Mathematical programming models suit policy makers' needs for assessing impacts of new policies and modellers' needs for new parameters, constraints and activities to represent the phenomenon under study. The AROPAj model aims at taking into account any geographical extension of the European Union as well as the continuously changing Common Agricultural Policy. As well as the European policies will include more and more environmental problems, AROPAj will be more and more designed toward environmental assessments. Two improvement axes are set up. Biophysical models are used to refine the design of farming systems represented in the economic model and to estimate nitrogen pollutant emissions. Down-scaling methods are coupled with the regional farm group models, aiming at providing results at a fine resolution scale useful for policy evaluation and for consistent analysis of environmental impacts calling for physical models. This helps to deal with new challenges like renewable energy production consistently with agricultural potential and environmental requirements.