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

PARALLEL SESSION 1B: TOWARDS LIFE CYCLE SUSTAINABILITY ASSESSMENT 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
conventional farms were selected, i.e., nearest neighbours, based on farm size (fat and protein corrected milk
(FPCM) production), intensity (FPCM production per ha) and site-specific circumstances, i.e., soil nitrogen
supply level, percentage of sandy, peat or clay soil, and percentage of poorly, moderately well or well
drained land. The ten farms selected per INC farm, are scaled to one, so they make up one farm matching
one INC farm.
2.2. Economic performance
To quantify economic performance we quantified net farm income (NFI) and labour productivity. NFI is
often used as an indicator for profitability (Dekker et al., 2011, Shadbolt et al., 2009, Blank et al., 2009, Van
Calker et al., 2008). We defined NFI as the remuneration for management, family labour and capital that is
left after all other costs are paid. To correct for differences in farm size we expressed NFI per 100 kg FPCM.
NFI, however, does not account for input of family labour. To give insight in the labour effort to realise the
NFI, a measure of labour productivity is required. Labour productivity is a ratio of a volume of output per
unit of labour input (OECD, 2001). To enable a comparison of labour productivity in hours of labour among
farms differing in scale, we expressed labour productivity in minutes of labour also per 100 kg FPCM.
2.3. Environmental performance
The environmental performance of farms was based on indicators derived from a cradle-to-farm-gate
LCA, i.e., land occupation (LO), non-renewable energy use (NREU), global warming potential (GWP),
acidification potential (AP) and eutrophication potential (EP), expressed per unit of FPCM. All farms were
highly specialised dairy farms, without other types of animal production. We performed an attributional
LCA. Whenever a multifunctional process occurred, economic allocation was used. For EP and AP we took
characterisation factors from Heijungs et al., (1992), for GWP from IPCC (2007).
Production of feed
On average, 71% of all feed was home grown for the farms in this study. All home grown feed was sampled.
Furthermore, all non-monetary input of pesticides, fertilisers, water, and energy was recorded in
FADN, as well as the application method and quantity of the animal manure (at field level). In the Netherlands,
farms are obliged to use low-emission techniques to apply animal slurry to the land. In the past, INC
farms have received a temporary exempt from this regulation because of assumed lower ammonia losses
under their specific practices. For each farm, detailed information on purchased feed was available, i.e. exact
quantity used per feed product, and dry matter (DM), energy (VEM), nitrogen (N) and phosphorus (P) contents.
The average composition of compound concentrates (i.e. main feed type) was based on monthly publications
of Nevedi (2008-2009). For each feed ingredient used, the environmental impact of crop cultivation,
processing and transport was based on Thomassen et al., (2009) and additional empirical data, literature or
expertise from feed processing companies.
Farm specific excretion and gaseous losses
For each individual farm, we computed the excretion of N and P via manure by subtracting N and P fixed
in milk and animals from the total uptake of N and P in feed. Uptake of non-grass products was known. In
order to quantify the intake of grass, the energy requirement of dairy cattle was computed per farm, based on
the level of milk production, breed, pasturing and housing system and number of animals including young
stock. Grass intake was computed by subtracting the energy uptake from non-grass feed from total energy
requirement. Subsequently, the energy uptake from grass was converted into N and P uptake, based on the
energy-nutrient ratio. The fixation of N and P in milk and animals was subtracted from the total uptake, resulting
in the gross N and P excretion (Anonymous, 2010a). Subsequently, for each farm gaseous N losses
were computed based on the total ammoniacal nitrogen (TAN) in manure. We assumed a TAN value of 68%
and 77% of the mineral N for dairy slurry in respectively the winter and summer period. (Van Bruggen et al.,
2011). Emission of NH3 was assumed to depend on housing system (Anonymous, 2010b). The NH3-emission
factor varied between 10.9 and 15.4% of TAN in the winter period, whereas in the summer period it varied
between 10.1 and 31.0%. Emissions of NOx and N2O were computed as 0.3% of TAN in manure for all
housing systems (Velthof et al., 2010; Oenema et al., 2000). Emissions in the pasture were computed based
on Velthof et al., (2010) and using the farm specific manure production and an emission factor of 3.5% of
TAN for NH3.
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