The results obtained indicate that an average primary energy
savings of about 3.0 105 GJ per year during 2002–2005 could
be achieved by recycling the construction materials examined.
Fig. 3 shows the relative contribution of the three materials assessed
to this savings. This amount is expected to increase if other
building materials are recovered and recycled efficiently.
It was observed that the use of waste wood for electric energy
had the largest contribution to the total energy savings with about
89%. The recycling of ferrous metals followed next with 8%, and the
down-cycling of concrete to aggregates contributed about 3%. One
factor responsible for the relatively low contribution of concrete to
this energy savings could be attributed principally to the low difference
in energy requirements between virgin and recycled production
of aggregates. Another reason for the relatively low
contribution of ferrous metals and concrete materials was because
this study did not include the quantities of these materials generated
from demolition activity. If these had been accounted for, then
it is expected that the energy savings attributable to their recycling
could be expected to be much higher. This is because, according to
Myhre (2003), both materials have the largest percentages when
all the waste generated from construction, renovation and demolition
activities are accounted for. This is clearly illustrated when the
material contribution to energy savings as a result of recycling
demolition waste from a 60,000 m2 commercial building (assumed)
is assessed. It should be noted that this estimation is simply
for illustrative purpose and is based on scenario analysis as the
data required to actually model waste generation from demolition
activity within Thailand’s building stock is unavailable as mentioned
earlier. The composition of demolition waste as obtained
in Bergsdal (2007) was utilized. The assumptions for recycling
the recovered materials are as stated earlier and also in Table 5.
An assessment of the recycling of recovered demolition waste
materials was made for a typical commercial building in Thailand
with an assumed gross floor area of 60,000 m2 and concrete envelope.
The average quantities of the different materials from demolition
of the building were computed using Eq. (1) and the same
procedure as that for utilized for determining waste materials
generated from new construction. Wood was assumed to be used
for process heat, ferrous metals substituted virgin materials and
the down-cycling of concrete was used as aggregates in concrete
or backfilling in new construction. For example the average
quantity of metal generated from demolition was computed
according to Eq. (1) based on an assumed area of construction of
60,000 m2, an average waste generation rate of 18.99 kg/m2 for
new non-residential buildings and an average composition of
waste metal of 4%. Substitution in (1) yields 1.14 103 tons of
waste generated from the building demolition, of which approximately
50 tons is metals. Assuming 30% of all metal waste is recovered
and recycled (Table 5), then the total amount of metal