All three French institutes for livestock science (IFIP, IDELE, ITAVI) collected over 160 samples of a huge range of different types of pig, poultry and ruminant manures. INRAE-Transfert then determined the biochemical methane potential (BMP) and the main chemical composition of the samples. Mean BMP of the panel was 48 Nm³ CH₄/t total matter (TM). The range of BMP spanned huge variability , from 4.5 up to 155 Nm³ CH₄/t TM. This variability was largely due to dilution of the manure, as BMP correlates with dry matter (DM) content (R² = 0.88). The energy potential of livestock manures can be estimated by determining DM content to give a simple yet satisfactory approximation. However, BMP proves a better measure for scaling an anaerobic digester when the project is designed to use farmyard manures as primary feedstock. Storage can lead to BMP losses that vary wildly depending on type of effluent, storage time and conditions. BMP losses ran from zero for duck slurry sampled at 160 days after first excreta up to 57% for pig slurry and 68% for dairy cow slurry held in storage for several months. Pascal LEVASSEUR (1), Vincent BLAZY (2), François GERVAIS (3), Bastien ZENNARO (4), Olivier AZAM (4), Sevan KABAKIAN (4), Hélène CARRERE (5)