level of technology applied on the landfill. The more efficient the biogas recovery, the better the results for
landfill compared to recycling.
Table 20 Influence of the methane extraction rate on the environmental assessment of landfill regarding climate changeLandfill^
Case
Methane
recovery
efficiency
Relative
difference of
landfill vs
recycling
1[PB] 55% ‐134%
3[PS] 50% 88%
3[EN] 50% 101%
5[PA] 25% 1260%
5[MC] 25% 1633%
The same level of importance could be attributed to incineration plants as well. However, only two studies
mention the selected efficiency as shown in the following table, while others assume an average incinerator
efficiency within their geographical scope. The limited efficiency interval, though, still renders the studies valid
and approximately comparable to each other.
Table 21 Overview of the incinerator efficiencies in the selected studies for paper and cardStudy
number
Energy produced
with incinerator
Efficiency
(^1) electricity 27.7%
(^2) electricity + heat n.a.
(^3) electricity + heat 32%
(^4) electricity n.a.
(^5) electricity + heat n.a.
Inclusion of carbon sequestration / storage
Carbon sequestration and carbon storage are two concepts developed in order to better describe the carbon
cycle. When the carbon uptake in a specific area (e.g. a forest) is higher than the release, then carbon is
sequestered in the biomass. In an LCA context, when recycling causes resource savings, the saved biomass
contributes to carbon sequestration. The net uptake of carbon from the atmosphere can be credited to the
recycling system as CO 2 savings.
Moreover, when biogenic carbon is stored in soil for more than a chosen time interval (usually 100 years), its
effect on global warming can, by convention, be ignored. According to this convention, the carbon stored in
landfills is not released in the atmosphere and the landfill system could be credited with the corresponding CO 2
savings. However, the calculation of the remaining carbon after a certain time period is quite complex and based
on many diverse assumptions such as the degradation ratio, weather conditions, etc. Since this period usually
extends far into the future, the estimate of the CO 2 savings due to carbon storage is uncertain.
Carbon sequestration is applied in only one study (no 4) for the recycling scheme. The resource (forest) savings
due to recycling increase the uptake of carbon dioxide by the remaining trees and the carbon is, therefore,
sequestered. This amount of carbon (0.55 or 0.83 metric tons of carbon equivalent) is credited to the recycling
system that provoked the phenomenon. In this study, recycling has a clear advantage in the affected impact
category (climate change) compared to all other options. Moreover, the difference in the impact assessment
results is quite high.
Although there is no carbon sequestration taken into account in the second study, recycling still is the best
option, according to Table 22. Carbon sequestration is not the sole decisive factor for the ranking of recycling and
many other parameters might have influenced the results. However, study no 2 does not reveal much
information about the incineration configuration rendering the investigation of this classification difficult.