Single Cylinder Direct Injection Research Articles

EXTRACTION, PERFORMANCE AND EMISSION CHARACTERIZATION OF DIESEL ENGINE USING WASTE LIPOLYTIC MICROORGANISM BIODIESEL

<p>In this study, milk waste water will be extracted, transformed into Lipolytic microorganism’s biodiesel (LMD) using transesterification, and tested for appropriateness as an alternative, sustainable, renewable source for IC engines. The properties of the created blends of biodiesel were investigated and compared to those of conventional diesel. The outcomes demonstrated that the fuel's fundamental characteristics are discussed with neat diesel. Investigated are the operation, combustion, and exhaust gas analysis of a test engine running on LMD. The studies involve running different biodiesel-diesel blends (B10, B20, B30, B40, B50, and B80) at varying loads (0, 25, 50, 75, and 100%) in a single-cylinder direct-injection diesel engine at a constant speed and comparing the results to the benchmark diesel. The values of break thermal efficiency(BTE) was decreased by 0.59, 0.68, 1.30 and 2.98% respectively for the blends of 10, 20, 30 and 50% of biodiesel mixing. The brake specific energy consumption (BSEC) is decreased by 0.1, 0.3, 0.44, and 0.77%. Any biodiesel-diesel combination reduces exhaust gas pollutants. At maximum load, the values of emissions like CO, HC, and smoke opacities of B30 decreased by 12.1%,3.94%, and 11% when compared to standard diesel. However, as per the analysis biodiesel of LMD is a potential alternative fuel that doesn't require significant alterations to be used in I.C engines.</p>

Synergetic effect of liquid fuel derived from various waste feedstocks on performance, combustion and emission in a compression ignition engine

ABSTRACT Diesel engines being predominant in transportation sector are limited in addressing the sustainable development goals. The pressing need of environmental concern and fossil fuel depletion enforces the research community toward search of alternative fuels. In such context, waste materials have emerged as a promising feedstock for producing sustainable alternatives for diesel, given their abundance and their significance in waste management. Consequently, in this work, the waste feedstocks identified were waste plastics, waste lubrication oil, waste animal fat obtained from tanneries, waste cooking oil and waste tyres. For extraction of oil from these plastics, lube and tyre oil, pyrolysis was used and transesterification process was adopted for extraction of DLF from waste animal fat and waste cooking oil. The collected DLF was given for fuel property testing and found to be at par to utilize in a CI engine. It was then blended with diesel in the form of B80 (80% DLF and 20% diesel) and named as WTO B80, WLO B80, WCO B80, WPO B80 and WAF B80. To identify the differences in various parameters like combustion, performance and emission of CI engine at various engine loads, a bench test of a single-cylinder direct injection diesel engine without engine modification was done. The blend B80 of waste oil is analyzed in this work for its combustion characteristics and emission of various gases like nitrogen oxide (NO), carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC) and smoke. Among various liquid fuels tested, WPO B80 blend resulted in 32.81% BTE with NO emission of 1885ppm. The results also show emission of 67.2% of smoke, 0.18% of CO and 48 ppm of HC. The cylinder peak pressure for WPO B80 was at 72.85 bar and 48.04 J/deg CA peak heat was released, which concludes it as a suitable fuel for diesel engine compared to other fuels without any engine customization.

Sustainability improvement by utilizing polymer waste as an energy source for a diesel engine with alcohol additives

Energy and fossil fuel supplies have been threatened by the depletion of fossil fuels on a global scale, as well as by the constant rise in oil prices and the continual increase in environmental degradation. On the other hand, polymer waste has increased due to its usage in a daily lifestyle because of its cheap cost, ease of production, and adaptability. Indirectly, these polymer wastes are causing some major problems for the ecosystem and other living things. By transforming waste polymers into usable energy, can address for both the non-biodegradability of polymers and the need for an alternative fuel. This research paper aims to evaluate the performance of fuel produced by the pyrolysis of polyethylene polymer. Three distinct alcohol additive blends with polymer fuel were investigated in a single-cylinder direct injection diesel engine for their performance and emission characteristics. The engine efficiency of pentanol was found to be about 3.4% higher than that of base diesel, and with 7% better fuel consumption. Additionally, alcohol additives reduced CO emissions by 3.6%–3.8% and HC emissions by 3.5%–3.8%. The results were further analysed using the design of experiment tool, "Full Factorial Design" to determine the most optimal running condition with fuel consumption of 0.4508 kg/kWh, hydrocarbon of 49 ppm and carbon monoxide 0.265% at half load conditions.

Performance and Emission Characteristics of a Diesel Engine Fueled with Calophyllum Inophyllum Biodiesel and Gasoline Additives

Production of fuel oil in Indonesia from year to year continues to decline. Calophyllum inophyllum biodiesel fuel is an alternative fuel that can be used in diesel engines. Gasoline is a fuel that can improve the characteristics of biodiesel. This research uses petrodiesel fuel, B30 (70% petrodiesel and 30% calophyllum inophyllum biodiesel), and B30 added with gasoline with a concentration of 10% vol/vol. The experiment was carried out with a direct injection single cylinder diesel engine connected to a generator that was used as a dynamometer and a gas analyzer was installed. Tests were carried out using lamp loads of 200, 400, 600, and 800 watts at a constant engine speed of 2000 rpm. The results of this research inform that the addition of gasoline to B30 fuel can reduce fuel consumption and increase thermal efficiency. The role of gasoline can also reduce CO, HC, and CO2 emissions. The addition of gasoline needs to be investigated further so that it can be applied to industry and transportation.
 

Thermal efficiency improvement of a spark ignition engine by stratified water distribution

The stratified water distribution was introduced on a single cylinder direct injection spark ignition engine by changing the direct Water Injection Timing (WIT) and Water Fuel Ratio (WFR) to control the water distribution states before ignition. Experiments were conducted to fundamentally understand the stratified water effects on combustion process control. The results show that different water injection timing could result in wall wetting state, homogeneous state, and stratified state. Stratified water distribution has more obvious suppression effects on knock combustion than other states. Furthermore, optimized combustion process of stratified water distribution case by advancing spark timing is with higher thermal efficiency than homogeneous case.Finally, with the experiment of increasing water injection amounts at stratified state, thermal efficiency increasing was realized by 2.1 %. The high correlation between ignition delay and knocking combustion was demonstrated, which substantiate that water stratified injection has much talent on knock combustion suppressing and thermal efficiency increasing. In further research, the stratified water effects by split injection strategy is hopeful to reduce the water amounts and avoiding oil dilution.

Performance of a single cylinder direct injection 4-stroke diesel engine under effect of using diesel and naphtha blends

The demand for diesel fuel in the transport industry is expected to rise due to greenhouse gas laws and global economic expansion, necessitating the search for alternative sources. If light distillate fuels can match diesel fuel's efficiency and cleanliness at a more affordable cost, they could potentially enter the market. This study assessed a 1-cylinder, 4-stroke diesel engine's performance using various blends of diesel and heavy naphtha: D100, D97.5N2.5, D95N5, D92.5N7.5, and D90N10. Tests were conducted at 3000 rpm and variable loads, revealing that the maximum permissible naphtha content in D100 is 10%. Higher naphtha proportions led to misfire and instability under heavy loads. 100% diesel demonstrated the lowest brake-specific fuel consumption and higher thermal efficiency, while 90% diesel + 10% naphtha showed the highest fuel consumption and lower thermal efficiency.

Prediction of single cylinder direct injection diesel engine performance fuelled with lemon peel oil biodiesel using artificial neural network

The aim of the present work is to predict the performance of single cylinder direct injection diesel engine fuelled with lemon peel oil biodiesel (B25) loaded by ceria nanoparticle additives and coated with yttria-ceria stabilized zirconia using Levenberg-Marquardt algorithm of single-input multiple-output artificial neural network (ANN). The dependent variables are brake power, indicated power, frictional power, brake thermal efficiency, indicated thermal efficiency, volumetric efficiency, fuel flowrate, air flowrate and specific fuel consumption at varying loads from 0 to 100%. The prediction ability of ANN was evaluated by determination coefficient (R 2 ) and root mean square error (RMSE). The average R 2 and RMSE of 0.93 and 0.82 show that the ANN fitted well to the experimental values of response variables at varying loads. The results also validate through correlation coefficient (R) of 0.99254.

Effects on ring wear of bioethanol/diesel fuel blends used at long term endurance tests in a DI engine

In this study, the long-term endurance tests were carried out in a diesel engine that used diesel and 90% diesel + 10% bioethanol fuels. The spray and temperature distributions of two different fuels in the AVL FIRE program also were examined. Tribological and morphological analysis of piston rings were investigated in a single-cylinder direct injection diesel engine using two different fuel types. The test engine used two different fuel types and was operated for approximately 110 hours under part engine load. Renewed rings in each fuelled engine operation were analyzed at Energy Dispersive X-ray Spectroscopy (EDX) and Scanning Electron Microscope (SEM). Results were also compared with the non-worked piston ring. Analysis results saw that abrasive wear was more intense on the first rings at both fuel types. Examining the effect of biofuels on engine wears, short wear lines were found at engine rings using diesel/bioethanol blend fuel compared to diesel fuel. It was being determined that this situation was a result of combustion parameters (such as pressure, and temperature) created with the different fuels used in diesel engines. As a result, that bioethanol has a content of low carbon (C) compared to diesel fuel, making a positive contribution to the reduction of ring wear.

An Exploratory Study of Direct Injection (DI) Diesel Engine Performance Using CNSL—Ethanol Biodiesel Blends with Hydrogen

The emissions from direct injection (DI) diesel engines remain a serious setback from the viewpoint of environmental pollution, especially for those who have been persuaded to use biofuel as an alternative fuel. The main drawbacks of using biofuels and their mixtures in DI diesel engines are increased emissions and decreased brake thermal efficiency (BTE) compared to using neat diesel fuel. The current study analyses the biodiesel made from cashew nut shell liquid (CNSL) using a single-cylinder, direct-injection diesel engine to validate the engine’s performance and discharge characteristics. In addition to the improved CNSL and a twin-fuel engine that runs on hydrogen, ethanol was added to the fuel at rates of 5%, 10%, and 15%. The investigation was conducted using a single-cylinder direct injection diesel engine at steady-state settings, above the sustained engine speed (1500 RPM). Several performance parameters and pollutant emissions, such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOX) were tracked during this study. According to the experimental findings, the biodiesel mixture’s brake heat was reduced by 26.79% in comparison to the diesel fuel. The brake-specific fuel consumption (BSFC) declined with the addition of hydrogen to the CNSL mixture. An increase in the BTE with increasing concentrations of hydrogen in the CNSL fuel blend was observed. The best blends of ethanol and CNSL–hydrogen perceptibly increased the exhaust gas temperature and NOX emissions, while also producing the fewest HC and CO emissions. The current research acts as a novel paradigm that makes it possible to comprehend the exergy related to mass or energy exchanges as a by-product of thermodynamic quality and quantity.

An experimental assessment of using waste plastic fuel as an additive in a DI diesel engine running on Jatropha biodiesel blends

The sole objective of the current work is to assess the effects of adding waste plastic fuel to diesel and jatropha biodiesel. In order to test this, seven distinct fuel samples made up of jatropha biodiesel-diesel, WPF-jatropha biodiesel-diesel, and regular diesel as a reference fuel were created using predefined volumetric proportions. After thorough characterization, studies are carried out employing spectroscopic methods such as FTIR, elemental analysis, and GC-MS. Finally, a direct-injection single-cylinder diesel engine underwent performance and emission tests. It has been discovered that adding WPF to biodiesel lowers its density, flash point, and viscosity. When WPF is added to biodiesel blends, the biodiesel’s cold flow properties are improved, and its calorific value and diesel index are raised. According to FTIR analysis of the fuel samples, the WPF mixed biodiesel, biodiesel, and diesel all share certain common functional groups. According to GC-MS examination of the fuel samples, all of the blends contain some aliphatic and aromatic chemicals as well as diglycerides, triglycerides, and ester components. WPF blended fuels exhibit improved thermal efficiency under partial loading situations, according to engine performance tests. It is discovered that the WPF blended fuel has a lower exhaust temperature than biodiesel. Compared to biodiesel and diesel, WPF mixed fuel has higher HC emissions but lower NOx emissions. Thus, it is advantageous to mix waste plastic fuel with biodiesel because doing so lowers NOx emissions while simultaneously raising the calorific value and diesel index of the biodiesel.

Effects of Hexane Addition in Waste Plastic Fuel-Biodiesel-Diesel Blends on the Performance and Emission Characteristics of DI Diesel Engine

The current study's sole objective is to evaluate the impact of hexane's addition to blends of diesel, waste plastic fuel, and jatropha biodiesel. Five fuel samples have been made in order to do this, including diesel-waste plastic fuel-jatropha biodiesel (D70WPF20JB10 and D70WPF10JB20), diesel-hexane-waste plastic fuel-jatropha biodiesel (D65HX5WPF20JB10 and D65HX5WPF10JB20), and plain diesel (D100) as a reference fuel. Following thorough characterization, studies using spectroscopic techniques such as FTIR, elemental analysis, and GC-MS are conducted. Finally, performance and emission tests on a direct-injection single-cylinder diesel engine were conducted. The density, flash point, and acid value of the diesel-waste plastic fuel-jatropha biodiesel blend are observed to decrease with the addition of hexane. With the addition of hexane, the calorific value and diesel index of the fuel both rise by 0.86% and 12.5%, respectively. In the case of the hexane mix fuel samples, it is discovered that the brake thermal efficiency and volumetric efficiency are higher and the brake-specific fuel consumption is lower. Hexane is added to the diesel-waste plastic fuel-jatropha biodiesel mixture, which results in a 34 percent rise in HC emissions and a 9 percent decrease in CO emissions. Additionally, it lowers by 8% and 15%, respectively, the temperature of the exhaust gas and the fuel's NOx emissions. The fuel sample with code D65HX5WPF10JB20 exhibits the best results among all the fuel samples in terms of performance and emission analyses.

A numerical approach in the investigation of the effects of diethyl ether and ethanol mixtures on combustion characteristics and NO emissions in a DI diesel engine

In this study, the effects of adding ethanol and diethyl ether to diesel fuel on combustion characteristics and NO emissions were numerically investigated. 100% diesel fuel (D100) and by volume 90% diesel+10% ethanol blend (D90E10), 80% diesel+20% ethanol blend (D80E20), 80% diesel+10% ethanol+10% diethyl ether blend (D80E10DEE10) and 85% diesel+ 10% ethanol+5% diethyl ether mixture (D85E10DEE5) was used as fuel. Analyzes were carried out using a single cylinder direct injection diesel engine at 2000 and 3000 rpm engine speed conditions. AVL FIRE software was used for numerical study. In-cylinder pressure, cumulative heat release rate, turbulent kinetic energy (TKE), NO emissions and velocity distributions in the combustion chamber were investigated for five different fuel types. As a result, the in-cylinder pressure and heat release rate of ethanol and diethyl ether blended fuels were lower than diesel fuel at both speeds. This is due to the calorific value of the fuel. It was observed that NO emissions decreased as the ethanol content in the fuel increased. For both engine speeds, the highest TKE value was obtained in D90E10 mixed fuel, and the lowest value was found in D80E10DEE10 mixture fuel. Ethanol positively affected the turbulent kinetic energy. The flow rate of ethanol was higher than diesel and diethyl ether fuel.

Environmental impact of waste plastic pyrolysis oil on insulated piston diesel engine with methoxyethyl acetate additive

The energy recovery from waste plastics as a prospective fuel source helps to overcome the issues of waste plastic management and the growing fuel shortage. In this article, High-Density Polyethylene (HDPE) plastics are used to convert into waste plastic pyrolysis oil (WPPO) through the pyrolysis process. An experimental investigation is carried out to evaluate the effectiveness of WPPO in a Thermal Barrier Coated piston engine (TBC) with an oxygenated additive of Methoxyethyl acetate (MEA). The incremental ratio of WPPO to pure diesel with the addition MEA and its performance, combustion, and emission characteristics are studied in a direct injection single-cylinder low heat rejection diesel engine. MEA and the coated piston resulted in improved performance of WPPO. Brake-specific fuel consumption is reduced by up to 9% under various load situations. D70W20MEA10 shows carbon monoxide elimination of up to 15% under various load conditions and a hydrocarbon reduction of up to 16%. At half load, D70W20MEA10 produces about 3% less HSU of smoke.

Optimization Design of Injection Pump Cam of Single Cylinder Direct Injection Diesel Engine Combined with Artificial Intelligence Algorithm

Optimization Design of Injection Pump Cam of Single Cylinder Direct Injection Diesel Engine Combined with Artificial Intelligence Algorithm

Evaluation and Optimization of Plastic Pyrolysis Blends Performance on Diesel Engine with Ethanol Additive using Full Factorial Design

Hydrocarbons, present in plastic, are a great fuel source because of their high energy density. The disposal of waste plastic offers major potential for energy conservation and recovery. This research focuses on recovering energy from waste plastics as a potential alternative fuel source for automobiles. This study aims to evaluate the performance of Plastic Pyrolysis Fuel (PPF) produced by the pyrolysis of low-density polyethylene. Ethanol is an attractive alternative fuel since it is produced from renewable bio-resources and acts as an oxygenated to allow for emission reductions in diesel engines. Three distinct ratios of PPF were mixed with 15% ethanol as an oxygenated addition to producing tertiary fuel blends. The performance and emission requirements of a single-cylinder direct injection diesel engine are examined in this study. Specific fuel consumption decreases for P20E15 about 3.5% to 7.8% with diesel. The carbon monoxide emissions from P20E15 were about 4.2% to 6.8% lesser than diesel and hydrocarbon reported with a decrease of 6% to 13.43%, at the different loading. The smoke produced by the P20E15 blend is decreased by around 24% when compared to diesel. The results were analysed further using the full factorial design technique to determine the most optimal running condition.

Extraction and characterization of coffee husk biodiesel and investigation of its effect on performance, combustion, and emission characteristics in a diesel engine

Biodiesel and its blends with diesel are used in engines to overcome the problems of environmental pollution and fast depletion of conventional fuels. The purpose of this research is to extract oil from coffee husk, convert it into coffee husk oil methyl ester (CHOME) by transesterification, and test the suitability of this biodiesel as an alternate, renewable, sustainable fuel for a diesel engine. The physicochemical characteristics of the developed biodiesel are studied and compared with regular diesel. The results showed that the fundamental properties of the produced fuel are comparable to that of diesel. The performance, combustion, and emission characteristics of a diesel engine fueled with CHOME biodiesel are investigated. The experiments are conducted in a single-cylinder direct injection diesel engine at a constant speed by varying the loads (0, 25, 50, 75, and 100%) for different biodiesel-diesel blends (B10, B20, B30, B40, B50, and B80), and the results are compared with the baseline diesel. The brake thermal efficiency (BTE) of the blends, B10, B20, B30, and B50 dropped by 0.6, 0.7, 1.29, and 3%, respectively compared with the neat diesel. Similarly the brake specific energy consumption (BSEC) is reduced by 0.1, 0.3, 0.44, and 0.77% for B10, B20, B30, and B50, respectively. Exhaust gas emissions are reduced for all biodiesel-diesel blends. Compared to regular diesel, at full load, CO, HC, and smoke opacity of B30 reduced by 13.2%, 4%, and 12%, respectively. CO2 of B30 at full load is increased by 8.63%. In general, it can be stated that CHOME biodiesel is a promising alternate biodiesel that can be used in an internal combustion engine without major modifications.

Energy recovery of waste plastics into diesel fuel with ethanol and ethoxy ethyl acetate additives on circular economy strategy

The widespread use of plastic goods creates huge disposal issues and environmental concerns. Increasing emphasis has been paid to the notion of a circular economy, which might have a significant impact on the demand for plastic raw materials. Post-consumer plastics recycling is a major focus of the nation’s circular economy. This study focuses on energy recovery from waste plastics as an alternative fuel source to meet the circular economy demand. Waste plastic fuel produced through pyrolysis has been claimed to be utilized as a substituted fuel. This work focuses to determine the performance and emission standards of Waste Plastic Fuel (WPF) generated from the pyrolysis of High-Density Polyethylene (HDPE) in a single-cylinder Direct Injection Diesel Engine (DIDE). Three different ratios of WPF were combined with 10% ethanol and 10% ethoxy ethyl acetate as an oxygenated additive to create quaternary fuel blends. The ethanol has a low viscosity, a high oxygen content, a high hydrogen-to-carbon ratio as favourable properties, the quaternary fuel results the improved brake thermal efficiency, fuel consumption and reduced emissions. The blend WEE20 exhibits 4.7% higher brake thermal efficiency, and 7.8% reduced fuel consumption compared to the diesel. The quaternary fuel blends demonstrated decreased carbon monoxide of 3.7 to 13.4% and reduced hydrocarbons of 2 to 16% under different load conditions.

Investigation on the knock characteristics in a gasoline direct-injection engine port-injected with water-methanol blends

Combustion knock is one of the key factors limiting the performance of spark-ignition engines, and thus great emphasis is placed on developing methods for effective and efficient knock suppression. The majority of works in this area are focused on the influence of these methods on the engine parameters, while maintaining the same “knock level” represented by a certain statistical parameter of knock combustion. The knock level defined as the mean or other statistical parameter of a stochastic process does not represent its characteristics. Thus, it is not evaluated on a sufficient level to show how different solutions for the knock reduction affect the knock probability distribution; nor is it known whether a universal treatment to characterise this influence can be developed. In this work we aim to fill this gap, and by the analysis of the knock combustion in a single-cylinder direct-injection gasoline engine with co-injection of water, methanol, and their blends, conclude on the effects of different additives on the probability distribution of in-cylinder pressure-related parameters. We also applied a method to normalise the knock phenomenon by a model representation of its probability distribution. The analysis was performed for knock-limited spark advance conditions for different amounts of co-injected water, methanol, and their blends. The method to normalise the knock distribution was based on the log-normal probability distribution, and it was successfully applied to obtain the knock characteristics at a quantified characteristic limit of knock, which was impossible to precisely meet directly in the tests. The results revealed that depending on the co-injected additive and its amount, the knock distribution undergoes slight but systematic changes, in terms of distribution skewness and kurtosis. At the selected knock limit, the injection of methanol resulted in knock characteristics more skewed to the knock limit comparing to the baseline case. Water addition resulted in opposite trends. Blending water and methanol gave a similar knock peak-to-peak distribution as in the gasoline-only case.

Multi‐fuel performance and emission characteristics of an optimized thermal barrier coated diesel engine

AbstractOwing to the depletion of world oil reserves and increased environmental issues, engine modifications amid alternative fuels to improve performance are alluring a lot of attention nowadays. More than half of the total energy generated in the internal combustion engines are dissipated from the system through frictional losses, engine part cooling, exhaust, etc. The minimisation of these energy losses through heat transfer can improve the engine performance to an extent. The finest alternative for minimizing the energy losses through heat dissipations from the engine is with the use of thermal barrier coated (TBC) combustion chambers. In this paper optimum working condition of a single cylinder Kirloskar diesel engine with a ceramic thermal barrier coating (Yttria‐stabilized zirconia) on the piston was determined using Design of Experiments (DOE) software and predictions were validated experimentally. Further the multi‐fuel performance of a diesel engine with ceramic coated piston was also analyzed. The fuels used were diesel, pure biodiesel and optimized biodiesel blend B20. The optimum working condition was determined by using central composite design method in Design Expert‐7 software. The B20 fuel with TBC engine resulted to the maximum efficiency. Further it was validated experimentally by performing experiment at rated revolutions per minute (RPM) in a Kirloskar made single cylinder direct injection computerized diesel engine. Eventually a mathematical equation for the relationship between brake power, brake specific fuel consumption and brake thermal efficiency was derived using DOE software.

Investigation of Performance and Emission Characteristics of Diesel-Ethanol PCCI Engine

Using numerical analysis and the ANSYS Forte 19.2 package, this study investigates the performance, combustion, and emission characteristics of dual-fuel operation using ethanol as a partial substitute for diesel in a direct injection compression ignition engine. The study discovered that adding ethanol to diesel engines reduces peak cylinder pressure and temperature due to its evaporative cooling qualities, with a maximum error of only 2.5%, exhibiting remarkable alignment between simulation and experimental data. The experiment was conducted on a modified single cylinder direct injection CI engine with an ethanol port injector controlled purely by Arduino software. The tests were carried out with different Ethanol substitutions at varied engine loads (0, 20%, 40%, 60%, 80%, and 100%). The study looked at the performance and emissions of a DI CI engine with ethanol substitutes of 10%, 20%, and 30%, with E10 outperforming and E30 outperforming, but caution is urged due to increased energy degradation. E10 and E20 ethanol replacements dramatically cut CO, HC, and NO emissions in diesel engines, improving environmental performance with modest changes.