Abstract :
[en] In the context of biobased materials, the accurate assessment of the environmental impact of the agricultural raw materials is crucial. In this study, the environmental impact of traditional or conventional wheat produced in Wallonia (Belgium) is evaluated. The system boundaries are from field to farm gates and the functional unit is the production of 1 kg of wheat.
The ILCD recommended methods are used. Surprisingly, the organic wheat has a higher impact on the environment in all the categories. This is due to its smaller yield and to the higher organic fertilizers used: These organic fertilizers result in higher field emissions because the nutritive elements are less available for plants.
A detailed analysis of the human toxicity categories underlines that most of the impact is due to heavy metal emissions: most of the impact in human toxicity, cancer effect, is due to chromium (Cr) emissions due to the use of fertilizers. But during fertilizers composition characterization only the total chromium is measured and therefore, unspecified chromium is used as emissions. However, the chromium in natural environment is most probably Cr (III) and this could decrease the impact as the characterization factor for unspecified chromium, is, the average of the one of Cr (III) (non-toxic) and Cr (VI) (toxic). The chromium emissions are in the same order on magnitude for organic and conventional wheat for one hectare, but, due to the smaller yield are larger for conventional wheat on a mass basis.
The impact for human toxicity, non-cancer effect is mostly related to zinc emissions in soil from organic fertilizer, especially pig manure. As more organic fertilizers are used for organic wheat, its impact is more than 10 time higher than the impact of conventional wheat. Nevertheless, the real toxicity of zinc is questionable, indeed, zinc is an important trace element in the human body. Surprisingly, for both toxicity categories, the contribution of pesticide is negligible: this also contributes to the worst results of organic wheat.
As this study is from field to farm gate, the potential impact wheat consumption on human health is not included. Moreover, the Belgian case study is not favorable to organic agriculture as the conventional agriculture has very good practice and high yields. This case study also underlines the limitation of the existing tool to asses to toxicity impact.
