Page 39 - Advances in Eco-Fuels for a Sustainable Environment

16 Advances in Eco-Fuels for a Sustainable Environment

Table 2.1 Properties of some conventional fossil fuels and biofuels [2, 3]

Gasoline Diesel Methanol Ethanol n-Butanol
Molecular formula C 4 –C 12 C 12 –C 25 CH 3 OH C 2 H 5 OH C 4 H 9 OH
Molecular weight 111.19 198.4 32.04 46.06 74.11
Cetane number 0–10 40–55 3 8 25
Octane number 80–99 20–30 111 108 96
RON 88–98 0 109 109 98
MON 80–88 0 89 90 85
Oxygen content (%wt.) – – 50 34.8 21.6
Density (g/mL) at 20°C 0.72–0.78 0.82–0.86 0.796 0.79 0.808
Autoignition temperature 300 210 470 434 385
(°C)
Flash point (°C) at closed 45 to 38 65–88 12 8 35
cup
Lower heating value 42.7 42.5 19.9 26.8 33.1
(MJ/kg)
Boiling point (°C) 25–215 180–370 64.5 78.4 117.7
Stoichiometric ratio 14.7 14.3 6.49 9.02 11.21
Latent heating (kJ/kg) 380–500 270 1109 904 582
at 25°C
Flammability limits (%vol) 0.6–8 1.5–7.6 6.0–36.5 4.3–19 1.4–11.2
Saturation pressure (kPa) 31.01 1.86 31.69 13.8 2.27
at 38°C
Viscosity (mm2/s) at 40°C 0.4–0.8 1.9–4.1 0.59 1.08 2.63
(20°C)
Energy density (MJ/L) 32 35.86 16 19.6 29.2

As many countries are promoting programs in favor of biofuels, a rapid growth of
biofuel production has occurred in the last decade, which is expected to grow further in
the next years. Fig. 2.1 shows biodiesel production trends in selected EU countries [6].
The EU estimated a 14% share of biofuels in 2020, which could significantly reduce
GHG emissions (by 101 103Mt CO 2 eq/year); the US Environmental Protection
Agency’s RFS2 (Renewable Fuel Standard, v. 2) drives definitions for the American
automotive market, requiring that 80 billion liters of renewable fuel be available in the
US market by 2022 [7].
The EU strongly aims at reducing its oil dependence, which nowadays amounts to
more than 300Mtoe/year (1Mtoe/year¼106t of oil equivalent per year). Attention is
especially focused on the transport system, traditionally based on oil and responsible
for more than 21% of overall GHG emissions, with an increasing trend higher than
other economic sectors. For this reason, the “Transport 2050” plan [8] aims at creating
a European common space able to improve the mobility of people and goods as well as
reducing CO 2 emissions in transport by 60% through year 2050 by:

(1) Halving the number of vehicles relying upon traditional fuels (diesel and gasoline) in cities
by 2030 and excluding them by 2050.
(2) Switching 30% of passenger and 50% of freight mean-range transport from road to other
means of transport such as rail and inland waterways by 2030 and 2050, respectively.