The arable farm sector and biofuel industry models have been coupled to build up a descriptive modelling approach of the biofuel system in France. This approach is based on micro-economic theory principles and is put into practice by means of mathematical programming. The arable farm sector which cultivates dedicated energy crops, is represented by a large number of farms, and the biofuel industry is divided into two main chains; namely, ETBE and bio-diesel, each of which has an intermediate stage (ethanol and seed-oil production, respectively) and a final transformation stage integrated into the petroleum refinery system. The variables, in the model, are the energy crops (wheat, sugar beet and rape-seed) and the biofuel (ether and ester) activity levels. Goverment allocates an earmarked budget for biofuels through tax exemptions per unit. The model enables the analyst not only to estimate biofuel opportunity costs for fixed individual biofuel quantifies and unitary tax exemption levels but also to allocate optimal quantities to each biofuel chain, thus maximising the global surplus of the activity. The results obtained indicate that the French biofuel system could operate with lower levels of tax exemptions for both biofuels, implying that, at the present time, excess surpluses are realised by the agents and particularly the industry.