Page 66 - Materials Chemistry, Second Edition

52 N. E. Korres

Fig. 9 Soil carbon alterations with management practices (based on US DOE 2006)

issues is vital if biofuels are to become a significant component of sustainable
energy and socioeconomic systems.
Nevertheless, this chapter, as mentioned earlier, focuses on agricultural LCA that
deal specifically with biogas and bioethanol production. In the following sections,
issues in relation to four distinctive phases of the LCA as they have been defined by
ISO 14040 (ISO 1997) series will be discussed. Grant et al. (2008) stated that when
LCA is applied to GHG emissions in agriculture all pre-farm, on-farm, and post-
farm emissions of carbon dioxide, methane, and nitrous oxide should be included.
As such, a full LCA of emissions takes into account downstream emissions but also
those associated with the fuel and other inputs during pre and on-farm activities
known as upstream emissions (Grant et al. 2008). In other words, all inputs are traced
back to primary resources, for example, electricity is generated from primary fuels
like coal or oil (Williams et al. 2006). Fertilizers that are based on ammonium use
methane as a feedstock and source of energy. Other fertilizers, such as phosphate and
potassium, also require energy for extraction from the ground, processing, packing,
and delivery. Machinery, including tractors and processing equipment, requires
steel, plastic, and other materials for their manufacture. This involves energy costs in
addition to the direct diesel use (Harris and Narayanaswamy 2009).

4.2.2 LCA Framework

Key components and critical phases of agricultural LCA will be dealt in this
section are the following: (1) goal and purpose of agricultural LCAs; (2) LCA
system boundary; (3) functional unit(s); (4) life cycle inventory (LCI) and