The development of biofuels has undergone a progressive evolution over the years, each generation marked by technological advancements, feedstock diversification, and sustainability considerations. Biofuels are renewable alternatives to fossil fuels, primarily derived from biological materials such as plants, algae, and waste. They play an important role in reducing greenhouse gas emissions, mitigating climate change, and ensuring energy security. The classification into first, second, third, and fourth generations is based on the source of biomass, conversion technology, and overall environmental and socio-economic impact. Each generation addresses the limitations of its predecessor, aiming to enhance efficiency, reduce costs, and minimize competition with food and land resources. The first generation of biofuels refers to fuels derived directly from food crops such as sugarcane, corn, wheat, and oilseeds. These biofuels are produced using conventional technology and primarily include bioethanol, biodiesel, and biogas. Bioethanol is typically produced from the fermentation of sugar and starch crops, while biodiesel is obtained through transesterification of vegetable oils or animal fats. Biogas is generated through anaerobic digestion of organic matter such as agricultural waste. The main advantage of first-generation biofuels lies in their relatively simple and established technology, making them commercially viable and widely available. For example, Brazil has been a global leader in sugarcane-based ethanol, and the United States has heavily invested in corn ethanol. However, the major limitation is the food-versus-fuel debate, as these biofuels compete directly with human and animal food supplies. Cultivation of energy crops on arable land can cause food price inflation, strain agricultural resources, and lead to deforestation. Additionally, the net energy balance and greenhouse gas reduction potential of some first-generation biofuels are not significantly better than fossil fuels when the entire lifecycle is considered, particularly in cases where intensive agricultural inputs such as fertilizers, irrigation, and pesticides are used. Thus, while first-generation biofuels laid the foundation for renewable fuel production, their environmental and ethical challenges necessitated the development of more sustainable alternatives. The second generation of biofuels emerged to overcome the limitations of the first generation by using non-food biomass as feedstock. These include lignocellulosic biomass from agricultural residues, forestry waste, grasses, and dedicated non-food crops such as switchgrass, miscanthus, and jatropha. Industrial and municipal solid wastes are also significant contributors. The key advantage is that second-generation biofuels do not compete directly with food production and make use of waste materials, thereby reducing environmental impact. The major products are cellulosic ethanol, advanced biodiesel, and Fischer-Tropsch diesel. Technologies such as enzymatic hydrolysis, gasification, and pyrolysis are central to converting complex lignocellulosic material into fermentable sugars or syngas for fuel production. Cellulosic ethanol,