How Products are Made
- use the search tool and type in a product name.
How Stuff Works -
Wikipedia -
Life Cycle Analysis of a Product:
Life
cycle analysis is a method to characterize the raw materials and energy
used to make a product. In addition, for each step also analyze how
much solid waste, water pollution, and air pollution is generated at
each life cycle step of the product's life.
1. Introduction: Give a general description of the product (technology), its uses, and why modern society needs this particular product.
Life Cycle Steps:
2.
Extraction and Processing of a Raw material - raw materials
(what chemical elements or compounds are part of the product?
What are the basic resources where you would find the elements
and compounds in the product?), energy sources, pollution (Be specific
about the type and location of pollution and specific molecules
involved)
3. Manufacturing and packaging - describe and/or
give chemical equations of the synthesis or methods to convert from the
raw material to the final product ( use specific names and/or formulas
of the chemical compounds), energy sources, pollution
4.
Transportation ( from raw material step to Mfg./Distribution of
Product) - energy sources and pollution (Be specific about the type and
location of pollution and specific molecules involved)
5. Useful life, maintenance of product, possible reuse
6.
Possible Recycling - connects back to # 2 or 3 - energy sources
and specific pollution and Final Disposal of Waste - specific
pollution possible or prevented by proper treatment.
To
answer this question, try to be specific for each life cycle step.
Specific means what source of energy, what specific types (molecules)
of air or water pollution.
You had a preliminary chance to think about this type of question in Topic 12 with the analysis of paper vs. plastic. Most people did not go into very much depth for that question. Here I am asking for more depth as it is a review of what you have learned in the entire course.
Polyvinyl chloride (PVC) Pipes
A sample student answer for the "Story of...."
1) PVC pipe has become very popular in the construction industry
and can be
found being used for a wide variety of purposes. It is used for
sanitary
sewer pipe, irrigation systems, electrical conduit systems, water
distribution systems and communication wiring systems conduit.
The
advantages of using PVC pipes as opposed to historically traditional
materials are many. In the case of sewer pipes PVC has the advantage
that
it is much easier to work with than the traditionally used materials
of iron
pipe or concrete, both which are much more difficult to cut and
heavier than
PVC. In addition, PVC pipes are chemically stable and do not oxidize
and
thus need replacing as often as iron pipes. PVC pipes also are
more
flexible than iron and concrete pipes and so do not crack or become
brittle
with age. For irrigation and water distribution systems, PVC pipes
again
offer ease of handling as well as lower costs than the traditional
materials
of copper or iron pipes.
2) The basic raw materials used in the production of PVC
pipes are
chlorine, which is derived from sodium chloride (NaCl) more commonly
know as
ordinary salt, and ethylene (C2H4) a product of the petroleum
refining
process. Obtaining these materials in order to manufacture PVC
pipe has
many consequences for the environment. It takes
fossil fuel energy to extract the oil from the ground using oil
rigs or oil drilling equipment. Obtaining the ethylene that is
used for the production of PVC
brings with it
all of the environmental problems associated with the petroleum
production
and refining industry. Drilling for petroleum disrupts the environment
at
the drill site. Transportation of raw crude oil is always risky
and the
effects of an accident (oil spills) in this respect are all too
obvious as witnessed by
recent history. Oil does not mix with water, but floats on top.
Any oil spill will be determental to all forms
of wildlife. Energy consumed in the petroleum refining
process
adds
further to the environmental impact of oil refining.
3. On an atomic level, PVC is composed of chlorine, hydrogen and
carbon
atoms. A mononer of vinyl chloride consists of three hydrogen
atoms, two
carbon atoms and a single chlorine atom.
PVC is produced by combining ethylene, which is produced
in the
petroleum refining process with chlorine, which is derived from
rock salt.
The process of producing PVC is as follows:
The ethylene and chlorine are combined to produce ethylene dichloride:
C2H4 (ethylene) + Cl2 (chlorine) = C2H4Cl2 (ethylene dichloride)
The ethylene dichloride is then heated to high temperatures where
it changes
into vinyl chloride and hydrogen chloride:
C2H4Cl2 (ethylene dichloride) = C2H3Cl (PVC) + HCl (hydrogen chloride)
The hydrogen chloride left after this reaction is then further
combined with
yet more ethylene in the presence of oxygen to yield more ethylene
dichloride and water.
C2H4 (ethylene) + HCl (hydrogen chloride) +02 = C2H4Cl2 (ethylene
dichloride) + H2O
The ethylene dichloride can then be recycled back into the production
process to make more PVC.
C2H4(ethylene) + Cl2(chlorine)+ O2(oxygen)=C2H3Cl(PVC) + H2O(water)
All of these processes require the use of fossil fuel for energy
and has the potential for prodicing air pollution of volatile orgranics
(VOC), nitrogen oxides, carbon monoxide, and carbon dioxide.
In the process of producing PVC, toxic waste in the form of
ethylene
dichloride tars are a by-product. This tar which must be disposed
of
contains dioxins. Current methods for disposing of this hazardous
waste is
either by burning it in incinerators or pumping it into deep wells.
In addition, there is air pollution associated with the production
of PVC. This is probably in the form of VOC (volatile organic
compounds).
4) After the PVC pipe has been produced, still other environmental
impacts
result from the energy required to deliver the product to the
consumer.
These impacts are largely the result of the use of fossil fuels
needed by
the machinery and vessels involved in the transportation. There
is air pollution in the form of nitrogen oxides, carbon monoxide
which produce smog which is a respiratory hazard. Smog may produce
ozone which is a pollutant close to earth and causes respiratory
problems. Nitrogen oxides react with water to produce acid rain
which can effect lakes, trees and fish. Carbon dioxide is also a
product of fossil fuel combustion and this leads to global warming
problems.
5) PVC pipes are a relatively new invention and for the most part
the PVC
produced to be used in pipes has yet to be replaced and then enter
the waste
stream. PVC pipes would be considered a long-life PVC product
unlike
short-life PVC products used in containers and packaging which
today pose
environmental problems relating to their disposal.
6) However, one
day even PVC pipe materials will inevitably join this waste stream and
have to be
dealt with. The disposal of PVC products is a difficult issue.
PVC, like
most plastics, does not biodegrade so three options exist to dispose
of it;
bury it, incinerate it or recycle it. While recycling PVC seems
to be the
obvious best choice of these options, it is not an easy goal to
accomplish.
In order for PVC to be recycled, it first must be separated from
all of the
other plastics because they all have different chemical compositions.
This
is difficult and expensive because it must be done by manual labor.
There
is no truly effective method to automate the process. Even if
the PVC is
separated and recycled, the recycled material is of a lower grade
than
virgin PVC material and cannot be directly reused for the same
purpose.
Incineration is not a great option for the disposal of PVC either.
Incineration of PVC material, like most plastics emits carbon
dioxide, a
green house gas and other toxic gases. In addition, the incineration
creates ash and residual materials that must be disposed of in
landfills.
Contaminated salt residues that are a by-product of incineration
must be
disposed of as a hazardous waste. Disposing of PVC in landfills
really
doesn't dispose of it, but instead only "stores" it
indefinitely.
Additionally, there are concerns that PVC materials in landfills
may release
heavy metals that are contained in them as additives into the
environment.