Environmental Engineering Reference
In-Depth Information
from plant sugars (succinic, fumaric, malic, 2,5-furandicarboxylic, 3-hydroxypropionic,
aspartic, glutaric, glutamic, itonic, and levulinic acids, and the alcohols 3-
hydroxybutyrolactone, glycerol, sorbitol, and xylitol). Combination of these acids and
alcohols can produce polyesters by direct condensation [44, 208, 209]. In particular, reactive
intermediates that can be produced by anaerobic fermentations are desirable, because
anaerobic processes typically lose much less of the feedstock carbon to CO2 than do aerobic
processes [210]. The success of the DuPont SoronaTM material, a polyester of such low
molecular-weight precursors (1,4- benzenedicarboxylic acid-dimethyl ester with 1,3 -
propanediol) shows that development of sustainable processes to take advantage of readily
available, renewable substances to produce additional biodegradable plastics deserves high
priority for its great potential to yield both homopolymeric and copolymeric materials with
new ranges and combinations of desirable properties.
5. Commercialization
Polymers based on polylactic acid are the leading success stories in bioplastics, moving
from the laboratory into the market within the last decade. PLA-based polymer synthesis is
protected by numerous patents to several different entities [10, 47, 211-214] and Natureworks
appears to have taken the lead in the United States with its opening in 2002 of the first
commercial manufacturing facility for PLA in Blair, Nebraska. Natureworks continues to be
the most internationally visible PLA producers, but Japan and Germany are showing interest
in developing PLA commercially as well (http://www.friendlypackaging.org.uk
/materialslist.htm).
Beyond issues of heat distortion and permeability described above, the greatest current
obstacle to greater market penetration of PLA is cost. Increasingly, higher oil prices are
enabling PLA to compete directly with petroleum-based plastics despite the fact that PLA is a
new entity in the plastics marketplace, but cost reductions would nevertheless allow greater
utilization. Accordingly, renewable materials such as starches, cellulose, and wood flours and
fibers that could be used in PLA blends to decrease costs without significantly degrading
performance are of great commercial interest. In this respect, bioplastics have a general
advantage over biofuels- they are already clearly cost competitive with fossil-resource based
materials.
R
EFERENCES
[1]
Carothers, W. H., G. L. Dorough, and F. J. Van Natta (1932).
Studies of polymerization
and ring formation. X. The reversible polymerization of six-membered cyclic esters
, J of
Am Chem Soc 54:761-772.
[2]
Lowe, C. E. (1954).
Preparation of High Molecular Weight Polyhydroxyacetic Ester
.
U.S. Patent 2,668,162, February 2, 1954.
[3]
Goodman, M., and M. D'Alagni (1967).
Investigations of poly-S-lactic acid structure in
solution
, Polymer Let 5:515-521.
