Prof. Christof Holliger, Marc Deront, Gabrielle Hack
Swiss Federal Office of Energy
May 2012 – September 2015
Hélène Fruteau de Laclos, Methaconsult, Préverenges, Switzerland; Andreas Schiller, AraBern, Switzerland; Julien Dovat, SATOM, Monthey, Switzerland
Biomethane potential (BMP) tests are used to determine the amount of methane that can be produced from organic matter. However, the outcome of such tests is not really reliable and it is not known how good these estimations are compared with biogas production from the same organic waste in full-scale installations. This project aims at doing this comparison and proposing extrapolation coefficients to link BMP test results and full-scale digesters.
Two AD plants were chosen, a dry AD plant treating green waste from urban areas and food waste from restaurants and supermarkets, and a liquid AD plant treating waste sludge from wastewater treatment and seven additional organic wastes. The BMPs of multiple samples of the individual organic materials collected during a period of seven months were determined. Separate tests of mixtures of organic materials confirmed that the BMP of the mixtures can be calculated from the BMPs of the individual materials. The total weekly methane production during the seven months period was calculated from the full-scale installation data on the feeding of the digesters and compared with the weekly methane production measured on-site. The latter was calculated from the most accurately measured entity, either the electricity or the volume of purified biomethane injected into the grid. The weekly methane production rates calculated from BMPs or measured on-site were very similar and followed the same pattern with some exceptions which could be explained by e.g. an overload of the full-scale installation. Based on the results obtained, an extrapolation coefficient of 0.8 to 0.9 should be used to estimate the methane production of full-scale AD plants from BMPs of the substrates to be digested and their specific organic loads.