Characterisation of the biodegradability of post-treated digestates via the chemical accessibility and complexity of organic matter

Géraldine Maynaud (1) , Céline Druilhe (2, 3) , Mylène Daumoin (2, 3) , Julie Jimenez (1) , Dominique Steyer (1) , Michel Torrijos (1) , Anne-Marie Pourcher (2, 3) , Nathalie Wéry (1)

1 LBE - Laboratoire de Biotechnologie de l'Environnement [Narbonne]
2 UR OPAALE - Optimisation des procédés en Agriculture, Agroalimentaire et Environnement
3 UBL - Université Bretagne Loire

The stability of digestate organic matter is a key parameter for its use in agriculture. Here, the organic matter stability was compared between 14 post-treated digestates and the relationship between organic matter complexity and biodegradability was highlighted. Respirometric activity and CH4 yields in batch tests showed a positive linear correlation between both types of biodegradability (R2=0.8). The accessibility and complexity of organic matter were assessed using chemical extractions combined with fluorescence spectroscopy, and biodegradability was mostly anti-correlated with complexity of organic matter. Post-treatments presented a significant effect on the biodegradability and complexity of organic matter. Biodegradability was low for composted digestates which comprised slowly accessible complex molecules. Inversely, solid fractions obtained after phase separation contained a substantial part of remaining biodegradable organic matter with a significant easily accessible fraction comprising simpler molecules. Understanding the effect of post-treatment on the biodegradability of digestates should help to optimize their valorization.

Mots clés: biodegradability; anaerobic digestion; respirometry; digestate; complexity

Mots clés: digestion anaérobie; biodégradabilité; dégradation de la matière organique; post traitement; respirométrie; digestat; spectroscopie à fluorescence

Domaines: Sciences du Vivant [q-bio]

Géraldine Maynaud, Céline Druilhe, Mylène Daumoin, Julie Jimenez, Dominique Steyer, et al.. Characterisation of the biodegradability of post-treated digestates via the chemical accessibility and complexity of organic matter. Bioresource Technology, 2017, 213, pp.65-74. ⟨10.1016/j.biortech.2017.01.057⟩. ⟨hal-01606007⟩