The productions of vegetable oil and methyl esters of vegetable oil lead to the generation of a lot of by-products. The purpose of this work was to study an alternative solution for a profitable use of vegetable oil by-products: anaerobic digestion. The potential for anaerobic digestion of 24 by-products was studied. The results show that most of oil by-products had a good capacity for anaerobic digestion. Then, the effects of the addition of oil by-products on the behavior of one reactor treating a mixture of grass, cow manure and fruit and vegetable waste and another reactor treating household waste were investigated. Most of the by-products tested improved significantly the production of methane indicating that the addition of by-products from oil production could represent a significant financial earning for the digester operators. Discussions are in progress involving oil producers and biogas plant operators to assess the opportunity of supporting the addition of by-products from oil refining in their facilities. A first evaluation of the costs and potential benefits of by-product treatment was performed. These costs should be reviewed in line with the increased development of anaerobic digestion and the expected benefits due to the digestion of by-products.