The risks of climate change are pressing the refining industry to minimize its greenhouse gas emissions, and chiefly CO2. To gain a closer understanding of these emissions, Total and IFP have joined hands to develop an appropriate linear programming model, tested on a French refinery. One element of the study addressed the problem of allocating CO2 emissions to the different refinery products. An infinite number of allocation methods are available. The one proposed by the authors, who demonstrate its relevance, is based on the calculation of a "marginal emissions content" of each product, which can be determined by linear programming models. The authors (using a very simple "theorem") identify the conditions in which marginal contents have ...