This document discusses including soil carbon changes in the climate impact assessment of food products. It presents previous work done by the author's research group on this topic. The goal of the current study was to assess the global warming impact of wheat production in two regions of Finland, including soil organic carbon changes, and to compare the impact of conventional wheat production versus adding a cover crop. The study used a soil carbon modeling approach combined with life cycle assessment methods. The results showed that assumptions around the initial soil carbon stock and timeframe of the assessment impacted whether the soil was estimated to be a net source or sink of carbon. The conclusions recommend considering the study goals and local context when determining these modeling assumptions.

1. 1
Maaperän hiilivarastomuutosten huomiointi osana
ruokatuotteiden ilmastovaikutuslaskentaa
Including soil carbon changes in the
climate impact of food products
Katri Joensuu,
Sustainability science and indicators (SUST) group
Luke
14.12.2021

2. 2
Content of the presentation
14.12.2021
• Previous work in Luke SUST group
• Background
• Goal and scope of the study
• Assessment of life cycle GHG emissions
• Soil carbon change modelling
• Results
• Conclusions

3. 3
Previous work in Luke SUST group
14.12.2021
● Soil carbon integration into LCA work has been studied in recent
years in Luke as an indicator of soil quality (Joensuu and Sinkko 2015,
Joensuu and Saarinen 2016) and as a part of climate impact
(Pulkkinen et al. 2018)
● In the SusBioEcon project, the goal was to integrate the modelling of
soil carbon change with LCA and apply the method in a case study

4. 4
14.12.2021
https://link.springer.com/article/10.1007%
2Fs11367-021-01967-1

5. 5
Background
14.12.2021
• Carbon dynamics in soils is affected by land use as well as various land
management measures within different land use types but also by climatic
conditions and plant litter input driven by ecosystem production
• There are high expectations that soils would sequester a considerable amount
of carbon and thereby offset global anthropogenic GHG emissions
• Increasing the amount of soil organic carbon (SOC) also improves soil fertility
and has thereby important co-benefits to food security
• Despite the current nature of the SOC management for climate change
mitigation, there is currently no consensus on how the impacts of land
management and LUCs on SOC stocks would be best quantified within LCA

6. 6
Goal and scope of the study
14.12.2021
• A model-based SOC change assessment was applied together with other GHG emission
estimates within the LCA framework to assess the global warming impact of wheat
production in two case study regions in Finland
• The assessment aimed at responding to two questions representing possible goals for an
LCA study:
• Q1: What is the life cycle global warming impact of wheat production in the case regions,
including the SOC change?
• Q2: What is the life cycle global warming impact of an alternative management option, i.e.
to add cover crops into the wheat production system?
• The objective of this study was to demonstrate the impacts of assumptions and decisions
related to land use history and the time frame of the analysis made within the SOC
assessment process on the overall global warming results and conclusions made

7. 7
Assessment of life cycle GHG emissions
14.12.2021
• General life cycle assessment (LCA) methodology (ISO
14040:2006; ISO 14044:2006) was applied to acquire an
overview of the climate impact
• The functional unit of the study was 1 kg of spring
wheat

8. 8
Soil carbon change modelling
14.12.2021
• To calculate the SOC changes of the mineral soils, the dynamic soil carbon
model Yasso07 model was used (Tuomi et al. 2009)
• Modelling based on carbon input level and chemical quality in crop residues
(based on yield level) and manure, as well as climate parameters (temperature,
precipitation), details presented in Palosuo et al. (2016)
• Initial soil carbon stock (for Q1)
• I1: soil in a steady state with the recent regional average field use (last 20 years,
1999–2018)
• I2: including historical land use change from forest in year 1900, followed by
average field use until 2018
• Time horizon of the assessment:
• T20: 20 years
• T100: 00 years

9. 9
14.12.2021
Total annual global warming impact of production of 1 kg of spring wheat in Southwest Finland a) and Northern
Savonia b). I1 represents emissions from soil C stock change calculated based on recent land use and I2 based
on historical land use. T20 represents calculations based on time frame over 20 years and T100 over 100 years
Results, Q1

10. 10
14.12.2021
The total global warming impact of of production of 1 kg of spring wheat with the clover cover crop including
CO2 emissions from SOC change (mineral soils) in Southwest Finland a) and Northern Savonia b) for Q2. T20
represents calculations based on a time frame over 20 years and T100 over 100 years
Results, Q2

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Conclusions (1/2)
14.12.2021
• In the case of this study, the assumptions turned the soil to be either a source or
sink of C
• The model used in this study was Yasso07, but the best model to apply depends
on the land use type and availability of locally calibrated and evaluated models
• Regarding the model initialisation and time horizon of the assessment period, no
definite rules can be set on the preferable assumptions that should be used in all
circumstances
• The choice of assumptions should be made based on the scope and goal
definition of the LCA study

12. 12
Conclusions (2/2)
14.12.2021
• Reference situation
• When the interest is in detecting the impact of a certain change in management
on SOC stock, the prevailing management should be used as the reference
situation
• If more general impacts of crop production are of interest, it is suggested that
the reference is chosen in a way that would reflect the current agricultural land
use situation in the region, e.g. the regional average field use, which represents
alternative crops that are possible and most likely to be produced in the same
area
• Timeframe
• To take into account long-term impacts, it is recommended that the SOC
changes are estimated with a time frame of at least 100 years
• However, if the goal of the study is to identify possible ways to enhance SOC
sequestration in the short term to acutely slow down global warming, choosing
a shorter timeframe could also be justifed with the goal of the study

13. 14.12