Methods for the Evaluation of Industrial Mechanical Pretreatments before Anaerobic Digesters

Abstract

Different methods were tested to evaluate the performance of a pretreatment before anaerobic digestion. Besides conventional biochemical parameters, such as the biochemical methane potential (BMP), the methane production rate, or the extent of solubilization of organic compounds, methods for physical characterization were also developed in the present work. Criteria, such as the particle size distribution, the water retention capacity, and the rheological properties, were thus measured. These methods were tested on samples taken in two full-scale digesters operating with cattle manure as a substrate and using hammer mills. The comparison of samples taken before and after the pretreatment unit showed no significant improvement in the methane potential. However, the methane production rate increased by 15% and 26% for the two hammer mills, respectively. A relevant improvement of the rheological properties was also observed. This feature is likely correlated with the average reduction in particle size during the pretreatment operation, but these results needs confirmation in a wider range of systems.

Cold-pressed fruit and vegetable juice pomaces: decision making about their suitability for anaerobic digestion

“…It is known the mechanical pre-treatments (such as the one used in this study) can break down complex organic compounds, increasing their solubilization, leading to an increment of methane production. 91–93 To assess the effect of mechanically pre-treating the fresh FVP, the FVPP BMP th values were converted to their original matter by considering the dilution factor (1 : 4). The converted values ranged between 1547.6 and 1861.6 mL CH 4 g TSV −1 which is considerably higher than the BMP th values of FVP (ranging from 410 to 412 mL CH 4 g TSV −1 ), meaning that the mechanical pre-treatment of FVP increases methane production by four times.…”

Chemically and Physically Pretreated Straw in Moderate Conditions: Poor Correlation between Biogas Production and Commonly Used Biomass Characterization

“…LFD n c (6) where n is the number of cellulose polymers perpendicular to the cross-section along one side of the square fibril cross-section, and c is a conversion factor of 0.57 nm per cellulose polymer [70,77]. In addition to the CI calculation, spectral fitting is also useful to estimate the supramolecular structures of cellulose [70,[77][78][79].…”

“…Mechanical pretreatment such as grinding helps to reduce the size of biomass which cannot only increase the surface area for microbial degradation but also be useful to intensify the AD process. Size reduction could avoid the problems of floatation and strengthen the mixing, heat, and mass transfer in the downstream process [6,7]. It consequently boosts the digester feeding conditions and reduces the digester size.…”

Research trends and strategies for the improvement of anaerobic digestion of food waste in psychrophilic temperatures conditions

“… Application of rheological mathematical models, such as the Herschel–Bulkley, Ostwald, and Bingham models. [ 24 , 86 , 155 ] Bioaugmentation Methane production could be increased by bioaugmentation, selecting strains of psychrophilic bacteria that can enhance their number and microbial activity. [ 119 ] Co-digestion of substrates: Application of mixtures of two or more substrates could increase the yield of CH4; this strategy is the focus of the most recent research and has a positive effect on the buffer capacity of the process.…”

“… The decrease in temperature results in an increase in sludge viscosity, which hinders mixing with FW and could affect methane production, for this reason it is important to rheologically characterize the inoculums. [ 86 , 155 , 177 ] …”