Improvement of Exhausted Sugar Beet Cossettes Anaerobic Digestion Process by Co-Digestion with Pig Manure

Abstract

Exhausted sugar beet cossettes (ESBC) are one of the main byproducts generated in the sugar industries. The pellets of dried pulp of ESBC used in this study are composed of 85% beet pulp and 15% molasses and have a high lignocellulosic-type organic matter content (91% volatile solids) and a nitrogen deficiency. Mesophilic anaerobic co-digestion in batch of dried pellets of ESBC and pig manure (PM) was studied in this paper for five mixture ratios. The mixtures were selected on the basis of the carbon/nitrogen ratio, leading to ESBC:PM percentages of 0:100, 32:68, 48:52, 72:28, and 100:0. Codigestion increased the methane yield in all cases relative to the digestion of ESBC alone. Acetic and propionic acids were the main volatile fatty acids observed in the tests. Initial accumulation of propionic acid in the reactors with higher ESBC content (and especially for the 100:0 reactor) indicated the difficulties associated with ESBC degradation. The best results were obtained for co-digestion of ESBC and PM in a 32:68 mixture, leading to 103% and 30% improvement in the specific methane production relative to the digestion of ESBC and PM, respectively. Furthermore, this mixture ratio was also optimal to minimize the lagphase period for methane production.

Enhancement of Methane Production in Thermophilic Anaerobic Co-Digestion of Exhausted Sugar Beet Pulp and Pig Manure

“…In addition, pig manure added microorganisms from its digestive tract which could enhance the hydrolysis of the lignocellulosic material present in the ESBP. These results were in line with what has been reported by several authors studying AD of agro-industrial wastes [45,46].…”

“…Nevertheless, it must be noted that the SMP obtained for the PM used in this study was clearly lower than that obtained in a previous study, conducted under mesophilic conditions [46], where a value of 468 mL/VS added was reached. Moreover, this effect seemed to extend to the assay with the ratio 10:90, due to its high PM proportion.…”

“…As was previously pointed out in Section 3.3, a significant improvement in methane production was obtained by applying the co-digestion option with respect to the anaerobic digestion of the individual substrates. However, the calculated SMPs were markedly lower than those obtained in the mesophilic process [46]. Figure 6 depicts the DOC evolution in this study, together with data from a previous mesophilic study of Aboudi et al [46].…”

“…However, the calculated SMPs were markedly lower than those obtained in the mesophilic process [46]. Figure 6 depicts the DOC evolution in this study, together with data from a previous mesophilic study of Aboudi et al [46]. Maximum values of DOC have been taken into account for this comparison, since they represent the situation of maximum unbalance between solubilization and consumption of organic matter in batch processes.…”

Improvement of Anaerobic Digestion of Lignocellulosic Biomass by Hydrothermal Pretreatment

“…Lignin is a structurally important polymer in biomass and is one of the most abundant organic substances on earth, next to cellulose [25]. Lignins are major structural components of higher plants and the primary cell wall provides structural support, impermeability confers to biomass its resistance to hydrolysis and microbial degradation [26,27]. Structurally, lignin is a complex three-dimensional polymer of phenylpropane units (approx.…”