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PARALLEL SESSION 2B: EMISSIONS MODELLING 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
Introduction of a national method to estimate direct nitrous oxide
emissions from mineral soils for Finnish product carbon footprinting
Hannele Pulkkinen 1, *, Kristiina Regina 2 , Juha-Matti Katajajuuri 1
1 MTT Agrifood Research Finland, Biotechnology and Food Research, FI-00790 Helsinki, Finland
2 MTT Agrifood Research Finland, Plant Production Research, FI-31600 Jokioinen, Finland
Corresponding author. E-mail: hannele.pulkkinen@mtt.fi
ABSTRACT
Direct nitrous oxide emissions from managed soils play a very significant role in climate impacts of food products. However, an
IPCC default emission factor is applied almost without exception to estimate emissions in climate impact studies of food products. A
more detailed method was developed for estimating direct nitrous oxide emissions in Finland for increased accuracy. Research on
nitrous oxide fluxes under Finnish conditions was conducted and a new method for estimating fluxes from mineral soils was developed
for Finland. The method results in markedly larger emissions to annual spring crops and smaller emissions to perennial crops
compared with the IPCC default. The new method also significantly increases emissions at the national level. Acknowledging the
substantial variation in nitrous oxide emissions, more accurate estimation methods need to be developed to understand the impacts of
food produced in different climatic and geographic circumstances.
Keywords: climate impact, food, nitrous oxide emissions, carbon footprint, potato
1. Introduction
Direct nitrous oxide emissions from managed soils play a very significant role in climate impacts of food
products. According to different studies they often contribute 20-30% to total climate impact of different
food products and even more to emissions from cultivation. However, IPCC default emission factors (IPCC
1996, 2006) are used to estimate direct nitrous oxide emissions from applied N from managed soils almost
without exception in carbon footprint studies of food products (Pulkkinen 2010). One exception is an Australian
study of bread (Biswas et al., 2008), which employed locally derived emission factors of Barton et al.,
(2008). Similar direct nitrous oxide emission factors are used for the Australian National Inventory Report
(Australian National greenhouse accounts 2012).
In the Finnish Foodprint-programme, harmonised national guidelines were developed to assess climate
impacts of food products. Calculation guidelines are based on other international life cycle assessment standards
and guidelines, and best practices, and give more practical instruction to the food industry than previously
published general standards. In addition to harmonising carbon footprint methodology, a more detailed
national method for estimating direct nitrous oxide emissions from mineral soils in Finland was developed to
gain a more accurate understanding of climate impacts of food products.
2. Methods
The uncertainties of nitrous oxide emissions are very high due to large spatial and temporal variation
(Snyder et al., 2009). To reduce the uncertainty of national estimates, Regina et al., (submitted) conducted
research on nitrous oxide fluxes under Finnish conditions from 13 fields for periods of one to three years in
2000-2009. Their main finding was that the annual direct emissions of nitrous oxide were lower from grass
crops than from annual spring crops. The long period between harvesting and sowing under boreal conditions,
when there is no vegetation during the long winter, increases the emissions from annual spring sown
crops. They were able to provide a method for estimating direct nitrous oxide fluxes from grass and annual
spring crops from mineral soils in Finland that reflected national conditions better than the IPCC default
method.
Statistical mixed models were based on the measured emissions of nitrous oxide and background variables
(Regina et al., submitted). Environmental and management data available for the analysis included
crop, fertiliser application rate, fertiliser type, soil characteristics and weather data. The crop type and the
amount of mineral N applied best explained the variation in nitrous oxide emissions, and the model is consequently
based on these two effects.
To estimate the burden of human activity (cultivation) only, a background emission was deducted from
the derived emission estimates of both crops by deducting the emissions at zero fertiliser application rate.
The emission estimate at fertiliser level zero of annual spring crops was 2.013 and of perennial crops 0.529.
Because the number of measurements results at zero fertilisation is limited, a conservative estimate of the
background emission was used and only the smaller value was subtracted (derived from measurements on
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