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19.16 GREEN MATERIALS

There is an increasing emphasis in so-called “green materials.” There are other terms often asso-
ciated with the term green materials. These other terms include renewable resource materials and
natural materials. The emphasis is the replacement of nongreen materials by these green materials.
Each of these terms has slightly different meanings. The term “renewable materials” is generally
employed for rapidly renewable materials such that are replenished within a short time such as a
year. The term “natural materials” emphasizes materials that are derived from nature. Along with
these descriptions, a green material also encompasses the energy requirements, processing proce-
dures, and recycling ability of the material
The shift from petroleum-based feedstock toward renewable, green, materials is rapidly acceler-
ating with much of this emphasis based on developing monomers from these green sources. In 2008,
the world market for biobased chemicals, excluding biofuels, was $1.6 billion and this is projected
to be about $5 billion by 2015. Concrete measures of this emphasis can be seen by the construction
of plants capable of producing 100 million pounds per year of such green monomers as PDO and
polymers such as polyhydroxyalkanoate, and polylactic (PLA).
Natural materials include materials that are “naturally” found about us. This includes oil, coal,
and natural gas. These materials are not considered green materials because they are not readily
replenished. Other natural materials include silicon dioxide-intense materials such as mica that
is utilized in some coatings producing clad-like coverings and diatomaceous earth that is being
employed in the construction of some tires to retain tire pressure. It also includes many renew-
able materials such as cellulose, chitosan, vegetable oils, and lignin. These renewable materials are
readily available in the billions of tons yearly, renewable on a regular yearly cycle, and are greatly
underused materials. Carraher and others have worked with chitosan to produce anticancer drugs
and lignin to produce materials with structural integrity as alternative industrial materials. Sperling
and coworkers have employed naturally derived oils producing various rubbers.
Here we will describe other green materials. We emphasize polymers that are commercially
available and that are really derived from natural sources, not simply said to be possibly derived
from natural sources. Nylon-66 was initially advertised to be derivable from various natural sources,
and it is, but today it is manufactured from monomers that are part of the stream of petroleum
derived feedstocks. Thus, nylon-66 is not included in this discussion as a green material though it
may become part of the green material revolution as natural, biomass-derived, sources for the reac-
tants become available on a large scale. This may change as industry seeks ways to produce already
employed monomers from biological feedstocks. For example, Coca-Cola will employ beverage
bottles that are traditionally produced from synthetic PET employing ethylene glycol derived from
sugar and molasses rather than ethylene glycol produced from petroleum and natural gas.
The movement from a petroleum-based material to a green material is not straightforward and
involves many considerations. It is a journey that we need to be careful of but a journey we must begin.
We also need to be aware that the large bulk of petroleum-based use is not as materials but rather as
fuel.
There are some concerns that need to be considered in the production of products from green
materials. A major emphasis in the production of materials from synthetic polymers is that they are
inert, not offering unwanted biological activity and decomposition. The idea that green materials
should be naturally recyclable runs against this concept. Another concern involves the actual net
energy and resources necessary to produce the monomers/polymer/product. An analysis needs to
be made concerning the various components such as energy and resource (including water) require-
ments before a green material is accepted as a replacement. Another consideration is the ready
availability of the particular green material. A material may be green but if it is not readily available
or can be seen as readily available in suffi cient amount then it may not be a strong candidate to be
employed on a large-scale commercial basis. Also, the behavior or properties of the green material
should as least approach the materials that may be replaced.

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