Bioethanol gasoline blending

Bioethanol is bio-fuel substitute of gasoline, i.e., it is ethanol obtained from biomass, not from fossil fuels, and is used as a gasoline blend. 

Bioethanol is the largest biofuel today and is used in low 5%—10% blends with gasoline (E5, E10), but also as E85 in flexible-fuel vehicles. Conventional production is a well known process, based on the enzymatic conversion of starchy biomass (cereals) into sugars, and fermentation of 6-carbon sugars with final distillation of ethanol to fuel grade. 

Bioethanol is suitable for internal combustion engines that run on gasoline. Similarly, biodiesel is designed for diesel engines. Biodiesel is a fuel manufactured from various oils and fats. These acids are chemically transformed to fatty acid methyl esters. By blending the fatty acid methyl or ethyl esters in the right proportions, the properties of the fuel can be influenced [59] and potentially mimic the properties of petrochemically derived diesel. Biofuel efficiency generally is the same as for fossil-derived diesel fuel [59]. 

In most cases the ethanol is blended with gasoline. The vast majority of cars and trucks can use a 10% blend with gasoline (E10) in USA. A 22% blend of ethanol with gasoline (E22) is the most sold fuel in Brazil. Flex-fuel vehicles (FFV) are capable of running on variable blends up to 85% bioethanol (E85). However, when using E85 the fuel consumption increases by 20-30% due to differences in energy per unit volume. 

Another important issue of ethanol is its water sensitivity, which affects the water tolerance of gasoline in the case ofwater presence in ethanol-added gasoline, there is, in fact, the formation of hydrogen bonds between water and alcohol and the blend separates into two phases, with loss of octane quality. As a consequence, bioethanol requires special handling with different storage and distribution facilities for alcohol and gasoline and the blend has to be carried out just before the final use. 

ETBE (ethanol tertiary butyl ether, CgH, 0, density = 760 kg/m, LHV = 36 MJ/kg) is a better ingredient than bioethanol because it is not so volatile, not so corrosive, and has less affinity for water. ETBE-15 fuel is a blend of gasoline with 15% in volume of ETBE. ETBE is obtained by catal5dic reaction of bioethanol with isobutene (45%/55% in weight), noting that isobutene comes from petroleum. The other gasoline-substitute ether, MTBE (methanol tertiary butyl ether, (CH3)3-CO-CH3), is a full petroleum derivate (65% isobutene, 35% methanol). 

In Germany, however, bioethanol will mainly be used as low blend of bioethanol and petrol (E5, ElO) and for the production of ETBE (ethyl-tertiary-butyl-ether). Similar to methyl-tertiary-butyl-ether (MTBE), ETBE is used to enhance the octane index and improve knock-resistance and combustion properties of gasoline." It is less challenging to handle, does not induce evaporation of gasoline and does not absorb moisture like ethanol does. ETBE is produced by reacting ethanol and isobutylene via acid catalyst ... 

In the USA, the bioethanol industry is based on com starch and has rapidly grown due to high crude oil prices and the Energy PoHcy Act of 2005. Most gasoline in the US contains 10% bioethanol and there needs to be a technological leap in car engines in order to process higher blends. 

Bioethanol can be produced from the fermentable sugars obtained in the hydrolysis step by bacteria, yeast, or filamentous fungi. In order to prevent the substrate inhibition effects enzymatic hydrolysis and fermentation steps can be combined in a bioprocess called simultaneous saccharification and fermentation (SSF) (Hahn-Hagerdal et al., 2006). At the end of fermentation, ethanol can be purified by distillation and molecular sieves or other separation techniques, which will be ready to be used as a fuel, either neat or blended with gasoline (Hahn-Hagerdal et al., 2006). 

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