Biomedical Engineering Reference
In-Depth Information
Li et al. [
62
] produced hydrogen by simultaneous saccharification and fermenta-
tion from steam-exploded corn straw (SECS) using
C. butyricum
AS 1.209. After
steam explosion pretreatment, straw was loose and soft, and the accessibility to
cellulase was increased. Many monosaccharides, such as glucose, xylose, lactose,
and so on, produced in the process of steam explosion could be used as feedstock by
C. butyricum
AS 1.209 for fermentation initiation. For straw that shows relatively
low density, the maximal hydrogen yield reached 68 mL
g
1
SECS using solid-state
fermentation.
Although the study of hydrogen production from lignocellulose has made
progress, the cost of each craft, mainly the cellulase cost, is still high. In addition,
the hydrogen production efficiency is still needs to be further improved. So, great
efforts are needed for actual utilization of lignocellulose resources.
6.4
Biogas Fermentation
Biogas typically refers to a gas produced by the biological breakdown of organic
matter in the absence of oxygen. It is primarily CH
4
and CO
2
and may have small
amounts of hydrogen sulfide (H
2
S), moisture, CO, and so on. The composition
of biogas varies depending on the materials and conditions. For example, biogas
fermented from human and livestock manure sometimes has methane concentrations
above 75 %, while using straw as a substrate can generally produce biogas with
about 55 % methane.
Biogas, fermented in biogas digesters, has been widely used for household
energy in China's rural areas. However, with the increasing severity of energy
and environmental issues, the requirements for traditional biogas are increasing. Its
use would include a large-scale centralized gas supply, gas-fired power generation,
transportation, and conversion of chemical products. In this sense, biogas would
become a new energy that uses various biomasses as raw materials and is produced
by large-scale automation of the modern industrial fermentation process in the future
[
93
]. Therefore, great efforts to develop biogas not only can solve the current fuel
shortage but also can be the way to produce alternative energy in the future. Thus, it
is an event of great strategic significance.
6.4.1
Biogas Utilization Around the World
Currently, biogas utilization development is in the large-scale, intensive direction.
Europe, the United States, and other developed countries commonly use livestock
manure as the anaerobic fermentation substrate to produce biogas. In Germany, the
annual power production from biogas reaches 6
10
10
kWh, equal to 11 % of the
