Environmental Engineering Reference
In-Depth Information
enzymes, and regulation are likely to contribute greatly to the microbial or plant-
based syntheses of novel polymers.
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Reactor and Processing Technology
. Gains in commercial feasibility are often found
in improving bioreactor yield and in diminishing processing costs. Without
reiterating topics addressed previously, it is nevertheless important to include these in
the research priorities for PHA efforts, with special note that the transfer of PHA
synthesis to plants may circumvent many limitations of both reactor efficiency and
processing costs.
G.
S
TARCHES
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P
ROTEINS
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P
LANT
O
ILS
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AND
C
ELLULOSICS
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Basic Biosciences
. From a long-term perspective, continued support for basic
biosciences that allow the manipulation of plants at the genetic level is absolutely
essential. Only through continued development of genetic and physiological
engineering techniques will the possibility of inducing organisms to produce
polymers directly, and thereby reducing the cost of bioplastics by minimizing
processing steps, be realized. In addition, the preference for anaerobic processes
among microbial fermentations should be recognized due to the minimization of
carbon loss from feedstocks. In the context of the plant-based plastics described in
this section, the required tools include the genetic engineering of the cellulose-lignin
and oil distribution in plants. Such basic genetic manipulation of plants is supported
by the USDA. Specific strategies for pollution prevention are necessarily more
narrow and should focus on developing cost-effective methods for producing plastics
from plant-based matter.
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Biodegradable Plastics
. Within the realm of starch-based plastics, commercial
interest and success is currently carrying the development of compostable disposable
packaging, including garbage bags, food wraps, diapers, as well as disposable food
service items such as plates, cups, and utensils. Commercial research and
development is even leading to improvements in water resistance and durability of
starch-based materials, with the result that these are not considered to be high
priorities for federal research funding. In contrast, the possibility of vastly improved
strength, lightness, durability, and heat and water resistance offered by natural fiber-
reinforced composites, particularly nanocomposites, cause this area to be highly
attractive for additional effort. Low-cost polysaccharide-based plastic materials have
the greatest potential to displace significant amounts of petroleum-based plastics.
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Green chemical processes
. Similarly, more benign greener chemical processes
should be investigated for transforming the available renewable resources.
Such activities should include enzymatic transformations when they are less
energy intensive than existing chemical routes.
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Plant proteins
. Genetic engineering of plant proteins for specific functionality
is a lower priority simply because the potential application, adhesives, is small
relative to the packaging and structural uses for plastics. If plant proteins can
be engineered for larger volume applications, for example, into thermoplastic
film or sheet materials, the promise of coproducing both fuels and materials in
