Environmental Engineering Reference
In-Depth Information
Material recycling (or reuse) does not preclude subsequent use of other
waste management options. The recycled resin in a secondary product
cannot be further recycled
ad infinitum
and has to be invariably disposed
of at some stage in its lifecycle using one of these options. This option is
discussed in the following section.
Feedstock recovery via gasification/pyrolysis is an attractive option as it is
not carbon emitting and yields valuable feedstock chemicals and/or fuels.
The carbon in the waste is not emitted as CO
2
but turned into fuel that
can be used. As it is carried out in a closed system there are no polluting
emissions except for inadvertent losses. The drawback here is that it
requires source-separation of plastics if high-value products are to be
expected. Waste to energy conversion via incineration when carried out
under controlled conditions is preferable to landfilling in terms of
environmental compatibility. It also has the advantage of not needing any
source separation of plastic waste.
As environmental impacts and energy demands associated with different
plastic waste management approaches are based on different LCA studies,
they are not strictly comparable. Also, the specific technologies used in
competing recovery methods influence these estimates. However, Perguini
et al. (2005) found material recycling to be a particularly attractive option.
Their findings summarized in
Table 9.9
compares several different options.
Low-temperature pyrolysis by BP polymer cracking process (Arena and
Mastellone, 2005) and hydrocracking by the Veba Combi-Cracking process
(Dijkema and Stougie, 1994) were considered. While these numbers are
by no means applicable to all waste management scenarios, performance
of recycling and combinations of recycling with resource recovery are
particularly significant. It has been proposed that landfilling plastics can be
more environmentally friendly compared to incineration (Finnveden et al.,
2005), where plastics are assumed to biodegrade in the long term yielding
GHGs or transport of waste over long distances is needed.
