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

Abstract

In this paper, the viability of thermophilic anaerobic co-digestion of exhausted sugar beet pulp (ESBP) and pig manure (PM) was evaluated. The effect of the proportion of ESBP on biogas production was investigated by using a series of lab-scale batch assays, in duplicates. The following five ESBP:PM mixture ratios were studied: 0:100, 10:90, 25:75, 50:50, and 100:0. The highest cumulative methane production (212.4 mL CH4/g VSadded) was reached for the mixture 25:75. The experimental results showed that the increase in the proportion of ESBP in the mixture led to the distortion of the process, due to acidification by the volatile fatty acids generated. Acetic acid was the predominant acid in all the cases, representing more than 78% of the total acidity. Moreover, the results obtained by operating at thermophilic temperatures have been compared with those obtained in a previous study conducted at mesophilic temperatures. The results have shown that in the individual digestion of ESBP, the activity of acetoclastic methanogens was affected in both temperatures, but especially in thermophilic conditions. Thus, the methane produced in the individual thermophilic digestion of ESBP came almost entirely from the activity of hydrogen-utilizing methanogenic archaea.

Biogas Production from Organic Wastes: Integrating Concepts of Circular Economy

“…Temperature accelerates the rate of degradation, leading to a shorter time needed to complete the full conversion of the substrate. There are several reports in the literature describing the influence of these parameters when operating under mesophilic and thermophilic regimens [28][29][30] and successfully evaluating different types of wastes, such as swine manure [31,32], sewage sludge [6,33,34], and lipid-rich wastes such as slaughterhouse wastes [35,36]. However, digestion is a complex process and may suffer from instabilities that are mainly associated with accidental overloading in the form of the presence of inhibitors such as sulfur compounds, high ammonia concentration, and volatile fatty acids (VFAs), or inadequate temperature control.…”

Thermophilic Anaerobic Co-Digestion of Exhausted Sugar Beet Pulp with Cow Manure to Boost the Performance of the Process: The Effect of Manure Proportion

“…A total organic carbon (TOC) analyzer (Analytik-Jena ® multi N/C 3100, Germany) was used for the dissolved organic carbon (DOC) determination and gas chromatography was applied for volatile fatty acids (VFAs) determination. Acetic (C2), propionic (C3), isobutyric (iC4), butyric (C4), isovaleric (iC5), valeric (C5), isocaproic (iC6), caproic (C6), and heptanoic (C7) individual acids were measured in a FID-GC (Shimadzu ® GC-2010, Japan) [22].…”

“…The substrate was presented in small cylindrical dry pellets which were stored at −20 • C prior their use. A 24 h rehydration procedure was applied in order to obtain the final total solids content of 8% [22]. On the other hand, the cow manure (CM) was collected from a medium sized local farm located in El Puerto Santa María (Cádiz, Spain) where the liquid slurry was discarded in an industrial sedimentation tank.…”

Editorial of the Special Issue “Anaerobic Co-Digestion of Lignocellulosic Wastes”

“…The tests were analyzed from a novel perspective, evaluating the uncoupling of anaerobic phases (hydrolysis, acidogenesis/acetogenesis and methanogenesis) through the calculation of indirect carbon-related parameters such as acidogenic substrate carbon (ASC). In the same way, Gómez-Quiroga et al [13] refer to a similar study with the same type of lignocellulosic material (exhausted sugar beet pulp) under thermophilic operating conditions, where batch tests were assayed, showing that the activity of acetoclastic methanogens was especially affected at thermophilic conditions while organic matter solubilization was more efficient. As a final colophon, the review of Sarker et al [14] focuses on the different types of bioreactors and configurations for the anaerobic process.…”