Abstract :
[en] Introduction
Corn is an important cereal with a lot of applications in the feed and food industries (e.g. starch production). To evaluate properly the environmental impact of its applications, for example in the growing context of biobased products, a better understanding of the impact of its production is needed, using Life Cycle Analysis (LCA). Any error made during the agricultural step could have a large impact on subsequent results obtained at the final product stage. The objective of this study is to have a good understanding of environmental impact of corn production in Belgium context with a special focus on water depletion.
Materials and methods
The studied system is the production of corn in Wallonia (South of Belgium), whose the primary data are taken from Van Stappen et al [1]. The functional unit is 1 hectare of corn crop in Wallonia. The LCI data are based on actual agricultural practices recorded in farms’ accounting data. The field emissions due to the application of inputs were assessed by emission models as recommended by Nemecek [2] The system has been modelled in GaBi 8 using GaBi datasets. Belgian datasets have been preferred when available, and if not, European datasets are used and if no European datasets are available, then German ones have been used.
The ILCD recommended method has been used for the impact evaluation. To have a better understanding of water depletion, some other methodologies have been tested for this specific impact categorie such as ReCiPe [3] and the AWARE model [4]. In ReCiPe, the water depletion is not regionalized whereas it is the case in the two other methods. The ReCipe method only adds the different water flow consumption to calculate the water depletion. The ILCD recommended method for water depletion is based on Swiss Ecoscarity model [5]. In this case, the water footpint is based on the water withdrawal-to-availability (WTA). This indicator measures the fraction of the water withdrawal, i.e., the total water input into a product system, which has become unavailable for the originating river bassin users due to evapo(transpi)ration, product integration or discharge into other bassins and the sea. On the other hand, the AWARE method wants to answer this question “What is the potential to deprive another freshwater user (human or ecosystem) by cunsuming freshwater in this region?” without including the potential deprivation from water degradation [4].
Results and discussion
The part of water resources depletion using ILCD recommended method that is not due to the fertilizers production is mostly related to the electricity used for maize drying and storage, especially associated with nuclear electricity (cooling needs). This is not the case if another method is used for assessing the water depletion. When AWARE method is used, most of the impact is coming from fertilizers production and from mechanization (due to the use of on unspecified flow for water consumption), whereas, using ReCiPe, most of the impact comes from fertilizers production only.
A study of the water origin has been realized using AWARE and ILCD recommended method and underlines the large variety of results. Using ILCD recommended method, most of the impact is coming from water depletion in Belgium and from unspecified origin (more than 90 %) whereas only 4 % of the water consumption using AWARE is in Belgium with low characterization factor for unspecified water. Moreover, the water that goes back to nature allows a reduction of the impact in this category but the countries where there is an uptake of water are not the same than the countries where the water is going back to the river.
The share of nuclear electricity in water depletion is really high when using ILCD recommended method, therefore special attention has been put on this process. Looking at the inventory of this process, 0.0319 m3 of water are consumed by MJ of electricity but 0.0313 m3 goes back to nature (river or lack) after the process. The higher water depletion using ILCD recommended method than the water in the inventory is due to the regionalization. Indeed, most of the water consumed for nuclear electricity in Belgium is from Belgium. Indeed, this characterization factor is equal to 2.84 m3 eq. However, in the ILCD method, only the water consumption is included and not the reduction of this consumption thanks to this water that goes back to river. To complete this discussion, we have compared the GaBi dataset with the Ecoinvent dataset. For the Ecoinvent dataset the calculation have been realized in GaBi but also in Simapro and underlines large differences between softwares, related to differences in method interpretation. The same comparison has been realized with the other methods studied here.
Conclusions
This contribution allows to underline the difference between method for water depletion calculation but also the differences induced by regionalized or not regionalized datasets and also highlights the problem of results that are dependant on the software.
References
[1] F. Van Stappen et al. 2018. Sensitive parameters in local agricultural life cycle assessments: the illustrative case of cereal production in Wallonia, Belgium. Int J Life Cycle Assess 23 2:225–250.
[2]T. Nemecek. 2013. Estimating direct field and farm emissions.
[3] M. Goedkoop, R. Heijungs, M. Huijbegts, A. De Schryver, J. Struijs, and R. van Zelm. 2009. ReCiPe 2008 : A life cycle impact assessment method which comprises harmonised category indicators at the midpoint and the endpoint level. Ruimte en Milei. 132 p.
[4] A. M. Boulay et al. 2018. The WULCA consensus characterization model for water scarcity footprints: assessing impacts of water consumption based on available water remaining (AWARE). Int J Life Cycle Assess 23 2:368–378.
[5] A. Rolf Frischknecht et al. 2013. Swiss Eco-Factors 2013 according to the Ecological Scarcity Method
