Fuels in Transportation - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 21

increase the proportion of biogenic fuels up to 10-20% in the worldwide fuel
supply [ 23 ].
Generally, a distinction can be made between first-, second-, third-, and fourth-
generation biogenic fuels produced by ligneous cellulose or woody sources via
new technologies and converted to the end product by the Biomass to Liquid
(BTL) technology.
The first generation consists of pressed and chemically improved oil from
plants, such as canola or sunflowers.
The second generation is produced from waste biomass, e.g., stalks of wheat,
corn, wood, and biomass crops with help of fermentation. Alcohols such as
methanol and ethanol are primarily used as alternative fuels for spark ignition
engines. Methanol can be produced from raw materials containing carbon such as
coal, natural gas, heavy oil, etc. Ethanol is produced from biomass, e.g., sugar cane
and grain through fermentation and is used as a fuel or fuel additive in certain
countries, e.g., in Brazil and in the USA. Many countries allow up to 53% ethanol
to be added to conventional fuel [ 24 ].
The third generation is made of gasified organic materials in reactors and by
artificial oils produced through the use of catalysts with the help of Fischer-
Tropsch synthesis (BTL).
The fourth generation concerns the production of artificial oils from algae. This
method is only at the beginning of the research phase.
The physical and chemical characteristics of synthetic and biogenic fuels are
presented in Table 2.9 [ 25 ].
Lubricity is a term used to describe the ability of compound to reduce friction
between moving parts in the engine. Low sulfur fuels have a lower lubricity than
high sulfur oils. Biogenic diesel fuels consisting of methyl esters of soybean oil
had provide optimal excellent scuffing and adhesive wear resistance which is
approximately equal to conventional diesel fuels features [ 31 ].
2.2.7 Blended Fuels
Experiences show that the utilization of 10% of alcohol can lead to small changes
in the spraying, mixing, and burning properties of fuels. The viscosity as a physical
parameter may figure the differences between fossil fuels and alcohols. At 40C
(104F), gasoline kinematic viscosity is 0.88-0.71 cSt, diesel fuel viscosity is
1.30-4.10 cSt, and depending on quality alcohol viscosity is 0.74-1.52 cSt [ 32 ].
Micro sensors in the exhaust gas system can discover changes under blended
fuel operation condition in the combustion process over time and can provide
signals for optimal regulation (see Fig. 2.3 ).