Determination of ecological efficiency in internal combustion engines: The use of biodiesel

This paper evaluates and quantifies the environmental impact from the use of some renewable fuels and fossils fuels in internal combustion engines. The following fuels are evaluated: gasoline blended with anhydrous ethyl alcohol (anhydrous ethanol), conventional diesel fuel, biodiesel in pure form and blended with diesel fuel, and natural gas. For the case of biodiesel, its complete life cycle and the closed carbon cycle (photosynthesis) were considered. The ecological efficiency concept depends on the environmental impact caused by CO₂, SO₂, NO_x and particulate material (PM) emissions. The exhaust gases from internal combustion engines, in the case of the gasoline (blended with alcohol), biodiesel and biodiesel blended with conventional diesel, are the less polluting; on the other hand, the most polluting are those related to conventional diesel. They can cause serious problems to the environment because of their dangerous components for the human, animal and vegetable life. The resultant pollution of each one of the mentioned fuels are analyzed, considering separately CO₂, SO₂, NO_x and particulate material (PM) emissions. As conclusion, it is possible to calculate an environmental factor that represents, qualitatively and quantitative, the emissions in internal combustion engines that are mostly used in urban transport. Biodiesel in pure form (B100) and blended with conventional diesel as fuel for engines pollute less than conventional diesel fuel. The ecological efficiency for pure biodiesel (B100) is 86.75%; for biodiesel blended with conventional diesel fuel (B20, 20% biodiesel and 80% diesel), it is 78.79%. Finally, the ecological efficiency for conventional diesel, when used in engines, is 77.34%; for gasoline, it is 82.52%, and for natural gas, it is 91.95%. All these figures considered a thermal efficiency of 30% for the internal combustion engine.     

Hydrogen addition to tea seed oil biodiesel: Performance and emission characteristics

Compression ignition engines are the dominant tools of the modern human life especially in the field of transportation. But, the increasing problematic issues such as decreasing reserves and environmental effects of diesel fuels which is the energy source of compression ignition engines forcing researchers to investigate alternative fuels for substitution or decreasing the dependency on fossil fuels. The mostly known alternative fuel is biodiesel fuel and many researchers are investigating the possible raw materials for biodiesel production. Also, hydrogen fuel is an alternative fuel which can be used in compression ignition engines for decreasing fuel consumption and hazardous exhaust emissions by enriching the fuel. In this study, influences of hydrogen enrichment to diesel and diesel tea seed oil biodiesel blends (B10 and B20) were investigated on an unmodified compression ignition engine experimentally. In consequence of the experiments, lower torque and higher brake specific fuel consumption data were measured when the engine was fuelled diesel biodiesel blends (B10 and B20) instead of diesel fuel. Also, diesel biodiesel blends increased CO₂ and NO_x emissions while decreasing the CO emissions. Hydrogen enrichment (5 l/m and 10 l/m) was improved the both torque and brake specific fuel consumption for all test fuels. Furthermore, hydrogen enrichment reduced CO and CO₂ emissions due to absence of carbon atoms in the chemical structure for all test fuels. Increasing flow rate of hydrogen fuel from 5 l/m to 10 l/m further improved performance measures and emitted harmful gases except NO_x. The most significant drawback of the hydrogen enrichment was the increased NO_x emissions.     

Ecological efficiency in CHP: Biodiesel case

This paper evaluates and quantifies the environmental impact resulting from the combination of biodiesel fuel (pure or blended with diesel), and diesel combustion in thermoelectric power plants that utilize combined cycle technology (CC). In regions without natural gas, the option was to utilize diesel fuel; the consequence would be a greater emission of pollutants. Biodiesel is a renewable fuel which has been considerably interesting in Brazil power matrix in recent years. The concept of ecological efficiency, largely evaluates the environmental impact caused by CO₂, SO₂, NO_x and particle matter (PM) emissions. The pollution resulting from biodiesel and diesel combustion is analyzed, separately considering CO₂, SO₂, NO_x and particulate matter gas emissions, and comparing them international standards currently used regarding air quality. It can be concluded that it is possible to calculate the qualitative environmental factor, and the ecological effect, from a thermoelectric power plant utilizing central heat power (CHP) of combined cycle. The ecological efficiency for pure biodiesel fuel (B100) is 98.16%; for biodiesel blended with conventional diesel fuel, B20 (20% biodiesel and 80% diesel) is 93.19%. Finally, ecological efficiency for conventional diesel is 92.18%, as long as a thermal efficiency of 55% for thermoelectric power plants occurs.     

Effect of ethanol blending with biodiesel on engine performance and exhaust emissions in a CI engine

The use of biodiesel as an alternative diesel engine fuel is increasing rapidly. However, due to technical deficiencies, they are rarely used purely or with high percentages in unmodified diesel engines. Therefore, in this study, we used ethanol as an additive to research the possible use of higher percentages of biodiesel in an unmodified diesel engine. Commercial diesel fuel, 20% biodiesel and 80% diesel fuel, called here as B20, and 80% biodiesel and 20% ethanol, called here as BE20, were used in a single cylinder, four strokes direct injection diesel engine. The effect of test fuels on engine torque, power, brake specific fuel consumption, brake thermal efficiency, exhaust gas temperature, and CO, CO₂, NO_x and SO₂ emissions was investigated. The experimental results showed that the performance of CI engine was improved with the use of the BE20 especially in comparison to B20. Besides, the exhaust emissions for BE20 were fairly reduced.     

Life cycle energy,environment and economic assessment of soybean-based biodiesel as an alternative automotive fuel in China

Life cycle energy, environment and economic assessment for conventional diesel (CD) and soybean-based biodiesel (SB) in China was carried out in this paper. The results of the assessment have shown that compared with CD, SB has similar source-to-tank (StT) total energy consumption, 76% lower StT fossil energy consumption, 79% higher source-to-wheel (StW) nitrogen oxides (NO_X) emissions, 31%, 44%, 36%, 29%, and 67% lower StW hydrocarbon (HC), carbon monoxide (CO), particulate matter (PM), sulfur oxides (SO_X), and carbon dioxide (CO₂) emissions, respectively. SB is thus considered to be much more renewable and cleaner than CD. However, the retail price of SB at gas stations would be about 86% higher than that of CD without government subsidy according to the cost assessment and China had to import large amount of soybean to meet the demand in recent years. Therefore, although SB is one of the most promising clean and alternative fuels, currently it is not a good choice for China. It is strategically important for China to diversify the feedstock for biodiesel and to consider other kinds of alternative fuels to substitute CD.     

Experimental determination and analysis of CO2, SO2 and NOx emission factors in Iran’s thermal power plants

Emission factors of CO₂, SO₂ and NO_x emitted from Iran’s thermal power plants are fully covered in this paper. To start with, emission factors of flue gases were calculated for fifty thermal power plants with the total installed capacity of 34,863 MW over the period 2007–2008 with regard to the power plants’ operation characteristics including generation capacity, fuel type and amount and the corresponding alterations, stack specifications, analysis of flue gases and physical details of combustion gases in terms of g kWh⁻¹. This factor was calculated as 620, 2.57 and 2.31 g kWh⁻¹ for CO₂, SO₂ and NO_x respectively. Regarding these results, total emissions of CO₂, SO₂ and NO_x were found to be 125.34, 0.552 and 0.465 Tg in turn. To achieve an accurate comparison, these values were compared with their alternatives in North American countries. According to this comparison, emission factor of flue gases emitted from Iran’s thermal power plants will experience an intensive decline if renewable, hydroelectric and nuclear types of energy are more used, power plants’ efficiency is increased and continuous emission monitoring systems and power plant pollution reduction systems are utilized.     

Biodiesel production from inedible animal tallow and an experimental investigation of its use as alternative fuel in a direct injection diesel engine

In this study, a substitute fuel for diesel engines was produced from inedible animal tallow and its usability was investigated as pure biodiesel and its blends with petroleum diesel fuel in a diesel engine. Tallow methyl ester as biodiesel fuel was prepared by base-catalyzed transesterification of the fat with methanol in the presence of NaOH as catalyst. Fuel properties of methyl ester, diesel fuel and blends of them (5%, 20% and 50% by volume) were determined. Viscosity and density of fatty acid methyl ester have been found to meet ASTM D6751 and EN 14214 specifications. Viscosity and density of tallow methyl esters are found to be very close to that of diesel. The calorific value of biodiesel is found to be slightly lower than that of diesel. An experimental study was carried out in order to investigate of its usability as alternative fuel of tallow methyl ester in a direct injection diesel engine. It was observed that the addition of biodiesel to the diesel fuel decreases the effective efficiency of engine and increases the specific fuel consumption. This is due to the lower heating value of biodiesel compared to diesel fuel. However, the effective engine power was comparable by biodiesel compared with diesel fuel. Emissions of carbon monoxide (CO), oxides of nitrogen (NO_x), sulphur dioxide (SO₂) and smoke opacity were reduced around 15%, 38.5%, 72.7% and 56.8%, respectively, in case of tallow methyl esters (B100) compared to diesel fuel. Besides, the lowest CO, NO_x emissions and the highest exhaust temperature were obtained for B20 among all other fuels. The reductions in exhaust emissions made tallow methyl esters and its blends, especially B20 a suitable alternative fuel for diesel and thus could help in controlling air pollution. Based on this study, animal tallow methyl esters and its blends with petroleum diesel fuel can be used a substitute for diesel in direct injection diesel engines without any engine modification.     

Exhaust emissions and electric energy generation in a stationary engine using blends of diesel and soybean biodiesel

The present work describes an experimental investigation concerning the electric energy generation using blends of diesel and soybean biodiesel. The soybean biodiesel was produced by a transesterification process of the soybean oil using methanol in the presence of a catalyst (KOH). The properties (density, flash point, viscosity, pour point, cetane index, copper strip corrosion, conradson carbon residue and ash content) of the diesel and soybean biodiesel were determined. The exhaust emissions of gases (CO, CO₂,C_xH_y,O₂, NO, NO_x and SO₂) were also measured. The results show that for all the mixtures tested, the electric energy generation was assured without problems. It has also been observed that the emissions of CO, C_xH_y and SO₂ decrease in the case of diesel–soybean biodiesel blends. The temperatures of the exhaust gases and the emissions of NO and NO_x are similar to or less than those of diesel.     

Trade-off in emissions of acid gas pollutants and of carbon dioxide in fossil fuel power plants with carbon capture

This paper investigates the impact of capture of carbon dioxide (CO₂) from fossil fuel power plants on the emissions of nitrogen oxides (NO_X) and sulphur oxides (SO_X), which are acid gas pollutants. This was done by estimating the emissions of these chemical compounds from natural gas combined cycle and pulverized coal plants, equipped with post-combustion carbon capture technology for the removal of CO₂ from their flue gases, and comparing them with the emissions of similar plants without CO₂ capture. The capture of CO₂ is not likely to increase the emissions of acid gas pollutants from individual power plants; on the contrary, some NO_X and SO_X will also be removed during the capture of CO₂. The large-scale implementation of carbon capture is however likely to increase the emission levels of NO_X from the power sector due to the reduced efficiency of power plants equipped with capture technologies. Furthermore, SO_X emissions from coal plants should be decreased to avoid significant losses of the chemicals that are used to capture CO₂. The increase in the quantity of NO_X emissions will be however low, estimated at 5% for the natural gas power plant park and 24% for the coal plants, while the emissions of SO_X from coal fired plants will be reduced by as much as 99% when at least 80% of the CO₂ generated will be captured.     

Combustion of fat and vegetable oil derived fuels in diesel engines

In this article, the status of fat and oil derived diesel fuels with respect to fuel properties, engine performance, and emissions is reviewed. The fuels considered are primarily the methyl esters of fatty acids derived from a variety of vegetable oils and animal fats, and referred to as biodiesel. The major obstacle to widespread use of biodiesel is the high cost relative to petroleum. Economics of biodiesel production are discussed, and it is concluded that the price of the feedstock fat or oil is the major factor determining biodiesel price.Biodiesel is completely miscible with petroleum diesel fuel, and is generally tested as a blend. The use of biodiesel in neat or blended form has no effect on the energy based engine fuel economy. The lubricity of these fuels is superior to conventional diesel, and this property is imparted to blends at levels above 20 vol%. Emissions of PM can be reduced dramatically through use of biodiesel in engines that are not high lube oil emitters. Emissions of NO_x increase significantly for both neat and blended fuels in both two- and four-stroke engines. The increase may be lower in newer, lower NO_x emitting four-strokes, but additional data are needed to confirm this conclusion. A discussion of available data on unregulated air toxins is presented, and it is concluded that definitive studies have yet to be performed in this area. A detailed discussion of important biodiesel properties and recommendations for future research is presented. Among the most important recommendations is the need for all future studies to employ biodiesel of well-known composition and purity, and to report detailed analyses. The purity levels necessary for achieving adequate engine endurance, compatibility with coatings and elastomers, cold flow properties, stability, and emissions performance must be better defined.     

Performance and exhaust emission characteristics of a CI engine fueled with Pongamia pinnata methyl ester (PPME) and its blends with diesel

Transport vehicles greatly pollute the environment through emissions such as CO, CO₂, NO_x, SO_x, unburnt or partially burnt HC and particulate emissions. Fossil fuels are the chief contributors to urban air pollution and major source of green house gases (GHGs) and considered to be the prime cause behind the global climate change. Biofuels are renewable, can supplement fossil fuels, reduce GHGs and mitigate their adverse effects on the climate resulting from global warming. This paper presents the results of performance and emission analyses carried out in an unmodified diesel engine fueled with Pongamia pinnata methyl ester (PPME) and its blends with diesel. Engine tests have been conducted to get the comparative measures of brake specific fuel consumption (BSFC), brake specific energy consumption (BSEC) and emissions such as CO, CO₂, HC, NO_x to evaluate the behaviour of PPME and diesel in varying proportions. The results reveal that blends of PPME with diesel up to 40% by volume (B40) provide better engine performance (BSFC and BSEC) and improved emission characteristics.     

Review of NOx reduction technologies in CI engines fuelled with oxygenated biomass fuels

Oxygenated fuels like biodiesel and alcohols have the potential to provide a reliable and a cost effective alternative to India's increasing future energy demands. They have a prospective future since they are renewable and can be produced easily in India's rural areas. Due to rapid industrialization and the increased number of vehicles on the road, the energy needs of the country are increasing rapidly. Oxygenated fuels can substantially replace the large demand for diesel to generate power for the industries and to fuel diesel engines of the vehicles. In spite of the many advantages of using them, most of the researchers have reported higher NO_x emissions, which is a deterrent to the market expansion of these fuels. The present program aims to review the NO_x emissions from the CI engines fuelled with oxygenated fuels. To meet the stringent emission norms, the various NO_x reduction technologies like use of additives, retarded fuel injection timing, biodiesel emulsion with water, and exhaust gas recirculation are reviewed. The results of the most effective and low cost technique of EGR in DI diesel engine fuelled with biodiesel–diesel blends and tri-compound oxygenated diesel fuel blends (ethanol–biodiesel–diesel fuel blends and methanol–biodiesel–diesel fuel blends) are presented.     

NOX emissions of compression ignition engines fueled with various biodiesel blends: A review

There are some challenges about NO_X emissions exhausted from diesel engines fueled with biodiesel. Due to increasingly stringent emission regulations, the different methods such as varying the engine operating parameters, treatment with antioxidant additive and blending fuels have been adapted to reduce emissions of biodiesel combustion. One of the effective methods is the combustion of dual or blending fuels. Various fuels such as gasoline, hydrogen, natural gas, biogas, different types of alcohols and also fuel additives have been used to reduce biodiesel disadvantages. This study reviews the potential of the different fuels as an additive in biodiesel fuel in correspond to reduce NO_X emissions. The general reduction of NO_X has been observed with the presence of gasoline, biogas and alcohols in biodiesel blends. The reduction of NO_X in biodiesel-hydrogen, biodiesel-diesel or biodiesel–CNG combustion has not been observed through all engine conditions. Moreover the retarding injection timing, the lower injection pressure, EGR higher than 30% can result in the reduced NO_X emissions. However it seems the decrease in NO_X emissions can be achieved by the use of most fuels in blending with biodiesel under all engine operating conditions, if only the proper injection parameters and blending proportions of fuels are set.     

Improving the low-temperature properties of biodiesel: Methods and consequences

Biodiesel is widely accepted as an additive for fossil derived diesel in compression ignition engines. It offers many advantages including: higher cetane number; reduced emissions of particulates, NO_x, SO_x, CO, and hydrocarbons; reduced toxicity; improved safety; and lower lifecycle CO₂ emissions. A characteristic of biodiesel limiting its application is its relatively poor low-temperature flow properties, which are primarily a consequence of the fatty acid make-up of the oil feedstock. Attempts to influence the fatty acid profile of either the oil feedstock or the biodiesel product include winterisation and fractionation which reduce the fraction of saturated fatty acids and result in large reductions in yield. A reduction in saturated fatty acids reduces ignition quality of the fuel, while an increase in unsaturation reduces oxidation stability. Additives designed for petroleum diesel have been used with limited success and specific additives for biodiesel remain in their infancy. The addition of branched moieties either to the alkyl head-group of the ester or as a side-chain to the tail-group can reduce the cloud point. Specifically, the removal of the double bonds on the ester group and the addition of a side-chain may provide a benefit in terms of low-temperature properties and offer improved oxidation stability. However, a negative impact on ignition quality and viscosity may result.     

Comparative study of regulated and unregulated gaseous emissions during NEDC in a light-duty diesel engine fuelled with Fischer Tropsch and biodiesel fuels

In this study, regulated and unregulated gaseous emissions and fuel consumption with five different fuels were tested in a 4-cylinder, light-duty diesel EURO IV typically used for the automotive vehicles in Europe. Three different biodiesel fuels obtained from soybean oil, rapeseed oil and palm oil, a Fischer Tropsch fuel and an ultra low sulphur diesel were studied. The test used was the New European Driving Cycle (NEDC), this allowed tests to be carried out on an engine warmed up beforehand to avoid the effect of cold starts and several tests a day. Regulated emissions of NO_X, CO, HC and CO₂ were measured for each fuel. Unburned Hydrocarbon Speciation and formaldehyde were also measured in order to determine the maximum incremental reactivity (MIR) of the gaseous emissions. Pollutants were measured without the diesel oxidation catalyst (DOC) to gather data about raw emissions. When biodiesel was used, increases in regulated and unregulated emissions were observed and also significant increases in engine fuel consumption. The use of Fischer Tropsch fuel, however, caused lower regulated and unregulated emissions and fuel consumption than diesel.     

A new approach for simplifying the calculation of flue gas specific heat and specific exergy value depending on fuel composition

In this paper, a new approach is proposed for simplifying the calculation of flue gas specific heat and specific exergy value in one formulation depending on fuel chemical composition. Combustion products contain different gases such as CO₂, SO₂, N₂, O₂, H₂O and etc., depending on the burning process. Specific heat and exergy of the flue gas differ depending on the chemical composition of fuels, excess air ratio and gas temperature. Through this new approach, specific heat and specific exergy value of combustion products can be estimated accurately in one formulation by entering the chemical composition of fuels, excess air ratio and gas temperature. The present approach can be applied to all carbon based fuels, especially biomass, fossil fuels and fuel mixtures for co-combustion and is so suitable for practical estimation of flue gas specific heat and specific exergy values provided that the fuel chemical composition is given.     

Oxides of nitrogen emissions from biodiesel-fuelled diesel engines

Biodiesel has received, and continues to receive, considerable attention for its potential use as an augmenting fuel to petroleum diesel. Its advantages include decreased net carbon dioxide, hydrocarbon, carbon monoxide, and particulate matter emissions, and fuel properties similar to petroleum diesel for ease of use in diesel engines. Its disadvantages include poorer cold flow characteristics, lower heating values, and mostly reported higher emissions of oxides of nitrogen (NO_x = NO + NO₂, where NO is nitric oxide and NO₂ is nitrogen dioxide). This latter disadvantage (i.e., higher emissions of oxides of nitrogen) is the focus of this review article. NO_x formation mechanisms are complex and affected by several different features (e.g., size, operating points, combustion chamber design, fuel system design, and air system design) of internal combustion engines. The slight differences in properties between biodiesel and petroleum diesel fuels are enough to create several changes to system and combustion behaviors of diesel engines. Combined, these effects lead to several complex and interacting mechanisms that make it difficult to fundamentally identify how biodiesel affects NO_x emissions. Instead, it is perhaps better to say that several parameters seem to most strongly influence observed differences in NO_x emissions with biodiesel, thus introducing several possibilities for inconsistency in the trends. These parameters are injection timing, adiabatic flame temperature, radiation heat transfer, and ignition delay. This article provides a review of the rich literature describing these parameters, and provides additional insight into the system responses that are manifested by the use of biodiesel.     

Biodiesel as alternative fuel: Experimental analysis and energetic evaluations

This paper presents the first results of an investigation carried out by the authors on the potentialities of biodiesel as an alternative fuel based on strategic considerations and field experiences in boilers and diesel engines.The operation of a biodiesel fuelled boiler has been checked for some months. The engines have been bench-tested and then installed on urban buses for normal operation. Distances, fuel consumption and emissions (CO₂, CO, HC and NO_X) have been monitored; in addition devices wear and tear, oil and air filters dirtiness and lubricant degradation have been checked.Further investigations have also been devoted to assess some environmental aspects of bio-diesel. In particular the benefit of biodiesel to the total net emission of CO₂ during the whole life cycle has been studied and the net energy requirement has been evaluated.Finally, the global environmental support to the production of biodiesel has been studied according to the emergy analysis.     

Effect of heavy fuel oil/natural gas co-combustion on pollutant generation in retrofitted power plant

The purpose of this paper is to examine effect of co-combustion of heavy fuel oil and natural gas on the pollutant formation: CO₂, SO₂, SO₃, NO_X and soot. The analysis was carried out by means of numerical simulation on the case of retrofitted steam generator furnace of Thermal Power Plant Sisak (Croatia). Comprehensive mathematical model of the furnace with detailed 3D mesh was set up to include all relevant aerodynamic and thermo-chemical processes in the furnace. Dedicated model for SO₃ formation was developed earlier and used in this work. By increasing the natural gas contribution in overall fuel fired in the furnace, emissions of CO₂, SO₂, soot, NO_X and SO₃ decreased. Heat transferred to the furnace walls and temperature field in the furnace were also examined in order to establish regions of safe and efficient boiler operation for different operational regimes.     

Estimate of ecological efficiency for thermal power plants in Brazil

Global warming and the consequent climatic changes that will come as a result of the increase of CO₂ concentration in the atmosphere have increased the world’s concern regarding reduction of these emissions, mainly in developed countries that pollute the most. Electricity generation in thermal power plants, as well as other industrial activities, such as chemical and petrochemical ones, entail the emission of pollutants that are harmful to humans, animals and plants. The emissions of carbon oxides (CO and CO₂) and nitrous oxide (N₂O) are directly related to the greenhouse effect. The negative effects of sulfur oxides (SO₂ and SO₃ named SO_x) and nitrogen oxides (NO_x) are their contribution to the formation of acid rain and their impacts on human health and on the biota in general. This study intends to evaluate the environmental impacts of the atmospheric pollution resulting from the burning of fossil fuels. This study considers the emissions of CO₂, SO_x, NO_x and PM in an integral way, and they are compared to the international air quality standards that are in force using a parameter called ecological efficiency (ε).