Because of the energy crisis and climate warming, humanity faces the need for a huge short­term supply of biofuels (see below). Bioethanol and biodiesel have been considered the best candidates for satisfying these needs and are what we consider the first generation of biofuels. Ethanol can be produced from a range of crops including sugarcane, sugar beets, maize, barley, potatoes, cassava, and mahua (Baker & Keisler 2011; Kremer & Fachetti 2000). Flexible-fuel motors have been developed that can burn hydrous ethanol/gasoline blends in any combination, including pure ethanol. The automatic adjustment of combustion parameters is controlled electronically in these engines as a function of the oxygen level needed by the fuel in the tank (Marris, 2006). The so-called "gasohol" is a blend of ethanol and gasoline. Ethanol is produced via fermentation of a sugar slurry that is typically prepared from sugar or grain crops. The action of yeast on the sugar produces a solution that contains approximately 12% ethanol. The yeast invertase catalyzes the sucrose hydrolysis into glucose and fructose. Subsequently, yeast zymase converts the glucose and the fructose into ethanol. The alcohol can then be concentrated by distillation to produce up to 96% ethanol (hydrous ethanol).

Ethanol is a polar solvent and its chemistry is very different from that of hydrocarbon fuels (which are non-polar solvents). As a result, blending ethanol into hydrocarbon fuels introduces some specific challenges. These challenges include (i) higher fuel volatility at low rates of ethanol/ gasoline blends, (ii) higher octane ratings, (iii) an increase in dissolved — water content in motor gasoline that promotes heterogeneity of fuel blends and resulting engine corrosion and (iv) higher solvency. However, Akzo Nobel Surface Chemistry and the Lubrizol Corporation have developed and produced a low cost additive that makes it possible to blend ethanol with diesel fuel to obtain a stable and clear fuel (Lu et al., 2004). This fuel is called "Dieshol".

Biomethanol can be produced from biomass using bio-syngas obtained from the steam­reforming processing of biomass. Biomethanol is considerably easier to recover from biomass than is bioethanol. However, sustainable methods of methanol production are not currently economically viable. The production of methanol from biomass is a cost-intensive chemical process. Therefore, under current conditions, only waste biomass, such as wood or municipal waste, is used to produce methanol.