The development of biofuels has progressed through four distinct generations, each marked by advancements in feedstock selection, conversion technologies, environmental sustainability, and overall efficiency. The first generation laid the foundation by utilizing conventional biomass resources, while the subsequent generations aimed to overcome its limitations, especially competition with food crops, land use concerns, and environmental impacts. In environmental biotechnology, these generations are understood not merely as chronological improvements but as shifts toward sustainability, circular resource use, and integration of biological processes for cleaner energy production. The salient features of each generation demonstrate how biotechnology has transformed the role of biomass in the global energy sector. The first generation of biofuels primarily uses food-based biomass such as sugarcane, corn, wheat, sugar beet, and vegetable oils. The key products are bioethanol and biodiesel produced through fermentation and transesterification processes. One major feature is the simplicity of technology, as these feedstocks contain readily accessible sugars, starches, and oils that microorganisms and chemical catalysts can easily convert into fuels. Another important aspect is that the energy yield is relatively high and the production systems are already well-established, allowing countries such as Brazil and the United States to scale bioethanol and biodiesel production rapidly. However, these fuels raise significant environmental concerns because they compete with food crops for land, water, and nutrients. Large-scale monoculture farming often results in deforestation, biodiversity loss, and soil degradation. The carbon neutrality of these fuels is also questionable since agricultural inputs, fertilizer use, and land conversion generate emissions. Although first-generation biofuels helped demonstrate the feasibility of biomass-based fuels, their environmental drawbacks motivated the search for more sustainable alternatives. The second generation of biofuels represents a major shift because it uses non-food biomass or lignocellulosic materials such as agricultural residues, forest residues, municipal solid waste, dedicated energy crops like switchgrass, and fast-growing trees like poplar. One salient feature is that these feedstocks are abundant and inexpensive, and do not interfere with food security. Environmental biotechnology