Soil organic matter accounting in the carbon footprint analysis of the wine chain

Purpose

Concerns about global warming led to the calculation of the carbon footprint (CF) left by human activities. The agricultural sector is a significant source of greenhouse gas (GHG) emissions, though cropland soils can also act as sinks. So far, most LCA studies on agricultural products have not considered changes in soil organic matter (SOM). This paper aimed to: (1) integrate the Hénin–Dupuis SOM model into the CF study and (2) outline the impacts of different vineyard soil management scenarios on the overall CF.

Methods

A representative wine chain in the Maremma Rural District, Tuscany (Italy), made up of a cooperative winery and nine of its associated farms, was selected to investigate the production of a non-aged, high-quality red wine. The system boundary was established from vineyard planting to waste management after use. The functional unit (FU) chosen for this study was a 0.75-L bottle of wine, and all data refer to the year 2009. The SOM balance, based on Hénin–Dupuis’ equation, was integrated and run using GaBi4 software. A sensitivity analysis was performed, and four scenarios were developed to assess the impact of vineyard soil management types with decreasing levels of organic matter inputs.

Results and discussion

SOM accounting reduced the overall CF of one wine bottle from 0.663 to 0.531 kg CO₂-eq/FU. The vineyard planting sub-phase produced a loss of SOM while, in the pre-production and production sub-phases, the loss/accumulation of SOM was related to the soil management practices. On average, soil management in the production sub-phase led to a net accumulation of SOM, and the overall vineyard phase was a sink of CO₂. Residue incorporation and grassing were identified as the main factors affecting changes in SOM in vineyard soils.

Conclusions

Our results showed that incorporating SOM accounting into the wine chain’s CF analysis changed the vineyard phase from a GHG source to a modest net GHG sink. These results highlighted the need to include soil C dynamics in the CF of the agricultural product. Here, the SOM balance method proposed was sensitive to changes in management practices and was site specific. Moreover, we were also able to define a minimum data set for SOM accounting. The EU recognises soil carbon sequestration as one of the major European strategies for mitigation. However, specific measures have yet to be included in the CAP 2020. It would be desirable to include soil in the new ISO 14067—Carbon Footprint of Products.