Page 70 - Materials Chemistry, Second Edition

56 N. E. Korres

X
i
E F ¼ ð ð F ci f c Þ=O ci Þ ð2Þ
1
-1
-1
where E F fuel energy consumed (MJ ha ), F ci fuel consumption (L h ) for
i field operation, f c heating value of the fuel, usually diesel that equals 36 MJ L -1
-1
and O ci work capacity for i operation (ha h ).
The environmental burden of field operations which is usually articulated as
GHG emissions expressed as kg CO 2 equivalent (kg CO 2 e) can be calculated
based on the fuel energy consumed for all field operations and the GHG emissions
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produced from the combustion of 1 MJ of diesel (0.888 kg CO 2 eMJ ) (Eq. 3)
(Korres et al. 2010):
GHG emissions kg CO 2 =hað Þ ¼ FE MJ=hað Þ 0:0888 kg CO e /MJð 2 Þ ð3Þ

As it can be noticed, the energy per unit volume of the fuel used in agricultural
-1
operations (diesel in this case) varies between 36 and 37.6 MJ L and according
-1
to Saunders et al. (2006) up to 41.2 MJ L . This adds up to uncertainty of
calculated parameters in LCA and signals the importance in data collection in
terms of accuracy, representativeness, and consistency (Korres 2013).
According to (Romanelli and Millan 2005), indirect energy in farm inputs can
be calculated as a fraction of the solid (e.g., seeds, lime, and fertilizers) and liquid
(e.g., pesticides in liquid form).
The energy enclosed in the solid fraction of farm inputs depends on the appli-
cation rate and the enclosed energy within each and can be obtained using Eq. (4).

E si ¼ Q t E ci ð4Þ
-1
where Q t quantity of input applied per hectare (kg ha ); E ci = energy content
-1
(energy index) of a solid input (MJ kg ). Some representative energy indices of
solid and liquid inputs are mentioned below (Table 1).
Indirect energy consumed by the liquid fraction of crop production inputs can
be calculated based on Eq. (5):

E li a:i V p
E Li ¼ Q ð5Þ
V a
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where E li energy content of the liquid input (MJ L ); a.i. concentration of the
active ingredient in the commercial product (%); V p used volume of the com-
-1
mercial product (L); V a volume to be applied (L); Q application rate (L ha ). The
calculations of emissions from the consumption of indirect (solid and liquid)
inputted energy in crop production (e.g., fertilizers, herbicides, lime) but also
emissions due to the application of fertilizer (e.g., direct and indirect nitrous oxide
emissions) or these from lime and pesticides (e.g., volatilization) are described in
detailed in Korres et al. (2010) and Korres (2013).
The energy consumed by irrigation can be estimated either as energy values
directly from the literature (Tsatsarelis 1991; Wanjura et al. 2002; Yilmaz et al.
2004; Oren and Ozturk 2006) or as energy calculated from volume of diesel fuel