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Conventional fossil fuels are being substituted with alternative green fuels because of their greenhouse gas emissions and pollution problems, which pose a severe threat to the environment. Several studies have reported the usage of biodiesel and gaseous fuels in both single and dual-fuel modes. Gaseous fuels such as producer gas, biogas, syngas, and hydrogen produced from renewable biomass could potentially be used along with biodiesel in dual-fuel engines. Still, these are the least investigated in terms of their use as potential energy carriers. This review article encapsulates the viability as well as the impact of various gaseous fuels, including producer gas, biogas, compressed natural gas, liquefied petroleum gas, syngas, and hydrogen, in dual-fuel mode diesel engines with the aim of evaluating the performance, emission, and combustion behavior at various induction as well as operational parameters. Considering emission behaviors of diesel engines fueled with producer gas, biogas, compressed natural gas, and hydrogen, it is found that hydrocarbon and carbon monoxide emissions increase in the range 17.5–31.4% and 11.73–23.6%, respectively. On the contrary, oxide of nitrogen and smoke opacity tend to reduce from 14.3 to 18.2% and 21.4%36.5–63.7%, respectively. Moreover, there is a slight deterioration in performance characteristics for diesel engines fueled with producer gas, biogas, compressed natural gas, and hydrogen in the range of 2.1–8.84% for brake thermal efficiency, and 3.1–7.3% for brake-specific energy consumption. In addition, the combustion characteristics of gaseous fuels is also discussed in detail. Moreover, a SWOT analysis has been carried out with an emphasis on possibilities for usage of gaseous fuels in dual-fuel diesel engines. Finally, the limitations and perspectives of using gaseous fuels are also critically presented. • Key applications of gaseous fuels to dual-fuel engines were critically presented. • Performance and emission of engines running on gaseous fuels were scrutinized. • Engines powered by gaseous fuels could increase global energy consumption. • NOx and greenhouse gas emissions could be remarkably reduced by using gaseous fuels. • SWOT analysis for gaseous fuels was discussed in detail. [ABSTRACT FROM AUTHOR]

The rising human population is causing the utilization of enormous amounts of fossil fuels to fulfill energy needs. Various renewable sources are used as fossil fuels however those resources are not powerful in supplanting customary non-renewable energy sources like gasoline in vehicles. The depletion of conventional fossil fuel utilized in a vehicle contributes to an increased portion of air contamination and is a danger to human well-being. Also, to maintain the supply demand, many active types of research have been carried out in mixing a higher percentage of ethanol over gasoline and further moving towards flex-fuel vehicles. But there arises a problem of knocking and higher CO, and HC emissions from the engine. To overcome the above problem, ethanol could be mixed in a higher percentage over gasoline with the help of hydrogen assistance and can completely avoid the problem of knocking and reducing CO and HC emissions. In this research, the combustion, emission, and performance characteristics of a variable-speed gasoline engine fuelled with ethanol-blended gasoline along with hydrogen assistance are taken for investigation at variable speeds like 1800, 1600, 1400, and 1200 rpm. Hydrogen is added to blended fuel (E30) which has better combustion, emission, and performance than other blended fuels. Hydrogen addition is done at 2, 3, and 4 ms respectively. The outcomes showed that the E30 + H 2 at 3 ms has better combustion, emission, and performance, still, the emission of NOx is higher in comparison with all the other blends due to complete combustion. Thus, a two-stage analysis has been done, one is making a comparison among various blends of ethanol, and the second one is the comparison among the various energy shares of hydrogen. • Hydrogen injection timing variation at 2, 3, and 4 ms over the E30 fuel blend. • Hydrogen injecting strategy enhancing the usage of flex fuels in SI engine. • Split hydrogen and E30 fuel over port injection at the inlet manifold. • BTE was highest with E30 + H 2 at 3 ms and also the emissions were optimum. [ABSTRACT FROM AUTHOR]

Municipal solid waste (MSW)-to-energy systems have gained significant attention in recent years for their potential to produce renewable energy from waste. These systems involve the conversion of MSW into electricity, heat or fuel. One of the most promising applications of MSW-to-energy systems is the production of hydrogen, which is considered a clean and sustainable fuel. Machine learning algorithms have the potential to revolutionize the way MSW-to-energy systems are managed. The integration of machine learning into MSW-to-energy systems has the potential to significantly improve the sustainability and profitability of this industry. In this study, a novel integrated MSW-to-energy system is modeled to produce hydrogen, power, and oxygen and with capacities of heating water and air. Hydrogen production, power production, oxygen storage, hot water, hot air, and system emission are predicted using machine learning algorithms based on regression models with high validity and R2 values more than 99.8% having errors smaller than 1%. The reduced regression models are developed by eliminating the insignificant variables from the full algorithms using the analysis of variance. The findings reveal high accuracy for the reduced regression models while their errors slightly decrease to 2%. This suggests that the machine learning algorithms can also be used as an effective tool to further improve MSW-to-energy systems. [Display omitted] • A novel municipal solid waste-to-energy system is modeled. • Hydrogen and oxygen are produced as well as electrical power, hot water and air. • Machine learning algorithms are developed using regression models. • Reduced regression models are developed using analysis of variance. • Machine learning algorithms show a high accuracy with errors less than 1%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biodiesel with a higher degree of unsaturation exhibits poor engine characteristics. • Increasing the degree of unsaturation of biodiesels limits H 2 induction tolerance. • Hydrogen enrichment enhances the performance of slow-burning oils. • Lower biodiesel unsaturation degree and higher H 2 induction reduce carbon emissions. • CO emissions decrease and NOx emissions increase with increasing H 2 induction rate. In this study, a comparison of the behavioural characteristics of CI engine operated under single-fuel mode with biodiesel and dual-fuel mode enriched with hydrogen was conducted. The influence of unsaturation degree on the engine behaviour has been assessed and compared between Grapeseed biodiesel (GSBD) and Wheat Germ biodiesel (WGBD) with Coconut biodiesel (CBD) since CBD has a very low level of unsaturation compared to the other two fuels in the single-fuel mode. In addition, this work also investigates the impact of unsaturation on the H 2 induction, performance, combustion and emission characteristics of a CI engine in dual-fuel operation. The obtained results showed that with the increasing degree of unsaturation, H 2 induction decreases, with CBD tolerating Hydrogen Energy Share (HES) of 13.8 % without knocking, followed by 13.5 % and 12.5 % for GSBD and WGBD, respectively. Comparing the industrial biomass residues alone in dual fuel mode for maximum HES, GSBD-H 2 exhibited superior characteristics with 34 % brake thermal efficiency, 0.22 g/kWh of hydrocarbon, 2.3 g/kWh of carbon monoxide and 35.4 % of smoke opacity as against 32.5 %, 0.31 g/kWh, 3.5 g/kWh and 40.3 % for WGBD, respectively. However, the nitric oxide emissions were slightly higher for GSBD compared to WGBD in both single-fuel and dual-fuel modes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biodiesel with a higher degree of unsaturation exhibits poor engine characteristics. • Increasing the degree of unsaturation of biodiesels limits H 2 induction tolerance. • Hydrogen enrichment enhances the performance of slow-burning oils. • Lower biodiesel unsaturation degree and higher H 2 induction reduce carbon emissions. • CO emissions decrease and NOx emissions increase with increasing H 2 induction rate. In this study, a comparison of the behavioural characteristics of CI engine operated under single-fuel mode with biodiesel and dual-fuel mode enriched with hydrogen was conducted. The influence of unsaturation degree on the engine behaviour has been assessed and compared between Grapeseed biodiesel (GSBD) and Wheat Germ biodiesel (WGBD) with Coconut biodiesel (CBD) since CBD has a very low level of unsaturation compared to the other two fuels in the single-fuel mode. In addition, this work also investigates the impact of unsaturation on the H 2 induction, performance, combustion and emission characteristics of a CI engine in dual-fuel operation. The obtained results showed that with the increasing degree of unsaturation, H 2 induction decreases, with CBD tolerating Hydrogen Energy Share (HES) of 13.8 % without knocking, followed by 13.5 % and 12.5 % for GSBD and WGBD, respectively. Comparing the industrial biomass residues alone in dual fuel mode for maximum HES, GSBD-H 2 exhibited superior characteristics with 34 % brake thermal efficiency, 0.22 g/kWh of hydrocarbon, 2.3 g/kWh of carbon monoxide and 35.4 % of smoke opacity as against 32.5 %, 0.31 g/kWh, 3.5 g/kWh and 40.3 % for WGBD, respectively. However, the nitric oxide emissions were slightly higher for GSBD compared to WGBD in both single-fuel and dual-fuel modes. [ABSTRACT FROM AUTHOR]