Alternative Fuels Research Articles

Economic and Environmental Assessment of Ammonia as a Sustainable Fuel for Tugboat Operations at the Port of Texas

This study assesses the feasibility of ammonia as a sustainable alternative fuel for tugboat operations in the Port of Texas, a major U.S. maritime, oil and gas hub. Tugboats, while critical to port logistics, contribute significantly to localized air pollution and greenhouse gas emissions, impacting both environmental quality and public health in surrounding communities. Given the International Maritime Organization’s (IMO) goals to reduce carbon emissions by 40% by 2030 and 70% by 2050, exploring alternative fuels has become imperative. Ammonia, a carbon-free fuel, presents both opportunities and challenges. While ammonia combustion produces no direct CO₂ emissions, making it attractive from a decarbonization standpoint, its lower energy density results in higher fuel volumes and increased operational costs compared to marine fuel oil (MFO). This paper presents a comparative analysis based on real-world data, mathematical modeling, and emission trade-offs, examining the economic implications, environmental impact, and safety concerns of adopting ammonia as a tugboat fuel. Results indicate that while ammonia could enable significant CO₂ reductions, challenges related to fuel storage, cost, and infrastructure must be addressed. The findings suggest that with appropriate policy support and investment in handling infrastructure, ammonia can become a viable fuel option for sustainable maritime operations.

Potential of Dry Leaf Waste as A Raw Material for Charcoal Briquettes Preparation as an Alternative Fuel

This research was motivated by the large potential of dry leaf waste in the campus environment of the University of North Sumatra and the awareness of the importance of appropriate innovation in the use of dry leaf waste as an environmentally friendly alternative fuel. The aim of this research was to determine the potential of leaf waste in the campus environment as a raw material for making environmentally friendly charcoal briquettes. The research method was observation, conducted in the campus environment of the University of North Sumatra, followed by calculating the amount of leaf waste produced per day, and testing continued with the production of dry leaf briquettes. The test results of the three combustions with different mixtures of raw materials in each combustion resulted in solid dry leaf briquettes that could ignite well. This study produced briquettes with proximate and ultimate tests that met SNI No.01-6235-2000 standards with a moisture content test of 4.35%, ash content test of 5.65%, carbon content test of 78.68%, calorific value of 6115 cal/g, and a burning rate of 1.5 grams/minute. Briquettes that meet SNI standards can become an environmentally friendly alternative energy source, a source of livelihood, and will certainly have a positive impact on waste management on the campus of the University of North Sumatra.

Decarbonization Strategies in the U.S. Maritime Industry with a Focus on Overcoming Regulatory and Operational Challenges in Implementing Zero-Emission Vessel Technologies.

The U.S. maritime industry plays a significant role in global trade and is a substantial contributor to carbon emissions, with the sector facing increasing pressure to decarbonize in line with global climate goals. This paper discusses the challenges and strategies for decarbonizing the U.S. maritime industry, laying emphasis on the adoption of zero-emission vessel (ZEV) technologies, such as battery-electric ships, hydrogen fuel cells, wind-assisted propulsion, and alternative fuels like bio-LNG and ammonia. Despite the availability of these technologies, the transition to ZEVs faces several barriers, including high capital costs, regulatory inconsistencies, and insufficient infrastructure. Existing regulatory frameworks, including the International Maritime Organization’s (IMO) emissions targets, the U.S. Clean Air Act, and the U.S. Coast Guard requirements, offer some guidance but are often fragmented and insufficiently aligned to foster widespread adoption of decarbonization technologies. Upcoming mandates, such as the IMO's 2050 target, further brings to view the urgency of this transition. However, gaps in regulations and the lack of incentives hinder technological innovation and fleet modernization. The paper also discusses the need for enhanced governmental involvement, with organizations like the Environmental Protection Agency (EPA), the Maritime Administration (MARAD), and the U.S. Coast Guard playing a critical role in streamlining policies and supporting the adoption of zero-emission technologies. It also emphasizes the importance of addressing infrastructure gaps related to fueling, charging, and port readiness for ZEVs. Furthermore, it highlights operational challenges such as range, performance, and energy density concerns that must be overcome for ZEVs to become commercially viable. The paper advocates for stronger policy frameworks, including subsidies, tax incentives, carbon pricing, and investment in research and development, to drive the transition. Public-private partnerships and industry collaboration are essential to overcoming financial barriers and creating a sustainable, decarbonized maritime sector. By implementing these strategies, the U.S. maritime industry can significantly reduce its emissions, contribute to global climate goals, and set a precedent for sustainable maritime practices worldwide.

Advancing combustion technologies and alternative fuels in hybrid electric vehicles: a pathway to high-efficiency, low-emission propulsion systems

Advancing combustion technologies and alternative fuels in hybrid electric vehicles: a pathway to high-efficiency, low-emission propulsion systems

Cu-Supported ZnO under Conditions of CO2 Reduction to Methanol: Why 0.2 ML Coverage?

By hydrogenating carbon dioxide to value-added products such as methanol, heterogeneous catalysts can lower greenhouse gas emissions and generate alternative liquid fuels. The most common commercial catalyst for the reduction of CO2 to methanol is Cu/ZnO/Al2O3, where ZnO improves conversion and selectivity toward methanol. The structure of this catalyst is thought to be Zn oxy(hydroxyl) overlayers on the nanometer scale on Cu. In the presence of CO2 and H2 under reaction conditions, the Cu substrate itself can be restructured and/or partially oxidized at its interface with ZnO, or the Zn might be reduced, possibly completely to a CuZn alloy, making the exact structure and stoichiometry of the active site a topic of active debate. In this study, we examine Zn3 clusters on Cu(100) and Cu(111), as a subnano model of the catalyst. We use a grand canonical genetic algorithm to sample the system structure and stoichiometry under catalytic conditions: T of 550 K, initial partial pressures of H2 of 4.5 atm and CO2 of 0.5 atm, and 1% conversion. We uncover a strong dependence of the catalyst stoichiometry on the surface coverage. At the optimal 0.2 ML surface coverage, chains of Zn(OH) form on both Cu surfaces. On Cu(100), the catalyst has many thermally accessible metastable minima, whereas on Cu(111), it does not. No oxidation or reconstruction of the Cu is found. However, at a lower coverage of Zn, Zn3 clusters take on a metallic form on Cu(100), and slightly oxidized Zn3O on Cu(111), while the surface uptakes H to form a variety of low hydrides of Cu. We thus hypothesize that the 0.2 ML Zn coverage is optimal, as found experimentally, because of the stronger yet incomplete oxidation afforded by Zn at this coverage.

An on-road experimental emissions evaluation of a diesel engine fueled with pyrolysis oil from waste plastics, pure and blended with biodiesel-A Mexican case

Pyrolysis of plastic waste generates alternative fuels that are useful for thermal devices. However, it is the subsequent fractionation process that truly distinguishes itself, refining these fuels to a quality comparable to petroleum derivatives such as diesel and gasoline, thereby making them suitable for direct use in internal combustion engines. This study evaluated the effect on emissions of an internal combustion engine fueled with waste plastic oil diesel-like fuel and its blend with biodiesel. The tests were conducted on-road using a typical light-duty diesel vehicle for passenger or courier transportation. Three tests were carried out, the first one with petroleum diesel (D100) as the reference fuel, the second one with waste plastic oil diesel-like fuel (WPO-DL), and the last with a blend of 80% WPO-DL and 20% biodiesel obtained from waste cooking oil (WPO-DL80WCO20). The main findings were a reduction in the generation of NOx when using WPO-DL. However, using WPO-DL increased the production of CO and HC, attributed to the presence of more heavy hydrocarbons compared to that of D100. Additionally, for the WPO-DL80WCO20 blend under acceleration conditions HC decreased under all acceleration conditions. These findings demonstrate that the distilled fuel obtained from the pyrolytic oil product of non-recyclable plastic waste by conventional methods would contribute to the global energy transition and reduce the presence of tons of non-recyclable plastic waste by traditional methods.

Thermal-hydraulic and safety analysis of alternative ceramic fuels in next generation of VVER-1000 reactor

Abstract The main aim of this study is the thermohydraulic and safety analysis of alternative UN and UC ceramic fuels in the next generation of VVER-1000/V446 reactor core. One of the advantages of these alternative fuels is their higher thermal conductivity and density relative to the UO2 conventional fuels. Thermohydraulic analysis has been performed under full power conditions. Also, the safety evaluation of alternative ceramic fuels has been researched by the Rod Ejection Accident (REA) scenario. RELAP5 Mod3.2 code is used for thermo-hydraulic analysis in both steady state and transient state in VVER-1000/V446 reactor. In addition, calculations of the fuel center temperature in mean and hot channels for steady state, the temperature of the hottest rod in the fuel assembly, the radial distribution of fuel temperature for both channels, and the maximum clad temperature during the reactivity injection have been performed. The results showed that in the steady state with full power, the fuel centreline temperature in UO2 is about twice the corresponding values for UN and UC alternative fuels which is very attractive from a safety point of view. In general, due to the large difference between the hot spot point and the melting point in alternative fuels, the thermal power and safety factors can be significantly increased in the next generation of VVER-1000/V446 reactors.

Comparative Study of Different Alternative Fuel Options for Shipowners Based on Carbon Intensity Index Model Under the Background of Green Shipping Development

The International Maritime Organization (IMO)’s annual operational carbon intensity index (CII) rating requires that from 1 January 2023, all applicable ships meet both technical and operational energy efficiency requirements. In this paper, we conduct a comparative study of different alternative fuel options based on a CII model from the perspective of shipowners. The advantages and disadvantages of alternative fuel options, such as liquefied natural gas (LNG), methanol, ammonia, and hydrogen, are presented. A numerical example using data from three China Ocean Shipping (Group) shipping lines is analyzed. It was found that the overall attained CII of different ship types showed a decreasing trend with the increase of the ship’s deadweight tonnage. A larger ship size choice can obtain better carbon emission reduction for the carbon emission reduction investment program using alternative fuels. The recommended options of using LNG fuel and zero-carbon fuel (ammonia and hydrogen) on Route 1 and Route 3 during the study period were analyzed for the shipowners. Carbon reduction scenarios using low-carbon fuels (LNG and methanol) and zero-carbon fuels (ammonia and hydrogen) on Route 2 are in line with IMO requirements for CII.

Use of butanol, pentanol and diesel in a compression ignition engine: A review

Using oxygenated alternative fuels in compression ignition (CI) engines is feasible for energy security problems and cli-mate change. Alcohols are regarded as alternative fuels for compression ignition engines because of their excellent physi-cochemical features, emission, and combustion characteristics. Research on alcohols and their additions has progressed significantly in recent years. Several researchers have examined the combined effect of higher alcohol with diesel and their impact and challenged that concentrations of higher alcohol reduce harmful particulate emissions in CI engines. This paper mainly focused on the performance and emissions properties of higher alcohols like butanol and pentanol. Alcohol has a low energy content, typically affecting engine brake-specific fuel consumption (BSFC). Low-temperature combustion (LTC) in compression ignition engines can lower NOx and smoke emissions, and improve the efficiency of the engine. LTC is done by combining higher alcohol with increased exhaust gas recirculation (EGR) rate and retarded fuel injection timing. The higher alcohol, along with the oxygen in the fuel reduces exhaust fumes, improves the air/fuel mixture by providing a longer ignition delay (ID), and can replace the fossil fuel like diesel (partially or whole) to allow efficient and clean combustion in CI engines. Finally, several significant findings and comments are provided regarding potential ave-nues for experimental research and future development. According to thorough analysis, bio-alcohols are considered to be a substitute fuel for CI engines.

Application of thermodynamic equilibrium modelling to predict slagging and fouling tendencies of bituminous coal and wheat straw blends

The combustion or co-combustion of biomass or alternative fuels is important in the energy sector because of the need to reduce the share of fossil fuels. This article is a continuation of previous studies on the behaviour of the mineral matter of selected fuels during the sintering processes. The blends of wheat straw biomass from Polish crops (WS) with bituminous coal from the Makoszowa mine (BC) were studied. The study included proximate and ultimate analysis and oxide analysis of ash blends with the following composition: 10wt% WS/90wt%BC, 25wt% WS/75wt%BC and 50wt% WS/50wt%BC. Based on the oxide content, a prediction (using FactSage 8.0 software) of the sintering process of the mixtures tested. The following parameters were determined: slag phase content, specific heat at constant pressure, and ash density. The fracture stresses tests were carried out using the mechanical test. Pressure tests were also performed using the pressure drop test method. The test results of all test methods used were compared with each other. On the basis of this comparison, a clear correlation was found between the sintering temperatures determined by the mechanical method and the pressure drop method and the physical properties of the ashes, such as density and heat capacity, as well as the chemical properties, i.e. the content of the slag phase. The results of the presented research are a valuable addition to the previous work of the authors. The goal of this work is to develop a precise and measurably simple method to determine the sintering temperature of ashes. This is an extremely important issue, especially in the case of the need to use a wide range of fuels in the energy industry.

Forecasting Electric Vehicle Adoption in the USA Using Machine Learning Models

Electric vehicles (Electric Vehicles) are at the vanguard of the global dispensation to sustainable transportation, depicting a pivotal step toward diminishing greenhouse gas emissions and reliance on fossil fuels. Notwithstanding, the adoption of Electric Vehicles has been growing in the USA, but their future remains at a crossroads. The objective of the research is to design and execute machine learning models capable of providing accurate predictions of future trends in electric vehicle adoption in the USA. The dataset gathered for analyzing EV adoption in the USA comprises data across three primary categories: environmental data, economic indicators, and policy-related data. The economic indicators include household income, fuel prices, electricity rates, and lithium battery costs that affect EV purchasing power obtained from the U.S. Census Bureau and the U.S. Energy Information Administration (EIA). Environmental data include greenhouse gas emissions and air quality indices from the EPA, providing information on regional environmental conditions that might affect EV attractiveness. Other policy data included federal and state incentives such as tax credits, rebates, and EV infrastructure data, collected from the U.S. Led by the U.S. Department of Energy's Alternative Fuels Data Center and the Energy Laboratory, additional EV sales trends were pulled from databases of the automotive industry. In this research project, credible and proven machine learning models were employed, most notably, Linear Regression, Random Forest, and XG-Boost. The performance of the models was tested for EV adoption prediction by considering a few important metrics: Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), and R-squared (R²). From the model performance metrics presented, the Gradient Boosting Regressor and Random Forest models performed far better by a big margin than Linear Regression. The prediction models, particularly, the Random Forest regressors and Gradient Boosting regressors demonstrated incredible forecasting of electric vehicle adoption. The model works excellently on the premise that historical data with relevant features can be utilized to gain some valuable insight into future trends. Policy-makers interested in stimulating the wider use of electric vehicles can ensure that targeted policies address both current barriers and future demands. Results of this analysis suggest incentives, such as tax credits, rebates, and subsidies, are some of the most common actions to reduce the upfront cost of an EV, a key circumventing factor in the choice that many consumers face.

Environmental and Cost Assessments of Marine Alternative Fuels for Fully Autonomous Short-Sea Shipping Vessels Based on the Global Warming Potential Approach

This research paper presents an effective approach to reducing marine pollution and costs by determining the optimal marine alternative fuels framework for short-sea shipping vessels, with a focus on energy efficiency. Employing mathematical models in a Python environment, the analyses are tailored specifically for conventional and fully autonomous high-speed passenger ferries (HSPFs) and tugboats, utilizing bottom-up methodologies, ship operating phases, and the global warming potential approach. The study aims to identify the optimal marine fuel that offers the highest Net Present Value (NPV) and minimal emissions, aligning with International Maritime Organization (IMO) regulations and environmental objectives. Data from the ship’s Automatic Identification System (AIS), along with specifications and port information, were integrated to assess power, energy, and fuel consumption, incorporating parameters of proposed marine alternative fuels. This study examines key performance indicators (KPIs) for marine alternative fuels used in both conventional and autonomous vessels, specifically analyzing total mass emission rate (TMER), total global warming potential (TGWP), total environmental impact (TEI), total environmental damage cost (TEDC), and NPV. The results show that hydrogen (H2-Ren, H2-F) fuels and electric options produce zero emissions, while traditional fuels like HFO and MDO exhibit the highest TMER. Sensitivity and stochastic analyses identify critical input variables affecting NPV, such as fuel costs, emission costs, and vessel speed. Findings indicate that LNG consistently yields the highest NPV, particularly for autonomous vessels, suggesting economic advantages and reduced emissions. These insights are crucial for optimizing fuel selection and operational strategies in marine transportation and offer valuable guidance for decision-making and investment in the marine sector, ensuring regulatory compliance and environmental sustainability.

Analysis of the Principle of Gas Turbine and State-of-art Applications

Abstract. As a matter of fact, gas turbines have become a cornerstone of modern energy systems, playing a pivotal role in power generation, the oil and gas industry, and the integration of renewable energy sources. This study provides an in-depth analysis of the principles underlying gas turbine operation, alongside a summary of state-of-the-art facilities that represent the pinnacle of current technological advancements. These turbines, known for their high efficiency and flexibility, are crucial for meeting the growing global demand for reliable and cleaner energy. However, significant challenges remain, particularly in terms of material limitations, emissions reduction, and the need for greater operational flexibility to accommodate renewable energy sources. The future of gas turbines may involve a shift towards alternative fuels like hydrogen, which could drastically reduce their environmental impact. These results highlight the ongoing evolution of gas turbines and underscore the importance of continuous innovation to address these challenges, ensuring that gas turbines can meet the energy needs of the future while minimizing their ecological footprint. The findings of this research are essential for advancing the understanding of gas turbine technology and guiding future developments in this field.

Accurately measuring slowly propagating flame speeds: Application to ammonia/air flames

Environmental concerns have driven the development of alternative fuels and refrigerant working fluids with low global warming potential. Ammonia (NH3) is a potential zero-carbon fuel, while hydrofluorocarbons (HFCs) like R-32 and R-1234yf are being adopted as refrigerants. When mixed with air, these compounds can sustain slowly propagating flames with laminar flame speeds less than 10 cm/s. Unlike typical hydrocarbon-fueled flames, these slow flames are influenced by buoyancy-induced flow and radiation heat loss. In this study, we experimentally investigate the flame speeds of NH3/air mixtures using the constant-pressure spherically expanding flame method, while circumventing gravity-induced natural convection, and account for radiation-induced inward flow. To mitigate buoyant convection, a low-cost drop tower was built and used to study slow spherically expanding flames in free fall. A computational model (SRADIF) is utilized that combines thermodynamic equilibrium and finite rate optically thin limit radiation heat loss calculations to estimate the inward flow. The developed methodology is utilized to investigate slowly propagating NH3/air flames over a range of equivalence ratios. A systematic approach was undertaken to understand and quantify the errors that could arise when deriving the laminar flame speed. It was found that attempting to study slowly propagating flames in a static configuration, as opposed to in free fall, results in large differences in flame dynamics and subsequently all derived quantities. It is necessary to study slowly propagating flames in free-fall. Additionally, using experimental data that has not been corrected for radiation-induced flow leads to large errors in all derived quantities. Furthermore, direct comparisons of experimental measurements and detailed flame simulations are found to be necessary to determine if existing extrapolation approaches are applicable to these slowly propagating flames, which are challenging to study.

Robust Adaptive Control System of Variable Sampling Period for Cement Raw Mix Quality Control

The advanced quality control of the raw mix remains a priority for the cement industry, particularly in recent years, where large quantities of alternative fuels and raw materials are used in clinker production, aiming to reduce the CO2 footprint. This study presents an adaptive control system with a variable sampling period for regulating raw mix quality in the raw mill (RM) output in a process with four independent inputs and four outputs: the lime saturation factor (LSF), silica modulus (SM), alumina modulus (AM), and SO3. The three pillars of the system are (1) mill dynamics calculation using exclusively industrial data, (2) the design of the controllers to meet robustness criteria, and (3) performance enhancement through simulators. Our technique periodically adjusts the gains of the controllers based on the mill’s dynamic parameters, which are computed from raw mix laboratory analyses. The presented results correspond to more than 14,000 h of mill operation. The standard deviation of the LSF at the mill outlet ranged from 1.5 to 3, which is equivalent to 1 to 2 standard deviations of LSF reproducibility. The standard deviation of the other moduli was close to the corresponding reproducibility of each. The presented adaptive gain-scheduling controller for LSF can be applicable to a broad range of raw meal grinding systems.

Investigation of an Ammonia-Fueled SOFC-mGT Hybrid System: Performances Analysis and Comparison With Natural Gas-Based System

Abstract Hybrid systems (HS) are highly attractive in power generation due to their potential for higher power outputs and efficiencies by integrating different technologies. Among solid oxide fuel cell (SOFC) plants, the SOFC-Micro-Gas Turbine (mGT) system is particularly innovative. In this setup, the SOFC replaces the mGT combustion chamber, with an afterburner completing fuel combustion before the expander. Various configurations and control systems have been explored over the years, and prototypes have demonstrated satisfactory efficiency. However, these systems have predominantly used NG and Biogas, which do not achieve zero carbon emissions. The growing global demand for carbon-free energy production is increasing, highlighting the importance of alternative fuels in the power generation sector: among them, thanks to its chemical and physical properties, ammonia is gaining more and more interest. This work investigates an innovative ammonia-to-power system based on an SOFC-mGT HS, focusing on thermodynamic parameters, system features, and technical and environmental challenges. A MATLAB/Simulink model, built on a validated HS model fueled by NG, was developed to analyze the new system configuration. This configuration replaces the SOFC prereformer with an ammonia cracker, allowing for the exploration of anode gas recirculation effects and optimal system design. Key operating parameters such as anodic recirculation factor, fuel utilization, performance, and gas turbine characteristics are discussed. Finally, a comparison is made between hybrid systems and mGTs powered by methane, biogas, and ammonia.

Prioritizing Criteria for Establishing a Green Shipping Corridor Between the Ports of Sines and Luanda Using Fuzzy AHP

As port authorities and cargo operators seek strategies to reduce carbon emissions while ensuring operational efficiency, some are turning to the concept of green corridors. These solutions aim to establish formalized partnerships among ports, carriers, shippers, and countries. During the process, the stakeholders must consider four priority areas (alternative fuels, bunkering infrastructure, vessel decarbonization pathways, and cargo demand dynamics) from seven angles (environmental, economic, infrastructure, regulatory, operational, technological, and social). This study explores the prioritization of these criteria for establishing a green maritime corridor between two major ports in Portugal and Angola, which would be a significant step toward promoting sustainable global trade. Utilizing the fuzzy AHP, this research analyzes all these factors and their associated sub-criteria derived from a comprehensive literature review and consultations with stakeholders from the Ports of Sines and Luanda. The findings show the dominance of environmental compatibility and economic viability, while social acceptance shows the lowest score. This framework guides the decision-making process for developing a sustainable shipping corridor. The results offer valuable insights for policymakers which can guide them in fostering resilient maritime transport routes, accelerating the adoption of decarbonization strategies and playing a critical role in achieving the IMO’s zero-emission targets by 2050.

Improvement of Brown Coal Quality through Variation of Acacia Wood Waste Biochar Composition in Producing Alternative Solid Fuel

Improvement of Brown Coal Quality through Variation of Acacia Wood Waste Biochar Composition in Producing Alternative Solid Fuel

Transforming wastewater-derived algae biodiesel with ammonium hydroxide emulsion for enhanced energy efficiency and emission reduction

The growing demand for sustainable energy has prompted a search for alternative fuels, with microalgae-based biodiesel emerging as a promising option. However, improving its energy efficiency and minimizing environmental impacts remain key challenges. This study presents a novel approach by integrating wastewater-derived algae cultivation with ammonium hydroxide emulsion to enhance biodiesel performance. Chlorella vulgaris microalgae were grown in a medium of diluted human urine, where nutrient removal efficiency was evaluated, and biooil was extracted via solvent extraction. The resulting biodiesel was analyzed for elemental, chemical, and physicochemical properties. A 30 % blend of Chlorella vulgaris algae biodiesel (CVAB) with normal diesel fuel (NDF) was prepared. To further boost energy efficiency and emissions performance, ammonium hydroxide emulsion was added at concentrations of 5 % and 10 %. Results confirmed that wastewater-sourced algae cultivation is a viable method for sustainable biodiesel production. While CVAB's combustion characteristics were similar to NDF's, it exhibited a 7 % decrease in brake thermal efficiency and a 5 % increase in nitrogen oxide emissions. The addition of ammonium hydroxide emulsion notably improved both energy efficiency and emission profiles. This study highlights a breakthrough in using ammonium hydroxide emulsion to enhance algae biodiesel, making it a more competitive alternative to fossil fuels. Economically, this approach offers a dual advantage: utilizing low-cost wastewater for biodiesel production while improving fuel performance and reducing emissions.

Exploring Fuel Characteristics and Performance in HCCI Engines with Alternative Fuels

Exploring Fuel Characteristics and Performance in HCCI Engines with Alternative Fuels