Page 55 - Biofuels Refining and Performance

38 Chapter One

the dynamism or thrust. Water vapor is transformed into ice particles
instantly due to the very low temperature in space. Liquid hydrogen for
such research or experiment is generated at a very high cost, i.e., elec-
trolytic splitting of water. The alternate resource of hydrogen is a by-
product in the caustic soda plant. A similar minor and indirect source
of hydrogen is water gas (C H O → CO H ), almost obsolete for any
2
2
large-scale production. None of these examples are renewable in nature,
continue to be energy and labor intensive, and cannot stand as com-
petitors as fuel or energy resources. Other commercial sources of hydro-
gen are dependent on the existing limited supply of natural resources,
i.e., coal, naphtha, and natural gas, which are not renewable. The mate-
rials are mainly based on fluidization or gasification of coal, and refor-
O
mation by superheated steam or from steam–iron process (3Fe 4H 2
→ F O 4H ); these processes can be broadly classified into (a) ther-
2
3
4
mochemical or solar gasification and (b) fast pyrolysis or other novel
gasification. These processes may be totally or partly catalytic. The
basic chemical principles are mostly similar to those of classical water gas:
O → CO H ; CO H O → CO H . Major sources of hydro-
C H 2 2 2 2 2
gen at present are directly or indirectly natural gas; electrolysis;
pyrolytic, thermal, and superheated steam; or geothermal, solar, ocean
current, ocean thermal gradient, and nuclear reactors. Biomass as a
source of hydrogen as well as energy has been discussed in Sec. 1.2.
1.16.1 Microbial conversion
Many or most organic cellulosic matter, after proper mechanical treat-
ment (homogenizing), can be put to microbial conversion for (a) bio-
methanation and/or (b) hydrogen production.

1. Biomethanation can utilize human or animal excreta as well as mixed
green/organic wastes. This part has been discussed earlier in Secs. 1.12
and 1.13.
2. Hydrogen production is discussed hereafter.

Biohydrogen. Major routes are
1. Enzymatic (partly microbial) through microbial routes
2. Klebsiella and Clostridium groups of microbes
3. Different cyanobacteria (blue-green algae)
4. Various photosynthetic bacteria
5. Many aerobes, i.e., bacilli and alkaligenes
6. Facultative groups, i.e., enterobacters, and coli forms
7. Various anaerobes, i.e., rumens, methanogenic, methylotropes, and
clostridia