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

Abstract

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 CH yields in batch tests showed a positive linear correlation between both types of biodegradability (R=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.

Microbial Strategies for Cellulase and Xylanase Production through Solid-State Fermentation of Digestate from Biowaste

“…In a preliminary experiment, a non-inoculated batch was performed in a 4.5L reactor in order to analyze the biological activity present in the digestate. Digestate is a material coming from an anaerobic digestion process and for this reason, it could have low easily available organic matter or even poor biodiversity of aerobic biomass [3]. In consequence, a low self-heating capacity at pilot or industrial scale is expected.…”

“…Characteristics of digestate make it an ideal replacement of inorganic fertilizers [2]. However, digestate is not fully stabilized and this necessitates a hygienization and stabilization process (such as composting) of the material, prior to its use as soil amendment [3]. Although digestate from sewage sludge has been widely studied, only a few studies assess the potential uses of digestate from biowaste and its potential effect on soil in agronomic applications [4,5].…”

Effect of the post treatments for biowaste‐based digestates on water solubility of nutrients and iron‐cyanide (Fe‐CN) complex mobility

“…However, during an 8‐year field experiment in Sweden, Odlare et al () showed contrasting results by application of compost or digestate from source‐separated organic household waste. Maynaud et al () recommend to only apply soil conditioners with high degradation stability. Thus, digestate properties and boundary conditions regarding climate, soil, and cultivation shall be assessed to ensure an optimal effect of digestate fertilization.…”

“…Whereas drying conserves the digestate in its current state, composting results in further OM degradation and an increase of OM stability (Knoop et al, 2018). This is underlined by a study from Maynaud et al (2017), who investigated various OM fractions using chemical sequential extraction after digestate treatment applying 3D fluorescence spectroscopy. After composting, OM contained less accessible compounds of higher structural complexity (Maynaud et al, 2017).…”

“…This is underlined by a study from Maynaud et al (2017), who investigated various OM fractions using chemical sequential extraction after digestate treatment applying 3D fluorescence spectroscopy. After composting, OM contained less accessible compounds of higher structural complexity (Maynaud et al, 2017). A study conducted by Knoop et al (2018) showed a significant reduction in volatile solids and carbon during composting process of solid digestates.…”