Environmental analysis of intensity level in wheat crop production using life cycle assessment

Abstract

Although a priori thinking would suggest that a low intensity crop is environmentally favourable, this assumption ignores the effect of reduced productivity which could simply lead to pollution shifting to other places. A life cycle assessment of the wheat ( Triticum aestivum L.) production system for breadmaking was performed to optimise fertilization. In European temperate climate conditions, fertilizing with nitrogen mostly influences the intensity of field production systems, the quality of agricultural products and the environmental degradation. To assess and compare environmentally relevant impacts of different intensities of production, adequate functional units were developed to take into account the main functions of agricultural activity: production and upkeep of agricultural landscape. The limits of these functional units were identified and the influence of the choice of functional unit was analysed. Assessment of the wheat production system shows that increased fertilization needs a sufficient increase in yield to justify additional emissions and to be environmentally favourable. This requirement relies on the variability among varieties concerning grain yield and quality. To compare different systems of production managed by fertilization intensities, it is necessary to consider both the yield and the quality of the product. A level of 13% protein in dry grain corresponds to a good quality for breadmaking, satisfying bakery requirements. For a consistent comparison, a correction in yield is necessary to obtain an equivalent quality at each level of fertilization intensity. Grain yields at different fertilizer rates that gave 13% protein content in a wheat production system were assessed. This new functional unit identified high fertilization intensity as favourable for most impact categories and demonstrated sufficient yield increases with a change in variety at each level of fertilizer application rate. On the other hand, the impact of wheat production per hectare increases with more intensive fertilizer for all environmental categories except land utilisation. This functional unit helps to explicitly highlight impacts caused by agricultural activity: energy consumption, greenhouse effect, acidification, terrestrial ecotoxicity and human toxicity. The assessment of fertilizers exposed important differences between types and improvement potentials due to heavy metals content, impact on terrestrial ecotoxicity and human toxicity. Optimal combinations of variety, fertilization and land utilisation are discussed to design best production strategies from an environmental perspective.