This chapter aims to discuss on biochemical conversionBiochemical conversion technologies—including pretreatmentPretreatment, hydrolysisHydrolysis, and fermentationFermentation—for producing liquid biofuelsLiquid biofuels such as bioethanolBioethanol, biobutanolBiobutanol, and biodieselBiodiesel, as well as gaseous fuels like biohydrogenBiohydrogen, biogasBiogas, and biomethaneBiomethane. Detailed discussion is provided on the role of microorganismsMicroorganisms and enzymes, types of fermentationFermentation systemsFermentation systems, and process optimization factors influencing yield and efficiency. Case studies highlight the influence of feedstock composition, microbial strains, and operating conditions on biofuel productivity. Despite significant progress, technical and economic challenges remain, particularly in pretreatmentPretreatment, enzyme cost, fermentationFermentation of mixed sugarsMixed sugar fermentation, and large-scale integration. The chapter underscores the importance of advanced bioprocessingAdvanced bioprocessing strategies and waste valorization approaches to enhance biofuel productionBiofuel production, reduce greenhouse gas emissionsGreenhouse Gas Emissions (GHG), and contribute to sustainable energy transitions.