Abstract
PurposeCurrently, there is no consensus on how the impacts of land use on the soil organic carbon (SOC) stocks would be best quantified within life cycle assessments (LCA) of agricultural products. The impacts of different decisions were tested within a model-based assessment of soil carbon changes on the life cycle global warming impact for spring wheat produced in two example regions in Finland (Southwest Finland and Northern Savonia) on mineral fields.MethodsGlobal warming impact for spring wheat was assessed, including CO2 emissions due to the SOC change. The SOC change assessment was made with the soil carbon model Yasso07. The effects of assumptions on land use history were tested, i.e. the initialisation of the model and time horizon of the analysis (20 or 100 years) on the SOC change estimates. Other greenhouse gas emissions contributing to the global warming impact of spring wheat production were assessed using general LCA methodology taking into account the greenhouse gas emissions caused by the production of input materials and fuels, as well as direct and indirect N2O emissions from the soil due to fertilising and the decomposition of crop residues and organic matter, nitrogen leaching and volatilisation and lime application.Results and discussionThe selection of the model initialisation method and timeframe remarkably affected the SOC change estimates. The global warming impact of wheat production, without accounting for SOC changes, was 0.68 and 0.89 kg CO2-eq/kg yield in Southwest Finland and Northern Savonia, respectively. The impact of SOC stock changes on the total global warming impact varied from –4 to 5% in Southwest Finland and from 5 to 21% in Northern Savonia, depending on the assumptions used to initialise the model or the timeframe applied in the analysis. Adding a cover crop as a means to increase the SOC stock removed between –67 and –26% of the total global warming impact in both regions.ConclusionsIt is essential that all the decisions made in the analysis are transparently reported and communicated. The choice of assumptions regarding the reference state, model initialisation and time horizon of the assessment period should be made based on the scope and goal definition of the LCA study.
Highlights
Life-cycle assessment (LCA) is a well-established tool to quantify the environmental impacts of products, including greenhouse-gas (GHG) emissions, and the contribution of the product to the C O2 mitigation (Guinée and Heijungs 2005; ISO 14040:2006; ISO 14044:2006)
The projected development of the soil organic carbon (SOC) stocks and, thereby, the estimated SOC stock change essentially depended on the assumptions on the land use history and applied climate data, i.e. the way the soil carbon model was initialised for the simulations
The estimated carbon inputs calculated based on the past land use were higher in Southwest Finland (Table 3), the initial SOC stocks were higher in Northern Savonia (Table 4, Fig. 3)
Summary
Life-cycle assessment (LCA) is a well-established tool to quantify the environmental impacts of products, including greenhouse-gas (GHG) emissions, and the contribution of the product to the C O2 mitigation (Guinée and Heijungs 2005; ISO 14040:2006; ISO 14044:2006). LCA is used for guiding and supporting decision-making, e.g. when making choice between two products or production systems or planning improvements of the systems or policies (European Commission, Joint Research Centre 2010). Fundamental principles of LCA include focus on environmental impacts, comprehensiveness of attributes or aspects of natural environment, human health and resources and transparency of analysis (ISO 14040:2006; ISO 14044:2006). Global climate change driven by human activity (Pachauri et al 2014) has made global warming a key category of LCA (European Commission, Joint Research Centre 2010). In the land-use based sectors, this has put special focus on integrating soils in LCA, as they are important terrestrial carbon stocks, acting either as a carbon sink or a source of atmospheric CO2 (Paustian et al 2016; Griscom et al 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
