Depletion of natural resources
Unfortunately, only study no 4 includes this indicator in its impact assessment. Both cases examined are quite
consistent with one another and they produce a clear classification of alternatives. Anaerobic digestion takes the
first place mainly because of the large benefits it brings to the system. Anaerobic digestion recovers both material
(fertiliser) and energy, saving at the same time the resources required for the primary production of both.
On the other hand, since composting is considered to be the worst option in this study, it appears that it is the
energy recovered by anaerobic digestion that brings the most benefits. Moreover, the differences in the results
are so great that it highlights that energy recovery (which in this study leads to the avoidance of fossil fuel
depletion) is much more beneficial than material recovery (fertiliser substitution). The reason for this observation
is that fossil fuels in an LCA context are considered to be a limited resource, while fertiliser is not. Landfill appears
to be performing better than composting, which is rather surprising. The explanation given in the study is that,
for this system, this impact category is greatly dependent on energy consumption and the consumed resources
are approached as energy carriers. Therefore the energy recovery of the landfill manages to overcome the
benefits from material recovery in composting.
In this study and for this impact category, anaerobic digestion is the most efficient method for recovering energy,
since incineration has much worse figures. Obviously, the additional function in anaerobic digestion of producing
a secondary material also plays a part in the results obtained.
The following tables and graphs confirm the superiority of anaerobic digestion. In Figure 37, incineration is
proved to be the worst option except for composting.
Table 71 Relative difference between the impacts from the different end-of-life options vs. composting for depletion of natural resources 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 4[FW1] 4[FW2]
Incineration with energy recovery ‐70% ‐70%
Landfill ‐300% ‐300%
Anaerobic digestion ‐420% ‐460%Composting versus other alternativesOnly sudy n°4 includes a comparison with composting for this indicatorTable 72 Relative difference between the impacts from the different end-of-life options vs. incineration with energy recovery for depletion of
natural resources 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 4[FW1] 4[FW2]
Composting 230% 230%
Landfill ‐770% ‐770%
Anaerobic digestion ‐1160% ‐1270%
Only sudy n°4 includes a comparison with incineration with energy recovery for this
indicatorIncineration with energy recovery
versus other alternatives