In India, a densely populated country, fossil fuel depletion affects the energy sector that fulfils the industrial and human needs. Concerning greenhouse gas emissions and pollutants, and sustainability, there is a great demand to search for alternate feedstocks to produce alternate fuels at a low cost. The present work focuses on waste coconut and fish oil as potential inexpensive feedstock for biodiesel production. Two-stage transesterification processes for biodiesel production from hybrid oils mixed in a 1:1 volume ratio by employing solid nano-catalyst Magnesium Oxide (MgO). Response surface methodology (RSM) was used to analyze the effects of the physics of transesterification variables, such as methanol-to-oil molar ratio (M:O), MgO catalyst concentration (MgO CC), and reaction temperature (RT), on biodiesel yield, based on experimental data gathered in accordance with the matrices of central composite design (CCD). MgO CC showed the highest contribution, followed by M:O and RT, to maximize biodiesel yield. All interaction factors showed a significant effect except the M:O with RT. Grasshopper optimization algorithm (GOA) determined optimal conditions (M:O: 10.65; MgO CC: 1.977 wt.%; RT: 80 °C) based on empirical equations, resulting in maximum biodiesel yield conversion experimentally equal to 96.8%. The physical stability of the MgO nano-catalyst and reactivity up to 5 successive cycles can yield 91.5% biodiesel yield, demonstrating its reusability for sustainable biodiesel production at low cost. The optimized biodiesel yield showed better physicochemical properties (tested according to ASTM D6751-15C) to use practically in diesel engines.

Concerns about the depletion of petroleum reserves and rising pollution led researchers to search for alternate and environmentally compatible fuels for compression ignition engines. As an excellent alternative fuel additive to biodiesel–diesel blends, higher alcohol exhibits outstanding fuel properties (such as high energy content and cetane number) and can operate in diesel engines without requiring engine changes. This study focuses on investigating the ternary blends comprising higher alcohols, namely 1-heptanol and n-octanol, in hybrid biodiesel (animal fat oil–rice bran oil–cottonseed oil) and diesel on compression ignition engine characteristics. The performance, combustion, and emissions of a diesel engine fuelled with mono (D100), binary (B20), and ternary fuel blends (B20H10, B20H20, B20O10, and B20O20) were analysed at a constant engine speed of 1500 rpm. The test fuels met the American Society for Testing and Materials standards for fuel properties and exhibited stable behaviour during testing. Experimental results showed that at 100% load, the least brake-specific fuel consumptions for diesel fuel, B20, B20H10, B20H20, B20O10, and B20O20 were 254.1 g/kWh, 302.14 g/kWh, 281.25 g/kWh, 310.94 g/kWh, 292.8 g/kWh, and 313.80 g/kWh, respectively. Meanwhile, the maximum brake thermal efficiency values were obtained as 38.65%, 37.01%, 37.76%, 36.84%, 37.12%, and 36.38%, respectively. At 100% load, the peak heat release rates for diesel, B20, B20H10, B20H20, B20O10, and B20O20 were found to be 64.65 J/deg, 59.07 J/deg, 62.34 J/deg, 56.12 J/deg, 57.95 J/deg, and 51.9 J/deg, respectively. The addition of 1-heptanol and n-octanol as oxygenated additives into the ternary blend resulted in decreased carbon monoxide and unburned hydrocarbon emissions while increasing carbon dioxide and nitrous oxide emissions compared to diesel fuel. Overall, the study concludes that ternary blends with 1-heptanol and n-octanol as additives improve performance and combustion behaviour and reduce exhaust emissions compared to binary blends.

The consumption of fossil fuels is continuously increasing due to large number of automobiles and high demand for energy. Fossil fuels will not only become extinct in near future, but also pollute the environment. The present research work is focused on finding an eco-friendly alternate energy source through the production of bio-diesel. Naturally available low-cost Garcinia Gummi-Gutta seed was used to produce the biodiesel employing the transesterification process widely utilised in industries. The maximum biodiesel yield was primarily dependent on the optimisation of transesterification parameters (reaction time, percent of methanol and sodium hydroxide). Response Surface Methodologies (RSM) such as Box-Behnken design (BBD) and Central composite design (CCD) were used to conduct the experiments and analyse the transesterification parameters relationship with biodiesel yield. Results showed that, the methanol contribution was more as compared to sodium hydroxide and reaction time towards the yield of the biodiesel. The mathematical regression equations developed, related to biodiesel yield and transesterification parameters by utilising both the CCD and BBD models. The performance of BBD was found to be slightly better than that of CCD in making prediction of the biodiesel yield. Experimentally, the Teaching Learning-based Optimisation (TLBO) determined optimal transesterification parameters resulting to 96.2% biodiesel yield.

The novel garcinia gummi-gutta seed is used for extraction of biodiesel using transesterification process. The impact of diethyl ether (DEE) in biodiesel on the fuel properties was examined. The performance and emission characteristics of six fuels (B20DEE10, B30DEE10, B40DEE10, B100, B100DEE10 and D100) are tested on diesel engine from no-load to full load conditions. The addition of 10% diethyl ether to 20% biodiesel (B20) closely resemble the fuel properties of diesel fuel (D100) compared to other tested biodiesel blends. The performance parameters (brake specific fuel consumption (BSFC) and brake thermal efficiency (BTE)) and emission characteristics (carbon monoxide (CO), nitrous oxide (NOx) and hydrocarbon (HC)) are examined for six fuels at different engine load conditions. BSFC of all biodiesel showed comparatively higher value to that of diesel fuel at all engine loading conditions. BTE of diesel fuel showed higher values compared to other biofuels. Biodiesel blends resulted in reduced carbon monoxide and hydrocarbon emissions compared to diesel fuel. NOx emissions are higher for biodiesel and its blends compared to diesel fuel at all loads. Addition of 10% diethyl ether to biodiesel (B100) fuel resulted in better performance and emission characteristics compared to B100 fuel tested at full load engine conditions.