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[Display omitted] • Shape characterizations of typical agricultural biomass are investigated. • Thermal conversion property of biomass combustion are studied. • An innovatively two-tube reactor is designed. • N1s spectra of the biomass and semicoke are investigated. • NO emission mechanism during biomass combustion is analyzed. The impact of mechanical pretreatment of corn straw (CS), pea straw (PS), and wheat straw (WS), on shape characterization and NO emissions during combustion were investigated in this research. Particle size ranges were obtained and characterized their shape factors using Image J correction. The thermal properties and NO emissions of the different-sized particles were investigated by TG-MS and fixed-bed reactor. Compared with CS and PS, WS is more likely to break into smaller particles due to its moderate strength. Amine-N completely disappeared after pyrolysis, whereas pyrrolic-N and pyridinic-N were the main N functionalities in char-N. During the volatile burning stage, the maximum peak of NO concentration was 270, 354 and 311 ppm for CS, PS and WS, respectively. NO was detected at a steady level during the semicoke combustion stage, and the duration increased with particle size. The NO concentration decreased sharply in a short duration during the fixed carbon combustion stage. [ABSTRACT FROM AUTHOR]

Thermo-chemical pretreatments of biomass typically result in environmental impacts from water use and emission. The degradation byproducts in the resulting sugars can be inhibitory to the activities of enzymes and yeasts. The results of this study showed that combining existing commercial comminution technology can reduce total energy consumption with improved saccharification yield while eliminating chemical use. Impact mill was found to be the most efficient milling for size reduction of forest residual chips from ca. 2 mm to a specific value below 100 µm. The further micronization effectively disrupted the recalcitrance of the woody biomass and produced the highly saccharifiable substrates for downstream processing. In addition, extrusion can be integrated into a clean cellulosic sugar process for further fibrillation in place of the conventional mixing processing. The highest energy efficiency was observed on the impact-milled samples with 0.515 kg sugars kWh −1 . [ABSTRACT FROM AUTHOR]

Impact of planetary ball milling on pre-milled wood fiber was studied to improve efficiency of energy consumption for bioconversion using post-harvest forest residuals. Crystalline cellulose decreased from 40.73% to 11.70% by ball milling. Crystallinity index of ball milled wood samples had a negative correlation with glucose yield (r = −0.97, p  < .01), xylose/mannose (r = −0.96, p  < .01), and a positive correlation with median particle size (r = 0.77, p  < .01). Range of glucose yield and xylose/mannose yield for ball milled samples was found to be 24.45–59.67% and from 11.92% to 23.82%, respectively. Morphological changes of the lignocellulosic biomass were observed; the compact fiber bundles of the forest residuals were cleaved to smaller particles with lower aspect ratio with increasing intensity of ball milling. The required energy ranged from 0.50 to 2.15 kWh/kg for 7–30 min of milling respectively. [ABSTRACT FROM AUTHOR]

The effect of ensiling fermentation and mechanical pretreatment on the methane yield of lignocellulosic biomass was investigated in order to determine the optimum pretreatment conditions for biogas production. Wheat straw was treated using the following techniques: mechanical disintegration by chopping and extruder-grinding to particle sizes of 2.0 and 0.2 cm, respectively, and ensiling by 30% and 45% total solids with addition of enzymatic, chemical and biological silage additives individually and in combination. The total and volatile solid content, biochemical methane potential and products of silage fermentation of 32 variants were tested. The results indicate that the methane potential increased by 26% (from 179 to 244 mL CH 4 g −1 VS) by reducing particle size. The maximum methane potential of 275 mL CH 4 g −1 VS was obtained from silage with 30% total solids and extruder grinding. However, the effect of the addition of silage additives on the methane potential was limited. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrodynamic disintegration intensified co-digestion of sewage sludge & maize silage. • 15% increase in methane production did not allow for net energy profit. • No impact of hydrodynamic disintegration on methanogenic consortia. • Inoculum shaped the structure of methanogenic community. • Previously unclassified taxa were key players in anaerobic digestion. The aim of this project was to study the combination of two methods to increase methane production: feedstock pretreatment by hydrodynamic disintegration and co-digestion of maize silage (MS) with thickened excess sludge (TES). Disintegration of TES alone resulted in a 15% increase in specific methane production from 0.192 Nml/gVS (TES + MS) to 0.220 Nml/gVS (pretreated TES + MS). The energy balance revealed additional energy (0.14 Wh) would cover only the energy expenditure for the mechanical pretreatment and would not allow for net energy profit. Identification of the methanogenic consortia by 16S rRNA gene amplicon sequencing revealed that Chloroflexi , Bacteroidota, Firmicutes , Proteobacteria and Actinobacteriota were five most abundant bacteria phyla, with Methanothrix and Methanolinea as the dominant methanogens. Principal component analysis did not show any effect of feedstock pretreatment on methanogenic consortia. Instead, the composition of inoculum was the decisive factor in shaping the microbial community structure. [ABSTRACT FROM AUTHOR]

Animal manure digestion is associated with limited methane production, due to the high content in fibers, which are hardly degradable lignocellulosic compounds. In this study, different mechanical and thermal alkaline pretreatment methods were applied to partially degradable fibers, separated from the effluent stream of biogas reactors. Batch and continuous experiments were conducted to evaluate the efficiency of these pretreatments. In batch experiments, the mechanical pretreatment improved the degradability up to 45%. Even higher efficiency was shown by applying thermal alkaline pretreatments, enhancing fibers degradability by more than 4-fold. In continuous experiments, the thermal alkaline pretreatment, using 6% NaOH at 55 °C was proven to be the most efficient pretreatment method as the methane production was increased by 26%. The findings demonstrated that the methane production of the biogas plants can be increased by further exploiting the fraction of the digested manure fibers which are discarded in the post-storage tank. [ABSTRACT FROM AUTHOR]

As the biogas sector is rapidly expanding, there is an increasing need in finding new alternative feedstock to biogas plants. Meadow grass can be a suitable co-substrate and if ensiled it can be supplied to biogas plants continuously throughout the year. Nevertheless, this substrate is quite recalcitrant and therefore efficient pretreatment is needed to permit easy access of microbes to the degradable components. In this study, different mechanical pretreatment methods were applied on ensiled meadow grass to investigate their effect on biomass biodegradability. All the tested pretreatments increased the methane productivity and the increase ranged from 8% to 25%. The best mechanical pretreatment was the usage of two coarse mesh grating plates. Additionally, simple analytical methods were conducted to investigate the possibility of rapidly determining the methane yield of meadow grass. Among the methods, electrical conductivity test showed the most promising calibration statistics ( R 2 = 0.68). [ABSTRACT FROM AUTHOR]