were assessed, which showed a decrease in lipid content after the feast-famine cycling (from 12.2% initially to 5.2% after four cycles at pH 9). This decrease in lipid content was not correlated with an increase in carbohydrate storage within biomass, nor an increase in bacterial biomass abundance relative to algal biomass in the reactors. The eukaryotic microbial communities from reactors operated at pH 9 diverged from reactors operated at pH 7.5 during cycling, with the pH 9 reactors becoming dominated by a single Operational Taxonomic Unit aligning to the Scenedesmus genus. These results suggest that high pH and feast-famine nutrient cycling may select for a less diverse algal community with a lower lipid content within a secondary wastewater polishing scheme.

Effect of triacetin as an oxygenated additive in algae biodiesel fuelled CI engine combustion, performance, and exhaust emission analysis

In this experimental investigation, oxygenated additive triacetin is used in an algae oil biodiesel-diesel blend (ABD40) to examine the combustion, performance and exhaust emissions from a single-cylinder 3.5 kW diesel engine. Different percentages of additive (2 %, 4 %, 6 % and 8 % by volume) are mixed in ABD40, and the experiments are performed at varying engine loads by maintaining a fixed engine speed. The combustion results at full load (100 %) reveal that 4 % triacetin in ABD40 achieves high combustion pressure than diesel fuel (DF) and other biodiesel blends. Similarly, a high BTE of 30.39 % is achieved for 4 % triacetin in ABD40 than other biodiesel blends. However, it is 7.23 % lesser than mineral diesel fuel. Due to high density and kinematic viscosity, the fuel consumption for biodiesel blends is recorded as higher than DF. Furthermore, low exhaust emissions are acclaimed for 4 % additive triacetin in ABD40 than DF, and a drop of CO (25.51 %), NOx (12.81 %), UHC (70.53 %) and Smoke (14.85 %) is recorded at 100 % load compared to DF. Hence, it is concluded that 4 % triacetin in ABD40 is the better choice as a diesel fuel replacement, and significant performance and emissions results are possible with the addition of oxygenated additive triacetin, which enhanced fuel properties of high heating value and cetane number.

The Key to A Sustainable Future- Algal Biofuel

The depletion of fossil fuel reserves is posing a significant challenge in meeting the increasing energy demands. In response to concerns related to pollution, global warming, and rising oil costs, the exploration for alternative energy sources has gained momentum. Among these alternatives, macroalgae has emerged as a promising renewable energy option. Furthermore, various alternative fuels, such as hydrogen, natural gas, propane, ethanol, methanol, butanol, vegetable and waste-derived oils, and electricity, can be utilized either in a standalone fuel system or in combination with conventional fuels like gasoline, diesel, and petrol within hybrid-electric or flexible fuel systems. A particularly noteworthy advancement in next-generation biofuels is the production of biofuels derived from microalgae. Although further research is required to optimize algae production methods, equal attention must be given to downstream processing, particularly the generation of biofuels. In the face of the severe global consequences associated with the fossil fuel energy crisis, biofuels are progressively establishing themselves as a potent and sustainable source of renewable energy.

Effects of various alkaline carbonic solutions on the growth of the freshwater algae Chlorophyceae

Modern day fossil fuels are prone to polluting our environment, which can provide major habitat loss to many animals in our ecosystems. Algae-based biofuels have become an increasingly popular alternative to fossil fuels because of their sustainability, effectiveness, and environmentally-friendly nature. To encourage algae growth and solidify its role as an emerging biofuel, we tested basic (in terms of pH) solutions on pond water to determine which solution is most efficient in inducing the growth of algae. We hypothesized that a calcium carbonate solution would induce the most algae bloom, because calcium is a catalyst in photosynthesis. Alkaline carbonate solutions were used to create an optimal environment for the growth of algae; three carbonic alkaline solutions were tested in samples of pond water with algae measured through visible light absorbance using a spectrophotometer. As hypothesized, calcium carbonate induced the most algae growth compared to the control sample, potassium carbonate, and sodium bicarbonate. In conclusion, calcium-containing solutions stimulated algae growth the most, likely due to this solution having properties to stimulate the photosynthetic process by enhancing the transcription and translation process for genes related to chloroplast proteins and enzymes. Our results suggest that calcium is important in enhancing algae growth, which may be important as alternatives for fossil fuels are developed.

Performance test of dual fuel engine using octagonal with algae biodiesel

In comparison to internal combustion engines, diesel engines are high thermal-efficient. However, the application of diesel engines is still dependent on fossil fuels. This fuel has limited availability and the effects are also very dangerous, especially its emission. Octagonal has been used as an alternative fuel to replace fossil-based diesel fuel. The purpose of this work is to explore the performance of the dual fuel engine-octagonal diesel. The performance test has been carried out by running the indirect injection engine that is modified to direct injection at 1500 rpm using four types of like diesel fuel, and diesel mixed with octagonal 2.5, 5 and 10%. The results show that there was an increasing effect of engine-indicated mean effective pressure (IMEP) value and brake-specific fuel consumption (BSFC) reduction when the engine is operated using octagonal diesel fuel blends. The emission of hydrocarbon (HC) tended to increase, while the emission of smoke and carbon monoxide (CO) decreased when the engine is operated using dual fuel-octagonal diesel.

Machine learning for algal biofuels: a critical review and perspective for the future

Machine learning applications in microalgae biofuel production are reviewed; the current states and major trends in research as well as the challenges to overcome are identified.

An investigation of characteristics of a diesel engine with low heat rejection fuelled by spirulina algae biodiesel

An investigation of characteristics of a diesel engine with low heat rejection fuelled by spirulina algae biodiesel