Page 29 - Biofuels Refining and Performance

12 Chapter One

TABLE 1.2 Comparison of Some Common Fuels
Thermal Effective heat
Fuel Kcal efficiency (%) (kcal)

Gobar gas, m 3 4713 60 2828
Kerosene, L 9122 50 4561
Firewood, kg 4708 17 800
Dry cow dung, kg 2092 11 230
Charcoal, kg 6930 28 1940
Soft coke, kg 6292 28 1762
LPG (butane), kg 10,882 60 6529
Coal gas, m 3 4004 60 2402
Electricity, kWh (hot plate) 860 70 602
SOURCE: Permission from KVTC, Mumbai.

values of different fuels, i.e., coal, kerosene, firewood, and so forth (see
Table 1.2). Taking glucose as a model carbohydrate,

C H O 6O → 6CO 6H O 686,000 cal
6
2
6
12
2
2
(molecular weight, MW 180 g).
686,000 cal
3800 cal/g
180 g
and taking palmitic acid as model fatty acid,
C H O 23O → 16CO 16H O 2,338,000 cal (MW 256 g)
2
2
2
2
32
16
2,338,000 cal
9133 cal/g
256 g
Similarly, in amino acids, peptides show roughly the same value as that
of carbohydrates. In biological systems (measurement through metabolic
cage), it has been found that the biological energy values are slightly
higher than those shown theoretically. This is more so by “specific
dynamic action.” When mixed foods particularly protein are taken, the
total calorific value is enhanced. The exact reasons are not yet clear. Let
us concentrate on a few examples in the following:
In ethanol fermentation (pH 7.0),

C H O → 2[C H OH CO ] 56,000 cal
2
6
6
2
5
12
In lactic fermentation,
H O → 2[CH CHOHCOOH] 47,000 cal
C 6 12 6 3