LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PLENARY SESSION 2: METHODOLOGICAL CHALLENGES FOR ANIMAL PRODUCTION SYSTEMS 8 th Int. Conference on
LCA in the
Agri-Food Sector, 1-4 Oct 2012
instead of grass requires different fertilisation and land management, changing N2O emissions from crop
cultivation and emissions related to production of fertilisers (Schils et al., 2005; Basset-Mens et al., 2009).
To illustrate the importance of life cycle thinking in animal production, we assessed the GHG reduction
potential of increasing maize silage at the expense of grass silage in a dairy cow’s diet at three interdependent,
hierarchical levels, i.e. the animal, farm, and chain level. A mechanistic model to predict enteric CH4
emission at cow level is combined with a linear programming (LP) model to predict effects of a dietary
change at farm level, and with life cycle assessment (LCA) to predict GHG emissions at chain level. The
impact of the level of analysis is demonstrated using the case of an average Dutch dairy farm (Van Middelaar
et al., 2012b).
Results of this case study showed that per ton of fat-protein-corrected milk (FPCM), with an emission of
955 kg CO2-e, increasing maize silage with one kg DM per cow per day at the expense of grass silage resulted
in an annual emission reduction of 11 kg CO2-e at animal level, 16 kg CO2-e at farm level, and 17 kg
CO2-e at chain level. At farm and chain level, however, land use change (e.g. ploughing grassland for maize
land) resulted in non-recurrent CO2 and N2O emissions of 720 kg CO2-eq per t FPCM. From an animal perspective,
therefore, we would conclude that this feeding strategy offers potential to reduce GHG emissions,
whereas from an LCA perspective it takes up to 42 years before annual emission reductions compensate for
emissions related to land use change.
This example demonstrates the potential of using LCA to assess the GHG reduction potential of an innovation.
2.2 Anaerobic digestions of manure
An important form of renewable energy is bio-energy produced from biomass. Biomass can be converted
into biogas, composed of CH4, CO2 and some trace gases (e.g., hydrogen gas), by means of anaerobic digestion
(AD) (De Vries et al., 2012a; Hamelin et al., 2011). This biogas can be used to produce bio-energy in
the form of electricity, heat, or transport fuel. The remaining product after AD, i.e. digestate, can be recycled
as organic fertiliser for crop cultivation to substitute mineral fertiliser (Börjesson and Berglund, 2007). Anaerobic
digestion of pig manure is expected to reduce the environmental impact of manure management by
reducing storage emissions and substituting fossil fuel, but current efficiency of bio-gas production from
manure only is low (EU-biogas, 2010). To increase efficiency of bio-gas production, co-substrates, such as
maize silage, glycerine or food waste are generally added. De Vries et al., (2012b) compared the life cycle
environmental consequences of producing bio-energy by anaerobic digestion of pig manure only (monodigestion),
and co-digestion with maize silage; maize silage and glycerin; beet tails; wheat yeast concentrate
(WYC); and roadside grass. They assessed impacts on climate change, terrestrial acidification, marine and
freshwater eutrophication, particulate matter formation, land use, and fossil fuel depletion. Results showed
that mono-digestion performed well for most impacts, but represents a limited source for bio-energy. Codigestion
with maize silage, beet tails, and WYC (all competing with animal feed), and glycerine increased
bio-energy production, but at the expense of increasing climate change (through land use change), marine
eutrophication, and land use. Co-digestion with like roadside grass gave the best environmental performance.
Hence, technologies that increase efficiency of bio-gas production from animal manure and from organic
waste with limited value elsewhere, have most potential to mitigate GHG emissions (De Vries et al., 2012b).
This example demonstrates the importance of including the environmental impacts related to production of
substitutes to replace initial use of co-substrates in the analysis, or in other words evaluating the full consequences
of an innovation.
This example demonstrates the potential of LCA to evaluate the environmental consequences (i.e. consequential
LCA) of an innovation.
2.3 Increasing annual milk yield per cow
In 2010, the FAO quantified emission of GHGs along the life cycle of milk in many countries across the
world (FAO, 2010). From their study you could conclude that GHG emissions per kg milk reduce as annual
milk production increases. Research indeed showed that if one is able to use feed more efficiently (i.e. produce
more milk with the same amount of feed or use less feed to produce the same amount of milk), GHGs
per kg milk produced is reduced (Thomassen et al., 2009). Can we directly compare smallholder systems in
which cows produce 500 kg of milk annually with specialised systems in which cows produce 7000 to 8000
kg? Cows in many smallholder systems in developing countries generally are not kept to produce milk or
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