Enhanced methane production from cellulose using a two-stage process involving a bioelectrochemical system and a fixed film reactor

Abstract Background It is desirable to improve the anaerobic digestion processes of recalcitrant materials, such as cellulose. Enhancement of methane (CH4) production from organic molecules was previously accomplished through coupling a bioelectrochemical system (BES); however, scaling-up BES-based production is difficult. Here, we developed a two-stage process consisting of a BES using low-cost and low-reactive carbon sheets as the cathode and anode, and a fixed film reactor (FFR) containing conductive material, i.e., carbon fiber textiles (CFTs) (:BES → FFR). By controlling the cathodic current at 2.7 μA/cm2 without abiotic H2 production, the three-electrode BES system was operated to mimic a microbial electrolysis cell. Results The thermophilic BES (inlet pH: 6.1) and FFR (inlet pH: 7.5) were operated using hydraulic retention times (HRTs) of 2.5 and 4.2 days, respectively, corresponding to a cellulose load of 3555.6 mg-carbon (C)/(L day). The BES → FFR process achieved a higher CH4 yield (37.5%) with 52.8 vol% CH4 in the product gas compared to the non-bioelectrochemical system (NBES) → FFR process, which showed a CH4 yield of 22.1% with 46.8 vol% CH4. The CH4 production rate (67.5 mM/day) obtained with the BER → FFR process was much higher than that obtained using electrochemical methanogenesis (0.27 mM/day). Application of the electrochemical system or CFTs improved the yields of CH4 with the NBES → FFR or BES → non-fixed film reactor process, respectively. Meta 16S rRNA sequencing revealed that putative cellulolytic bacteria (identified as Clostridium species) were present in the BES and NBES, and followed (BES→ and NBES→) FFR. Notably, H2-consuming methanogens, Methanobacterium sp. and Methanosarcina sp., showed increased relative abundances in the suspended fraction and attached fraction of (BES→) FFR, respectively, compared to that of (NBES→) FFR, although these methanogens were observed at trace levels in the BES and NBES. Conclusions These results indicate that bioelectrochemical preprocessing at a low current effectively induces interspecies H2 transfer in the FFR with conductive material. Sufficient electrochemical preprocessing was observed using a relatively short HRT. This type of two-stage process, BES → FFR, is useful for stabilization and improvement of the biogas (CH4) production from cellulosic material, and our results imply that the two-stage system developed here may be useful with other recalcitrant materials.

Download Full-text

Economic Feasibility Study of a Small-scale Biogas Plant Using a Two-stage Process and a Fixed Bio-film Reactor for a Cost-efficient Production

Energy Procedia ◽

10.1016/j.egypro.2016.09.042 ◽

2016 ◽

Vol 95 ◽

pp. 385-392 ◽

Cited By ~ 6

Author(s):

Roberto Renda ◽

Emanuele Gigli ◽

Andrea Cappelli ◽

Silvano Simoni ◽

Elisa Guerriero ◽

...

Keyword(s):

Feasibility Study ◽

Economic Feasibility ◽

Biogas Plant ◽

Small Scale ◽

Efficient Production ◽

Two Stage ◽

Film Reactor ◽

Stage Process ◽

Cost Efficient

Download Full-text

Changes in the microbial consortium during dark hydrogen fermentation in a bioelectrochemical system increases methane production during a two-stage process

Biotechnology for Biofuels ◽

10.1186/s13068-018-1175-z ◽

2018 ◽

Vol 11 (1) ◽

Cited By ~ 3

Author(s):

Kengo Sasaki ◽

Daisuke Sasaki ◽

Yota Tsuge ◽

Masahiko Morita ◽

Akihiko Kondo

Keyword(s):

Methane Production ◽

Microbial Consortium ◽

Bioelectrochemical System ◽

Two Stage ◽

Stage Process

Download Full-text

Starting-Up of an Anaerobic Fixed-Film Reactor

Water Science & Technology ◽

10.2166/wst.1983.0173 ◽

1983 ◽

Vol 15 (8-9) ◽

pp. 305-308 ◽

Cited By ~ 44

Author(s):

M S Salkinoja-Salonen ◽

E.-J Nyns ◽

P M Sutton ◽

L van den Berg ◽

A D Wheatley

Keyword(s):

Fixed Film ◽

Film Reactor

Download Full-text

Tertiary nitrification in pilot-plant plug-flow fixed-film reactors with long-term ammonium deficiency

Water Science & Technology ◽

10.2166/wst.1994.0746 ◽

1994 ◽

Vol 29 (10-11) ◽

pp. 61-67 ◽

Cited By ~ 2

Author(s):

M. Fruhen ◽

K. Böcker ◽

S. Eidens ◽

D. Haaf ◽

M. Liebeskind ◽

...

Keyword(s):

Pilot Plant ◽

Effective Means ◽

Plug Flow ◽

Nitrification Rate ◽

Industrial Project ◽

Transfer Processes ◽

Fixed Film ◽

Film Reactor ◽

Observation Period

The objective of this study is to investigate to what extent the nitrification capacity of a pilot-plant fixed-film reactor changes during extensive periods of nutrient supply deficiency. The examined pilot-plant was an upflow reactor filled with swelling clay of medium grain size (6 to 8 mm). The experiments revealed that the maximum nitrification rate remained practically constant during the first weeks after the onset of unregulated ammonium supply. The capacity declined slowly, dropping to approximately 66% of the initial capacity after about ten weeks. Still ammonium peaks of up to 8 mg/l were readily nitrified throughout the entire period of the experiment. The reduction in nitrification capacity during the observation period did not result from decay processes of biomass but from the reactor becoming blocked and thus hampering transfer processes. It could be observed that the detached organisms attached again further up. This semi-industrial project demonstrated that a plug-flow fixed-film reactor can be used as effective means of tertiary nitrification.

Download Full-text

Two-Stage Biodiesel Synthesis from Used Cooking Oil with a High Acid Value via an Ultrasound-Assisted Method

Energies ◽

10.3390/en14123703 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3703

Author(s):

Ming-Chien Hsiao ◽

Wei-Ting Lin ◽

Wei-Cheng Chiu ◽

Shuhn-Shyurng Hou

Keyword(s):

Acid Value ◽

Molar Ratio ◽

Optimal Conditions ◽

Two Stage ◽

Cooking Oil ◽

High Acid ◽

Used Cooking Oil ◽

Biodiesel Synthesis ◽

Stage Process ◽

Ultrasound Assisted

In this study, ultrasound was used to accelerate two-stage (esterification–transesterification) catalytic synthesis of biodiesel from used cooking oil, which originally had a high acid value (4.35 mg KOH/g). In the first stage, acid-catalyzed esterification reaction conditions were developed with a 9:1 methanol/oil molar ratio, sulfuric acid dosage at 2 wt %, and a reaction temperature of 60 °C. Under ultrasound irradiation for 40 min, the acid value was effectively decreased from 4.35 to 1.67 mg KOH/g, which was decreased to a sufficient level (<2 mg KOH/g) to avoid the saponification problem for the subsequent transesterification reaction. In the following stage, base-catalyzed transesterification reactions were carried out with a 12:1 methanol/oil molar ratio, a sodium hydroxide dosage of 1 wt %, and a reaction temperature of 65 °C. Under ultrasound-assisted transesterification for 40 min, the conversion rate of biodiesel reached 97.05%, which met the requirement of EN 14214 standard, i.e., 96.5% minimum. In order to evaluate and explore the improvement of the ultrasound-assisted two-stage (esterification–transesterification) process in shortening the reaction time, additional two-stage biodiesel synthesis experiments using the traditional mechanical stirring method under the optimal conditions were further carried out in this study. It was found that, under the same optimal conditions, using the ultrasound-assisted two-stage process, the total reaction time was significantly reduced to only 80 min, which was much shorter than the total time required by the conventional method of 140 min. It is worth noting that compared with the traditional method without ultrasound, the intensification of the ultrasound-assisted two-stage process significantly shortened the total time from 140 min to 80 min, which is a reduction of 42.9%. It was concluded that the ultrasound-assisted two-stage (esterification–transesterification) catalytic process is an effective and time-saving method for synthesizing biodiesel from used cooking oil with a high acid value.

Download Full-text