Anaerobic digestion of by-products from production and refining of vegetable oils for on-site energy production
Résumé
The purpose of this work was to investigate the anaerobic digestion of 21 by-products and residues from the crushing of oil seeds, the refining of vegetable oils and the production of biodiesel. Each residue was individually fed, for about 1 month, into a 5L reactor, which was operated in fed-batch mode. The volume of biogas produced over time was monitored online making it possible to measure the total volume of biogas and the kinetics of biogas production for all the batches of each residue. The results show that: 3 The meal, by-product of the crushing of the oil seeds, had quite a low methane potential (200 ml CH4/g VS) and the anaerobic digestion of the meal can then hardly be competitive in comparison with the current solution of recovery in animal feed. 3 The residues from the refining of oils had the following characteristics: - Most of the residues had a high fat content, - High methane potentials were measured with most of the residues and 50% of them had a methane potential above 500 ml CH4/g VS indicating a very good potential for anaerobic digestion, - No clear correlation was found between the composition of the residues, the plant of origin or the type of oil processed and the methane potential making it necessary to evaluate the methane potential of the residues from each plant, - For used bleaching earth, the type of process used seemed to play an important role on the biodegradability of the organic matter, - Mass loading rates were quite low with values < 0.14 g VS/g VSS.d. 3 Glycerine, the by-product of biodiesel production, had a high potential for methanisation with 100 % of biodegradability and a high methane potential (425 ml CH4/g VS).