Algal Biofuel Research Articles

Viability of Reclaiming Municipal Wastewater for Potential Microalgae-Based Biofuel Production in the U.S.

Reclaimed municipal wastewater is a crucial component in biofuel production, especially in regions experiencing increasing freshwater scarcity. However, accurately estimating the potential for fuel production is challenging because of the uneven distribution of biofuel feedstock regions and wastewater treatment plants (WWTPs). This study assesses the viability of using reclaimed municipal water for algal biomass production in pond systems co-located with WWTPs under scenarios driven by biomass production and based on water transport logistics. We performed state- and county-level analysis of reclaimed water resources throughout the United States based on WWTP facility data. We overlaid these data onto estimated algae facility sites and examined the temporal resource availability to address seasonal variations in cultivation demand. Our findings reveal that 2694 billion liters per year of reclaimed water could potentially be used to produce 42.2 million metric tons (ash-free dry weight) of algal biomass, equivalent to 29.2 billion liters of renewable diesel equivalent (RDe). The use of reclaimed water would double current national water reuse and expand such reuse significantly in 455 counties across the United States. However, when we limit the construction of algae facilities to counties that can fully meet their water demand in order to minimize water transport burdens, the available supply decreases by 80%, to 512 billion liters, resulting in annual production of 12.2 billion liters of RDe, which still doubles current biodiesel production. Our analysis highlights the degree to which the location and flow of WWTPs and water transport affect the deployment of algae biofuel facilities and tradeoffs. These findings underscore the importance of improving the current WWTP infrastructure for reclaimed water reuse, especially in southern states.

A novel solar reactive distillation based production of algal biodiesel: Retrofitting, carbon cost and process economics

In this contribution, solar power driven reactive distillation based process is developed for the production of algal biodiesel. For industrial scale operation, the conventional reactive distillation (cRD) is designed to retrofit with a parabolic trough collector (PTC) that yields cRD-PTC based scheme. To serve the same purpose, we have subsequently proposed a solar reactive distillation based configuration. The optimal design and operating conditions of both processes are determined with two conflicting objectives: minimising the total annual cost (TAC) and maximising the purity of biodiesel. For this, the optimisation is performed by the technique for order of preference by similarity to ideal solution embedded non-dominated sorting genetic algorithm-II. Further, we evaluate those process units in terms of the emission trading system based carbon pricing (ETS-CP) and social cost of carbon (SCC) considering the availability of solar energy during day time only. The attractiveness of the proposed solar reactive distillation based process lies in its total annual cost savings of 9.92% (ETS-CP) and 19.06% (SCC), whereas they are 6.67% (ETS-CP) and 16.14% (SCC), respectively for the conventional reactive distillation coupled with parabolic trough collector (cRD-PTC) process. It is further investigated that the total annual cost savings comes down when the proposed configurations are operated with solar (2000 working hours/year) and thermal energy (6000 working hours/year) throughout the year. Finally, the economic feasibility of the biodiesel production processes is studied with the usage of solar heat for the entire operating time.

Influences of various metal oxide-based nanosized particles-added algae biodiesel on engine characteristics

Nano fuel technology is widely used to enhance fuel capability to improve combustion, performance and emission behaviors of the engines. On the other hand, biodiesel is the best alternative to the conventional fossil fuels. However, it may worsen the engine characteristics, and should be modified. In this framework, this investigation aims to improve algae oil biodiesel by employing nano fuel technology by mixing metallic oxide nanoparticles like CeO2, SiO2 and TiO2 with a concentration of 150 mg/lit. The base fuel B25 blends consist of Algae oil-based biodiesel 25 vol% and 75 vol% of diesel. The B25 blends and 150 mg/lit concentration of nanoparticles were preferred through basic experimentation. An ultrasonicator was employed in the preparation of nano fuels such as B25CeO2, B25SiO2, and B25TiO2. The prepared Nano fuels were characterized and tested in a diesel engine at varying engine speeds ranging from 1250 rpm to 2500 rpm with the step of 250 rpm. The results revealed that the use of B25TiO2 recorded the maximum engine cylinder pressure at 72.2 bar was recorded at the 5O crank angle and maximum heat release rate of 63.2 J/OCA. The maximum speed of the engine leads to higher BTE. In comparison to that of conventional diesel fuel, the use of the B25+TiO2 blend increased in-cylinder pressure by 23.4%, heat release rate by 16.6%, BTE by 32.4%, CO2 by 65.09%, and decreased BSFC by 25.62%, CO by 33.4%, NOx by 68.3%, UHC by 22.75%, and smoke opacity by 30.99%. Hence, this investigation found a novel blend of B25TiO2 for lowering emissions and improving diesel engine performance.

Genome editing for biodiesel production in oleaginous microalga, Nannochloropsis species

Algae are oxygen-producing photosynthetic aquatic organisms. Algal biodiesels have attracted attention because these fuels are produced via photosynthesis, which assimilates CO2. Algal biodiesels are sustainable, not competitive with food production, and have higher productivity compared with terrestrial plants. However, the production costs of algal biodiesels are much higher than those of fossil fuels. Therefore, improvement of algal lipid productivity is essential for the practical use of algal biodiesels. To achieve this, the application of genome-editing systems for the molecular breeding of algae is expected to generate “high-performance algae.” Here, we review the genome-editing technologies developed for the oleaginous microalgae, Nannochloropsis species, which are the most promising algae for producing algal-biodiesel feedstock. In this review, we discuss the development of genome-editing systems for gene disruption, transgene-free genome-editing systems, transcriptional regulation systems using nuclease-deficient Cas proteins, and the applications of genome editing in Nannochloropsis species.

Global Life Cycle and Techno-Economic Assessment of Algal-Based Biofuels.

Techno-economic analyses (TEAs) and life cycle assessments (LCAs) of algal biofuels often focus on locations in suboptimal latitudes for algal cultivation, which can under-represent the sustainability potential of the technology. This study identifies the optimal global productivity potential, environmental impacts, and economic viability of algal biofuels by using validated biophysical and sustainability modeling. The biophysical model simulates growth rates of Scenedesmus obliquusbased on temperature, photoinhibition, and respiration effects at 6685 global locations. Region-specific labor costs, construction factors, and tax rates allow for spatially resolved TEA, while the LCA includes regional impacts of electricity, hydrogen, and nutrient markets across ten environmental categories. The analysis identifies optimal locations for algal biofuel production in terms of environmental impacts and economic viability which are shown to follow biomass yields. Modeling results highlight the global variability of productivity with maximum yields ranging between 24.8 and 27.5 g m-2 d-1 in equatorial regions. Environmental impact results show favorable locations tracked with low-carbon electricity grids, with the well-to-wheels global warming potential (GWP) ranging from 31 to 45 g CO2eq MJ-1 in South America and Central Africa. When including direct land use change impacts, the GWP ranged between 44 and 55 g CO2eq MJ-1 in these high-productivity regions. Low-carbon electricity also favors air quality and eutrophication impacts. The TEA shows that minimum algal fuel prices of $1.89-$2.15 per liter of gasoline-equivalent are possible in southeast Asia and Venezuela. This discussion focuses on the challenges and opportunities to reduce fuel prices and the environmental impacts of algal biofuels in various global regions.

Valorization of lignocellulosic wastes for low-cost and sustainable algal biodiesel production using biochar-based solid acid catalyst

Recently, carbon-based solid acid catalysts have come into prominence among different types of catalyst for production of biodiesel. Solid acid catalysts can be produced from carbon based materials such as biomass wastes by reducing the cost. Utilization of these wastes to prepare solid acid catalyst provides solid waste management and the potential greenhouse gas emissions decreases. Since algal biodiesel production is not so economical and needs to be improve, using these catalysts produced from waste biomass can be promising for making the process more cost effective and a low cost applicable zero-waste biorefinery approach can be put forth. In this study, walnut shell, olive stone and macroalgae were utilized to produce biochar based solid acid catalyst to be evaluated in microalgal biodiesel production. Walnut shell carbonized at 500 °C and then sulfonated by sulfuric acid was selected for biodiesel production due to having higher sulfonic acid density (0.35 mmol/g) and preferable structural properties. The statistical evaluation of transesterification parameters effect on microalgal biodiesel yield were evaluated and yield of 82% was found as the highest which was obtained by using 5 wt% catalyst, 12:1 methanol/oil molar ratio at the reaction time of 60 min. Stability test also showed the catalyst can be re-used up until the 5th cycle. Low cost feedstock and reusability of the catalyst presented a simple, cost-effective and environment-friendly process. At last, lignocellulosic wastes can be suggested for not only as biochar production also can be evaluated as solid acid catalyst and provide a cost-efficient biodiesel production.

Screening of wastewater Oedogonium oblangum algae for hyper-oil transformation into biodiesel by response surface methodology

The algae have gained more significance as a renewable third-generation feedstock for being easily available and a hyper-production source for lipids and biodiesel. Sustainable and cost-effective production of algal biodiesel requires screening and optimization of various culture conditions. Screening of algae on the basis of its lipid content is crucial for exploring its potential for production of biodiesel. In the current study, the screening of six indigenous algal strains was performed based on lipid contents, out of which Oedogonium oblangum (O. oblangum) exhibited hyper-lipid content (15.76%). Bold basal media and wastewater media were compared as culture media to evaluate the growth of O. oblangum; the respective strain showed better growth on wastewater media, therefore, this media was used for further experimentation. A laboratory-based integrated approach was used to enhance production of algal lipids by applying the effects of temperature, pH, and wastewater dilutions. The oil contents were interestingly improved under the optimal culture conditions of temperature (25°C), pH (6.5), wastewater dilution (45%) with oil contents of 18.35%, 17.15%, and 17.95%, respectively. The extracted oil was transformed into biodiesel by alkali-mediated transesterification reactions using four factors (Oil/methanol ratio, temperature, time, and catalyst) by response surface methodology (RSM). The RSM successfully optimized the transesterification reactions with 86.73% of biodiesel under optimal conditions of oil/alcohol ratio (1:7.6 v/v), temperature (60.5°C), time (59 ​min), and catalyst (0.53 ​wt. %). Physical properties of biodiesel (kinematic viscosity; 5.17; acid value; 0.63; flash point; 152; specific gravity; 0.74; calorific value; 42.11; and water contents; 0.03) comply with the ASTM standards and lead to enhance the quality of produced biodiesel. The optimized culture conditions, transesterification reactions, and wastewater medium can be employed for the economically production of biodiesel at commercial scale. Overall, the results showed that biodiesel derived from an indigenous novel algal strain, O. oblangum, has the potential to compete and replace commercially available petro-diesel using wastewater media. It might contribute to resolve the energy challenges being faced by Pakistan and the entire world.

BRIEF REVIEW ON ALGAE BASED BIOFUEL

This Utilization of algae as a sustainable biofuel source is summarized in this critical assessment. Biohydrogen is a third generation feedstock for the manufacture of biofuels(bioethanol,biodiesel,or biogas)biofuel made from gas cannot reach its maximum potential because of the higher Costs of farming, reaping, extraction other stages. Consequently, this evaluationgrants Deriving biofuels starting from algae biomass is explained in great detail systems such as raceway ponds and photo bioreactors along with their bottlenecks. Evolution of biofuel The first section of this manuscript addressed feedstock’s, from edible oils to algae. Here are some insights into the various generation of biofuels. Ultimately, Algal cultivation pretreatments and future dimensions .These steps were explained in detail in order to make carefullypractical algal biofuel.

Indicators of Engine Performance Powered by a Biofuel Blend Produced from Microalgal Biomass: A Step towards the Decarbonization of Transport

According to the EU Directive, the so-called RED II, there is increasing significance for biofuels produced from biomass with low indirect land use change (ILUC) risk. Such an alternative and sustainable feedstock could be microalgae, among others, used for biodiesel production. This is due to the high lipid content of their cells and their potential ability to accumulate significant amounts of carbon dioxide in their biomass, which has a positive effect on the carbon footprint of the product. The aim of this study was to determine the effect of adding algal biodiesel to conventional diesel fuel on selected performance parameters of a diesel engine, taking into account the composition of the emitted exhaust gas. Energy-related engine performance parameters such as power, hourly and specific fuel consumption, engine thermal efficiency, and indicated efficiency were determined. No significant differences were found in the energy parameters of engine operation with the fuels tested. In terms of carbon monoxide and NOx emissions, at the highest engine torque, more favorable parameters were obtained for fuel with biodiesel produced from rapeseed oil (B/RME). Under the same conditions, carbon dioxide emissions for the fuel with the addition of biodiesel from microalgae (B/Algae) were 8.1% lower.

Investigations on biomass gasification derived producer gas and algal biodiesel to power a dual-fuel engines: Application of neural networks optimized with Bayesian approach and K-cross fold

The adoption of sustainable energy sources is a crucial step towards achieving a low-carbon economy and mitigating the effects of climate change. One promising approach is the use of Producer Gas (PG) derived from solid biomass materials, which can be burned as fuel in internal combustion engines to generate power. Biomass gasification, the process of converting solid biomass into PG through thermochemical means, offers a sustainable alternative to traditional fossil fuels. However, using PG in dual-fuel engines poses a significant challenge due to its complex combustion characteristics. Fortunately, modern machine learning techniques offer a promising solution to this problem. In this study, we propose a Bayesian optimized neural network (BONN) to predict the performance and emissions of PG-algal biodiesel (ABD) -powered dual-fuel engines. The BONN is trained using experimental data obtained from a single-cylinder diesel engine retrofitted to run on PG as the primary fuel and algal biodiesel as the pilot fuel. The performance and emissions data are collected under various operating conditions, such as engine load, fuel injection pressure, biodiesel blending ratio, and injection timings. K-cross fold validation was used to reduce the chances of model overfitting while the Bayesian approach was used for hyperparameters finetuning. This strategy helped in the reduction of predicting errors and improved the accuracy of the model. The coefficient of determination was in the range of 0.9421–0.9989 and mean squared errors were in the range of 0.0026–15.77. The mean absolute errors in model-predicted values were in the range of 0.0027–2.945. In all the cases of the prediction results during the model, the test improved upon the model training predictions, indicating a robust generalization and negated the chances of model overfitting. The results demonstrate that the BONN can accurately predict the performance and emissions of the engine, making it a valuable tool for engine optimization and control. This approach offers a promising pathway toward achieving net-zero targets and a sustainable future.

Algae-based biofuels: Hope for future energy

Algae-based biofuels: Hope for future energy

Chemical extraction of Biodiesel and Parametric analysis of DI-Diesel Engine using Algae esterified Oil-Gasoline Blends

Of late, the automobiles of all categories are massively increasing which aggravates the dependency on fossil fuel thus, the accessibility of petro-fuel decreases relentlessly. Under these circumstances, the investigations are taking new dimensions to find alternative, renewable with cost-effective fuel exclusively biofuels. However, a newer approach has been attempted for the production of biodiesel from wild stuff of Spirulina algae which is explored directly in its aquatic systems of the natural environment. The chemical extraction process was attempted with wild biomass of algae via pre-treatment for obtaining promising lipid content then; the algal oil (lipid) was subjected to the production of biodiesel through sequential transesterification reactions. The obtained biodiesel was measured as 94.65% produced from 0.920kg of algal oil extracted out of 1.6kg of algal biomass in a stipulated duration of time (2.50hr) taken for attaining maximum temperature. Further, the produced biodiesel was evaluated for its distinctive properties and the outcomes were compared with ASTM standard specifications. All the results appeared to be within the standards limit thereby, the methodical analysis was done for the performance and emission parameters via interacting algal biodiesel in the experimental (DI) diesel engine test-rig configured with a variable injection pressure of 210, 220 & 230 respectively. The blending ratio of algal diesel and gasoline (AB10 & AB 20v/v) were prepared based on volume and the results were correlated with petro-diesel. The physico-chemical parameters like color, odour, viscosity, density, total acid number, initial boiling point, flash point, calorific value, cetane number etc. were found to be significant when compared with petro-fuel. Correspondingly, the interactive parameters like flash point, pour point, cloud point, carbon residue, sulfur, ash, and water contents were correlated with the standard specifications. The substantial approach was observed in emission characteristics such as hydrocarbon (HC), carbon monoxide (CO), oxides of nitrogen (NOX) respectively in engine-algal fuel interactions. Whereas, a slight increase than petro-diesel with respect to sulfur oxide (SOX) emission and smoke opacity were also recorded. However, the marginal increase in Brake specific fuel consumption (BSFC) and Brake thermal efficiency (BTE) was noticed and the brake power (BP) was found slightly lower than petro-diesel. In conclusion, the protocol of producing biodiesel from wild stuff biomass of Spirulina maxima was found to be techno-economically feasible and this potential algal biodiesel can be recommended for the current engine applications without any alterations.

Production of Biodiesel from Algae

Abstract: Microalgae provide a large amount potential for the utilization, which contains the large amount of biodiesel, but the method is not very advance. In the this idea the knowledge we want is very less. In this paper we are going to look at the potential of microalgae to take the dynamic steps to improve our study about the microalgae to understand the patterns of changes. In doing this we required the combination of biology and engineering. In this review, We present an overview of potential algal biofuel pipelines and highlight current work to optimize algal biomass production and the molecular fuel content of algal cells. Using hexane as a solvent and simultaneous extraction and transesterification, the highest possible yield of biodiesel was achieved. To determine the potential of microalgae to produce biodiesel, Algal biomass, algae oil, and algae biodiesel were all thoroughly characterized.

Life cycle assessment of microalgae-derived biodiesel

PurposeMicroalgae-derived biofuels are considered a low-carbon alternative to fossil fuels. Nevertheless, as with all biofuels, there is still uncertainty around their sustainability. Most life cycle assessments (LCA) of microalgae biofuels so far used lab-based, scaled-up lab experimental data or data from the scientific literature. This article, provides evidence and analysis, undertaking an LCA using real-world data from an industrial facility that uses a combination of photobioreactor and fermenter systems.MethodsThe current well-to-wheel LCA study aimed to compare the environmental impacts of microalgae biodiesel production—under different energy regimes—and with petroleum-derived diesel. The functional unit was considered as “combustion of 1 MJ (Lower Heating Value) of algal biodiesel in an internal combustion engine (as B100)”. This LCA study considers the environmental and energy impacts from the construction of the facility, as well as those impacts from the operation of the facility. The foreground LCI data was collected from a real-world one-hectare microalgae production pilot facility. ReCiPe, IPCC AR5 (GWP100 and GWP20) and Global Temperature Potential (GTP) were implemented to assess the life cycle environmental impacts.Results and discussionThe assessment shows that when infrastructure is included, microalgae-derived biofuels are not yet favourable over petroleum-derived fuels on GWP100, and this becomes worse over shorter timescales. In terms of climate change (GWP100), whilst 1 MJ (LHV) of fossil-derived diesel would emit 8.84 × 10−2 kg CO2eq, 1 MJ of microalgae-derived biodiesel from a solar photovoltaic powered facility would emit 1.48 × 10−1 kg CO2eq. To be equal to petroleum-derived diesel in terms of GWP100, or perform better, productivity of the microalgae production system needs to be improved as the most effective solution. The results also showed that electricity and infrastructure were major sources of environmental impacts, as well as the yeast used within the fermenter. Moreover, it takes 0.99 MJ of direct energy per 1 MJ of microalgae biofuel produced, similar to the fossil fuel industry for 1 MJ of diesel.ConclusionsUsing infrastructure and operational models, the study shows that the facility does not compare well with petroleum-derived diesel unless productivity can be increased. Productivity improvements, be it through improvements to microalgae strains or improved photobioreactor designs, should be a priority to ensure microalgae become a sustainable fuel feedstock. Electricity use should be reduced as well, again, through improved cultivation system designs. In terms of the current system, the high impacts of yeast should be addressed, either through co-locating yeast production or through ensuring specific sources with lower impacts. Extracting lipids will effectively waste some high-value products, whilst the waste can be expected to be a mixture of unextracted lipids, polysaccharides or fibre, some proteins and minerals. It is also shown that harmonisations of the assessments are needed for future studies and real-world operation facilities to conclusively decide if microalgae should be used as fuel or if they would be better used for other products, such as feed or high-value products.

Algae biofuel: A futuristic, sustainable, renewable and green fuel for I.C. engines

The major need for the economical development of any nation is to provide uninterrupted supply of energy to its increasing demand year-on-year. The worldwide scenario of declining petroleum reserve and the problem of environmental damage caused due to the emissions by petroleum fuels have created a focus on biofuels. At present, the algae fuel is considered as a third generation biofuel, as the source is non-edible and can been grown in any kind of water of any nature, even in waste and sea water, without the requirement of fertile land. Further, Algae has become a prominent feedstock to fulfill the growing demand for biofuels by virtue of its rich energy content, faster and high growth rate per unit cultivation area. But, still there are many practical challenges to implement the algae biofuel as a leading source of energy. This article provides an overview of the prospects and challenges of algae biofuel to become a futuristic, sustainable, renewable, and green energy fuel of the world.

Sustainable alternative fuel derived from different feedstocks and its comparative life cycle assessment

The objective of the current study is to extract oil and derive biodiesel from three different scenarios karanja (S1), algae (S2), and hybrid oil (S3), and further conduct the life cycle assessment (LCA) of derived biodiesel. Biodiesel derived from hybrid oil had higher oxidation stability than algae biodiesel and lower density and viscosity than karanja biodiesel. Additionally, using GREET software, comparative life cycle assessment studies were performed for all three scenarios. One kg of biodiesel output was used as the functional unit. The total emission of CO2 from biodiesel production in S1 is 2.03 kg, 1.60 kg in S2, and 1.85 kg in S3. Further, the environmental impact factor was calculated for all the scenarios. The EIF for scenario 1 was maximum, 0.235 followed by 0.1363 and 0.0989 for scenario 3 and scenario 2 respectively. The results of the overall effect evaluation showed that Algae or Hybrid biodiesel production is preferred to lower the emission and improve the biodiesel quality. More studies on life cycle costs and sensitivity analysis should be undertaken to assess economic viability and encourage sustainable biodiesel production.

Biodiesel Production from a Naturally Grown Green Algae Spirogyra Using Heterogeneous Catalyst: An Approach to RSM Optimization Technique

The present study focuses on oil extraction and biodiesel production from naturally grown green Spirogyra algae. Solvent oil extraction and oil expeller techniques were used to extract the Spirogyra algae oil (SALO), and the oil yields were compared to identify the most productive method. Using chicken eggshell waste (CESW) heterogeneous catalyst (HC) was prepared for the production of Spirogyra algae oil biodiesel (SALOBD). Furthermore, Box–Behnken (BB) assisted response surface method (RSM), an optimisation technique, was used in this study to achieve maximum algae biodiesel yield. From the 29 experimental trails, 96.18 % SALOBD was achieved at molar ratio (10:1), heterogeneous catalyst (0.6 wt.%), temperature (48 oC), and time (180 minutes). The predicted values of R2 (97.51%) and Adj. R2 (95.02 %) is found to be encouraging and fits well with the experimental values. The output results show that HC was identified as the significant process constraint followed by the time. The fatty acid composition (FAC) analysis by Gas Chromatography (GCMS) reveals the presence of 29.3 % unsaturated composition and 68.39 wt. % of the saturated composition. Finally, the important fuel properties of SALOBD were identified in accordance with ASTM D6751. The results obtained using chicken eggshell waste (CESW) for the production of biodiesel were recommended as a diesel fuel replacement to resist energy and environmental calamities.

Techno-economic identification of production factors threatening the competitiveness of algae biodiesel

The majority belief is that microalgae is the most promising potential feedstock for biodiesel production while it can also be used for treating wastewater. After the microalgae biodiesel is mixed with proper additives, it can even outperform some conventional fossil fuels, not to mention its environmentally friendly nature. Although the mainstream view is that microalgae production costs are small and will be even smaller once mass production is implemented, no reviewable reports are traceable to support these claims. Only a few studies are available that address the commercialization aspects of microalgae mass production and the economy of its subsequent refining into biodiesel. The prevailing view is that microalgae cultivation is fully mastered, while most production costs refer to energy consumption, where there is much room for optimization. The current review focuses on the financial aspects of microalgae production via bioreactors. Economic considerations are also given to the less common alternatives such as harvesting from natural habitats, production of biogas, or nutrient regeneration. Synergies from the combination of these methods are also taken into account. Our analysis confirmed that the cost-competitive microalgae biodiesel business strongly depends on the microalgae production cost, which is strongly defined by the running cost of the production technology. However, it is claimed that no technology could be found that was ready to be transformed into commercial dimensions and made it possible to produce microalgae at a price that creates at least a remote possibility of running profitable algae biodiesel business in the current state of the market.

Performance analysis on a compression ignition engine fueled with algae, rice bran methyl esters, and their diesel blends at optimized blend proportion, injection timing and load

The production of biodiesel from algal oil is the subject of a lot of research. There hasn't been a thorough examination of the performance, combustion, and emission analyses of algal biodiesel when engine factors like load, injection timing, etc. are varied and optimization studies are used. This research attempts to address the void in the literature on thorough engine studies for algal oil biodiesel. Herein, pure diesel with three different algae and rice bran oil blends (B5-5% biodiesel with 95% pure diesel, B10-10% biodiesel with 90% pure diesel and B20- 20% biodiesel with 80% diesel) are synthesized. The properties of the biodiesel samples were examined and verified with standard ASTM limits (kinematic viscosity at 40 °C for macro algae is 3.51 cSt and microalgae is 4.84 cSt). The blend, load and injection timing were optimized through the performance, combustion, and emission characteristics of a compression ignition engine. The brake thermal efficiency (BTE) increasing trend is observed for both diesel & biodiesel up to 75% load, and advanced injection timing (26° BTDC) improved the BTE for all biodiesel blends. Besides, an increase of 5% peak pressure is observed in all blends 1°–9° crank angle ATDC. Biodiesel blends have minimal carbon emissions, except NOX emissions. Further, the experimental values are optimized through Taguchi/Grey Grade Relational procedure and the best combination for MAME blends is MAME 20, 100% load, 20° BTDC for AME blends is AME 20, 100% load, 23° BTDC and for RME blends is AME 20, 100% load, 20° BTDC.

Hydrothermal liquefaction could be a sustainable approach for valorization of wastewater grown algal biomass into cleaner fuel

Studies highlighting the actual roadblocks in sustainability of algal fuels require systemic analysis using real-time experimental inventories. In view of this, the authors performed Life Cycle Assessments (LCAs) for 3 previously developed algal biofilms-based conversion systems; 1) wastewater grown algae (WWA) processed via anaerobic digestion (AD), 2) WWA processed via hydrothermal liquefaction (HTL) and 3) synthetic media grown algae (SMA) processed via HTL. Their environmental impacts were compared for resources depletion, ecosystem damage, human health deterioration and climate change. Results showed that HTL of WWA had 41.1 % lesser impact compared to AD of the same biomass, because of the huge energy input, production of CO2 and huge volume of algal digestate. Due to the short reaction time in HTL (20 min), energy input and resources usage was minimal. Further, the HTL of WWA showed 98% lesser impact than HTL of SMA. HTL of SMA had larger impact on the human health (3.95Pt), compared to HTL of WWA (0.25Pt). The latter also showed positive impact on the eutrophication reduction due to the treatment of wastewater during algal cultivation. The global warming potential for biocrude production from WWA was 10 times lower than biomethane production from the same biomass and 21 times lower than the biocrude production from SMA. The results of the comparative LCAs proved that HTL of WWA is a sustainable route for valorizing the biomass. Based on the LCA outcomes, shortcomings of the respective algal technologies were identified, and improvement strategies were suggested.