Page 249 - Biofuels for a More Sustainable Future

224 Biofuels for a More Sustainable Future

categories with a contribution lower than 15%. A negligible impact is caused
by the pumps production, except for the impact on RD that is about 51% of
the total. The impact of the remaining components (digester, storage tanks,
and pipes) varies from 45% (HT nc ) to 80% (TFW) and is lower than 4% for
E FW , FE, HT c , IR, OD, and RD. These impacts are mainly caused by the
steel use in the manufacturing process of the digester.

3 Conclusion
This paper presented an experience of LCA application to a tri-generation
plant in a developing country. This kind of approach represents a novelty in
the Tunisian area and can be easily disseminated and applied in other devel-
oping countries in the Mediterranean area. The analysis allowed pointing
out some important considerations and closing remarks.
First, the critical issues to be tackled for the environmental improvement
of the system wereidentified. In detail,the useof steel in themanufacturing of
the digester was identified as a key issue for reducing the primary energy con-
sumption and some environmental impacts of the selected functional unit.
Furthermore, the biogas production and combustion are critical processes
to be taken into account for improving the environmental sustainability of
the examined system. These processes are influenced by different parameters
to be carefully assessed and monitored, for example, the biomass waste in
input to the plant, its composition, and the biogas production from the input
waste. In detail, the yield of biogas and its percentage of methane are depen-
dent on the biomass composition. Using the most appropriate biomass waste
compositioncan helpimprovingthe efficiencyof thetri-generation plant and
to reduce the environmental impacts of the selected functional unit.
The study also highlighted the low contribution of the biomass transport
to the total impacts, due to the short distance between the plant and the areas
within which biomass wastes are collected. Thus the supply of local
resources is one of the main issue to be assessed in order to avoid that the
transport of biomass would reduce and, potentially, cancel the environmen-
tal benefits of producing energy from a renewable energy source.
The obtained results can help stimulate the debate with local policy
makers and organizations about policies that can be applied in order to opti-
mize the biomass waste use for energy generation and to improve its
sustainability.
The valorization of waste biomass can generate benefits that not only
involve the examined supply chain, but also all the geographically