Greenhouse gas emissions from life cycle assessment of Norwegian food production systems

Abstract

This paper presents an assessment of atmospheric emissions of greenhouse gases (GHGs) and associated land use for the production of milk, beef, grain and potatoes. It compares the less intensive (i.e. organic) farming system with the more intensive (i.e. conventional) food production system. The emission sources, trade-offs with land and potential for reduction of GHG emissions were analysed. The sources for farm accounts data on inputs and outputs are representative farm types constructed from data from the Norwegian Farm Accountancy Data Network. The analysis was carried out with life cycle assessment, including processes from manufacturing of inputs to farms, and on-farm production up to the farm gate. The results show that it is worthwhile considering a greater proportion of food energy from vegetable rather than from animal products, analysing grass-based meat production in more detail and reducing mineral fertilizer use.

Keywords:

• GHG emissions
• farming systems
• life cycle assessment

Acknowledgements

This work was performed in the research project “Socio-economic and environmental impacts of organic farming” (2008–2011), funded mainly by The Research Council Norway and with additional funding from Oikos, the County Governor Sør-Trøndelag and KSL Matmerk. We thank Prof. John M. Bryden for valuable comments to the manuscript and John Hille for providing us with a compilation of relevant references.

Notes

1. As in Nemecek et al. (2011), we define conventional farming in this study as a mode of production not respecting the organic farming rules. The agricultural system's main goal is to achieve high yields and a high economic output.

2. Although the production of potatoes is conventional.

3. One hundred and forty-three kilogramme CH₄ emissions/dairy cow/year (Sundstøl & Mroz, 1988; Volden & Nes, 2006; Sandmo, 2009; Pettersen, 2010).

4. The average annual milk production from conventional dairy production is 830 kg higher than the organic dairy production (see Figure 3).

5. Of about 1.5 kg CO₂e (0.005 kg N₂O) per kg N together with about 3 kg CO₂ from use of gas in the hydrogen production; in total, 4.5 kg CO₂e per kg N (personal information from Yara).

6. We use 0.0269 kg N₂O per kg mineral fertilizer N, which includes the indirect contribution through evaporation to ammoniac and nitrogen run-off and direct contribution from N₂O–N (Pettersen, 2010). Trømborg et al. (2007) use 0.019 kg N₂O per kg N.