Page 180 - Materials Chemistry, Second Edition

MODELING THE AGRI-FOOD INDUSTRY WITH LIFE CYCLE ASSESSMENT 165

two wine systems (red wine and red quality wine) assuming volume, alcoholic
degree and hedonistic value as functional unit, respectively. This study puts
in evidence the enormous importance of the functional unit and the need to
consider functional units not necessarily based on mass or volume.
In conclusion, in defining the functional unit of a food product, according to
the objectives of the study, aspects related to the various functions of the prod-
uct should also be included. Especially, in comparative studies the qualitative
aspects of the product need to be considered. The choice of which elements
play a key role in the definition of the quality of the product will, of course, be
made individually for each product.

7.2.2 System Boundaries, Carbon Balance and Data Quality

The system boundaries definition for agri-food products is more significant
than that of other product systems due to the particular importance of the
agricultural and zootechnical phases. The definition of the system boundaries
implies the definition of a boundary between natural system (biosphere) and
technical system (technosphere). In food production the inclusion of biological
processes renders the distinction between these two systems more difficult.
The crop has to be considered as an industrial process, by taking into account
all the inputs and outputs occurring during its life, including water and car-
bon, referred to the functional unit. The quantity of carbon sequestered dur-
ing photosynthesis by the plant, for instance, has to be considered, but that
same quantity of carbon will be emitted to the atmosphere during all the com-
bustion processes, including the consumption of the food, human digestion,
respiration, and metabolism activity. Consequently, if one accounts for the
carbon sequestered, one has also to account for the carbon that will be emit-
ted by the human body, as a consequence of the food consumption. Carbon
dioxide emissions to atmosphere during human body respiration or, more in
general carbon emission during digestion-excretion will counterbalance the
biologic carbon sequestered by the plant from atmosphere. Human digestion
and excretion remains the least studied life cycle stage of food products, it
is comparable to the waste management stage for industrial products and its
omission from LCA may compromise the results in identifying hot spots and
opportunities for environmental improvement in the life cycle (Munoz, et al.
2008; McLaren, 2010).
One of the aspects of growing interest in environmental assessments of
products is the carbon balance, sometimes also called carbon footprint. For
products of plant origin such as food, there is a need to verify if and how
to insert data from the biogenic carbon in the system boundaries of a LCA
analysis; the question naturally concerns the analysis of the carbon cycle and
its inclusion in an LCA.
As is well known, the carbon cycle is the phenomenon by with which
carbon circulates from the atmosphere to plants, animals, soil and back into
the atmosphere. The cycle can be started with the fixation or sequestration of
atmospheric carbon by plants through photosynthesis and the production of