Dry fermentation of manure with straw in continuous plug flow reactor: Reactor development and process stability at different loading rates

Abstract

In this work, a plug flow reactor was developed for continuous dry digestion processes and its efficiency was investigated using untreated manure bedded with straw at 22% total solids content. This newly developed reactor worked successfully for 230days at increasing organic loading rates of 2.8, 4.2 and 6gVS/L/d and retention times of 60, 40 and 28days, respectively. Organic loading rates up to 4.2gVS/L/d gave a better process stability, with methane yields up to 0.163LCH/gVS/d which is 56% of the theoretical yield. Further increase of organic loading rate to 6gVS/L/d caused process instability with lower volatile solid removal efficiency and cellulose degradation.

Dry Anaerobic Co-Digestion of Citrus Wastes with Keratin and Lignocellulosic Wastes: Batch And Continuous Processes

“…5. In this study, process 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Cumulative methane yield (Nml/gVS) Daily biogas (Nml/d) Time (days) 1 3 instability was observed at a lower organic loading rate of 3.8 gVS/L/d compared to an OLR of six gVS/L/d reported previously for instability while treating MS at 22% TS using the continuous plug flow reactor [27]. This can be attributed to the presence of CW in the co-digestion mixture in this study.…”

“…1. Other studies reported methane yields between 100 and 300 NmlCH 4 /gVS for the WS and MS obtained under different conditions [5,9,27,28,46]. Figure 2 shows the cumulative methane production curves obtained for the anaerobic dry co-digestion of CF, CW, WS, and MS during 82 days of digestion period.…”

“…Prior to analysis, the feedstocks being solids were prepared according to Zupančič and Roš [33] by blending 1 g of the sample with water (dilution factor of 50) to allow homogenization. Thereafter, the theoretical methane potential (BMP thCOD ) of the feedstocks used were calculated related to their chemical oxygen demand (COD) content as described previously [27], after determining the COD content for the individual feedstocks using Eq. (1) [34] assuming that the equation is valid for any substance or product [35].…”

“…This impeller allowed mixing of the feedstock at the bottom part of the inlet, and transported the materials very slowly towards the outlet taking several rotations depending on the viscosity of feedstock and working volume of reactor. The plug flow reactors worked as described previously [27], with a working volume of 5 L.…”

“…There has been great concern over large volume of water used during anaerobic digestion of solids wastes and in the digestate residue. To address this challenge, recent studies have focused on dry anaerobic digestion of these waste streams [26][27][28][29][30]. However, dry digestion of these wastes requires further improvement for industrial applications; there is a challenge of longer retention time and low mass transfer at higher solid content [31,32].…”