Page 22 - Biofuels Refining and Performance

Energy and Its Biological Resources 5

7. Coal conversion: Many models for fluidization and gasification of
coal are available.
8. Black box or hydrogen fuel cell: Usually, these use hydrogen as
input fuel based on reverse hydrolysis (see last part of Sec. 1.6):

At anode: H → 2H 2e
2

At cathode: O 4H 4e → 2H O
2
2
9. Hydrogen as fuel: Hydrogen as fuel is gaining popularity. The
most common sources are from (a) excess of nuclear energy, (b)
windmills, (c) hydroelectric power, (d) biological sources to some
extent, (e) fuel cell (see Sec. 1.6), and (f ) microbial hydrogen pro-
duction (see Sec. 1.16).
10. Biological energy: A number of biological energy transformation
principles, very attractive, remain at the conceptual state.

1.2 Energy
A body can do work, or work can be done upon a body; a body of water
can turn a turbine, or one may pedal a bike to move it. If work is done
on a body, it will possess energy. When energy is possessed by a body,
the body can do work.
An agent may do work when it possesses energy, i.e., the amount of
work that an agent can do is the amount of energy it possesses. So a body
may gain kinetic and potential energy or lose the gained energy by pro-
ducing heat or converting it to other forms of work.

Kinetic energy is due to the motion of a body.
Potential energy is due to the position or status of a body.
Frictional or colligative motion energy is produced in a water-
fall; heat evolves to overcome a frictional resistance or checks the
motion of a body but sets useless motion to others (e.g., rolling of peb-
bles in a stream or dust behind a vehicle). Mechanical friction causes
a matchstick to ignite.
Units of energy are the same as those of work and are assigned equiv-
alent quantities. Some important definitions and units are given in the
appendix. Energy content of some common substances are provided in
Table 1.1.

1.2.1 Thermodynamics
All three principles of thermodynamics are very much applicable in the
area of biological energy and chemical changes related to it. It is worth-
while to review a few fundamental points. Chemical reaction can take