The concept of biofuels has evolved across decades as scientists and engineers have sought to develop renewable, sustainable, and environmentally friendly alternatives to fossil fuels. Biofuels are essentially energy carriers derived from biological sources, and the shift from first to fourth generation biofuels reflects the progress of environmental biotechnology in addressing issues such as food security, land use, greenhouse gas emissions, and energy efficiency. Each generation of biofuels represents improvements in feedstock choice, conversion technologies, and environmental performance, showing how innovation in biotechnology can balance energy needs with ecological sustainability. First generation biofuels emerged as the initial attempt to replace fossil fuels with renewable substitutes. These are primarily derived from food crops rich in sugars, starch, or oils. Ethanol produced from sugarcane, corn, or wheat and biodiesel derived from vegetable oils such as soybean and rapeseed are typical examples. The production process involves relatively straightforward biochemical or chemical conversions. For instance, starch-rich crops undergo fermentation after hydrolysis to release fermentable sugars, while plant oils are transesterified to yield biodiesel. A major advantage of first generation biofuels lies in the established agricultural base and simple technology, which allowed rapid commercialization and large-scale adoption. However, the environmental and ethical implications soon became clear. Because they rely on food crops, their production competes directly with food supply, raising the issue of “food versus fuel.” This has the potential to exacerbate global hunger and increase commodity prices. Additionally, large-scale cultivation of monocultures for biofuel feedstock leads to deforestation, biodiversity loss, and soil degradation, while the overall greenhouse gas savings compared to fossil fuels are often modest when the entire life cycle is considered. Thus, while first generation biofuels marked an important milestone, their sustainability was limited, necessitating the transition toward more advanced generations. Second generation biofuels were developed to overcome the limitations of the first generation by utilizing