Environmental Engineering Reference
In-Depth Information
plastic material was commercialized as Bakelite in 1908 (made from phenol and
formaldehyde), and as phenol resin still used in electronic devices or impregnated
wood.
Most of today's most important plastic materials: polyvinyl chloride (PVC),
polystyrene (PS), polyethylene (PE)) were developed in the 1920s and 1930s. How-
ever, it was after the end of World War 2 that the real breakthrough of plastics oc-
curred. World-wide consumption of various plastics was just 7000 t in 1960 and is
expected to top 300 million t in 2015 with an annual average growth rate of 9 %. The
volume of plastic production today is higher than that of steel and this is the reason
why we can call our era the plastic age!
11.1.1
From Resource to Waste
To produce most plastics, energy and chemicals are used which are both derived
from fossil fuels. About 5 % of crude oil production is converted into chemicals; the
remaining 95 % is used as an energy source in cars, homes, and power plants. Since
crude oil is not directly usable, the oil has to be processed before it can be used.
Crude oil consists of thousands of compounds, mostly hydrocarbons, which are as a
first step separated by their boiling points- a process called rectification carried out
in refineries with typical annual capacities between 500,000 and 1,000,000 t. The
products still contain hundreds of compounds and are classified by their boiling
points: gases below room temperature; gasoline, naphtha, kerosene as liquid prod-
ucts; paraffin wax and asphalt are solid products at room temperature.
Crude oil contains a high content of high boiling point compounds with a low
market value, so these are upgraded by chemical reformation: their long molecule
chains are reduced by heat and catalytic cracking. High boiling fractions are also
burnt to provide the energy necessary for processing crude oil in refineries and
cracking facilities.
Valuable compounds can be separated for use in the chemical industry. Gases
such as ethene, propene, and butadiene are directly used for the production of poly-
mers such as PE, polypropylene (PP), butadiene rubber (BR), and also in the pro-
duction of other chemicals important for plastic production: i.e. vinyl chloride, eth-
ylene oxide, acryl nitrile. Important liquid compounds from crude oil are benzene,
toluene, and xylene. These compounds are not directly used for plastic production,
but represent important raw chemicals for the production of styrene, phenol, toluene
diisocyanate or terephthalic acid, which are used for PS, phenol resin, polyurethane
(PU), and polyethylene terephthalate (PET), respectively.
Most plastics are disposed of soon after production and use; sometimes by conven-
tional incineration; sometimes by landfill. The establishment of a resource-oriented
recycling society which includes plastic recycling poses challenges because of the
many different plastic materials which have to be treated separately in order to gain
valuable products. This means that rather similar to the specific production methods
of plastics, so too a specific treatment method for each plastic has to be found.
