A review on the engine performance and exhaust emission characteristics of diesel engines fueled with biodiesel blends

Exhaust emissions of gaseous and particle size-segregated water-soluble organic compounds from diesel-biodiesel blends

This study assessed the emissions of gaseous pollutants and particle size distributed water-soluble organics (WSO) from a diesel vehicle fuelled with ultralow sulphur diesel (B0) and 10 (B10), 20 (B20), and 30% (B30) biodiesel blends in a chassis dynamometer tested under transient mode. Particulate emission sampling was carried out in an ultraviolet (UV) test chamber using a 10-stage impactor. Samples were grouped into three size fractions and analysed by gas chromatography-mass spectrometry. Increasing the biofuel ratio up to 30% in the fuel reduced WSO emissions by 20.9% in comparison with conventional diesel. Organic acids accounted for 82-89% of WSO in all tested fuels. Dicarboxylic acids were the most abundant compound class, followed by hydroxy, aromatic, and linear alkanoic acids. Correlations between compounds demonstrated that adding biodiesel to diesel fuel reduces the emissions of nitrogen oxides (NOx), benzene, toluene, ethylbenzene and xylenes (BTEX), methane (CH4), total and nonmethane hydrocarbons (THC and NMHC), and dicarboxylic and hydroxy acids, but increases emissions of carbon dioxide (CO2) and alkanoic and aromatic acids. Emissions of dicarboxylic and hydroxy acids were strongly correlated with the biodiesel content. WSO emissions of coarse and fine (1.0-10 μm) particles decreased with the increasing biofuel content in fuel blend. The total share of ultrafine (0.18-1.0 μm) and nanoparticles (< 0.18 μm) increased in WSOs emissions from B20 and B30 blends, when compared with petrodiesel. The biodiesel content also affected the chemical profile of WSO size fractions.

Review of physicochemical properties and spray characteristics of biodiesel

The United Nations Sustainable Development Goals by 2030 deal with seventeen goals for the planet's sustainability. The present review focuses on affordable and clean energy through the effective combustion of fuels with minimal pollution. Effective fuel spray characteristics are essential for combustion among various parameters and fuel properties. The inherent nature of the fuel has a functional relationship with the injection and injectors' conditions. Therefore, the study of fuels' physicochemical properties is essential. This review deals with the spray characteristics of biodiesel. Biodiesels in its purest form and blended with diesel, di-n-butyl ether, dimethyl ether, diethyl ether, ethanol, and butanol are considered for the study. The physicochemical properties of biodiesels, injection conditions, and injector constraints are analyzed to understand the spray process. The atomization features such as spray tip penetration, Sauter mean diameter, spray cone angle, spray area, and spray volume are analyzed. The chemical properties of biodiesel are utilized to describe the spray's transient behavior. In addition, supporting systems for spray diagnostics and models are also discussed. The highlighted significant spray challenges features and future research direction benefit the fuel and combustion community.

The coexpression of two desaturases provides an optimized reduction of saturates in camelina oil

Reducing the saturate content of vegetable oils is key to increasing their utility and adoption as a feedstock for the production of biofuels. Expression of either the FAT5 16 : 0-CoA desaturase from Caenorhabditis elegans, or an engineered cyanobacterial 16 : 0/18 : 0-glycerolipid desaturase, DES9*, in seeds of Arabidopsis (Arabidopsis thaliana) substantially lowered oil saturates. However, because pathway fluxes and regulation of oil synthesis are known to differ across species, translating this transgene technology from the model plant to crop species requires additional investigation. In the work reported here, we found that high expression of FAT5 in seeds of camelina (Camelina sativa) provided only a moderate decrease in saturates, from 12.9% of total oil fatty acids in untransformed controls to 8.6%. Expression of DES9* reduced saturates to 4.6%, but compromised seed physiology and oil content. However, the coexpression of the two desaturases together cooperatively reduced saturates to only 4.0%, less than one-third of the level in the parental line, without compromising oil yield or seedling germination and establishment. Our successful lowering of oil saturates in camelina identifies strategies that can now be integrated with genetic engineering approaches that reduce polyunsaturates to provide optimized oil composition for biofuels in camelina and other oil seed crops.

The effect of biodiesel production method on its combustion behavior in an agricultural tractor engine

In this study, biodiesel fuel was produced from waste cooking oil (WCO) using a heterogeneous catalyst under microwave (MB) and conventional (CB) heating, and fueled in an agricultural tractor engine to evaluate the engine performance as well as emissions. The biodiesels presented different fatty acid methyl ester (FAME) profiles where MB had lower unsaturated FAME chains. Beyond the transesterification reaction time, the energy consumed for MB biodiesel production diminished by around eight times compared to that required for CB production. The engine results confirmed the positive influence of blending net diesel fuel with biodiesel for enhancing the engine performance and reducing the emissions. More than 20% increment in the engine power and torque was detected at all engine loads (the engine speed was adjusted at 1500 rpm). The hydrocarbon (HC), carbon monoxide (CO), and smoke opacity (SO) indicated significant reductions compared to when net diesel fuel was used. According to statistical analysis, CB25 and MB25 fuels presented a suitable combination as fuel where MB25 provided better engine performance, lower HC and SO emissions, with CO emissions reaching the minimum amount by CB fuels.

Experimental Study on the Performance-Influencing Factors of an Aviation Heavy-Oil Two-Stroke Direct-Injection Ignition Engine

To study the influence of control parameters under cold-start and low-load conditions on the performance of a heavy-oil, two-stroke, direct-injection, ignition engine for use in aviation, the operation of a two-stroke, direct-injection engine was studied in a bench test. The results were as follows: ① When the ambient temperature is 15 °C, the battery voltage is 12.4 V, and the peak speed of the starting motor is 1200 r/min. As the concentration factor increases, the cold-start speed increases, and the fuel consumption increases. The influence on the cold start is reduced after reaching a certain concentration. The cold-start time decreases with the increasing magnetization pulse width. The cold-start time is the shortest at an oil–gas interval of 6 ms. ② Under small-load conditions of 3000 r/min and 14% to 16% throttle, a higher ignition energy increases the engine power. Pollutant emissions are the lowest when the fuel injection is 7.5 mg and the excess air coefficient is approximately 1.1.

Emerging Technologies for Enhancing Microalgae Biofuel Production: Recent Progress, Barriers, and Limitations

The world has heavily relied on fossil fuels for decades to supply energy demands. However, the usage of fossil fuels has been strongly correlated with impactful problems, which lead to global warming. Moreover, the excessive use of fossil fuels has led to their rapid depletion. Hence, exploring other renewable and sustainable alternatives to fossil fuels is imperative. One of the most sustainable fossil fuel alternatives is biofuel. Microalgae-based biofuels are receiving the attention of researchers due to their numerous advantages compared with those obtained from other types of feedstocks. Hence, it is essential to explore the recent technologies for biofuel produced from microalgae species and define the possible challenges that might be faced during this process. Therefore, this work presents the recent advancements in biofuel production from microalgae, focusing on emerging technologies such as those using nanomaterials and genetic engineering. This review focuses on the impact of nanoparticles on the harvesting efficiency of various microalgae species and the influence of nanoparticles on biofuel production. The genetic screening performed by genome-scale mutant libraries and their high-throughput screening may assist in developing effective strategies for enhancing microalgal strains and oil production through the modification of enzymes. Furthermore, the barriers that limit the production of biofuels from microalgae are introduced. Even though microalgae-based biofuels are perceived to engage with low negative impacts on the environment, this review paper touches on several environmental issues associated with the cultivation and harvesting of microalgae species. Moreover, the economic and technical feasibility limits the production of microalgae-based biofuels.

Molecular signatures of organic particulates as tracers of emission sources

Chemical signature of airborne particulates and deposition dusts is subject of study since decades. Usually, three complementary composition markers are investigated, namely, (i) specific organic compounds; (ii) concentration ratios between congeners, and (iii) percent distributions of homologs. Due to its intrinsic limits (e.g., variability depending on decomposition and gas/particle equilibrium), the identification of pollution sources based on molecular signatures results overall restricted to qualitative purposes. Nevertheless, chemical fingerprints allow drawing preliminary information, suitable for successfully approaching multivariate analysis and valuing the relative importance of sources. Here, the state-of-the-art is presented about the molecular fingerprints of non-polar aliphatic, polyaromatic (PAHs, nitro-PAHs), and polar (fatty acids, organic halides, polysaccharides) compounds in emissions. Special concern was addressed to alkenes and alkanes with carbon numbers ranging from 12 to 23 and ≥ 24, which displayed distinct relative abundances in petrol-derived spills and exhausts, emissions from microorganisms, high vegetation, and sediments. Long-chain alkanes associated with tobacco smoke were characterized by a peculiar iso/anteiso/normal homolog fingerprint and by n-hentriacontane percentages higher than elsewhere. Several concentration ratios of PAHs were identified as diagnostic of the type of emission, and the sources of uncertainty were elucidated. Despite extensive investigations conducted so far, the origin of uncommon molecular fingerprints, e.g., alkane/alkene relationships in deposition dusts and airborne particles, remains quite unclear. Polar organics resulted scarcely investigated for pollution apportioning purposes, though they looked as indicative of the nature of sources. Finally, the role of humans and living organisms as actual emitters of chemicals seems to need concern in the future.

Experimental Studies of the Effect of Air Filter Pressure Drop on the Composition and Emission Changes of a Compression Ignition Internal Combustion Engine

This paper presents an experimental evaluation of the effect of air filter pressure drop on the composition of exhaust gases and the operating parameters of a modern internal combustion Diesel engine. A literature analysis of the methods of reducing the emission of toxic components of exhaust gases from SI engines was conducted. It has been shown that the air filter pressure drop, increasing during the engine operation, causes a significant decrease in power output and an increase in fuel consumption, as well as smoke emission of Diesel engines with the classical injection system with a piston (sectional) in-line injection pump. It has also been shown, on the basis of a few literature studies, that the increase in the resistance of air filter flow causes a change in the composition of car combustion engines, with the effect of the air filter pressure drop on turbocharged engines being insignificant. A programme, and conditions of tests, on a dynamometer of a modern six-cylinder engine with displacement Vss = 15.8 dm3 and power rating 226 kW were prepared, regarding the influence of air filter pressure drop on the composition of exhaust gases and the parameters of its operation. For each technical state of the air filter, in the range of rotational speed n = 1000–2100 rpm, measurements of exhaust gas composition and emission were carried out, as well as measurements and calculations of engine-operating parameters, namely that of effective power. An increase in the pressure drop in the inlet system of a modern Diesel truck engine has no significant effect on the emissions of CO, CO2, HC and NOx to the atmosphere, nor does it cause significant changes in the degree of smoke opacity of exhaust gases in relation to its permissible value. An increase in air filter pressure drop from value Δpf = 0.580 kPa to Δpf = 2.024 kPa (by 1.66 kPa) causes a decrease in the maximum filling factor value from ηυ = 2.5 to ηυ = 2.39, that is by 4.5%, and a decrease in maximum power by 8.8%.

Rapid rise in premature mortality due to anthropogenic air pollution in fast-growing tropical cities from 2005 to 2018

Tropical cities are experiencing rapid growth but lack routine air pollution monitoring to develop prescient air quality policies. Here, we conduct targeted sampling of recent (2000s to 2010s) observations of air pollutants from space-based instruments over 46 fast-growing tropical cities. We quantify significant annual increases in nitrogen dioxide (NO₂) (1 to 14%), ammonia (2 to 12%), and reactive volatile organic compounds (1 to 11%) in most cities, driven almost exclusively by emerging anthropogenic sources rather than traditional biomass burning. We estimate annual increases in urban population exposure to air pollutants of 1 to 18% for fine particles (PM_2.5) and 2 to 23% for NO₂ from 2005 to 2018 and attribute 180,000 (95% confidence interval: -230,000 to 590,000) additional premature deaths in 2018 (62% increase relative to 2005) to this increase in exposure. These cities are predicted to reach populations of up to 80 million people by 2100, so regulatory action targeting emerging anthropogenic sources is urgently needed.

Comparison of fuel characteristics of hydrotreated waste cooking oil with its biodiesel and fossil diesel

Compression ignition engines powered by diesel are the work horses of developing countries like India. However, burning fossil fuel causes a lot of air pollution and the depletion of fuel at an alarming rate. Fuels produced from biomass or wastes can partially substitute fossil diesel to decrease its consumption. One such feedstock is waste cooking oil (WCO) which can be easily converted into fuel for diesel engines. The hydrotreating process stands out among the methods available for converting WCO into fuel, since its properties are almost similar to fossil diesel with little or no oxygen content. In this study, the physico-chemical properties of the hydrotreated waste cooking oil (HVO), biodiesel of waste cooking oil, diesel and blends of HVO and diesel are compared. The blends were prepared by mixing 10%, 20%, 30%, 40% and 50% of HVO on volume basis in diesel. The evaporation rate and ignition probability of the fuel samples were found by using a hot-plate test setup. HVO had higher ignition probability than all the test sample. As the percentage of HVO increased in the test samples, the ignition probability increased. The Sauter mean diameter (SMD) of the samples was also found using Malvern Spraytec. The SMD of HVO was larger than diesel but smaller than biodiesel. The study shows that blends of HVO up to 30% are feasible for present use in diesel engines, as the viscosity (2.54, 2.59 and 2.62cSt) and calorific value (42.41, 42.29, 42.08 MJ/kg) of the three blends (10%, 20% and 30%) is close to diesel (2.51cSt and 42.58 MJ/kg). Also, due to high cetane index, neat HVO or blends having higher HVO content (> 30%) cannot be used in the existing engines as the engine power output may be affected. Therefore, to use these fuels, the engine needs to be modified which is not feasible for existing engines. The FTIR and GC-MS analysis shows that the HVO has low oxygen content and high amount of paraffins, whereas biodiesel of waste cooking oil has high unsaturation and high oxygen content.

An Extensive Analysis of Biodiesel Blend Combustion Characteristics under a Wide-Range of Thermal Conditions of a Cooperative Fuel Research Engine

Examining the influence of thermal conditions in the engine cylinder at the start of fuel injection on engine combustion characteristics is critically important. This may help to understand physical and chemical processes occurring in engine cycles and this is relevant to both fossil fuels and alternative fuels like biodiesels. In this study, six different biodiesel–diesel blends (B0, B10, B20, B40, B60 and B100 representing 0, 10, 20, 40, 60 and 100% by volume of biodiesel in the diesel–biodiesel mixtures, respectively) have been successfully tested in a cooperative fuel research (CFR) engine operating under a wide range of thermal conditions at the start of fuel injection. This is a standard cetane testing CFR-F5 engine, a special tool for fuel research. In this study, it was further retrofitted to investigate combustion characteristics along with standard cetane measurements for those biodiesel blends. The novel biodiesel has been produced from residues taken from a palm cooking oil manufacturing process. It is found that the cetane number of B100 is almost 30% higher than that of B0 and this could be attributed to the oxygen content in the biofuel. Under similar thermal conditions at the start of injection, it is observed that the influence of engine load on premixed combustion is minimal. This could be attributable to the well-controlled intake air temperature in this special engine and therefore the evaporation and mixing rate prior to the start of combustion is similar under different loading conditions. Owing to higher cetane number (CN), B100 is more reactive and auto-ignites up to 3 degrees of crank angle (DCA) earlier compared to B0. It is generally observed in this study that B10 shows a higher maximum value of in-cylinder pressure compared to that of B0 and B20. This could be evidence for lubricant enhancement when operating the engine with low-blending ratio mixtures like B10 in this case.

Physicochemical Properties of Biodiesel Synthesised from Grape Seed, Philippine Tung, Kesambi, and Palm Oils

The production of biodiesel using vegetable oil is an effective way to meet growing energy demands, which could potentially reduce the dependency on fossil fuels. The aim of this study was to evaluate grape seed (Vitis vinifera), Philippine tung (Reutealis trisperma), and kesambi (Schleichera oleosa) oils as potential feedstocks for biodiesel production to meet this demand. Firstly, biodiesels from these oils were produced and then their fatty acid methyl ester profiles and physicochemical properties were evaluated and compared with palm biodiesel. The results showed that the biodiesel produced from grape seed oil possessed the highest oxidation stability of 4.62 h. On the other hand, poor oxidation stability was observed for Philippine tung biodiesel at 2.47 h. The poor properties of Philippine tung biodiesel can be attributed to the presence of α-elaeostearic fatty acid. Furthermore, synthetic antioxidants (pyrogallol) and diesel were used to improve the oxidation stability. The 0.2 wt.% concentration of pyrogallol antioxidant could increase the oxidation stability of grape seed biodiesel to 6.24 h, while for kesambi and Philippine tung, biodiesels at higher concentrations of 0.3% and 0.4 wt.%, respectively, were needed to meet the minimum limit of 8 h. The blending of biodiesel with fossil diesel at different ratios can also increase the oxidation stability.

Effect of ultrasonic irradiation on the properties and performance of biodiesel produced from date seed oil used in the diesel engine

In the present study, the effect of ultrasound irradiation on the transesterification parameters, biodiesel properties, and its combustion profiles in the diesel engine was investigated. Moreover, date seed oil (DSO) was firstly utilized in the ultrasound-assisted transesterification reaction. DSO was extracted from Zahidi type date (Phoenix dactylifera) and was esterified to reduce its Free Fatty Acid (FFA) content. Biodiesel yield was optimized in both heating methods, so that the yield of 96.4% (containing 93.5% ester) at 60 °C, with 6 M ratio of methanol/oil, 1 wt% of catalyst (NaOH) and at 90 min of reaction time was reported. The ultrasound irradiation did not influence the reaction conditions except reaction time, reduced to 5 min (96.9% yield and 91.9% ester). The ultrasonic irradiation also influenced on the physicochemical properties of DSO biodiesel and improved its combustion in the diesel engine. The analysis results related to the engine and gas emission confirmed that the ultrasound-assisted produced biodiesel has lower density and viscosity, and higher oxygen content facilitating injection of fuel in the engine chamber and its combustion, respectively. Although, B40 (biodiesel blend consisting of 40% biodiesel and 60% net diesel fuel) as a blend of both fuels presented higher CO₂ and lower CO and HC in the emissions, the DSO biodiesel produced by ultrasound irradiation presented better specifications (caused about 2-fold improvement in emissions than that of conventional method). The findings of the study confirmed the positive effect of the ultrasound irradiation on the properties of the produced biodiesel along with its combustion properties in the diesel engine, consequently reducing air pollution problems.

Experimental Investigation, Techno-Economic Analysis and Environmental Impact of Bioethanol Production from Banana Stem

Banana stem is being considered as the second largest waste biomass in Malaysia. Therefore, the environmental challenge of managing this huge amount of biomass as well as converting the feedstock into value-added products has spurred the demand for diversified applications to be implemented as a realistic approach. In this study, banana stem waste was experimented for bioethanol generation via hydrolysis and fermentation methods with the presence of Saccharomyces cerevisiae (yeast) subsequently. Along with the experimental analysis, a realistic pilot scale application of electricity generation from the bioethanol has been designed by HOMER software to demonstrate techno-economic and environmental impact. During sulfuric acid and enzymatic hydrolysis, the highest glucose yield was 5.614 and 40.61 g/L, respectively. During fermentation, the maximum and minimum glucose yield was 62.23 g/L at 12 h and 0.69 g/L at 72 h, respectively. Subsequently, 99.8% pure bioethanol was recovered by a distillation process. Plant modeling simulated operating costs 65,980 US$/y, net production cost 869347 US$ and electricity cost 0.392 US$/kWh. The CO2 emission from bioethanol was 97,161 kg/y and SO2 emission was 513 kg/y which is much lower than diesel emission. The overall bioethanol production from banana stem and application of electricity generation presented the approach economically favorable and environmentally benign.

Valorization of sewage sludge via non-catalytic transesterification

To seek a way to valorize sewage sludge (SS), it was chosen as a raw material for biodiesel production. As such, non-catalytic transesterification of dried SS was carried out, to enhance its value. Note that picking a waste material such as SS as an inexpensive lipid feedstock for biodiesel production, without lipid extraction, greatly increases the economic viability of biodiesel. Also, to enhance biodiesel sustainability, ethanol (EtOH) was employed as the acyl acceptor, in this study, and this was experimentally justified by results showing that employing EtOH as an acyl acceptor provided an effective means for compensating for the lower heating value arising from the large amount of palmitic (C₁₆) acid in SS. This study experimentally proved that the fatty acid ethyl ester (FAEE) yield at 380 °C reached up to 13.33 wt% of dried SS. Given that the lipid content of dried SS is 14.01 ± 0.64 wt%, the FAEE yield of 13.33 wt% implied that 95.14 wt% of lipid in dried SS had been converted into FAEEs. The introduced SS valorization in this study offered an excellent opportunity to address diverse environmental hazards arising from SS and associated emerging contaminants. Given that the optimal temperature for the non-catalytic conversion for biodiesel production from SS was found to be 380 °C, emerging contaminants, such as microplastics and antimicrobials, were simultaneously degraded, due to their inferior thermal stabilities. Lastly, considering that the introduced biodiesel conversion process is thermally induced, the SS reside after the biodiesel conversion process can be further used in thermo-chemical processes as raw materials for gasification and pyrolysis (future work).

Techno-Economic Analysis and Physicochemical Properties of Ceiba pentandra as Second-Generation Biodiesel Based on ASTM D6751 and EN 14214

Processing biodiesel from non-edible sources of feedstock seems to be thriving in recent years. It also has also gathered more attention than in the past, mainly because the biodiesel product is renewable and emits lower pollution compared to fossil fuels. Researchers have started their work on various kinds of biodiesel product, especially from a non-edible feedstock. Non-edible feedstocks such as Ceiba pentandra show great potential in the production of biodiesel, especially in the Southeast Asia region because the plants seem to be abundant in that region. Ceiba pentandra, also known as the Kapok tree, produces hundreds of pods with a length of 15 cm (5.9 in) and diameter 2–5 cm (1–2 in). The pods consist of seeds and fluff in the surrounding areas inside the pod, which itself contains yellowish fibre, a mixture of cellulose and lignin. The seeds of Ceiba pentandra can be used as feedstock for biodiesel production. The study for Ceiba pentandra will involve techno-economic, as well as a sensitivity analysis. Moreover, the study also shows that the techno-economic analysis of a biodiesel processing plant for 50 ktons Ceiba pentandra with a life span of 20 years is around $701 million with 3.7 years of the payback period. Besides that, this study also shows the differences in operating cost and oil conversion yield, which has the least impact on running cost. By improving the conversion processes continuously and by increasing the operational efficiency, the cost of production will decrease. In addition, the study also explains the differences of final price biodiesel and diesel fossil fuel, both showing dissimilar scenarios subsidy and taxation. Biodiesel has a subsidy of $0.10/L and $0.18/L with a total tax exemption of 15%. The value was obtained from the latest subsidy cost and diesel in Malaysia. Finally, further research is needed in order to fully utilize the use of Ceiba pentandra as one of the non-edible sources of biodiesel.

Performance Analysis of a Compression Ignition Engine Using Mixture Biodiesel Palm and Diesel

The present investigation analyzes the performance of a Hatz diesel engine that has 912 cubic centimeters (cc), stationary type, two cylinders, an air cooled feature and B10 (90% diesel and 10% palm biodiesel), using a test bench to improve statistically the repeatability and reproducibility of the runs. The experimental reference tests were carried out under defined conditions at a fixed speed of 1800 revolutions per minute (rpm) and four load levels: 35%, 50%, 65% and 80%. The repeatability analysis was based on the technical standard NTC-ISO / IEC17025. The variables of torque, fuel consumption (FC), air consumption (AC) and exhaust gas temperatures (EGT) showed an increase related with the load increase, showing a lower variation of AC and emissions. With the mechanism’s implementation of attenuator of air blows, adjustment mechanism for rpm and preheating air chamber for intake manifold, it was observed that the rpm presented the lowest statistical variability. The variables that presented the highest Pearson correlation with respect to the FC are the CO2, NOX and O2, this is because the engine does not have the Common Rail system, which causes the fuel supply to not be injected accurately and uniformly, therefore the evaluation of performance of the engine could not be repeatable.

Numerical evaluation of pollutant emissions of a two-stroke linear engine

Combustion engines bring a lot of pollution products to human living environment. This study introduced a green engine called free-piston linear engine (FPLE), and performed an evaluation on the pollutant emissions of a diesel FPLE by comparison with a corresponding conventional crankshaft engine (CCE). The combustion reaction and pollutant formation were described by a comprehensive model which considers the special operation mechanism of the FPLE. The effect of dynamic and fuel quantity on the unclean combustion products of the FPLE and the CCE was compared. Results indicate that in the case of the fuel quantity of 7.1 mg condition, the pollutant forming in the FPLE is generally later than that in CCE because of the higher speed of FPLE around the reverse point of stroke, and a significant advantage in nitric oxide (NO) emission is found for the FPLE, although it emits more carbon monoxide (CO) and soot. Moreover, compared with the CCE, the FPLE is cleaner in lean fuel conditions because the NO production of the FPLE is only half of that of the CCE, and that of other pollutants is almost at the same level. However, in heavy fuel conditions, the FPLE shows a disadvantage in CO and soot emission due to the serious afterburning effect and poor oxygen environment in some local areas, although its NO production is still lower than that of the CCE.

Latest development in microalgae-biofuel production with nano-additives

BACKGROUND

Microalgae have been experimented as a potential feedstock for biofuel generation in current era owing to its' rich energy content, inflated growth rate, inexpensive culture approaches, the notable capacity of CO₂ fixation, and O₂ addition to the environment. Currently, research is ongoing towards the advancement of microalgal-biofuel technologies. The nano-additive application has been appeared as a prominent innovation to meet this phenomenon.

MAIN TEXT

The main objective of this study was to delineate the synergistic impact of microalgal biofuel integrated with nano-additive applications. Numerous nano-additives such as nano-fibres, nano-particles, nano-tubes, nano-sheets, nano-droplets, and other nano-structures' applications have been reviewed in this study to facilitate microalgae growth to biofuel utilization. The present paper was intended to comprehensively review the nano-particles preparing techniques for microalgae cultivation and harvesting, biofuel extraction, and application of microalgae-biofuel nano-particles blends. Prospects of solid nano-additives and nano-fluid applications in the future on microalgae production, microalgae biomass conversion to biofuels as well as enhancement of biofuel combustion for revolutionary advancement in biofuel technology have been demonstrated elaborately by this review. This study also highlighted the potential biofuels from microalgae, numerous technologies, and conversion processes. Along with that, the study recounted suitability of potential microalgae candidates with an integrated design generating value-added co-products besides biofuel production.

CONCLUSIONS

Nano-additive applications at different stages from microalgae culture to end-product utilization presented strong possibility in mercantile approach as well as positive impact on the environment along with valuable co-products generation into the near future.

Palm oil and its wastes as bioenergy sources: a comprehensive review

Due to global warming and increasing price of fossil fuel, scientists all over the world have been trying to find reliable alternative fuels. One of the most potential candidates is renewable energy from biomass. The race for renewable energy from biomass has long begun and focused on to combat the deteriorating condition of the environment. Palm oil has been in the spotlight as an alternative of bioenergy sources to resolve fossil fuel problem due to its environment-friendly nature. This review will look deep into the origins of palm oil and how it is processed, bioproducts from this biomass, and oil palm biomass-based power plant in Malaysia. Palm oil is usually processed from oil palm fruits and other parts of the oil palm plant are candidates for raw material of bioproduct generation. Oil palm biomass can be turned into three subcategories: bioproduct, biofuels, and biopower. Focusing on biofuel, the biodiesel from palm oil will be explored in detail and its implication in Malaysia as one of the biggest producers of oil palm in the world will also be emphasized comprehensively. The paper presents the detail of a schematic flow diagram of a palm oil mill process of transforming oil palm into crude palm oil and it wastes. This paper will also discuss the current oil palm biomass power plants in Malaysia. Palm oil has been proven itself as a potential alternative to reduce negative environmental impact of global warming.

Enhancement in combustion, performance, and emission characteristics of a diesel engine fueled with diesel, biodiesel, and its blends by using nanoadditive

This article presents the results of investigations carried out to evaluate the improvement in combustion, performance, and emission characteristics of a diesel engine fueled with neat petro-diesel (PD), soybean biodiesel (SB), and 50% SB blended PD (PD50SB) by using carbon nanotube (CNT) as an additive. The acid-alkaline-based transesterification process with sodium hydroxide (NaOH) as a catalyst was applied to derive the methyl ester of SB. A mass fraction of 100 ppm CNT nanoparticle was blended with base fuels by using an ultrasonicator and the physiochemical properties were measured based on EN standards. The measured physiochemical properties are in good agreement with standard limits. The experimental evaluations were carried out under varying brake mean effective pressure (BMEP) conditions in a single-cylinder, four-stroke, and natural aspirated research diesel engine at a constant speed of 1500 rpm. The results reveal that the SB and its blend promote shorter ignition delay period (IDP) that is resulting in lower in-cylinder pressure (ICP) and net heat release rate (NHR) compared to PD. The SB and its blend increase the brake specific fuel consumption (BSFC), and reduce the brake specific energy consumption (BSEC) and exhaust gas temperature (EGT), due to lower heating value, and efficient combustion, respectively. As far as the emission characteristics are concerned, the SB and its blend promote lower magnitude of hydrocarbon (HC), carbon monoxide (CO), carbon dioxide (CO₂), and smoke emissions compared to PD except for oxides of nitrogen (NO_x) emission. The CNT nanoparticle inclusion with base fuels significantly improves the combustion, performance, and emissions level irrespective of engine load conditions.

Generation of biodiesel from industrial wastewater using oleaginous yeast: performance and emission characteristics of microbial biodiesel and its blends on a compression injection diesel engine

Microbial-derived biodiesel was tested on a lab scale CI diesel engine for carrying out exhaust emission and performance characteristics. The performance, emission, and combustion characteristics of a single cylinder four stroke fixed compression ratio engine when fueled with microbial bio-diesel and its 10-30% blends with diesel (on a volume basis) were investigated and compared with conventional diesel. The bio-diesel was obtained from microbes which were grown by combining distillery spent wash with lignocellulosic hydrolysate at nutrient deprived conditions. The microbes consumed the wastes and converted the high strength waste water into lipids, which were trans-esterified to form bio-diesel. Testing of microbial bio-diesel blends with ordinary diesel at different loading pressures and the emission characteristics were compared. Results indicate that with increasing of the blends, reduction of HC and CO emissions were observed, whilst brake thermal efficiency maxed out at 20% blending. Further increase of blends showed a tendency of increasing of both emissions in the exhaust stream. The Brake Specific Fuel consumption was observed to decline with blending until 20% and then increased. The nitrogen oxide emissions, however, were found to increase with increasing blend ratios and reached a maximum at 20% blend. The escalation of HC, CO, CO₂, and NOx emissions was also observed at higher blending ratios and higher engine loads. The performance studies were able to show that out of the three blends of biodiesel, 20% biodiesel blend was able to deliver the best of reduced hydrocarbon and carbon monoxide emissions, whilst also delivering the highest Brake thermal efficiency and the lowest Brake Specific Fuel consumption.

Fundamental Characteristics and Kinetic Analysis of Lignocellulosic Woody and Herbaceous Biomass Fuels

Biomass fuels are increasingly being viewed as viable alternatives for energy production in biomass-fired power plants and coal-fired power plants, which aim to employ co-firing technologies to achieve CO2 emission reductions. In this study, wood pellets (woody biomass) and kenaf (herbaceous biomass) were fully characterized in terms of their elemental compositions, pyrolysis, and char oxidation kinetics. Kinetic parameters were obtained through the application of the multi-Gaussian distributed activation energy model (DAEM) and Kissinger equation. Analyses of the ash indicated that, unlike coal, the biomass fuel is mostly composed of metal oxide ash. The calorific values of wood pellets were slightly higher than those of kenaf. Detailed kinetic analyses are presented so that steps can be taken to combust the biomass fuels in power plants. The kinetic data suggested that the mechanism for the char oxidation of wood pellets may be more complex than that for kenaf. In summary, these torrefied and pyrolyzed materials were found to represent potentially useful biomass fuels.

Impact of rice husk nanoparticle on the performance and emission aspects of a diesel engine running on blends of pine oil-diesel

With the increase in vehicle density, the amount of pollution along with the dependence on the diesel fuel also increases, which might be on the verge of depletion. The increase in fuel price is an important economical factor. Hence, finding a suitable substitute energy source which is economic and also meets the energy necessity is of great need. During this study, the utilization of pine oil biofuel in which rice husk (RH) nanoparticles was added as an additive was proposed. The test was carried out in a single cylinder, diesel engine at 1500 rpm. Fuel is blended at two ratios (B10, B20) and 0.1% of RH nano-additive is added with each blend and their characteristics in terms of performance and emission are analyzed for varied load conditions. At full load condition for B10-0.1% RH, there is a slight reduction of about 3.04% for BTE and 4.1% increase in BSFC than diesel fuel was observed. Likewise, for B20-0.1% RH at full load condition CO and HC decreases about 27.27% and 19.64% respectively, with a rise in CO₂ and a slight increase of NOx level at 15.63%, 8.76% respectively than diesel fuel. This small replacement of diesel fuel by biodiesel helps in reducing the increasing cost and also the complete dependency on the fossil-based fuel. Thus, pine oil with additive can perform well without any engine modifications and helps in reducing the pollutions.

Multi-objective optimization of diesel engine performance and emissions fueled with diesel-biodiesel-fusel oil blends using response surface method

The interest in research on alcohol-based biofuels is on the rise. Fusel oil is a long-chain alcohol and a by-product of bioethanol synthesis. This study analyzed the effects of blended levels of fusel oil and biodiesel in diesel fuel on the performance and exhaust emissions of a single-cylinder diesel engine. The effects of input parameters (i.e., fusel oil content (%), biodiesel content (%), engine speed (rpm), and engine load (%), each at five levels) on response parameters (i.e., power, torque, fuel consumption, and emission factors, namely NO_X, UHC, CO, and CO₂) were investigated. Different levels were used for analyzing fusel oil (0, 5, 10, 15, and 20%), biodiesel (0, 5, 10, 15, and 20%), engine load (0, 25, 50, 75, and 100%), and engine speed (1400, 1700, 2000, 2300, and 2600 rpm). Response surface method (RSM) was employed to maximize engine performance and minimize exhaust emissions. A blend of D₉₀F₅ B₅ (5% fusel oil, 5% biodiesel, and 90% petro-diesel) and engine speed of 2026 rpm at load 46% were predicted to be an optimal value. Using a 72% desirability function, optimum results for torque (14.2 Nm), power (3.37 kW), and brake-specific fuel consumption (356.9 g/kWh) were also obtained from RSM. Based on the optimized inputs, the optimized values of different output pollutants were 0.14 vol.% for CO, 1.62 vol.% for CO₂, 23.7 ppm for UHC, and 85.17 ppm for NO_X. The result illustrated that use of fusel oil decreased NO_X emissions up to 20%, while UHC and CO emissions increased up to 32% and 22%, respectively. In addition, the use of fusel oil content (up to 10%) in the blended fuels improved the engine power by 5.6%.

Biodiesel Production from a Novel Nonedible Feedstock, Soursop (Annona muricata L.) Seed Oil

This study investigated the optimal reaction conditions for biodiesel production from soursop (Annona muricata) seeds. A high oil yield of 29.6% (w/w) could be obtained from soursop seeds. Oil extracted from soursop seeds was then converted into biodiesel through two-step transesterification process. A highest biodiesel yield of 97.02% was achieved under optimal acid-catalyzed esterification conditions (temperature: 65 °C, 1% H2SO4, reaction time: 90 min, and a methanol:oil molar ratio: 10:1) and optimal alkali-catalyzed transesterification conditions (temperature: 65 °C, reaction time: 30 min, 0.6% NaOH, and a methanol:oil molar ratio: 8:1). The properties of soursop biodiesel were determined and most were found to meet the European standard EN 14214 and American Society for Testing and Materials standard D6751. This study suggests that soursop seed oil is a promising biodiesel feedstock and that soursop biodiesel is a viable alternative to petrodiesel.