Environmental Engineering Reference
In-Depth Information
Middle lamella
Primary wall
Secondary wall
Plasma membrane
FIGURE 5.5
Plant cell walls.
DID YOU KNOW?
Cellulose microfibrils are composed of parallel and linear chains of glucose
molecules that are tightly cross-linked by intermolecular hydrogen bonds.
girders stabilizing a skyscraper's structure, the mechanical strength of the primary
cell wall is due mainly to the microfibril scaffold (i.e., crystalline cellulose core)
(USDOE, 2007).
FEEDSTOCKS
*
F
irst
-g
eneration
F
eedstocks
For first-generation feedstocks, the type of major end-use product is easily catego-
for ethanol production. Soybean and other vegetable oils and animal fats are used
for the production of biodiesel (and bioproducts). Manure and landfill organic waste
are used for methane production and the generation of electricity. Corn is used for
ethanol production and currently is the leading feedstock used in the United States.
Several factors favor a positive outlook for further near-term growth in corn ethanol
production. Continued high oil prices will provide economic support for the expan-
sion of all alternative fuel programs, including corn ethanol. Technology improve-
ments that increase feedstock productivity and fuel conversion yields and positive
spillovers from second-generation technologies (biomass gasification in ethanol
refiners) will also help to lower production costs for corn ethanol. Among the factors
likely to limit future growth of corn ethanol production are increased feedstock and
*
Adapted from BR&Di,
The Economics of Biomass Feedstocks in the United States: A Review of the
Literature
, Biomass Research and Development Initiative, Washington, DC, 2008.
