What is lignocellulose

1
FACT SHEET
BIOFUEL CROPS -- Cellulosic ethanol
What are biofuel crops? Biofuel crops are
crops used to make ethanol or biodiesel. These
crops are called "feedstocks" for biofuel
production. Large quantities of biomass are
needed as feedstocks for biofuel production. A
goal set by the U.S. Department of Energy is to
produce over a billion tons of biomass for
biofuels by 2030. What is cellulosic
ethanol? Cellulosic ethanol is a next
generation biofuel. Ethanol is currently made
from corn grain but is limited in supply to meet
huge U.S. demands for both food and fuel.
Cellulose is more abundant because most of the
leafy or woody parts of plants contain cellulose.

What is lignocellulose? Cellulose and
lignin together are referred to as
lignocellulose. Cellulose is deposited in plant
cell walls along with other components
primarily lignin, hemicellulose and pectin. Cell
walls are complex, but somewhat similar in
engineering properties to reinforced concrete in
which cellulose and hemicellulose are the
structural elements (the reinforcing bars) and
lignin and pectin are the cement. Scientists are
interested in reducing lignin in biofuel plants
because lignin is thought to interfere with
cellulosic ethanol production.
L.G. Smith, Plant cell DivisionBuilding walls in
the right places. Nature Reviews Molecular Cell
Biology 2 (2001) pp. 33-39
What feedstocks produce cellulose? Most all
plants produce cellulose, but some are better
than others. Crops plants produce cellulose as
do trees and forest vegetation. Among the crops,
some of the most efficient cellulose producers
are the grasses. Desirable biofuel crops produce
more cellulosic biomass per acre with less inputs
(requirements for fertilizer and pesticides).
ISU Agronomy graduate student Andrew
Heggenstaller studies switchgrass.
What biofuel crops are best suited for
Iowa? Perennial grasses, such as switchgrass
(Panicum virgatum L.) and Miscanthus, are adapted
to the temperate climate of Iowa. Important
agronomic properties of these grasses are
described at http//www.agron.iastate.edu/research
/biorenewables.aspx. As perennial crops, these
grasses have advantages over annual crops in
having a longer open window during the growing
season for capturing solar energy, in saving
resources needed for re-planting and in
preventing soil erosion.
Iowa State University Plant Sciences Institute
Fact Sheet (2008)
2
FACT SHEET
BIOFUEL CROPS -- Cellulosic ethanol
Can perennial grasses be harvested all year
round? No. Perennial grasses in Iowa grow
primarily through the warm summer months of June,
July and August and undergo senescence during the
fall. During senescence, minerals and nutrients
are returned to the roots (soil). After a
killing frost, the dried aerial parts of the
plants are harvested leaving minerals and
nutrients in roots to maintain soil fertility.
Chariton Valley Biomass Project
How do switchgrass and Miscanthus compare in
biomass production? Some of the highest yielding
varieties of switchgrass are 'Alamo,'
'Cave-in-Rock,' 'Shawnee and Kanlow. However,
a hybrid Miscanthus (Miscanthus x giganteus)
generally produces more biomass than switchgrass.
Production figures average about 10 dry
tons/acre for Miscanthus and 4.5 dry tons per
acre for switchgrass. (E. Heaton, T. Voight and
S.P Long, A quantitative review comparing the
yields of two candidate C4 perennial biomass
crops in relation to nitrogen, temperature and
water, Biomass and Bioenergy 27 (2004), pp.
21-30).
Why do switchgrass and Miscanthus produce
more biomass than other crops? One reason is that
these plants are C4 grasses, which means that
they use a more highly specialized
photosynthesis. C4 grasses, in contrast to C3
leafy plants, "fix" carbon with an enzyme called
PEP carboxylase that has higher affinity for
carbon dioxide. In addition, C4 grasses do not
burn off as much fixed carbon through a competing
process called photorespiration. How are
switchgrass and Miscanthus propagated? Switchgrass
can be produced from seed or clonally
propagated. The Miscanthus hybrid (Miscanthus x
giganteus) is sterile and is propagated
vegetatively through rhizomes.
Switchgrass plantlets propagated in tissue
culture. McLaughlin, S., J. Bouton, D. Bransby,
B. Conger, W. Ocumpaugh, D. Parrish, C.
Taliaferro, K. Vogel, and S. Wullschleger. 1999.
Developing switchgrass as a bioenergy crop. p.
282-299. In J. Janick (ed.), Perspectives on new
crops and new uses. ASHS Press, Alexandria, VA.
Iowa State University Plant Sciences Institute
Fact Sheet (2008)
3
FACT SHEET
BIOFUEL CROPS -- Biodiesel
What is biodiesel? Biodiesel is a biofuel
that can power diesel engines in trucks, trains
and tractors. Unlike diesel fuel, which is made
from petroleum sources, biodiesel is made from
renewable resources -- oils or fats from plants
or animals. In Iowa, the most abundant source of
plant oil is from soybeans. Soybeans have been
traditionally grown in the state for their
protein content for animal feed. Soybean oil is
being used increasingly for biodiesel production.
In 2006, Iowa produced a record of 60 million
gallons of biodiesel (Iowa Renewable Fuels
Association).
How is biodiesel made? Biodiesel is made by
a process called transesterification of plant oil
or animal fat. Oils and fats are triglycerides,
fatty acids linked to glycerol.
Transesterification generates biodiesel (fatty
acid monoesters) and liberates glycerol which is
not good for diesel engines. Biodiesel is usually
blended with diesel to produce various blends
such as B2 (2 biodiesel) or B10 (10 biodiesel).
Are soybeans the best source of oil for
biodiesel? Soybeans have been used as a source of
oil for biodiesel because the oil is a byproduct
of producing soybeans for animal feed. Soybeans
are not an exceptionally good oil crop. An acre
of Iowa land produced on average about 43
bushels/acre of soybeans in 2007 yielding about
63 gallons of biodiesel per acre. Canola
produces about three times more oil per acre and
oil palm trees produce about ten times more than
soybeans. However, the comparison with oil palm
isnt fair because oil palms are grown in warmer
climates with longer growing seasons.
Nonetheless, scientists are interested in
increasing oil content in soybeans without
sacrificing protein production. What
other improvements are being made in soybean for
biodiesel production? Iowa State scientists are
working to improve the quality of oils for better
biodiesel or biolubricants. Certain bacteria
modify oils by making branched chain fatty acids,
which increase oil fluidity at low temperature
and oxidative stability at high temperature.
These bacterial genes are being introduced into
soybeans in the effort to make plant oils with
these enhanced properties. In addition, genes
from jojoba plants are being introduced into
soybeans to promote the production of fatty acid
monoesters in soybeans. By doing so, ISU
scientists hope to produce a ready-made biodiesel
in soybeans.
Iowa State University Plant Sciences Institute
Fact Sheet (2008)