Page 120 - Materials Chemistry, Second Edition

Chapter 9

Life cycle assessment and agriculture: challenges
and prospects

Ralph E Horne and Tim Grant

9.1 Introduction
Food is a basic human need, and the production of food is a considerable activity. The vast
majority of our food involves farming – a practice that has endured for thousands of years.
This longevity may suggest that agriculture is an essentially ‘sustainable’ activity. The inevita-
ble wealth of experience associated with such a well-established industry suggests there has
been ample opportunity to test and develop sustainable practices. However, there are several
reasons to question the sustainability of different agricultural practices. Food and drink pro-
duction – one of the outputs of farming – is a significant contributor to environmental impact.
For example, in Australia, food represents 35% of the ecological footprint (Global Footprint
Network and the University of Sydney 2005).
Technologies for and the scale of agricultural endeavour have changed radically over recent
decades, with resultant widespread land use conversion and increasing demand for a range of
fossil-fuel based agricultural inputs. Water and land resources are often recognised as local or
regional impact issues, and the global contribution to greenhouse gas emissions from farming
-1
is significant, at some 8.5–16.5 Pg CO -eq y or 17% to 32% of the total, with major contribu-
2
tions to this coming from nitrous oxide (N O) emissions from soils and enteric methane (CH )
2 4
emissions from livestock (Bellarby et al. 2008). However, the largest single contribution comes
from the clearing of native vegetation for agriculture rather than directly from tillage. Cropland
soils have relatively low carbon concentrations, and this raises the prospect of agriculture
shifting from being the second largest sectoral emitter of greenhouse gases globally to being a
major carbon sink in the future, if framing practices can be changed to reduce fossil fuel use
and build carbon concentrations in soils. Such an outcome will require considerable changes
in practice since, for example, global CH and N O emissions increased by 17% from 1990 to
4 2
2005, and N O emissions are predicted to rise by 50% over the period 1990 to 2020, given
2
current trends (US EPA 2006).
World food prices are rising, which may indicate that the capacity of supply to meet rising
demand is dropping. Climate change is also contributing to the failing sustainability of agri-
culture through water shortages, fiercer and more intense droughts and soil loss, compounded
by increased competition from crops grown for biofuels and rising meat consumption. As a
major producer (and exporter) of agricultural products, Australia has a strong case for focusing
on the environmental impacts of agriculture. State of the Environment (SoE) reports indicate
that agriculture is a major consumer of rural resources in Australia (SoE 2006). As indicated in

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