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Life cycle assessment and agriculture: challenges and prospects

presents complex challenges for the design of policy and practices to reduce environmental 113
impact. Some impacts are more controllable than others and there is significant risk of burden
shifting and/or inefficient outcomes where particular environmental issues in parts of the chain
are targeted. For example, a support mechanism for UHT milk designed to reduce wastage may
lead to higher transport emissions unless it were accompanied by reconfiguration of the UHT
production system. Other policy implications are discussed further in Section 9.7.

9.5 Following maize from seed to chip: impact versus value?
The sugar cane and dairy case studies (Sections 9.3 and 9.4) illustrate some of the data and
methodological issues raised by the application of LCA to farm-scale agricultural impact
assessment. In this case study, we build further on the approach of looking beyond the farm
gate, and examine the system of corn chip production from seed to retail shelf, including
growing, transport, processing, manufacturing, packaging and distribution. This account is
drawn substantially from Grant and Beer (2008), based on research led by CSIRO into the life
cycle impacts of irrigated maize production (Beer et al. 2005; Edis et al. 2008; Kirkby et al.
2006; Meyer et al. 2006; Grant and Beer 2008). The Grains Research and Development Corpo-
ration and the Australian Greenhouse Office contracted CSIRO, the CRC for Greenhouse
Accounting and the University of Melbourne to undertake the study.
Although the impacts assessed are limited, with a particular focus on life cycle greenhouse
gas emissions, the study takes a system that is more extensive than many agricultural LCAs.
First, it incorporates primary research on soil greenhouse gas balances, including emissions
associated with additions and changes in soil nitrogen. Second, it extends the system to include
processing of the agricultural product into a final retail food, and includes packaging of the
food. Third, it includes an investigation of economic value (and specifically, the value added
during each production step). In keeping with the extended system boundary, one 400 g packet
of corn chips is adopted as the functional unit, with the measurement unit being kg CO eq per
2
packet of corn chips (see Fig. 9.1).
Irrigated summer crop maize was chosen as it has been identified as a potentially strong
emitter of greenhouse gases, particularly of nitrous oxide (N O), since fertiliser use leads to
2
N O emissions (Flessa et al. 2002), and the maize industry uses high rates of fertiliser applica-
2
tion. Data was identified as a key issue early in the project, and the project team was in Griffith
in February 2004 to inspect the farm, and then to obtain relevant energy-use data by visiting
the Bendigo factory of the corn chip manufacturer. Recognising that farms may use different
irrigation techniques, different soil management techniques, and different fertiliser applica-
tion regimes to those used on the field site, consultation was undertaken with growers in the
field in order to determine the representativeness of the study parameters being examined on
the experimental farm (to inform the uncertainties associated with the life cycle estimates).
On-farm measurements of N O emissions from nitrogen fertiliser applied to maize crops
2
o
o
were conducted at Commins Brothers property at Whitton, New South Wales (34.5 S 146.2 E).
The measurements were conducted on a site already established for 5 years, to investigate the
interactions between nitrogen and stubble retention on soil carbon dynamics. The fluxes of
N O and CO were measured on three of the established treatments:
2 2
s zero N fertiliser application and stubble removed by burning
s 329 kg N/ha, stubble removed by burning
s 329 kg N/ha, stubble mulched and incorporated into the soil.

The basic LCA was for irrigated maize supplied to corn chip producers. It was assumed
that:

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