Page 122 - Materials Chemistry, Second Edition

Life cycle assessment and agriculture: challenges and prospects

indicating that ‘natural’ (crop-derived) products often cause more environmental burdens 109
than ‘synthetic’ manufactured alternatives. Moreover, agriculture generally is becoming more
industrialised and systematic and, while this is not necessarily environmentally benign, the
increasing use of digital technologies and automated factory-style processes on-farm holds out
the possibility of better data and potentially improved LCA accuracy. Concurrently, there is
rising interest in the environmental (and especially greenhouse and water) impacts of food and
agriculture, partly in recognition that food is a major component of the eco-footprint of most
households in the developed world. Since food is a basic commodity that invariably and
increasingly involves agricultural technologies and practices, the systematic approach of LCA
to assessment of the various environmental burdens across different agricultural options is a
logical response to questions about the relative environmental impact of different foods.

9.3 Sugar cane: options and optimisation
In the work of Marguerite Renouf et al. (e.g. Renouf 2006; Renouf 2007; Renouf and Wegener
2007; Renouf et al. 2005), sugar cane production systems in Queensland are analysed and
compared to other sugar production systems, and the use of sugar cane crops as a substrate for
other products is also considered through LCA.
One of the key challenges of scoping this work was the difficulty in defining a functional
unit. First, from a farm perspective, the functional value of the crop is return on investment
from a given area of productive land. While most capitalist enterprises have this as a primary
function, what makes agriculture different is the flexibility of farm capital (e.g. land, tractions
and water) to switch between crop types and rotation systems. Second, from the sugar perspec-
tive, sugar cane has multiple production alternatives for both the sugar syrups and the residual
cane fibre. The issue then becomes an assessment of the optimal use of the land, given the
alternative ways of producing each of the product options available from cane production.
The initial goal and scope of the work included characterisation of the system of sugar pro-
duction from sugar cane based on production practices in Queensland (which accounts for
about 94% of Australia’s total production). The scope used is ‘cradle-to-gate’ and the func-
tional unit is a tonne of raw sugar leaving the mill gate. Life cycle impact assessment results
were generated for the following impact categories, using the impact assessment model Eco-
Indicator 95 (Goedkoop 1995, cited in Renouf 2006):
s energy input, as megajoules of fossil-fuel energy (MJ)
s greenhouse gas emissions, as kilograms of carbon dioxide equivalent (kg CO eq)
2
s acidification potential, as grams of sulphate equivalent (g SO eq)
-2
4
s eutrophication potential, as grams of phosphate equivalent (g PO 4 -3 eq)
s water use, as kilolitres of fresh water (kL).
Initial findings indicated that crop production generally dominates as a source of environ-
mental burdens, and two problems are identified here. First, there is apparent variability in
crop production systems within Queensland, and so three scenarios were chosen to explore
and reflect this variability, as follows:
1. a ‘state average’ farming system consisting of area-weighted state averages for cane yields,
inputs, harvest practices and transport
2. a wet tropics scenario reflecting cane growing in north Queensland, with relatively low
nitrogen input, nil irrigation, and lower cane and sugar yield
3. a high yield scenario reflecting cane growing in the Burdekin region with relatively high
nitrogen input and irrigation.

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