Page 68 - Materials Chemistry, Second Edition

54 N. E. Korres

quantity and quality, for example, 1 tonne of bread-making wheat. In many
studies, the FU is typically one unit of weight of product (e.g., kg or tonne), or one
hectare of land used (Haas et al. 2000; Haas et al.2001; Nicol and Sage 2003;
Casey and Holden 2006). Consensus is needed on the FU for livestock, e.g., 1 kg
of bone free leaving the gate, 1 kg of live weight leaving the farm gate, or 1 t of
carcass dead weight. The choice can help avoid allocation (Harris and Naray-
anaswamy 2009).

System Boundaries

System boundaries are a set of criteria specifying which unit processes/tasks are
part of a product system (ISO 14040: 2006). The system boundary should include
as far as possible all relevant life cycle stages and processes (EC 2010). Hayashi
et al. (2005) reported that one of the methodological characteristics of agriculture
LCA studies, since they are analyzing production processes, is that their system
boundaries are defined as the cradle-to-gate type (Baumann and Tillman 2004—
cited in Hayashi et al. (2005)). Nevertheless, the system boundary will largely
depend on the goal of the study if, for example, the scope is for environmental
improvement of the farm or the whole supply chain to consumer (Harris and
Narayanaswamy 2009).

Life Cycle Inventory

A LCI analysis is the process of quantifying the energy and raw material
requirements, atmospheric emissions, waterborne emissions, solid wastes, and
other releases for the entire life cycle of a product, process, or activity. In this
stage, all relevant data are collected and organized. The evaluation of comparative
environmental impacts or potential improvements without LCA is not possible
whereas the level of accuracy and detail of the collected data should be reflected
throughout the remainder of the LCA process (WEC 2004).
The key steps of a LCI include the (1) development of a flow diagram of the
processes under evaluation (Figs. 2, 5 and 10); (2) development of data collection
plan (Korres, 2013); (3) collection of the data based on certain rules and protocols
regarding their quality (Korres 2013) or calculation when possible/necessary (see
below); and (4) evaluation and reporting of the results (Korres 2013).
A generic flow process model for agricultural production within each opera-
tional unit or task consists of four main tasks, namely seedbed preparation, sowing/
planting, field operations, and harvesting. The field operations are divided into
fertilization, irrigation and weed and pest control (Fig. 10). The task and subtasks
during crop production stage can be characterized as mechanical and/or non-
mechanized (e.g., human labor). Fertilization can be characterized either as con-
ventional (inorganic), organic (e.g., manure or digestate or mulching), or mixed
(combination of inorganic/organic).