Microsoft Word - Environmental benefits of recycling 2010 update.doc

Table 60 Influence of the carbon sequestration issue on the performances of landfill and composting regarding the climate change potential in

study n°2

Assumption Landfill Composting Relative ranking

No carbon sequestration 1234 landfill< composting

Carbon sequestration ‐ 355 ‐ 1009 composting < landfill

Climate change potential

(kg CO2 eq/t)

The issue of the degradation rate and carbon sequestration is also linked to the inclusion or exclusion of the
biogenic CO 2 which influences the climate change potential. When biogenic CO 2 is taken into consideration, it
means that the CO 2 that is emitted due to the degradation of biomass-based substances is assumed not to
contribute to global warming since it was taken from the atmosphere during the growth of the plant. In addition,
following this approach, the biogenic carbon that is not emitted in landfills or in compost can be considered to
have been removed from the natural cycle, thus reducing CO 2 emissions when looking at the full life cycle, as
explained in the following:

 Growing phase: X kg of CO 2 absorbed

 End-of-life phase:

In case of incineration: X kg of CO 2 emitted  0 kg of CO 2 for the whole life cycle

In case of landfill or composting: 0 kg of CO 2 emitted  X kg of CO 2 absorbed for the whole

life cycle

Among the studies selected, studies no 2 and 4 clearly indicate that biogenic CO 2 has been taken into account.
Study no 1 also refers to biogenic carbon but it is not clear how it has been taken into account in the calculations.
The influence of this parameter can be seen on Table 61 which presents the influence of the inclusion of biogenic
CO 2 for study no 4. When biogenic CO 2 is excluded, it means that the emissions of biogenic CO 2 are assumed to
contribute to global warming as fossil CO 2 and the sequestered carbon is not assumed to save any emissions. The
results show that the inclusion of biogenic CO 2 has a very significant influence on the results and affect the
ranking between the different options:

 Ranking with biogenic CO2

Composting < Incineration without energy recovery < Landfill

 Ranking without biogenic CO2

Incineration without energy recovery < Composting < Landfill

The choice of assumptions regarding how carbon issues (degradation, sequestration, biogenic CO 2 ) should be
taken into account is thus of major importance and should be clearly presented.

Table 61 Influence of the inclusion of biogenic CO 2 on the performances of landfill and composting regarding the climate change potential in study
n°4

With

biogenic CO 2

Without

biogenic CO 2

With

biogenic CO 2

Without

biogenic CO 2

[MUB1] ‐0.248 1.92 1.21 3.05

[MUB2] ‐0.213 1.95 3.46 5.08

Composting Landfilling

Climate change potential (kg CO 2  eq)