Environmental Engineering Reference
In-Depth Information
Table 9.8
Calculated GHG Emissions from incineration of
Different Plastic Resins
Source: WARM (Waste Reduction Model) Version 12 USEPA (2012).
Plastic
material
CO
2
from incineration
(MT CO
2
/short ton of
Plastic)
Energy content
of plastic
(MBTU/ton)
HDPE 2.82
1.42
40.0
LDPE/
LLDPE
2.82
1.41
39.8
PET
2.06
0.75
21.2
PP
2.82
1.42
39.9
PS
3.04
1.28
36
PVC
1.28
0.56
15.8
a
Net emissions after adjusting for avoided utility emissions from burning
conventional fuel for utilities.
9.2.7 Biological Recovery Technologies
Composting and anaerobic breakdown of waste with gas recovery are
practical biological recovery options. Composting is the accelerated aerobic
breakdown of material facilitated by thermophilic species of microbes.
Commercial composting is carried out at temperatures of 40-62°C where
no pathogens can survive. In anaerobic digestion, biomass is converted to
biogas (CH
4
and CO
2
) that is used as a replacement for natural gas or as
a fuel to cogenerate heat and electricity. Unlike in composting, anaerobic
digesters can operate under thermophilic, mesophilic (35-40°C), or
psychrophilic (15-25°C) conditions. Even mesophilic temperatures are
reported to reduce (but not eliminate) (Wright et al., 2001) any pathogen
content in the waste; however, the digesters are enclosed and only the gas
is removed for use. However, as already pointed out, the plastic content in
the MSW is predominantly, if not exclusively, nonbiodegradable. They will
survive either of the biological treatments, though with composting, some
oxidationandevenfragmentation canoccur.Assuch,boththeseoptionsare
not strictly applicable to plastics fraction in MSW.
