Continuous environmental degradation, volatility in the oil market, and unimpressive functioning of fossil-based (FB) fuels in compression ignition engines have expanded the tempo of the search for alternative fuels. Due to the astronomical rise in global population, improved agricultural, commercial, and manufacturing activities, enhanced farming and other food production and utilization ventures, agricultural waste generation, renewable fuel consumption, and emission of toxic gases. The need for cost-effective, readily available, and environmentally benign agricultural waste to biofuels has never been more crucial. Biofuels are renewable, biodegradable, low-cost, and eco-friendly fuels that are produced by microorganisms from waste lignocellulosic biomass. Conversion of agricultural wastes to biofuel does not exacerbate food security, contributes to waste management, prevents environmental degradation, and ensures energy security. This study reviews the conversion of agricultural wastes into biofuels with special emphasis on bioethanol, biohydrogen, biobutanol, biomethane, biomethanol, and biodiesel for various applications. It is safe to conclude that wastes generated from agricultural activities and processes are useful and can be harnessed to meet the affordable and accessible global renewable energy target. The result of this investigation will improve the body of knowledge and provide novel strategies and pathways for the utilization of agricultural wastes. Going forward, more collaborative and interdisciplinary studies are required to evolve state-of-the-art, ecofriendly, and cost-effective conversion pathways for agricultural wastes to promote the utilization of the generated renewable fuels. More human, financial, and infrastructural investments are desirable to motivate the conversion of agricultural waste into biofuels to ensure environmental sanitation and sustainability, promote renewable fuel utilization, and avert the raging implosion of our planet.

Vegetable oils have been used as a feedstock for fatty acid methyl ester (FAME) production. The high cost of neat vegetable oil and its impact on food security have necessitated its replacement as a feedstock for FAME by used vegetable oil, also known as waste cooking oil (WCO). This study compares the properties and fatty acid (FA) compositions of samples of neat vegetable oil with those of samples of WCO, collected from restaurants and takeaway outlets at the point of disposal. The samples were subjected to property determination and pyrolysis gas chromatography mass spectrometer (PYGCMS) analysis. Analysis showed that degree of usage and the type of food items originally fried in the oil substantially affected its properties and FA composition. Density of neat vegetable oil varied between 904.3 and 919.7 kg/m3 and of WCO between 904.3 and 923.2 kg/m3. The pH of neat vegetable oil varied between 7.38 and 8.63 and of WCO between 5.13 and 6.61. The PYGCMS analysis showed that neat palm oil contains 87.7% unsaturated FA and 12.3% saturated FA, whereas neat sunfoil contains 74.37% saturated FA and 25% polyunsaturated FA. Generally, neat vegetable oils consisted mainly of saturated FAs and polyunsaturated FAs, whereas the WCO contained mainly of saturated FAs and monounsaturated FAs. This research confirms the suitability of WCO as feedstock for FAME.

Biofuel, a cost-effective, safe, and environmentally benign fuel produced from renewable sources, has been accepted as a sustainable replacement and a panacea for the damaging effects of the exploration for and consumption of fossil-based fuels. The current work examines the classification, generation, and utilization of biofuels, particularly in internal combustion engine (ICE) applications. Biofuels are classified according to their physical state, technology maturity, the generation of feedstock, and the generation of products. The methods of production and the advantages of the application of biogas, bioalcohol, and hydrogen in spark ignition engines, as well as biodiesel, Fischer–Tropsch fuel, and dimethyl ether in compression ignition engines, in terms of engine performance and emission are highlighted. The generation of biofuels from waste helps in waste minimization, proper waste disposal, and sanitation. The utilization of biofuels in ICEs improves engine performance and mitigates the emission of poisonous gases. There is a need for appropriate policy frameworks to promote commercial production and seamless deployment of these biofuels for transportation applications with a view to guaranteeing energy security.

Researchers have shown considerable interest in finding a sustainable, low cost, and readily available substitute for the commercial calcium oxide (CaO) catalyst. In this work, raw chicken eggshell was modified by boiling and calcination at 900 °C for 3 h. The x-ray diffraction characterization revealed that while the proportion of CaCO3 in the raw and boiled samples was found to be 79.3 % and 99.2 % respectively, the CaCO3 had been converted to 63.8 % CaO and CO2 in the calcined sample. This was due to the thermal decomposition during calcination. The outcome of the infrared spectroscopy showed that the raw and boiled chicken eggshell presented a similar absorption profile with peaks at 1 394 cm−1, 873 cm−1, and 712 cm−1, which were as a result of the presence of asymmetric stretch, out-of-plane bend, and in-plane bend vibration modes. The major peaks presented by the calcined sample at 3642 cm−1 can be attributed to the OAH stretching vibration and bending hydroxyl groups present in Ca(OH)2. The Brunauer-Emmett-Teller surface areas for the raw, boiled and calcined chicken eggshell were found to be 2.33 m2/g, 3.26 m2/g, and 4.6 m2/g respectively, indicating increased catalytic activity of the calcined sample. Overall, boiling was found to have a negligible effect on the chicken eggshell, while high-temperature calcination greatly affected the pore size, surface area, composition, and thermal decomposition profile of the chicken eggshell sample.