Appraisal of the environmental sustainability of milk production systems in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Science in Life Cycle Management at Massey University, Manawatū, New Zealand
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Date
2016
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Massey University
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Abstract
Life Cycle Assessment (LCA) plays an important role in the environmental assessment
of agricultural product systems, including dairy farming systems. Generally, an LCA
study accounts for the comprehensive resource use and environmental emissions
associated with the life cycle of a studied product system. The inventoried inputs and
outputs are then transformed into different environmental impact categories using
science-based environmental cause-effect mechanisms. There are different LCA
modelling approaches (e.g. attributional LCA [ALCA] and consequential LCA
[CLCA]) that can be used to address different research questions; however, there is
currently no consensus on the most appropriate approach and when to use it. These
LCA approaches require different types of data and methodological procedures and,
therefore, generate different sets of environmental information which may have
different implications for decision-making.
In the present research, a series of studies utilising different LCA modelling approaches
were undertaken of pasture-based dairy farming systems in the Waikato region (the
largest dairy region in New Zealand). The purposes of the studies were to: (i) assess the
environmental impacts and identify environmental hotspots of current pasture-based
dairy farming systems, (ii) compare environmental hotspots between high and low
levels of dairy farm intensification, (iii) investigate the environmental impacts of
potential alternative farm intensification methods to increase milk productivity, and (iv)
assess the environmental impacts of different future intensified dairy farming scenarios.
Twelve midpoint impact categories were assessed: Climate Change (CC), Ozone
Depletion Potential (ODP), Human Health Toxicity - non-cancer effects (Non-cancer),
Human Health Toxicity - cancer effects (Cancer), Particulate Matter (PM), Ionizing
Radiation - human health effects (IR), Photochemical Ozone Formation Potential
(POFP), Acidification Potential (AP), Terrestrial Eutrophication Potential (TEP),
Freshwater Eutrophication Potential (FEP), Marine Eutrophication Potential (MEP) and
Ecotoxicity for Aquatic Freshwater (Ecotox).
Firstly, the environmental impacts of 53 existing pasture-based dairy farm systems in
the Waikato region were assessed using ALCA. The results showed that both the offfarm
and on-farm stages made significant contributions to a range of environmental
impacts per kg of fat- and protein-corrected milk (FPCM), and the relative contributions
of the stages varied across different impact categories. Farms classified as high
intensification based on a high level of farm inputs (i.e. stocking rate, level of nitrogen
(N) fertiliser and level of brought-in feeds) had higher impact results than low
intensification farms for 10 of 12 impact categories. This was driven mainly by the offfarm
stage, including production of brought-in feeds, manufacturing of agrichemicals
(e.g. fertilisers and pesticides), and transport of off-farm inputs for use on a dairy farm.
The exceptions were the environmental indicators PM, POFP, AP and TEP; their results
were determined mainly by ammonia emissions from the on-farm activities.
Secondly, environmental consequences resulting from meeting a future increase in
demand for milk production (i.e. 20% more milk production per hectare relative to that
in 2010/11) by using different farm intensification scenarios for dairy farming systems
in the Waikato region were assessed using CLCA. In this study, only technologies/flows
that were actually affected by use of different intensification options to increase milk
production were accounted for. The identified intensification methods were: (i)
increased pasture utilisation efficiency, (ii) increased use of N fertiliser to boost on-farm
pasture production, and (iii) increased use of brought-in feed (i.e. maize silage). The
results showed that improved pasture utilisation efficiency was the most effective
intensification option since it resulted in lower environmental impacts than the other
two intensification options. The environmental performance between the other two
intensification options varied, depending on impact categories (environmental tradeoffs).
Thirdly, prospective ALCA was used to assess the environmental impacts of six
prospective (future) dairy farming intensification scenarios in the Waikato region,
primarily involving increased stocking rate, that were modelled to increase milk
production per hectare by 50% in 2025. In this study, prospective (future) average flows
that were derived from extrapolation were accounted for. The potential intensification
scenarios were: (i) increased animal productivity (increased milk production per cow),
(ii) increased use of mixed brought-in feed, (iii) improved pasture utilisation efficiency,
(iv) increased use of N fertiliser to boost on-farm pasture production, (v) increased use
of brought-in maize silage, and (vi) replacement of total mixed brought-in feed in the
second scenario by wheat grain. The results showed that, apart from improved animal
productivity which was considered the best option, improved pasture utilisation
efficiency was the second environmentally-preferential option compared with other
intensification options for pasture-based dairy farming systems in the Waikato region.
There were environmental trade-offs between other intensification options.
The present research demonstrated that pasture-based dairy farming systems in the
Waikato region contribute to a range of environmental impacts. More intensive farming
systems not only have increased milk productivity (milk production per hectare) but
also increased environmental impacts (per kg FPCM) in most environmental impact
categories. Farm intensification options associated with improved farm efficiency (e.g.
animal productivity or pasture utilisation efficiency) are promising as they have lower
environmental indicator results (per kg FPCM) compared with other intensification
methods. Increased use of off-farm inputs (e.g. N fertilisers and brought-in feeds)
increases some, and decreases other, environmental indicator results. Therefore,
decision-making associated with choice of alternative farm intensification options
beyond farm efficiency improvements will require prioritisation between different
environmental impacts and/or focusing on the ability of key decision-makers to effect
change (for example, by distinguishing between local and global activities contributing
to environmental impacts).
The present research has shown that different LCA modelling approaches can be used in
a sequential manner to maximise the usefulness of environmental assessment. Initially,
ALCA (based on current average flows) can be used to identify environmental hotspots
in the life cycle of dairy farming systems. This will generate environmental information
that can assist in selection of improvement options. Subsequently, the improvement
options selected should be evaluated using CLCA (based on marginal flows). This will
produce comparative environmental information resulting from implementing the
selected improvement options, strategies or policies in relation to a non-implementation
scenario, when the wider contribution of co-products is accounted for. Finally,
prospective ALCA (based on future average flows) can be used to assess total or net
environmental benefits.
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Keywords
Dairy farming, Agricultural intensification, New Zealand, Waikato