Environmental Engineering Reference
In-Depth Information
Utilizing mixtures of microorganisms or recombinant microorganisms (DOE 2006), together
with enzyme technology for hydrolysis, can contribute to making cellulosic ethanol cost-effective
(Solomon et al. 2007) and environmentally beneficial, because its energy output is greater that its
energy input (Kemppainen and Shonnard 2005). For unit energy outputted from lignocellulosic
material as ethanol, 14% of the energy must be added from fossil fuels, showing a global thermal
efficiency of 86% (Kemppainen and Shonnard 2005). Because of the cost- effectiveness and
thermal efficiency of cellulosic ethanol technology, there are presently four demonstration plants
in operation, three in North America, and the other in Europe. Iogen, located in Ottawa, Canada,
has operated since 2004 and has a production capacity of 3000 m
3
/year of ethanol using wheat,
oat, and barley straw. Operating since 2007, ClearFuels Technology of Kauai, Hawaii in the United
States has a production capacity of 11,400 m
3
/year of ethanol using bagasse and wood residues.
Celunol, located in Jennings, LA, in the United States, processes bagasse and rice hulls and has
produced 5000 m
3
/year of ethanol since 2007. Scheduled to open in 2009, Etek EtanolTeknik will
have a capacity of producing 30,000 m
3
/year of ethanol from softwood residues of spruce and pine
(Solomon et al. 2007).
As stated previously, several products, including biofuels, may be obtained through anaerobic
degradation of glucose. The biofuels that could be produced in addition to ethanol are hydrogen and
butanol. Antonopoulou and collaborators (2008) produced hydrogen from whey cheese, obtaining
a yield of 0.9 mol per mol of glucose. Also, butanol has been produced achieving a yield of 0.4 g of
butanol per gram of glucose (Lee et al. 2008). Other biofuels produced by fermentation of sugars
are shown in Table 8.10.
8.4.4.5 Fermentation of Five- and six-carbon sugars
to hydrocarbons and high-value Products
The fermentation of five- and six-carbon sugars can produce hydrocarbon chains that could be
used instead of gasoline and diesel and allow for the production of other high-value products
such as solvents (acetone in Table 8.10), intermediaries to produce plastics, and sweeteners. Park
and collaborators (2005) reported that
Vibrio furnissii
M1, when grown in a 50-mL scale with a
carbon source of 3 mmol provided by glucose, xylose, starch, or sucrose, yielded between 10 and
27 mg of a mixture of alkanes and alkenes. The chain length of the alkanes and alkenes produced
was in the range of C
14
-C
27
. LS9, Inc. of San Francisco, CA, produces gasoline-like hydrocarbons
from renewable sugars. These sugars are first converted to fatty acids and subsequently to
hydrocarbons by certain microorganisms. Roa-Engel and collaborators (2008) reported the
taBle 8.10
Biofuels from Fermentation of Five- and six-carbon sugars
Product and
substrate
Fermentation
type
yield (g product/
g substrate)
microorganism
reference
Clostridium
saccharoperbutylacetonicum
Hydrogen from cheese
whey
Batch
0.01
Antonopoulou
et al. 2008
Clostridium beijerinckii
NCIMB 8052
Butanol from glucose
Batch and
continuous
0.40
Lee et al. 2008
Clostridium
sp.
Hydrogen from wheat
bran
Batch
0.01
Pan et al. 2008
Citrobacter
sp.
Hydrogen from
glucose
Batch
0.03
Oh et al. 2003
Clostridium
sp.
Acetone and butanol
from hydrolyzed
agricultural waste
Continuous
For acetone 0.05
For butanol 0.09
Zverlov et al.
2006
