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[Display omitted] • Development of a new reactor for continuous dry anaerobic digestion (D-AD) • Yield stress, cohesion, and friction angle of biomass during D-AD were studied. • Similar physical degradation patterns of coarse biomass in batch and continuous. • Volatile solids decreased in 11% and yield stress in 25% at 30 days of digestion. • Yield stress evolution was well correlated with cellulose destruction (R2 = 0.99) Knowledge of rheological evolution of biomass during dry anaerobic digestion (D-AD) is important in the engineering design, modeling, and operation of D-AD reactors. In this work, two methods of rheological analysis, the slump test and the shear-box, were used to measure the evolution of the yield stress, cohesion and friction angle of the straw-cattle manure (SCM) during the D-AD. Firstly, four 60 L batch leach-bed reactors (LBR) were started in parallel and stopped at different stages of the D-AD process on days 0, 10, 21 and 31. Secondly, a 500 L and 2 m length plug flow reactor (PFR) was operated with 40 days of solid retention time and samples were recovered at different positions. The solid degradation during D-AD process was monitored by analysis of the degradation of volatile solids, the fiber content and the Flash BMP. Similar degradation patterns of SCM and rheological evolution were observed in both reactors type. VS content decreased of 10.7% and 10.2% in 30 days in PFR and LBR respectively. VS degradation in both cases was well explained by hemicellulose and cellulose consuming in D-AD process. Considering the rheological analysis, the results showed that D-AD induced a reduction of the yield stress of 28.1 and 24.2% in 30 days in PFR and LBR respectively. Moreover, a similar evolution of cohesion and friction angle value for samples from both reactors was observed. This study demonstrates the close relationship between the state of degradation of the solid biomass and its rheological properties. [ABSTRACT FROM AUTHOR]

The biogas produced in the methane fermentation is valuable due to its use as a renewable energy source. A promising method of biogas production intensification is sludge flocs disintegration via ozonation. The aim of this study was to check the impact of the ozonation on the efficiency and kinetics of biogas production from surplus activated sludge (SAS). Processes were carried out batchwise at 37 °C. The following analyses were performed: pH, alkalinity, dry matter, dry organic matter, chemical oxygen demand, total organic carbon, total nitrogen, elemental analysis (CHNS), the biochemical potential of methane by NIR spectroscopy, and the amount and composition of biogas. The results showed that the ozonation process had no effect on the elemental composition and chemical structure of SAS. The chemical formula of SAS (C2.97H4.68O1.20N0.3) and a simplified equation describing the methane fermentation process were determined. Ozonation caused the hydrolysis of some organic compounds from sludge flocs and increased the efficiency of biogas production. The methane content in biogas was higher by about 2.5%, while the amount of produced biogas rose by up to 21% for the ozonized sludge. The kinetic constants of first-order reaction were between 0.219 and 0.323 d−1, with an upward trend due to ozonation. [ABSTRACT FROM AUTHOR]

Sorghum currently contributes to the species portfolio that is supporting bioenergy production including anaerobic digestion. Although agro‐morphological ideotypes maximizing biogas production have been recently proposed, there is a crucial need to refine our understanding of the impacts of the stem composition and structure on this processing trait in order to ensure genetic gains in the mid to long terms. This study aims to assess the potential of Sorghum bicolor ssp bicolor stem genetic diversity to maximize genetic gains for biogas production and define a biogas stem ideotype. In this context, a panel of 57 genotypes, encompassing most of the stem composition variability available in cultivated sorghum, was characterized over five sites. Simultaneous histological and biochemical characterizations were performed. A high broad sense heritability associated with a moderate genetic variability was detected for stem biogas potential ensuring significant genetic gains in the future. In addition, the development of a stem histological phenotyping pipeline made it possible to describe the genetic diversity available for the internode anatomy and the repartition of key cell wall components. Consistently with previous studies, moderate to high heritability was observed for stem biochemical components. Genetic correlation, hierarchical clustering, and multiple stepwise regression analyses identified soluble sugar content as the first main driver of biogas potential genetic variability. Nevertheless, breeding programs should anticipate that biogas yield improvement will also rely on the monitoring of the cell wall components and their distribution in the stem jointly with the soluble sugar content. According to the assets of sorghum in terms of adaptation to environmental stresses and the present results regarding the identification of stem ideotypes suitable for different value chains, this species will surely play a key role to optimize the economic and environmental sustainability of the agrosystems that are currently facing the effects of climate change. [ABSTRACT FROM AUTHOR]