Surface-Related Kinetic Models for Anaerobic Digestion of Mi-crocrystalline Cellulose: The Role of Particle Size

Abstract

In this work, for modelling the anaerobic digestion of microcrystalline cellulose, two surface-related models based on cylindrical and spherical particles were developed and compared with the first-order kinetics model. A unique dataset consisting of particles with different sizes, the same crystallinity and polymerisation degree was used to validate the models. Both newly developed models outperformed the first-order kinetics model. Analysis of the kinetic constant data revealed that particle size is a key factor determining the anaerobic digestion kinetics of crystalline cellulose. Hence, crystalline cellulose particle size should be considered in the development and optimization of lignocellulose pre-treatment methods. Further research is necessary for the assessment of impact of the crystalline cellulose particle size and surface properties on the microbial cellulose hydrolysis rate.

Keywords: anaerobic digestion; microcrystalline cellulose; modelling; surface-related kinetics.

Figure 1

SEM micrographs of MCC particles with sizes of (a) 20–32 μm; (b) 32–45 μm; (c) 56–100 μm; (d) 150–212 μm.

Figure 2

Biogas production experimental and model data for each sample. Circles denote the means of three samples, and vertical bars denote standard deviations. Blue, red, and green lines denote the first-order kinetic model and the approximations for the cylindrical and spherical particles, respectively.

Figure 3

Measured k constants for the cylinder (top) and spherical (bottom) shaped particles models. Points represent measured values and lines represent model approximations.

Figure 4

WRV compared to spherical shaped particle model kinetic constant values. For k constant (top) and WRV (bottom) points, the error bars represent the 95% confidence interval and standard error, respectively.

Figure 5

Specific surface area compared to the spherical shaped kinetic constant values. For the k constant (top) and SSA (bottom) data points, the error bars represent the 95% confidence interval and the standard error, respectively.