recovered would be 15 tons. The production of virgin metals requires
8.9 MJ/kg (Table 5). Therefore the energy required to produce
15 tons of virgin metal is 15,000 kg 8.9 MJ/kg = 1.34 105
MJ. Recycling the metals results in energy savings of up to 60%.
Thus, the production of recycled metals would result in an energy
savings of 1.34 105 MJ 0.60 = 7.9 104 MJ of energy. The same
procedure was applied in determining the savings obtainable for
all the materials considered in the scenario and the results
aggregated.
For the scenario assessed, the results indicated that about
2.2 102 GJ of energy could be saved for the assumed case study
60,000 m2 building. Of this amount, the largest share of about
57% originated from the recycling of wood. Ferrous metals and
concrete followed next with contributions of about 37% and 6%,
respectively. This result shows an increased contribution of both
ferrous metals and concrete recycling to energy savings when compared
to their relative proportions obtained for the recycling of
their construction waste scenario. The difference in relative proportions
of energy savings between the construction and demolition
scenarios is principally due to the fact that the waste
fractions of these two materials are much higher during demolition
than construction as explained earlier. Also because demolition
clearly dominates total waste amounts, the profile of the relative
contributions of recycling different materials to energy savings in
Thailand is expected to be different from the result presented in
Fig. 3 when C&D waste data based on a national scale characterization
study is utilized for the analysis. It should be noted that the
results obtained from this scenario analysis are largely dependent
on the composition of C&D waste utilized, which varies in different
countries.
It is important to realize that the computation was carried out
simply to illustrate the benefit of recycling. This, however, does
not imply that other strategies cannot be applied to manage construction
waste. For example, the recycling of wood waste for fuel,
pulpwood, and feedstock for products such as particleboard depends
on the quantity and quality of the recovered material as well
as economic and environmental considerations (US Energy Information
Administration, 2006). Consequently the benefits of recycling
some materials such as construction wood waste should
only be assessed within an integrated waste management model
for which adequate information is presently unavailable.
Recycling, being one of the strategies in the minimization of
waste, offers several benefits – reduction in demand for new resources,
reduction of transport and production energy costs and
use of waste which would otherwise be lost to landfill sites.
Although there are many material recycling schemes recommended,
actual administering of C&D waste recycling is limited
to a few types of solid wastes. Therefore, when considering a recyclable
material, the economy, compatibility with other materials
and material properties are three major considerations. Many viable
technologies for recycling construction waste exist (Tam and
Tam, 2006b). However, there is a lack of knowledge within the construction
industry regarding these. Education awareness campaigns
could serve as vehicles to promote the use of these
technologies.