The book first explores previously studied supercritical processes for the production of biodiesel. Two of the main drawbacks of said processes are discussed: the high energy requirements and the hazards due to the conditions under which the processes are operated. The authors present a review of the experimental excess enthalpy of mixtures of dibutyl ether or butanol, with representative hydrocarbons. The most relevant functional groups of gasoline hydrocarbon types are considered: heptane, iso-octane, 1-hexene, cyclohexane, methylcyclohexane, benzene, and toluene. Continuing, this compilation briefly explores the production of biofuel from different edible and non-edible feedstock, mentioning the various types of homogeneous and heterogeneous acid or base catalysts applied for reactions. The benefits and drawbacks of biodiesel as compared to diesel fuel are also described. Several yeasts are examined for their capability to produce xylanolytic enzymes that degrade xylan, the major polysaccharide in the hemicellulose structure. The production of hydrolytic enzymes for the enzymatic hydrolysis process is reported by optimizing lignocellulose degradation and increasing the yield of simple sugars.