MUNICIPAL SOLID WASTE MANAGEMENT AND DISPOSAL - Environmentally Conscious Materials Handling - page 162

was not the case for the other processes such as landfilling or incineration. It has
also been reported that, in general, recycling is a better option than landfilling with
respect to environmental impacts (global warming gases, acidification potential
and nitrification potential) and energy consumption (Chang and Bindiganavile
2005a 2005b, Chang Elobeid 2005, Chang and Chisolm 2007).
Molgaard (1995) describes ecoprofiles—assessment of environmental and
resource impacts—for six different ways of disposing the plastic fraction in
MSW: two different material recycling processes involving the separation of
plastic waste; material recycling without separation of plastic waste; pyrolysis;
incineration with heat recovery; and landfilling. The results indicate that
recycling of plastic from MSW is only environmentally and resource sound if
it is separated into its generic plastic types, which makes it possible to produce
a recycled plastic with properties comparable to virgin plastic. Alternatively, if
it is not possible to separate the plastic, incineration with heat recovery is the
most environmentally and resource-sound process. Beigl and Salhofer (2004)
compare the ecological effects and costs of different waste management systems
for individual waste types—waste paper, plastic packaging, metal packaging,
and waste glass—by means of a life-cycle assessment and a cost comparison.
The results indicate that the waste paper recycling scenario has clear energy
savings and reduces acid emissions with a similar cost and amount of global
warming emissions. The recycling of waste glass and metal packaging leads to
clear ecological benefits, whereas recycling of plastic packaging is ecologically
advantageous, although it causes much higher collection and treatment costs.
Multicriteria methods have been used in evaluating and comparing the various
technologies for treatment and disposal of solid waste. They are particularly
useful in the valuation stage in the life-cycle assessment. The commonly used
methods in evaluating the various disposal systems include the following:
• Weighted aggregate method . This method consists of identifying a list of
alternative courses of actions and a set of evaluative criteria, as well as
weights that reflect the importance of the criteria. Further, a dominance
pairwise comparison of the alternatives wherein each alternative is evalu-
ated against the other is performed, or the scores are finalized by comparing
the arithmetic total of the scores of each of the alternatives in determining
the best alternative solution. This method has been used in the selection
of solid waste management and disposal options such as landfilling, waste
to energy, recycling, composting, and incineration (Chung and Poon 1996;
Powell 1996).
• Goal programming method . The goal programming method is designed to
combine the logic of optimization in mathematical programming with the
decision maker's desire to satisfy several goals. Two main types of goal
programming are recognized: preemptive (lexicographic) and nonpreemp-
tive (weighted) goal programming. Solution techniques of both types of