• Energy Research

Biogas is an important renewable energy resource that has been considered as carbon neutral. The advantage that it can also reduce volumes of biowaste makes it an attractive option for secondary source of energy. In this scenario, large amounts of banana wastes are observed around the world with minimum work in anaerobic digestion. Hence, the present study demonstrates the anaerobic digestion of banana pseudo stem (BP) and cow dung (CD) feedstock by co-digesting them in different proportions (5 levels of BP – 0%, 30%, 50%, 70%, and 100%) and varying digester temperatures (3 levels: 42.5 °C, 45 °C, and 47.5 °C). Batch scale 1 liter feedstocks are prepared and digested for a period of 30 days. Initial studies suggested that the optimal temperature for digesting BP is between 40 and 50 °C which falls in the transition of mesophilic and thermophilic range. At all the digester temperatures, pure BP feedstock produced an average of 74% lower biogas as compared to CD feedstock. However, co-digesting CD with about 30% BP had a negligible loss in biogas production (1.2%). Further experimental data was subjected to regression, ANOVA, and optimization analyses. The optimization study results reveal that more than 5000 ml/liter of feedstock can be obtained for BP feedstock within 30-40% proportions if the temperature is maintained between 45 to 47 °C.

The use of ethanol blending for gasoline has been found to have a significant effect in reducing emissions without any loss in the performance of a spark ignition engine. However, an increase in the emissions of oxides of nitrogen (NOx) may be seen due to the increased oxygen content in the fuel. On the contrary, emulsifying fuel with hydrogen peroxide (H2O2) has shown a substantial effect in reducing all the emissions, including NOx in a compression ignition (CI) engine. In this study, 10% ethanol is blended with gasoline (E10) and further emulsified with H2O2 up to 1.5%. When compared to neat gasoline, a 4.8% increase in brake thermal efficiency (BTE) is obtained with 10% ethanol and 1.5% H2O2. The corresponding average decrease in the emissions of carbon monoxide (CO), hydrocarbons (HC), and NOx were 80%, 43%, and 17%, respectively. The results of the experimental trials are used to model an artificial neural network (ANN) to derive a relationship between the input factors of ethanol concentration, H2O2 concentration, and engine speeds with the output responses of BTE, CO, HC, and NOx. The ANN models of each response are optimized using a multi-objective particle swarm optimization (PSO) for maximizing BTE and minimizing emissions of CO, HC, and NOx. The PSO results showed that operating the engine at 2000 rpm using ethanol blending between 4 and 6% and H2O2 emulsification of 1.5% are the best optimal conditions.

AbstractHydrogen peroxide (H2O2) is an excellent oxidant carrier that finds its use in combustion and fuel applications. In the present study, H2O2 (30% assay) is used as an emulsifier in waste cooking oil biodiesel blend (B20) and the emissions and performance in a compression ignition engine are assessed. Along with the neat B20, three blends of B20 with 0.5%, 1%, and 1.5% H2O2 concentrations are used. Increasing the concentration of H2O2 beyond 1.5% resulted in vapor lock in the fuel pump leading to a loss in injection pressure. An increase in the exhaust gas temperature was recorded with the increase in H2O2 concentration due to improved fuel properties, like, cetane number, thermal conductivity, and microexplosions of fuel droplets. However, NOx emissions decreased mainly due to the presence of the hydroperoxyl group from H2O2. Analysis of variance was also carried out to assess the statistical significance of H2O2 on the responses and is seen that the maximum impact of H2O2 was positively influencing brake thermal efficiency (BTE), brake‐specific fuel consumption (BSFC), hydrocarbon (HC), and NOx. Compared with the B20 blend, H2O2 emulsified fuel with a concentration of 1.5% showed a substantial reduction of 53.7%, 28.6%, 14.2%, and 16.2% in the average emissions of CO, HC, smoke, and NOx, respectively. Similarly, 7.9% and 7.1% improvement in the BTE and BSFC is obtained. However, more studies are required to ascertain the NOx reduction mechanism and address issues of fuel vaporization at higher concentrations of H2O2.

AbstractSelective catalytic reduction (SCR) systems using solid ammonia carriers like carbamates, carbonates, etc., have gained interest in the recent past for NOx abatement from compression ignition engines. Solid ammonia carriers have successfully demonstrated their use in SCR systems. In this experimental study, the thermal dissociation study of ammonium carbonate is made using nonisothermal thermogravimetric analysis. Ammonium carbonate is subjected to three heating rates, $$\emptyset$$ ∅ of 2, 4, and 8 K/min. The corresponding highest rates of reaction are obtained at temperatures ($$T_{p}$$ T p ) of 96, 118, and 128 °C, respectively. At these points, the mass of the samples has been reduced to 1/3rd of the initial mass. From the Arrhenius plots, the average activation energy obtained is 77.39 kJ/mol which is 15% higher than that of ammonium carbamate. An expression for $$T_{p}$$ T p as a function of activation energy, $$\emptyset$$ ∅ , and order of the reaction is developed using kinetic model. The model can predict the temperatures at which the reaction rates are maximum for a given heating rate.

Biofuels are one of the most sought-after renewable energy sources to overcome the current energy crisis in the world. Diesel blended with esters derived from oils has shown appreciable results for its use in compression ignition engines. In this work, B20 (20% biodiesel + 80% diesel by volume) fuel blend comprising 80% diesel and 20% biofuel extracted from waste cooking oil is used as a fuel. Two different metallic oxide nanoparticles (NPs), namely, cerium oxide (CeO2) and aluminium oxide (Al2O3) each having size of 30 nm, are dispersed in B20 biodiesel blend and used to investigate their combined influence on engine combustion. Experiments are conducted to study the engine exhaust emissions of a single cylinder four-stroke diesel engine running at constant speed of 1,500 rpm with varying engine loads. Experiments are carried out with B20 fuel and adding mixtures of CeO2 and Al2O3 nanoparticles in 50–30, 40–40 and 30–50 ppm, respectively, to B20 biodiesel blend. Responses recorded are the emissions of CO, HC, CO2, NOx and smoke. The results reveal that, on adding the nanoparticles, the engine observed a smooth combustion with reduction in the exhaust emissions compared to neat B20 biodiesel operation. B20 blend with 50 ppm of CeO2 and 30 ppm of Al2O3 nanoparticles showed lower exhaust emissions compared to other fuel blends. For the best fuel blend, CO, HC, NOx and smoke are reduced by 57.3%, 22.3%, 24.3% and 7.36%, respectively, compared to neat B20 operation.

Carbon capture and storage has been recognized as the most promising method for CO2 control. Among the many sorbents, char derived from pyrolysis and hydrothermal carbonization (HTC) of biomass have demonstrated excellent CO2 adsorption capability. This paper reviews the different parameters to produce a higher yield of biochar and hydrochar suitable for carbon sequestration. The mechanism of physisorption and chemisorption is briefly presented. The different kinetic models, diffusion models to describe adsorption mechanism, and adsorption isotherms for CO2 uptake from biomass-derived hydrochar are reviewed. The different factors that affect the CO2 uptake are the type of activation, surface area and porosity, the ratio of activation agent to char, activation temperature, adsorption pressure and temperature, additives, and other physicochemical properties. The optimal conditions for CO2 uptake with chemical activation of KOH is a KOH/char ratio of 2-3, activation temperature of 700 °C, and an adsorption temperature below 50 °C.