artificial conditions aim at providing a range of values for global warming. Exclusively aerobic conditions are
impossible to obtain in home composting and anaerobic conditions are likely to arise if the compost is not often
aerated properly. This virtual ‘anaerobic’ case attempts to demonstrate the (rather large) effect that the aeration
assumption has regarding the contribution to climate change. For the rest of impact categories, study no 3
presents identical figures for both cases of home composting.
Figure 34 illustrates where composting stands compared to the other routes in terms of global warming
contribution only. It instantly becomes clear that anaerobic digestion is absolutely better, in the sense that there
is relative consensus among studies (three out of four cases). The situation is not as clear for incineration. There
are studies that classify compost as a better option and one that supports the opposite statement. Study no 2
includes two cases of composting from which incineration is superior. In this study, state-of-the-art technologies
are assumed for a Danish context. Therefore, it is safe to say that a high-standards incinerator provides more
advantages for climate change than composting, despite the low heating value of wet organic waste. The rest of
the cases are in favour of composting, but in two cases the results are very close. Composting is clearly better
than landfill according to the diagram below. The only case where composting is worse is contained in study no3
where artificial anaerobic conditions are assumed for composting resulting in the release of high concentrations of
methane - which is particularly harmful for climate change. The rest of the studies agree that composting is
better.
Figure 35 illustrates the relative superiority of incineration with energy recovery to other treatment options. It is
also quite clear that incineration is superior to landfill with respect to climate change. All four cases support this
statement and they even belong to the upper side of the positive axis (above 150%) which means that the
figures for the two options differ greatly. As mentioned above, the results of the comparison to composting are
not that clear.
As a general rule of thumb, from all comparisons among options, landfill appears to be the worst option, while
anaerobic digestion is the best.
Table 69 Relative difference between the impacts from the different end-of-life options vs. composting for climate change for food and garden
waste. A positive value means that composting is preferable to the other end-of-life option. A negative value means that composting causes a
larger environmental burden than the other end-of-life option.
N° case 1[OR] 2[GW1] 2[GW2] 3[FW1] 3[FW2] 3[FW3] 4[FW1] 4[FW2] 5[OR] 6[OR]
Incineration with energy recovery ‐1320% ‐410% 20% 20% 0% 150%
Landfill 630% 60% 2720% ‐70% 1980% 1980% 220% 4550%
Anaerobic digestion ‐740% ‐790% ‐350%Composting versus other alternativesStudy n°7 does not include a comparison with incineration with energy recovery for this indicator and thus is not included in this table*
- Composting scenario assuming total anaerobic degradation
Table 70 Relative difference between the impacts from the different end-of-life options vs. incineration with energy recovery for climate change
for food and garden waste. A positive value means that incineration with energy recovery is preferable to the other end-of-life option. A negative
value means that incineration with energy recovery causes a larger environmental burden than the other end-of-life option.
N° case 2[GW1] 2[GW2] 4[FW1] 4[FW2] 5[OR] 6[OR] 7[OR]
Composting 90% 80% ‐20% ‐20% 0% ‐300%
Landfill 1600% 1600% 220% 8800%
Anaerobic digestion ‐620% ‐670% ‐1000% 40%
Studies n°1 and 3 do not include a comparison with incineration with energy recovery for this indicator and
thus are not included in this tableIncineration with energy recoveryversus other alternatives