Environmental Engineering Reference
In-Depth Information
Dry
Moist
Others
Agricultural, livestock, fishery
Household waste & Food
Rapeseed
Palm oil
Black liquor
Scrap wood
Wood
Cellulose
(recycled paper)
Bagasse
Bagasse
Seafood processing
waste
Construction waste
Used
cooking oil
Livestock excrement
Cattle/hogs/poultry
Fisheries waste
Food industry waste
water/food waste
Rice straw
Maize, Rice husks
Wheat straw
Sewage sludge
Excreta
Woody biomass,
Forestry waste,
Scrap timber
Garbage
Biochemical conversion
Thermo-chemical conversion
Direct combustion
Crushed into chips or
pelletized for boiler
combustion
Methane/Ethanol/
Hydrogen generation
via fermentation, etc.
Fuel generation by
gasification/esterification/
slurryingthrough high-
temperature and high-
pressure process, etc.
Power generation and Transportation
Fig. 8.1
Biomass resources and biomass energy utilization
Various methods available for producing hydrogen are shown in Fig.
8.3
. In-
cluded in these are three ways to produce hydrogen biologically, with no external
energy input required: bio-photolysis, photo-fermentation, and dark-fermentation.
Among these technologies, dark fermentation is considered the most promising;
at 3-4 mol H
2
/mol glucose, the hydrogen yield is the highest and various types of
organic wastes can be utilized. In recent years, a group of bacteria has been discov-
ered that has the remarkable property of growing near and above 100 ºC. Under such
hyper-thermophilic anaerobic conditions, yields of hydrogen close to the theoretical
stoichiometry have been obtained using glucose as the carbon source. These yields
are superior to those found in other studies using fermentative microorganisms but
many challenges remain before this could be used to produce hydrogen from the
most abundant source of biomass—cellulose
1
.
To date, many studies have been carried out on fermentative hydrogen pro-
duction from pure sugars and from feedstocks, such as by-products from the
agricultural and food industry, municipal waste, or wastewaters. However, few
studies have been dedicated to continuous hydrogen production using cellulose
because cellulose is particularly difficult to hydrolyze and break down to its
component glucose monomers. Moreover, most studies on bio-H
2
production
from cellulose have used batch reactors, and bio-hydrogen production from cel-
lulose using continuous mode under hyper-thermophilic conditions has not yet
been reported.
1
Leith and Whittaker (
1975
) estimated the global stock of cellulose as ~ 9.2 × 10
11
tons, produced
at an annual rate of 0.85 × 10
11
tons.
