Page 248 - Biofuels for a More Sustainable Future

A life cycle assessment of tri-generation from biomass waste 223

AP
100
TFC EFW

75
RD FE
50

POF 25 HTc
Production
Operation
End-of-life
PM HTnc

OD IR

TE GWP
ME
Fig. 7.2 Contribution of each life cycle step to the total environmental impacts.

A dominance analysis of the operation step shows that the biogas produc-
tion in the digester causes about 95% of the impact on GWP and ME and
about 83.5% of the impact on TE; in addition, this step is responsible of
about 68% and 58.5% of the impacts on AP and PM, respectively.
The higher impacts on POF, about 64%, are caused during the cogen-
eration process, while the water use process is the main responsible (about
99.9%) of the impact on TFC. More than 97% of the impact on E FW , FE,
and HT are caused during the final treatment of the digestate, and more than
98.5% of the impacts on RD, IR, and OD are caused by the lubricating oil
consumption. A contribution to the impacts lower than 1% is due to the
transport of the biomass waste to the plant.
Looking at the production step, the main impacts on FE (about 54%),
HT c (about 63%), IR (about 85%), and OD (about 89%) are caused by
the cogeneration plant manufacturing, while the contribution of this system
to the other impact categories ranges from 13.5% (RD) to 32.5% (E FW ). The
absorption chiller causes the main impact (about 66.6%) to E FW and it is
responsible for about 45% of the impact on FE and for about 31%–33%
of the impact on HT and RD. In addition, it influences the other impact