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A life cycle assessment of tri-generation from biomass waste 217

2 The LCA applied to the “agro-combined” system
of Thibar
2.1 Goal and scope definition
The analysis was developed by applying the LCA methodology, according
to the international standards of the ISO 14040 series (ISO 14040, 2006; ISO
14044, 2006), for assessing the eco-profile of energy production by biogas in
a tri-generation plant.
The research was carried out in an agricultural district, which has been
named by the local authorities as the “agro-combined” system of Thibar.
Thibar is a town with 3500 inhabitants located in northern Tunisia,
50km west of the city of Beja. The Delegation of Thibar has over 11,000
inhabitants, and administratively it is attached to Beja.
The agricultural area of Thibar is owned by the central State and man-
aged by the Office for Public Lands. The above area covers 2704ha of which
1061ha are uncultivated (828.5ha are forests and 161ha are pastures). There
are various agricultural and livestock activities, such as fruit growing, olive
growing, viticulture field crops, sheep and cattle breeding. The cattle are
made from 336 dairy cows, 190 heifers, 171 calves, 350 sheep. The agricul-
tural practices are both extensive and intensive. Water for irrigation comes
from a hill lake located in the heart of the area and from wells and surface
water sources. Water is drawn and collected in a basin through proper water
pumping stations. The distribution of irrigation water is made via a network
of irrigation. The agricultural and livestock products are mainly cereals,
olives, fruits, milk, and calves. Furthermore, wine (350,000 bottles per year)
and spirits (80,000 bottles per year) are produced in the agricultural area
of Thibar.

2.1.1 Functional unit, system boundaries, impact assessment
methodologies, and impact categories
The functional unit defines the quantification of the identified function of
the system and provides a reference to which the inputs and outputs are
related (ISO 14040, 2006).
The function of the examined supply chain is the tri-generation of elec-
tricity, thermal energy for heat, and refrigeration energy. According to
Masoni and Zamagni (2011), to measure the performance of a system with
a single parameter when both electricity and thermal energy are valuable
products and to take into account the different quality of these forms of
energy, the functional unit can be expressed in MJ of exergy.